Boulder Creek, Colorado Segment 2b: From 13th Street to the Confluence with South Boulder Creek
Total Maximum Daily Load Escherichia coli
City of Boulder
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Boulder Creek, Colorado Segment 2b: From 13th Street to the Confluence with South Boulder Creek
Escherichia coli Total Maximum Daily Load (TMDL)
Prepared for: City of Boulder, Colorado and State of Colorado Department of Public Health and Environment and U.S. Environmental Protection Agency, Region VIII
Prepared by:
August 23rd, 2011
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Table of Contents List of Tables ................................................................................................................................................ 4 List of Figures ............................................................................................................................................... 5 List of Abbreviations .................................................................................................................................... 6 Executive Summary ...................................................................................................................................... 7 1
Introduction ......................................................................................................................................... 11
2
Problem Statement .............................................................................................................................. 12 2.1
Description of the Watershed ...................................................................................................... 12
2.2
Impairment Overview ................................................................................................................. 14
2.2.1
Land use .............................................................................................................................. 15
2.2.2
Climate ................................................................................................................................ 18
2.3
3
Beneficial Uses and Standards Addressed in this TMDL ........................................................... 18
2.3.1
Beneficial Uses ................................................................................................................... 18
2.3.2
Water Quality Standards ..................................................................................................... 19
Data Inventory and Analysis ............................................................................................................... 19 3.1
Data Inventory ............................................................................................................................ 20
3.1.1 3.2
Watershed Flows ................................................................................................................. 21
Water Quality Data Analysis ...................................................................................................... 23
3.2.1
Monthly Monitoring Results ............................................................................................... 23
3.2.2
Weekly Monitoring Results ................................................................................................ 24
3.2.3
Outfall Monitoring .............................................................................................................. 26
4
Numeric Target Selection ................................................................................................................... 28
5
Source Assessment.............................................................................................................................. 28 5.1
5.1.1
NPDES Regulated Municipal Separate Storm Sewer Systems (MS4s) .............................. 28
5.1.2
Other (Non-MS4) NPDES Facilities................................................................................... 30
5.2
6
Point Sources .............................................................................................................................. 28
Nonpoint Sources ........................................................................................................................ 30
5.2.1
Upstream Nonpoint Sources ............................................................................................... 30
5.2.2
Open Areas and Open Space ............................................................................................... 31
5.2.3
Other Potential Nonpoint Sources....................................................................................... 31
Linkage Analysis ................................................................................................................................ 32 6.1
Flow Duration Curve Methodology ............................................................................................ 32
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
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8
6.2
Load Duration Curve Methodology ............................................................................................ 35
6.3
Loading Assessment of Boulder Creek ....................................................................................... 37
TMDL Calculations and Allocations .................................................................................................. 39 7.1
Establishment of the TMDL ....................................................................................................... 39
7.2
Wasteload Allocations ................................................................................................................ 40
7.2.1
Wasteload Allocations: MS4 .............................................................................................. 40
7.2.2
Wasteload Allocations: Other NPDES facilities ................................................................. 44
7.3
Load Allocations ......................................................................................................................... 45
7.4
Margin of Safety ......................................................................................................................... 45
7.5
Seasonal Variations and Critical Conditions............................................................................... 46
Implementation and Monitoring Recommendations ........................................................................... 46 8.1
Implementation Prioritization ..................................................................................................... 47
8.2
Recommended Actions ............................................................................................................... 50
References ................................................................................................................................................... 51 Appendix A: Boulder Creek Monitoring Data ............................................................................................ 53 A.1
Monthly Monitoring.................................................................................................................... 53
A.2
Weekly Monitoring ..................................................................................................................... 56
A.3
Storm Drain Outfall Monitoring ................................................................................................. 62
Appendix B: TMDL Analyses .................................................................................................................... 66 B.1
Water Quality Duration Curves .................................................................................................. 66
B.1.1
BC-Eben .............................................................................................................................. 67
B.1.2
BC-13th ................................................................................................................................ 70
B.1.3
BC-CU ................................................................................................................................ 73
B.1.4
BC-30th ................................................................................................................................ 76
B.2
Summary of Bi-Monthly Geometric Mean Evaluation ............................................................... 79
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
List of Tables Table 1: Total Maximum Daily Load for E. coli in Boulder Creek (Segment COSPBO02b) Impaired Waterbody Information. .......................................................................................................................................................... 8 Table 2: Summary of Total Maximum Daily Load for E. coli in Boulder Creek Segment COSPBO02 TMDL Methodology. ........................................................................................................................................................ 9 Table 3: Boulder Creek Segment COSPBO02b Total Maximum Daily Load Summary (E. coli, CFU/day). ............. 10 Table 2-1: Detailed land use within drainage to the impaired stretch of Boulder Creek. ............................................ 16 Table 2-2: Average monthly climate of Boulder, Colorado. ....................................................................................... 18 Table 2-3: Beneficial uses within the impaired portion of Segment 2b of Boulder Creek. ......................................... 19 Table 3-1: Stream gauges used to evaluate flow in Boulder Creek. ............................................................................ 23 Table 3-2: E. coli two month geometric mean evaluation of combined years 2003-2010 at monthly monitoring sites (CFU/100 mL). ................................................................................................................................................... 24 Table 3-3: Two month geometric mean assessment of available Boulder Creek weekly E. coli data. ........................ 25 Table 3-4: Description of outfalls routinely monitoring within the impaired reach. ................................................... 26 Table 3-5: Two month E. coli geometric mean analysis of storm drain outfalls identified as a concern along the impaired stretch of Boulder Creek (CFU/100mL). ............................................................................................. 27 Table 5-1: MS4 stormwater permit holders within the impaired reach of Boulder Creek. .......................................... 29 Table 5-2: NPDES Permit holders along Boulder Creek Segment 2b. ........................................................................ 30 Table 6-1: Range of flow conditions within each flow category. ................................................................................ 35 Table 7-1: Identification of E. coli TMDL based on flow conditions within the impaired stretch of Boulder Creek. 40 Table 7-2: TMDL E. coli wasteload and load allocations (CFU/day) by flow condition. ........................................... 41 Table 7-3: Percent jurisdictional WLA and LA. .......................................................................................................... 41 Table 7-4: Observed E. coli loads under dry weather conditions at outfalls identified as a concern within the impaired reach of Boulder Creek. ....................................................................................................................... 44 Table 7-5: Observed Boulder Creek E. coli load by flow tier at site BC-30th calculated with weekly monitoring data from May through October (considering all data available 6/14/2006-10/27/2010). .......................................... 44 Table 8-1: Reductions required to ensure outfalls do not contribute to instream E. coli standard violations. ............ 47 Table 8-2: Percent reductions per outfall subcatchment and jurisdictional area. ......................................................... 49
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
List of Figures Figure 1: View of Boulder Creek near 30th Street, photo taken September 10th, 2010. ................................................ 7 Figure 2-1: View of Boulder Creek west of Folsom Street (at site BC-CU) (photo by Andrew Taylor, City of Boulder). ............................................................................................................................................................. 12 Figure 2-2: Subwatershed drainages within the Boulder Creek watershed. ................................................................ 13 Figure 2-3: Impaired reach of Boulder Creek in Boulder, Colorado. .......................................................................... 14 Figure 2-4. Drainage area (ongoing contribution in brown) as well as potential tributary drainage (Bear Canyon, Skunk Creek and Twomile Canyon /Goose Creek.............................................................................................. 15 Figure 2-5: Land use within drainage to the impaired reach of Boulder Creek. .......................................................... 17 Figure 3-1: Boulder Creek instream and storm drain outfall monitoring locations. .................................................... 20 Figure 3-2: Historical Boulder Creek flow data at BOCOROCO (Orodell) from 1980- 2010. ................................... 21 Figure 3-4: Hydrograph comparing flow gauges at Orodell (BOCOROCO) and urban corridor (BOCOBOCO) from 1/1/2009 to 11/2/2010. ........................................................................................................................................ 22 Figure 3-3: Boulder Creek (at site BC-CU) taken during low-flow and high-flow conditions. .................................. 22 Figure 3-5: Analysis of bimonthly geometric means considering all E. coli data from 2004-2010 supporting impairment downstream (east) of 13th Street. Note E. coli standard in red (126 CFU/100 mL). ....................... 24 Figure 5-1: Storm drain outfall located adjacent to Boulder Creek, regulated under Phase II MS4 general permit (photo by Andrew Taylor, City of Boulder). ...................................................................................................... 29 Figure 6-1: Regression relationship between flow recorded at Orodell (BOCOROCO) and instream monitoring data gathered by the City at the ‘Below Broadway’ site. ........................................................................................... 34 Figure 6-2: Flow duration analysis of extrapolated flow within the impaired reach of Boulder Creek. ...................... 35 Figure 6-3: Load duration curve used to represent E. coli loading capacity of the impaired reach of Boulder Creek.36 Figure 6-4. Water quality duration curve of annual trends at site BC-30th. ................................................................ 38 Figure 6-5. Water quality duration curve of annual trends at site BC-30th. ................................................................ 38 Figure 7-1. MS4 jurisdictional areas. ........................................................................................................................... 42 Figure 7-2. Identified storm drain outfalls with concentrations of concern within the impaired reach of Boulder Creek. .................................................................................................................................................................. 43 Figure 8-1. Outfall subcatchment percent reduction. ................................................................................................... 48
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
List of Abbreviations BMP BST CFS CFU CDPHE CDPS Commission CWA Division E. coli EPA GIS KICP LAs LDC LID MGD mg/L MOS MS4 NPS NPDES SWMP TMDL USGS WLAs WQO WQS WWTF
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Best Management Practices Bacterial Source Tracking Cubic Feet per Second Colony Forming Units Colorado Department of Public Health and Environment Colorado Discharge Permit System Water Quality Control Commission Clean Water Act Colorado Water Quality Control Division Escherichia coli U.S. Environmental Protection Agency Geographic Information System Keep it Clean Partnership Load Allocations Load Duration Curve Low Impact Development Million Gallons per Day Milligrams per Liter Margin of Safety Municipal Separate Storm Sewer System Nonpoint Source National Pollutant Discharge Elimination System Stormwater Management Program Total Maximum Daily Load United States Geological Survey Wasteload Allocations Water Quality Objective Water Quality Standard Wastewater Treatment Facility
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Executive Summary A portion of Boulder Creek Segment 2b (from 13th Street to the confluence with South Boulder Creek) has been identified by the State of Colorado 303(d) List of water-quality impaired waterbodies for nonattainment of the Escherichia coli (E. coli) water quality standard. The impairment is located within the urban corridor of Boulder, Colorado; the stream environment is shown in Figure 1. This impairment affects the beneficial use of existing recreation (Recreation E) and is therefore of high priority for the completion of a total maximum daily load (TMDL) due to the nonattainment of human health standards. Table 1 summarizes waterbody information regarding this impairment. In accordance with the Federal Clean Water Act (CWA), a TMDL must be developed to determine the maximum amount of a pollutant (i.e., E. coli) a waterbody can receive and still attain water quality standards (WQSs) and maintain beneficial uses. The methodology used to determine the TMDL is summarized within Table 2 and discussed throughout this TMDL document. Sources of E. coli identified within the impaired stretch include permitted discharges, urban runoff, illicit discharges, wildlife and upstream sources (from the impaired stretch). Contributions and allowable loads for identified sources and varying flow conditions are presented in Table 3; these are discussed in more detail throughout this TMDL document.
Figure 1: View of Boulder Creek near 30th Street, photo taken September 10th, 2010.
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011 Table 1: Total Maximum Daily Load for E. coli in Boulder Creek (Segment COSPBO02b) Impaired Waterbody Information.
State
Colorado
County
Boulder
Watershed
Boulder Creek
Waterbody ID
COSPB002b
Constituents of Concern
Escherichia coli (E. coli)
Segment Description
Mainstem of Boulder Creek, including all tributaries, lakes, reservoirs, and wetlands from the point immediately below the confluence with North Boulder Creek to a point immediately above the confluence with South Boulder Creek.
Affected Portion of Segment
13th Street to the confluence with South Boulder Creek in Boulder
Designated Uses and impairment Status
Aquatic Life Cold 1: Recreation E: Water Supply: Agriculture:
State Priority Ranking
High
National Hydrography Dataset Identification
BocoBoco BocoRoco Additional flow relationship established with City of Boulder low flow monitoring.
Size of Watershed
447 square miles1 (286,080 acres); direct drainage 2,303 acres.
Land use/cover
Significant land use includes: Public (22.9%); Light Industry (14.9%); Low Density Residential (11.8%); High Density Residential (9.1%); Park Urban and Other (6.3%); and, Open Space (Acquired, development rights, other) (8. 5%).
Water Quality Goal
Protection of public health and recreational uses of Boulder Creek.
Water Quality Target
Attainment of two month geometric mean E. coli water quality standard of 126 colony forming units (CFU) of bacteria per 100 milliliters of water.
1
Not Impaired Impaired Not Impaired Not Impaired
Murphy, 2006, State of the Watershed: Water Quality of Boulder Creek, Colorado. U.S. Geological Survey Circular 1284. Available at: http://pubs.usgs.gov/circ/circ1284/pdf/circ1284.pdf. 8
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Table 2: Summary of Total Maximum Daily Load for E. coli in Boulder Creek Segment COSPBO02b TMDL Methodology.
TMDL Scope
Waterbody was first identified on the 2004 303(d) List as impaired due to Escherichia coli. This TMDL is developed for the impaired reaches of Boulder Creek, Segment 2b, specific to portion below 13th Street.
Analysis/ Methodology
The Boulder Creek TMDL was developed using the Load Duration Curve (LDC) methodology to ensure TMDL targets comply with the E. coli 126 CFU / 100 mL standard during fluctuating flow conditions.
Load Duration Curve Method
A duration curve is a cumulative frequency graph that represents the percentage of time during which the value of a given parameter is equaled or exceeded. Load duration curves are developed from flow duration curves and can illustrate existing water quality conditions (as represented by loads calculated from monitoring data), how these conditions compare to desired targets, and the portion of the waterbody flow regime represented by these existing loads. Load duration curves were used to determine the load reductions required to meet the target maximum concentrations for E. coli.
Critical Conditions
Water quality data collected over a period of nearly seven years (2004 to 2010) and data representing a range of recorded flow conditions for load duration curve analysis were used to assess compliance with the water quality standards over a range of hydrologic and meteorological conditions. The critical period was identified by the large majority of exceedances during summer months. To ensure proper protection of beneficial uses, the critical period was identified as recreational months of May through October.
Seasonal Variation
The 30‐year period (1980‐2010) used for hydrologic conditions and for load duration curve analysis included all seasons and a full range of flow and meteorological conditions; load duration calculations are based on such flow conditions to ensure the TMDL target aligns with the assimilative capacity of the stream in varying seasonal and flow conditions.
Margin of Safety (MOS)
This TMDL includes both an implicit and an explicit margin of safety. The implicit MOS includes conservative assumptions such as assuming E. coli concentrations from outfalls do not degrade or die‐off. In addition, to account for any uncertainty in the TMDL development, a five percent (5 %) explicit MOS is also included.
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011 Table 3: Boulder Creek Segment COSPBO02b Total Maximum Daily Load Summary (E. coli, CFU/day).
High Flows
Moist Conditions
Mid‐Range Flows CFU/day
Dry Conditions
Low Flow
TMDL
5.80E+11
1.44E+11
4.92E+10
2.05E+10
3.08E+09
MOS (‐5%)
2.90E+10
7.19E+09
2.46E+09
1.02E+09
1.54E+08
MS4 Allocatable Load*
4.10E+11
7.92E+10 WLA
2.59E+10
7.67E+09
2.40E+09
San Lazaro WWTF
5.25E+08
5.25E+08
5.25E+08
5.25E+08
5.25E+08
City of Boulder
2.66E+11
5.14E+10
1.68E+10
4.97E+09
1.56E+09
University of Colorado Boulder Valley School District
6.85E+10
1.33E+10
4.34E+09
1.28E+09
4.02E+08
5.53E+09
1.07E+09
3.50E+08
1.03E+08
3.24E+07
Boulder County
7.19E+09
1.39E+09 LA
4.56E+08
1.35E+08
4.22E+07
Upstream Load Allocation
1.41E+11
5.69E+10
2.02E+10
1.12E+10
0.00E+00
City of Boulder
4.26E+10
8.23E+09
2.70E+09
7.97E+08
2.50E+08
University of Colorado Boulder Valley School District
3.78E+09
7.31E+08
2.39E+08
7.08E+07
2.22E+07
6.07E+08
1.17E+08
3.84E+07
1.14E+07
3.56E+06
Boulder County
1.57E+10
3.04E+09
9.96E+08
2.94E+08
9.23E+07
Note: The MS4 allocatable load is the remainder of load after the MOS, the upstream LA, and San Lazaro WWTF are considered.
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
1 Introduction Section 303(d) of the Clean Water Act (CWA) requires that each state identify waterbodies within its boundaries for which effluent limitations are not stringent enough to meet applicable water quality standards (WQSs), which consist of beneficial uses, water quality objectives, and an antidegradation policy. The CWA also requires states to establish a priority ranking for these impaired waters under Section 303(d) - List of Water Quality Limited Segments (referred to as the 303(d) List). Within the State of Colorado, the 303(d) List is adopted by the Water Quality Control Commission (Commission) as part of Regulation 93 – Colorado Section 303 (d) List of Impaired Waters and Monitoring and Evaluation List. The most current Colorado 303(d) List was adopted in 2010. A total maximum daily load (TMDL) is required for the waterbodies identified as impaired in the 303(d) List. A TMDL is defined as the sum of the individual wasteload allocations (WLAs) for point sources, and load allocations (LAs) for nonpoint sources and natural background such that the capacity of the waterbody to assimilate pollutant loading (i.e., the loading capacity) is not exceeded. Additionally, the TMDL includes a margin of safety (MOS) to account for uncertainty that may arise during the TMDL process. A TMDL represents the maximum amount of the pollutant of concern that the waterbody can receive and still attain water quality standards. Additionally, a TMDL represents a strategy for meeting WQSs by allocating quantitative limits for point and nonpoint pollution sources. Specifically, once this total maximum pollutant load has been calculated, it is divided up and allocated among the known contributing sources in the watershed. The purpose of this technical report is to support the development of a TMDL for a portion of Boulder Creek Segment 2b from 13th Street to the confluence with South Boulder Creek. A TMDL is needed to achieve beneficial uses in Boulder Creek, which was first listed as impaired in the 2004 303(d) List for E. coli. The TMDL process begins with the development of a technical analysis which includes the following seven required components:
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Problem Statement – describes which standards are not being attained and which beneficial uses are threatened or impaired (Section 2). Data Inventory and Assessment – presents available data used to evaluate the impairment (Section 3). Numeric Targets – identifies numeric targets which will result in attainment of the standards and protection of beneficial uses (Section 4). Source Assessment – identifies all of the point sources and nonpoint sources of the pollutant in the watershed (Section 5). Linkage Analysis – establishes the relationship between pollutant sources and receiving water conditions. The linkage analysis for this TMDL is achieved through flow and load duration curve analysis (Section 6). With a load duration curve analysis, the Loading Capacity (i.e., the maximum load of the pollutant that may be discharged to the waterbody without causing exceedances of standards and impairment of beneficial uses) of the waterbodies for the pollutant is calculated at varying flow conditions. Allocation of the TMDL – presents the division of the TMDL among each of the contributing sources in the watershed; wasteload allocations (WLAs) for point sources and load allocations (LAs) for nonpoint and background sources (Section 7). The Seasonal Variation and Critical Conditions as well as the Margin of Safety (MOS) which accounts for uncertainties in the analyses are also addressed.
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
2 Problem Statement The problem statement consists of a description of the watershed, identification of applicable water quality standards and beneficial uses, a summary of available monitoring data, and a description of the impairment. The description of impairment is supported by the source assessment and conceptual models linking sources to impairment as completed in Sections 5 and 6, respectively.
2.1
Description of the Watershed
The Boulder Creek watershed is located along the front range of the Colorado Rocky Mountains. The watershed covers approximately 447 square miles and includes the communities of Boulder, Nederland, Erie, Superior, Lafayette, Longmont, and Louisville. Bordered by the St. Vrain River and Clear Creek watersheds, the Boulder Creek watershed is tributary to the South Platte River watershed and eventually Boulder Creek flows reach the Mississippi River (Murphy, 2006). Elevation within the watershed ranges from over 13,000 feet in the upper watershed, to approximately 5,000 feet at the confluence of Boulder Creek and the St. Vrain River, approximately 20 miles northeast of the City of Boulder near Longmont. Primary tributaries of Boulder Creek include North, Middle, and South Boulder Creeks, Fourmile Creek, Coal Creek, and Rock Creek, along with several smaller streams such as Goose Creek, Bear Creek, and Skunk Creek. Figure 2-1 shows stream flow during high flow conditions in Boulder Creek while Figure 2-2 identifies the general location of the Boulder Creek watershed as well as subwatershed drainages within the watershed.
Figure 2-1: View of Boulder Creek west of Folsom Street (at site BC-CU) (photo by Andrew Taylor, City of Boulder).
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
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Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
2.2
Impairment Overview
As required by CWA Section 303(d), Colorado Regulation 93 identifies bodies of water that fail to meet water quality standards and therefore fail to attain designated beneficial uses. The Colorado 2004 303(d) List first identified Boulder Creek, Segment 2b, as impaired by E. coli. Additionally, this listing is identified as ‘high priority’ due to existing recreational uses and potential public health risk.
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Broad wa y
Br
Boulder Creek, Segment 2b, is defined by Colorado Regulation 38 as the point immediately below the confluence with North Boulder Creek to a point immediately above the confluence with South Boulder Creek. Additionally, the 303(d) List further identifies the impairment specific to the stretch of Boulder Creek from 13th Street to the confluence with South Boulder Creek (refer to Regulation 93). The impaired portion of the segment (Figure 2-3) flows through Boulder, Colorado and receives drainage from approximately 2,303acres within the urban corridor.
Dr y
C re
ek
Figure 2-3: Impaired reach of Boulder Creek in Boulder, Colorado.
Identification of areas draining to the impaired reach was performed using geographical information systems (GIS), aerial photography, and ground truthing. The impaired drainage was limited to areas draining to Boulder Creek within the urban corridor. Although the confluences of Bear Canyon Creek, Twomile Canyon/Goose Creek and Skunk Creek occur within the impaired reach, monthly data show a consistent decline in bacteria concentration below the confluences of these tributaries with Boulder Creek (from site BC-47th to BC-61st). In addition, as discussed below, the TMDL critical period occurs during low flow conditions when the contribution from these tributaries is minimal (for example, much of the dry weather flow from Bear Creek is diverted to a ditch approximately 0.5 miles from the confluence with 14
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Boulder Creek and storm flows can enter Boulder Creek over a spillway while low flows can be controlled by a flow gate on the spillway). Additionally, tributaries (such as Goose Creek) often run dry during low flow conditions and would therefore, not contribute flow (or bacteria) to Boulder Creek during critical conditions. For these reasons, Bear Canyon, Twomile Canyon/Goose Creek and Skunk Creek drainages are not included within the impaired, ongoing contribution drainage (see Figure 2-4for an illustration of the drainage area).
Fo u
Dry Creek
The Boulder Creek watershed is diverse with extreme variation in elevation, geology, climate, land cover and land use. This TMDL is specific to the urban reaches (referred to as ‘ongoing contribution’) of the watershed. Figure 2-4highlights subbasins that have the potential to contribute E. coli concentrations. Due to reasons stated above, the subbasin drainages identified in the map below are not included within the ongoing contribution area for this TMDL. The sections that follow (land use, climate, and watershed flows) are specific to the ongoing contribution drainage area.
rm il e
Cre e
k e uld Bo
Cr
r ee
k
k ee
k
C
e
ry D
rC
Be
a
an yo n
re
Cr
eek
Bo u l d er
rC
Legend Majo r Strea ms/Ri ve rs Ong oin g Con tr ibu ti on Subbas ins Bea r Can yon C ree k Skun k C ree k
ek
Twom ile Ca nyo n / G oo se Cre ek
NAD_1983_H AR N_StatePlane_Colorado_N orth_F IPS_0501 Map produced 08-19-2011 by E. Moreno
0
1
ld e rC
0.5
B ou
0
0.5
So u th
City of Boulder Contributing Drainage Areas
re
2 Kilometers 1
2 Miles
al Co
Cr
k ee
Figure 2-4. Drainage area (ongoing contribution in brown) as well as potential tributary drainage (Bear Canyon, Skunk Creek and Twomile Canyon /Goose Creek.
2.2.1 Land use It is important to identify land uses within a watershed to determine potential sources and loading mechanisms. For example, sources of bacteria within open space or natural lands likely include wildlife; however, sources in residential areas are more likely to include illicit discharges, failing septic systems or poor pet waste management. 15
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Land use within the drainage of the impaired stretch are listed in Table 2-1 and shown in Figure 2-5. In general, land uses shown on the map include: public land (includes University of Colorado), open space and environmental protection (38 percent) and high, medium and low density as well as mixed residential uses (24 percent). A more detailed land use summary, including jurisdictional area, is provided in Table 2-1. It should be noted that, in addition to the City of Boulder (City) (1732. 9 acres, approximately 75 percent of drainage), significant areas of the impaired drainage are owned and maintained by the University of Colorado and Boulder County. Specifically, 406 acres (18 percent) and 129 acres (6 percent) of the impaired drainage are identified as under the jurisdiction of the University of Colorado and Boulder County, respectively. Schools, under jurisdiction of the Boulder Valley School District, are also located in the impaired drainage area, encompassing a total of 34.5 acres (1.5 percent). Table 2-1: Detailed land use within drainage to the impaired stretch of Boulder Creek. Total area within impaired drainage (Acres)
Percent of land in drainage (%)
City of Boulder Area (Acres)
Boulder County Area (Acres)
Boulder Valley School District Area (Acres)
University of Colorado‐ Boulder Area (Acres)
Community Business
29.76
1.29
26.72
2.78
0.25
Community Industrial
63.97
2.78
63.97
General Business
40.87
1.78
40.87
General Industrial
22.16
0.96
21.91
0.25
High Density Residential
209.89
9.12
202.50
5.62
1.77
Light Industrial
342.97
14.89
336.68
2.38
3.91
Low Density Residential
270.58
11.75
269.63
0.01
0.21
0.73
Manufactured Housing
25.08
1.09
0.00
25.08
Medium Density Residential
29.54
1.28
29.52
0.02
Mixed Density Residential
33.43
1.45
33.43
Mixed Use Business
50.35
2.19
50.35
Mixed Use Residential
1.03
0.04
1.03
Performance Industrial
38.24
1.66
38.22
0.02
Public
528.15
22.94
126.93
24.53
376.69
Regional Business
65.06
2.83
64.94
0.13
Transitional Business
33.61
1.46
31.45
0.71
1.46
Roadways
165.54
7.19
155.39
10.15
Environmental Protection
11.46
0.50
11.46
Open Space, Acquired Open Space, Development Rights
65.96
2.86
21.73
44.19
0.04
55.24
2.40
26.20
29.03
Open Space, Other
74.33
3.23
43.78
15.16
15.40
Park, Urban and Other TOTAL
145.39
6.31
136.16
3.41
5.81
2302.60
100%
1732.88
128.81
34.48
406.43
16
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Figure 2-5: Land use within drainage to the impaired reach of Boulder Creek.
17
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
2.2.2 Climate The semi-arid climate of Boulder, Colorado brings hot dry summers and cold winters. At either extreme, temperatures recorded since 1897 reach a monthly average maximum of 86oF in July and an average monthly minimum of 20.6oF in January. Precipitation (in the form of rainfall) recorded since 1893 shows an annual average of nearly nineteen inches (18.9”), with the greatest average amount of precipitation falling in May (3.04”) and lowest monthly average amount of precipitation falling in January (0.60”) not including snowfall totals. Average monthly climate statistics are presented in Table 2-2. It should be noted that stream flows in the arid west, although highly controlled by dams and reservoirs, are also heavily influenced by precipitation and snow melt; as shown in Section 3.1.1, the hydrology of Boulder Creek varies dramatically between seasons. Table 2-2: Average monthly climate of Boulder, Colorado. Month
Average Temperature Maximum (F)
Average Temperature Minimum (F)
Average Precipitation (Inches)
January
44.9
20.6
0.60
February
47.0
22.7
0.78
March
52.9
27.8
1.72
April
61.6
35.7
2.63
May
70.3
44.3
3.04
June
80.5
52.8
1.93
July
86.3
58.7
1.83
August
84.6
57.5
1.61
September
77.0
49.1
1.55
October
66.0
39.2
1.50
November
53.7
28.9
1.03
December 45.9 22.2 0.79 Source: Temperature data downloaded 10-5-10 at http://www.esrl.noaa.gov/psd/boulder/getdata.html Precipitation data downloaded 10-5-10 at http://www.esrl.noaa.gov/psd/boulder/Boulder.mm.precip.html
2.3
Beneficial Uses and Standards Addressed in this TMDL
Colorado Regulation 31 - Colorado Basic Standards and Methodology for Surface Waters identifies potentially applicable uses and standards for waterbodies within the state’s boundaries. Standards are established to ensure beneficial uses are maintained. The assigned beneficial uses and standards applicable to the impaired reach of Boulder Creek are identified in Regulation 38 – Classification and Numeric Standards for South Platte River Basin, Laramie River Basin, Republican River Basin and Smoky Hill River Basin. Standards associated with Boulder Creek are presented below.
2.3.1 Beneficial Uses In Colorado, “Beneficial uses” are defined in Regulation 31, Section 31.5 (5) to mean those uses of state waters to be protected such as those identified in the classification system. Any waterbody can be designated for any or all beneficial uses; however, according to Regulation 31.6: Waters shall be classified for the present beneficial uses of the water, or the beneficial uses that may be reasonably expected in the future for which the water is suitable in its present condition or the beneficial uses for which it is to become suitable as a goal.
18
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Four beneficial uses are identified in Colorado, and include: aquatic life use; recreational use; agricultural use; and, domestic water supply. All four uses apply to Segment 2b of Boulder Creek. Recreational use in Segment 2b of Boulder Creek occurs frequently and a bike trail and multiple park areas lie adjacent to Boulder Creek along the length of the impaired reach. During summer months, tubing and wading occur throughout the segment. Additionally, a large park (Eben G. Fine) with water access is located directly above the impaired stream reach and includes a kayak course built by the City of Boulder. A description of each beneficial use, as it applies to the segment, is shown in Table 2-3. Table 2-3: Beneficial uses within the impaired portion of Segment 2b of Boulder Creek. Beneficial Use
Designation
Recreation
E
Aquatic Life
Cold 1
Water Supply Agriculture
Description
Status
Existing primary contact; waters suitable for recreational activities where ingestion is likely. Recreational activities include: swimming, kayaking, and tubing. Cold waters capable of sustaining a variety of aquatic life, including sensitive species. After treatment, surface waters suitable for drinking‐ water supplies Waters suitable for crop irrigation and livestock drinking water
Impaired
Not Impaired Not Impaired Not Impaired
2.3.2 Water Quality Standards Each beneficial use is associated with a series of pollutant specific water quality standards, such assigned numeric standards are set forth in Regulation 38. E. coli serves as an indicator species to measure the health of designated recreational uses. The pollutant of concern within the impaired reach of Segment 2b of Boulder Creek (from 13th Street to the confluence with South Boulder Creek), specific to this TMDL, is limited to E. coli. In 1986, the Environmental Protection Agency (EPA) published the Ambient Water Quality Criteria for Bacteria (EPA 440/5-84-002) which established national water quality criteria for bacteria in surface waters. The criteria recommended a geometric mean value of 126 colony forming units (CFU) per 100 milliliters (mL) as the primary contact criterion based on a risk factor of acute gastrointestinal illness corresponding to eight illnesses per 1,000 swimmers. The E. coli water quality standard established for existing primary contact recreation is promulgated by Colorado Regulation 31, Section 31.16. In Section 31.16, the State of Colorado interprets the E. coli water quality standard as a two month geometric mean of 126 CFU per 100 mL. This standard is applicable year-round in Boulder Creek.
3 Data Inventory and Analysis This section provides an inventory of data and a summary of data analyses used to evaluate the impairment and support TMDL development. Complete bacterial results and analysis used for this TMDL can be found in Appendices A and B, respectively.
19
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
3.1
Data Inventory
Extensive E. coli monitoring of Boulder Creek has been ongoing since 2003 and at least thirteen sites are evaluated monthly. After the 2004 303(d) listing, monthly monitoring was expanded to include additional sites within the Boulder city limits, within Segment 2b of Boulder Creek. Monthly bacterial monitoring results from 2003 through 2010 are found in Appendix A. Additionally, the City and Boulder County conducted weekly monitoring of at least four instream sites within or just upstream of the reach of concern. Routine weekly instream sample locations include:
Boulder Creek at Eben Fine Park (site BC-Eben), located above the impaired reach Boulder Creek at 13th Street (site BC-13th) Boulder Creek at the University (west of Folsom Street) (site BC-CU) Boulder Creek at 30th Street (site BC-30th)
As shown in Figure 3-1, sites BC-13th, BC-CU and BC-30th are located within the impaired reach. Weekly monitoring results from 2004-2010 are summarized below and found in Appendix A. Additionally, in 2007, the City received an EPA grant to investigate the sources and persistence of pathogens in the urban reaches of Boulder Creek. The study, A Multifaceted Approach to Microbial Source Tracking within Secondary Environments (Monroe, 2009), was a cooperative effort by the City of Boulder, the U.S. Geological Survey (USGS), and the Colorado School of Mines. One of the study’s objectives was to identify any potential human source of bacteria, looking primarily at storm sewer outfalls with discharges releasing to Boulder Creek during dry weather (no precipitation for previous 48 hours). This study established a storm drain outfall monitoring practice that has continued since 2008 (in a more limited capacity) as part of the weekly monitoring events. Figure 3-1 identifies the location of weekly monitoring sites as well as outfalls identified as a concern by the 2007 study. Bacterial results collected at storm drain outfalls are summarized in Section 3.2.3 and presented in Appendix A.
Figure 3-1: Boulder Creek instream and storm drain outfall monitoring locations. 20
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
3.1.1 Watershed Flows The stream flow and the hydrology of Boulder Creek is primarily driven by snowmelt and spring runoff originating from the Continental Divide; for this reason, extreme seasonal variability is seen within the stream’s hydrograph dependent on snow pack and air temperature (Figure 3-2). As an example, Figure 3-3 demonstrates the range of flow conditions in Boulder Creek at monitoring station BC-CU. Immediately above the impaired stretch, two stream gauges are located on Boulder Creek. A historical flow record dating back to 1906 is available for stream gauge station BOCOROCO. This station, located near Orodell, approximately three miles upstream of the impaired reach, has been operated by the USGS and Colorado Division of Water Resources. The second gauge (BOCOBOCO), operated by the Colorado Division of Water Resources since 2005 is located approximately 500 meters upstream of the impaired stretch. Significant diversions can occur through the Boulder and White Rock Ditches which are located between these gauges and the impaired reach. To represent the stream’s variability, BOCOROCO was selected due to the long period of flow data recorded.
Figure 3-2: Historical Boulder Creek flow data at BOCOROCO (Orodell) from 1980- 2010.
Limited historical flow gauge data are available within the impaired reach of Boulder Creek; however, as part of the City’s minimum stream flow monitoring program, City staff began monitoring low flow conditions in 2004. Although only low flow monitoring occurred from 2004 to 2006, in 2006 the City installed an automated flow recorder, expanding the amount of flow data available in 2006. For this analysis, measured flow at Orodell was paired with City low flow monitoring as explained in Section 6. Table 3-1 presents the locations, dates of available stream flow data and a description of the locations of stream gauges used to analyze flow within Boulder Creek.
21
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Figure 3-3: Boulder Creek (at site BC-CU) taken during low-flow and high-flow conditions.
Figure 3-2 shows a historical hydrograph (1980-2010) of Boulder Creek at station BOCOROCO; while Figure 3-4 compares the available data from BOCOBOCO to the historical gauge BOCOROCO showing similar hydrographs at the two sites and illustrating the occurrence of high-flow conditions from May through June, and low-flow (aligning with critical conditions as explained in Section 7.5) in late summer through early spring (July through March). The relationship between the City low flow monitoring data and historical flow measured at Orodell (BOCOROCO) is discussed further in Section 6.1.
Figure 3-4: Hydrograph comparing flow gauges at Orodell (BOCOROCO) and urban corridor (BOCOBOCO) from 1/1/2009 to 11/2/2010.
22
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011 Table 3-1: Stream gauges used to evaluate flow in Boulder Creek. Stream Gage Location Description
Available Data Range
Boulder Creek Near Orodell; located above the 10/01/1906 – Current City limits and upstream of both the impairment and flow diversions at Broadway. BOCOBOCO* Lat: 40.1477 Boulder Creek at Boulder; located near the City’s 10/1/2005 – Current Long: ‐105.28 library, above both the impairment and flow diversions at Broadway. City Monitoring** Lat: 40.014866 Minimum flow monitoring location; located 5/19/2004‐10/6/2010 “Below Broadway” Long: ‐105.28 immediately downstream of Broadway and diversion that occurs at Broadway, and immediately upstream of the impaired reach. *Source: http://www.dwr.state.co.us/SurfaceWater/Default.aspx **Minimum flow monitoring collected by City staff, primarily during the low flow season. BOCOROCO* “Orodell”
3.2
Lat: 40.00637 Long: ‐105.33
Water Quality Data Analysis
Monthly, weekly, and storm drain outfall data are summarized below. In general, City monitoring, as well as the special study that took place in 2007, confirm that the impaired portion of Boulder Creek Segment 2b is limited to the reach from 13th Street to the confluence with South Boulder Creek. In addition, a seasonal trend was identified, with exceedances of the water quality standards occurring most often during periods of low flow and/or elevated stream temperatures (July to October), as shown in Figure 3-5. In the impaired reach, storm sewer outfalls contributing high concentrations of E. coli were also identified and are discussed in Section 3.2.3.
3.2.1 Monthly Monitoring Results Monthly sampling is conducted along Boulder Creek in its entirety, from the upper watershed to the plains east of Boulder by City staff. E. coli was added as an analyte in 2003. Data from 2003 through September of 2010 were analyzed to confirm the spatial and temporal trends of the listed reach. Four sites above the impairment were included within the analysis; these include sites at Boulder Creek above North Boulder Creek (BC-aNBC); Boulder Creek at Orodell (BC-Oro); Boulder Creek at the mouth of the Canyon (BC-Can); and, Boulder Creek at the Library (BC-Lib). Monthly sites within the impaired reach include Boulder Creek at the University (west of Folsom Street) (BC-CU) and Boulder Creek at 47th Street (BC-47th). Sites downstream of the impaired stretch include Boulder Creek at 61st Street (site BC61st) and Boulder Creek above the City’s wastewater treatment facility (site BC-aWWTP). E. coli samples collected downstream of the wastewater treatment facility were not used in this analysis since water quality monitoring indicates this segment (Segment 9) is not impaired. Two month E. coli geometric means were calculated to evaluate spatial and temporal trends of the impaired reach. A two month period was used in order to evaluate the E. coli standard (as discussed in Section 2.3.2). Considering all monthly data collected, as shown in Table 3-2, no exceedances of the 126 CFU/100 mL water quality standard (represented by bold font in the table) occurred above the impaired reach. Exceedances occurred within the impaired reach at sites BC-CU and BC-47th between July and October. These exceedances appear to have a minimal impact downstream, beyond the impaired reach at site BC-61 where there is a significant decrease in E. coli concentrations. No exceedances of the E. coli standard were identified at site BC-aWWTP, which is also below the impaired reach and directly above the City’s WWTF, which discharges to segment 9 of Boulder Creek. Additionally, BC-47th is sampled above the confluences of Bear Canyon Creek, Skunk Creek and Twomile Canyon/Goose Creek; data collected at BC-47th compared to BC-61st demonstrate decreasing concentrations as the distance from the 23
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
urban corridor increases. Finally, it is expected that improving water quality within the listed reach will positively affect water quality at BC-61st as well. Table 3-2: E. coli two month geometric mean evaluation of combined years 2003-2010 at monthly monitoring sites (CFU/100 mL). Downstream of Impaired Upstream of Impaired Reach Impaired Reach Reach (CFU/100 mL) (CFU/100 mL) (CFU/100 mL) Month BC‐ BC‐aNBC BC‐Oro BC‐Can BC‐Lib BC‐CU BC‐47th BC‐61st aWWTP NS 0.00 5.56 18.54 59.51 104.45 27.11 7.45 Jan/Feb 1.23 1.38 7.23 22.42 43.03 109.68 29.39 13.05 Mar/April 2.71 7.98 18.10 61.67 47.27 120.62 87.96 71.39 May/June 5.57 14.47 32.90 98.10 207.73 373.89 157.34 48.68 July/Aug 2.13 4.43 48.00 71.42 245.57 227.94 174.07 89.12 Sept/Oct 1.26 1.40 10.89 31.86 61.63 84.54 46.98 42.08 Nov/Dec NS = not sampled due to frozen conditions and lack of stream access. Exceedances of the 126 cfu/100 ml E. coli standard are shown in bold.
3.2.2 Weekly Monitoring Results Weekly samples have been collected in a coordinated effort by the City and Boulder County Public Health since 2004. Sites monitored are Boulder Creek at Eben Fine Park (BC-Eben); Boulder Creek at 13th Street (BC-13th); Boulder Creek at the University (west of Folsom Street) (BC-CU); and, Boulder Creek at 30th Street (BC-30th) (Figure 3-1). Beginning in 2004 and 2005, samples were collected only during summer months. In 2006, sampling was extended to include late spring and winter months. Weekly monitoring expanded in 2007, and has been conducted year round since then.
Figure 3-5: Analysis of bimonthly geometric means considering all E. coli data from 2004-2010 supporting impairment downstream (east) of 13th Street. Note E. coli standard in red (126 CFU/100 mL).
24
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
As shown by Figure 3-5, considering all available weekly data per two month period, exceedances occurred most often from July to October, while no exceedances occurred from January to June. Continuing to use all years of data, no exceedances occurred at BC-Eben, above the impaired reach, while BC-13th and BC-CU exceeded the standard from July through October and BC-30th exceeded from July through December (Figure 3-5). Further analysis of weekly data included the evaluation of annual trends (Table 3-3). Similar to the overall trends, exceedances occurred most often between July and October at sites BC-13th, BC-CU, and BC-30th. One exceedance occurred at BC-Eben, above the impaired reach in 2007, likely due to an episodic event. This analysis supports the impairment downstream of 13th Street. Table 3-3: Two month geometric mean assessment of available Boulder Creek weekly E. coli data. YEAR 2004 2005
2006
2007
2008
2009
2010
Assessment Period
BC‐ Eben
BC‐13th
BC‐30th
(CFU/100 mL)
June*
26.42
26.42
102.43
151.36
Jul/Aug
64.81
270.18
520.22
217.37
Jul/Aug
25.16
136.62
598.57
527.20
May/Jun
33.96
84.13
55.17
90.71
Jul/Aug
83.43
97.72
170.48
332.01
Sept/Oct
115.16
191.90
324.53
627.51
Nov/Dec
27.13
42.93
52.55
135.48
Jan/Feb
10.89
7.04
31.89
62.97
Mar/April
30.82
35.64
78.15
71.13
May/Jun
32.71
47.43
41.82
79.56
Jul/Aug
216.56
125.81
216.62
468.07
Sept/Oct
40.75
135.80
393.24
629.77
Nov/Dec
23.23
15.07
72.45
114.61
Jan/Feb
13.73
49.25
67.13
82.58
Mar/April
7.83
10.24
56.78
88.04
May/Jun
26.94
43.63
58.37
82.14
Jul/Aug
46.42
129.24
134.11
297.53
Sept/Oct
50.49
120.30
216.18
462.30
Nov/Dec
9.04
44.01
110.53
220.32
Jan/Feb
7.67
26.09
64.81
93.23
Mar/April
6.23
11.07
24.89
61.38
May/Jun
28.68
46.58
58.30
64.54
Jul/Aug
39.45
101.55
150.39
250.57
Sept/Oct
64.34
147.97
255.64
591.20
Nov/Dec
11.02
30.45
71.14
130.57
Jan/Feb
1.34
17.24
40.56
66.35
Mar/April
8.90
22.09
61.24
111.73
May/Jun
15.25
29.69
29.95
48.08
Jul/Aug Sept/Oct
49.95 62.32
202.94 200.20
343.62 230.25
524.55 526.30
*Limited to one month of data for geometric mean calculation Note: E. coli standard exceedances (above 126 CFU/100 mL) are shown in bold. 25
BC‐CU
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
3.2.3 Outfall Monitoring It should be noted that this TMDL addresses instream concentrations of E. coli; however, to assess sources of E. coli, the City monitored E. coli concentrations discharged from outfalls along Boulder Creek (Figure 3-1). Outfalls that were routinely monitored included those that consistently had dry-weather flow (characterized by flow occurring during periods of 48 hours or greater since last rainfall event). Additionally, some outfalls were identified as a concern due to citizen complaints associated with odors and/or visual concerns. Outfall monitoring began in 2007 and was completed with the assistance of an EPA grant (#X797865101-0). This specific study involved bacterial sources tracking (BST) with the intention of identifying potential human sources of bacteria. The BST data collected throughout this study will enhance implementation planning in specific areas identified as a concern. Additionally, in 2008, flow measurements were also completed at all outfalls that consistently exhibited dry-weather flow and were shown to have elevated E. coli concentrations. Outfalls routinely monitored by the City are described in Table 3-4 and shown on Figure 3-1. Two month geometric mean calculations on outfall data are shown in Table 3-5. In general, E. coli concentrations were extremely variable, with many outfalls discharging concentrations well above the instream standard of 126 CFU/100 mL. No significant seasonal outfall E. coli trends were evident from the data; however, additional wet weather monitoring could enhance the understanding of sources of E. coli during runoff events. Table 3-4: Description of outfalls routinely monitoring within the impaired reach. Storm Drain Outfall
Latitude
Longitude
1
‐105.277622
40.014458
Arapahoe and 13th Street, north side of stream.
2
‐105.277759
40.01415
Arapahoe and 13th Street, south side of stream.
3
‐105.272762
40.01206
West of 17th Street, south side of stream.
4
‐105.268302
40.01122
Between 19th Street and Grandview Ave., located on the south side of stream.
5
‐105.266275
40.0109
Between Grandview Ave. and Folsom Street, located on the south side of the stream near CU‐walkway.
6
‐105.263975
40.01121
Immediately west of Folsom Street, located on south side of stream.
7
‐105.258836
40.01109
8
‐105.253157
40.01108
9
‐105.24747
40.01294
26
Cross Street Description
Immediately east of 28th Street, located on south side of stream. Immediately east of 30th Street, located on north side of stream. Located off of Marine Street between 33rd Street and Arapahoe, located on north side of stream.
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
2008
2007
Year
Table 3-5: Two month E. coli geometric mean analysis of storm drain outfalls identified as a concern along the impaired stretch of Boulder Creek (CFU/100mL). Two Month Geometric Assessment Period March/April
2009
1
2
3
4
5
6
7
8
9
(CFU/100 mL) 8.1
1,004.0
NS
560.4
11.3
NS
464.2
14.6
345.4
May/June July/Aug
61.7 121.5
859.9 1,849.3
191.8 210.8
97.2 138.5
19.7 31.8
10.9 311.3
488.3 661.6
50.0 44.8
46.7 144.7
Sept/Oct
42.3
2,419.2
NS
461.1
151.9
1,326.2
1,411.2
2,419.2
1,364.9
Nov/Dec Jan/Feb
51.8 90.7
2,419.2 7,650.2
NS NS
2,419.2 8,032.4
159.9 188.3
1,986.3 971.7
686.7 382.0
NS NS
2,419.2 4,727.6
March/April May/June
19.1 32.0
406.1 2,345.5
4.10 4.10
7,165.5 720.1
8.4 47.1
962.1 1,735.1
909.7 1,221.7
776.0 NS
1,254.9 337.4
45.8 377.1 59.2 100.8
5,526.8 11,543.3 NS NS
124.2 139.6 NS NS
288.8 1,432.7 5,441.5 10,518.6
294.3 9.1 1,127.2 2,348.3
2,106.6 9,614.2 3,021.7 570.9
536.8 649.5 NS NS
2,481.0 2,329.4 NS NS
1,630.4 2,945.7 23,069.3 13,416.6
272.17
583.4
NS
2,408.6
73.7
1,820.0
NS
672.7
230.4
1.0 9.0 10.1 NS
472.7 1,822.9 3,400.3 24,196.0
NS NS NS NS
805.5 53.0 1,030.4 2,164.8
NS NS NS NS
272.2 2,278.8 2,372.5 1450.5
NS NS NS NS
434.7 NS 617.0 1,119.9
NS NS NS NS
11.3 39.86 19.76 84.29
2419.6 1,039.4 612.0 1,507.1
NS NS NS NS
2,136.4 261.3 11.2 16.0
144.8 92.0 42.6 44.7
380.3 381.9 352.4 588.1
NS NS NS NS
0.0 NS NS NS
NS NS NS 2,419.6
July/Aug Sept/Oct Nov/Dec Jan/Feb March/April
2010
Storm Drain Outfall
May/June July/Aug Sept/Oct Nov/Dec Jan/Feb March/April May/June July/Aug
Sept/Oct 30.56 2,104.2 NS 33.0 590.3 2,419.6 344.8 NS NS: Not Sampled: Outfalls typically not sampled due to lack of flow discharged from outfall, instream flow conditions that submerge the outfall, or sampling limited to outfalls identified as concern. Exceedances of the E. coli standard (126 CFU/100 mL) are shown in bold. Sample site locations are listed from upstream to downstream.
27
NS
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
4 Numeric Target Selection When calculating TMDLs, numeric targets are selected to ensure water will meet water quality standards and subsequently, establish measureable targets for the restoration and/or the protection of beneficial uses. For this TMDL, target values for E. coli are based on the water quality standard established by Colorado Regulation 31, Section 31.16 for existing primary contact recreation designations. The standard is applicable year round in Boulder Creek and defined as a two month geometric mean of 126 CFU per 100 mL. As a conservative approach, the two month geometric mean standard provides the basis for an instantaneous numeric target of 126 CFU/100 mL. This numeric target is applied across all flow regimes to ensure water quality standards are attained year round.
5 Source Assessment The purpose of the source assessment is to identify and quantify the sources of E. coli to Boulder Creek. Bacteria, such as E. coli, can enter surface waters from both point and nonpoint sources. Point sources typically discharge at a specific location from pipes, outfalls, and conveyance channels from, for example, municipal wastewater treatment facilities (WWTFs) or municipal separate storm sewer systems (MS4s). Point source discharges are regulated through the federal National Pollutant Discharge Elimination System (NPDES) program and, in the state of Colorado, point source discharges are regulated under Regulation 61, the Colorado Discharge Permit System (CDPS). Nonpoint sources are diffuse sources that have multiple routes of entry into surface waters. Point and nonpoint sources within the watershed that may contribute to the impairment are identified and discussed below.
5.1
Point Sources
Point source pollution is defined by the Federal CWA §502(14) as: any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged. This term does not include agriculture stormwater discharges and return flow from irrigated agriculture. Point sources can include facilities such as municipal WWTFs, industrial facilities, or MS4s. Additionally, overland runoff collected and conveyed through MS4 systems is considered a point source. Under the CWA, as discussed below, all point sources are regulated under the NPDES program. MS4 and NPDES permit holders within the project area are presented below.
5.1.1 NPDES Regulated Municipal Separate Storm Sewer Systems (MS4s) Stormwater runoff may be a significant source of E. coli to Boulder Creek (Figure 5-1). Under the NPDES program, municipalities serving populations over 100,000 people are considered Phase I MS4 communities while smaller municipalities are considered Phase II communities. All MS4 permittees within the drainage are considered Phase II. Within Colorado, Phase II communities are permitted through the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division (Division). Such permits are part of the CDPS according to Colorado Regulation 61 and stormwater discharges from Phase II MS4s are covered under a general permit. 28
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Figure 5-1: Storm drain outfall located adjacent to Boulder Creek, regulated under Phase II MS4 general permit (photo by Andrew Taylor, City of Boulder).
In accordance with the Phase II permit, MS4 operators must, “develop, implement, and enforce a stormwater management program designed to reduce the discharge of pollutants from MS4 to the Maximum Extent Practicable (MEP), to protect water quality, and satisfy the appropriate water quality requirements of the Colorado Water Quality Control Act (CCR 61.8(11)(a)(i))” (CDPHE, 2001). Six stormwater management programs are required by the Division for each Phase II permittee. These are: public education and outreach; public participation/involvement; illicit discharge detection and elimination; construction site stormwater runoff control; post-construction stormwater management; and, pollution prevention/good housekeeping for municipal sources. Within Colorado, Phase II permit holders are considered either “Standard” or “Non-Standard”. Standard MS4s include municipalities while institutions such as colleges or school districts are considered NonStandard MS4s. Although how permit requirements are applied to some Non-Standard MS4s will differ, the general requirements (CCR 61.8(11)(a)(i)) remain the same (CDPHE, 2002). Standard and NonStandard MS4s are both allocated WLAs. All land that drains to a storm drain system is considered a point source, and therefore, assigned a wasteload allocation. Drainage to an MS4 system includes all flows to the storm drain systems as well as ditches or canals that convey stormwater. MS4 permit holders discharging to the impaired stream reach of Boulder Creek are presented in Table 5-1 and include the City of Boulder, Boulder County, University of Colorado and Boulder Valley School District. Table 5-1: MS4 stormwater permit holders within the impaired reach of Boulder Creek. Permittee
Permit Number COR‐090019
Boulder County (Phase II)
COR‐090020
University of Colorado (Phase II)
COR‐070028
Boulder Valley School District (Phase II)
COR‐070029
29
City of Boulder (Phase II)
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
5.1.2 Other (Non-MS4) NPDES Facilities A facility or operation must apply for a discharge permit if effluent associated with activities at the facility is discharged to surface water. Such facilities are regulated under the NPDES program through the CWA §402. Of specific concern to the E. coli concentrations, both treated and untreated sanitary wastewater can contain coliform bacteria. There are three NPDES permitted WWTFs that discharge either directly or indirectly to the impaired reach of Boulder Creek. Only those facilities located within the impaired reach will be assigned a wasteload allocation (WLA) as discussed in Section 7.2. Wastewater treatment permits to which a WLA may be assigned are presented in Table 5-2. Table 5-2: NPDES Permit holders along Boulder Creek Segment 2b. Design Capacity Facility Permit # Expiration (mgd) COG588104 2010 Red Lion Inn 0.007 Boulder Mountain Lodge
CO0040819
2013
San Lazaro
CO0020184
2015
5.2
0.0045 0.11
Description of Location Upstream of impaired reach Upstream of impaired reach Within impaired reach
Nonpoint Sources
The term nonpoint source pollution is defined to mean any source of pollution that does not meet the legal definition of point sources (as discussed in Section 5.1). Nonpoint source pollution typically results from overland stormwater runoff that is diffuse in origin. It should be noted that stormwater collected and conveyed through conveyance systems such as an MS4 system are considered a controllable point source. Sources of nonpoint pollution within the impaired stretch include:
Upstream Nonpoint Sources (includes failing septic systems); Open Space (includes wildlife); Other Potential Nonpoint Sources: Overland illicit discharges/dumping and failing septic tanks; and, the persistence and re-growth of E. coli.
Nonpoint sources of coliform bacteria are diffuse sources that cannot be identified as entering a waterbody through a discrete conveyance at a single location. It is often difficult to quantify the concentrations of bacteria from specific sources as these sources generally, but not always, involve accumulation of coliform bacteria on land surfaces that wash off as a result of storm events. Likely nonpoint sources of E. coli to the impaired stretch are discussed below.
5.2.1 Upstream Nonpoint Sources Upstream from the impaired stretch, the Boulder Creek watershed consists largely of open areas with light residential development. These ‘upstream nonpoint sources’ may contribute bacteria from sources such as wildlife, septic systems, and recreational (or bodily) contact to the stream as discussed below.
Wildlife deposit bacteria, with their feces, onto land surfaces where it can be transported during storm events to nearby streams or MS4 systems. Due to the natural habitat and open areas upstream of the impaired segment, it is presumed that a portion of E. coli loading within the Boulder Creek watershed can be attributed to wildlife sources such as birds, deer, raccoons, and domesticated animals.
A number of septic systems exist in the Boulder Creek drainage basin and numerous septic systems are located directly above the municipal boundary and impaired reach. To a certain 30
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
degree, some of these systems can be reasonably assumed to be failing and for this reason, a portion of the E. coli loading in the Boulder Creek watershed may be attributed to failure of septic systems and illicit discharges of sewage.
Eben G. Fine Park is located above the impaired reach. In addition to a kayak course, this park is often heavily recreated by swimmers, tubers and dog owners. Recreational contact can wash bacteria from skin and contribute bacterial loading to the water column.
5.2.2 Open Areas and Open Space Numerous public parks or open spaces exist within Boulder, both along Boulder Creek and throughout the watershed. Land uses classified as open areas include: environmental protection; park, urban, other; and open space (acquired, development rights, other). Potential sources of bacteria within open areas include wildlife and recreation, as discussed below.
Along the length of the impaired stretch, a pedestrian and bike path offers easy public access points to the stream. In addition to recreational users, a transient population has been observed bathing and cleaning personal items in the stream. Such activities can wash bacteria from skin and into the stream. In addition, direct human waste may be discarded occasionally by recreational users, children and/or transient populations. Furthermore, open spaces, particularly along the creek tend to attract both wildlife and dog owners. Improperly discarded pet waste from open space is likely a source of bacteria to Boulder Creek.
Open space typically provides habitat for wildlife. As discussed above, wildlife deposit bacteria, with their feces, onto land surfaces where it can be transported during storm events to nearby streams. A recent study indicated birds, particularly pigeons, as a potentially significant bacterial source within the Fountain Creek watershed in Manitou Springs, Colorado (Stoeckel, 2010). Due to the natural habitat that surrounds Boulder Creek, it is presumed that a portion of E. coli loading within the Boulder Creek watershed can be attributed to wildlife sources such as birds, deer, raccoons, and domesticated animals.
5.2.3 Other Potential Nonpoint Sources Within the impaired reach, additional sources of bacteria may include failing septic systems, illegal dumping and/or the persistence and re-growth of E. coli. These sources are not currently quantified for the Boulder Creek TMDL and are therefore not assigned a LA. However, it should be noted that if these sources are currently occurring, then their loading is implicitly included within the allocation for their associated land use. Each of the other potential nonpoint sources is discussed below;
Within the City’s jurisdictional boundary, all wastewater is collected in the municipal sanitary sewer collection and treatment system. Despite this, illicit connections may release nonstormwater discharges. Illicit discharges may include failing septic/sewage systems, illegal connections to MS4 systems, illegal dumping practices, and improper disposal. When connected to, and conveyed through the MS4 system, illicit discharges are considered a point source and allocated to the associated municipality; however, illicit or illegal dumping that washes overland and into Boulder Creek may be considered a nonpoint source of E. coli.
Potential exists for the presence of failing septic systems or seepage from sanitary lines within the drainage. For this reason, a portion of the E. coli loading in the Boulder Creek watershed may be attributed to failure of septic systems, sanitary seepage, and illicit discharges of sewage.
31
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
The persistence and potential re-growth of E. coli in natural environments have been shown to contribute to water column concentrations (Ishii, 2005; Monroe, 2009; Garzio-Hadzick, 2010). In natural environments, it is suggested that warmer temperatures (or lower-flow conditions) will encourage re-growth or extended persistence and that a greater content of fine particles and higher organic contents slows the inactivation of E. coli (Garzio-Hadzick, 2010). Due to extreme seasonal fluctuations in seasonal flow and seasonal temperatures, the persistence and re-growth of E. coli within the stream bed and storm drain outfalls may be a significant source of bacterial concentrations in the stream, particularly during warmer temperatures or in highly organic outfall sediment.
6 Linkage Analysis The analysis of the relationship between pollutant loading from the identified sources and the response of the waterbody to this loading is referred to as the linkage analysis. The purpose of the linkage analysis is to quantify the maximum allowable bacteria loading that can be received by a threatened or impaired waterbody and still attain the water quality standards and applicable beneficial uses. This numeric value is, in fact, the TMDL. Because the TMDL calculations are based on beneficial uses and associated numeric standards, attainment of the TMDL numeric targets will result in attainment of water quality standards. After the TMDL for a waterbody is calculated, it is allocated to point and nonpoint sources. If the existing pollutant loading from the point and nonpoint sources exceeds their respective allocations, reductions required for individual controllable pollutant sources can be calculated to meet the TMDL, and thus water quality standards. In selecting an appropriate approach for calculating loading and TMDLs, technical and regulatory criteria were considered. Technical criteria include the physical system in question, including watershed or stream characteristics and processes, and the constituent of interest, in this case, bacteria. Regulatory criteria include water quality standards (including beneficial uses and standards) or procedural protocol. Flow is an important technical component of the assimilative capacity for E. coli and, in systems that experience extreme seasonal fluctuations, it is important that the chosen analytical tool considers changing flow conditions. For this reason, the flow variable load capacities for Boulder Creek were calculated with the development of load duration curves. Load duration curves are developed from flow duration curves and can illustrate existing water quality conditions (as represented by loads calculated from observed flow conditions and monitoring data), how these conditions compare to numeric targets, and the flow regime associated with existing loads. The methodology used to develop both flow and load duration curves is discussed below along with a summary of loading to Boulder Creek.
6.1
Flow Duration Curve Methodology
Flow duration curves are an important analytical tool used to evaluate historical flow conditions. According to the EPA 841-B-07-006 document: “Flow duration curve analysis looks at the cumulative frequency of historic flow data over a specified period. A flow duration curve relates flow values to the percent of time those values have been met or exceeded. The use of “percent of time” provides a uniform scale ranging between 0 and 100. Thus, the full range of stream flows is considered. Low flows are exceeded a majority of the time, while floods are exceeded infrequently. 32
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
A basic flow duration curve runs from high to low along the x-axis. The x-axis represents the duration amount, or “percent of time”, as in a cumulative frequency distribution. The y-axis represents the flow value (e.g. cubic feet per second) associated with that “percent of time” (or duration)…” Flow duration curves define intervals or groupings of flow conditions into a general indicator group. The percentage represents the percent of time a flow can be found within the stream, based on historical conditions. For example, the ‘high-flow’ group represents samples taken during the greatest 10 percent of flow episodes; while ‘moist conditions’ represents flow conditions found 10 to 40 percent of time, ‘mid-ranges’ 40 to 60 percent, ‘dry-conditions’ 60 to 90 percent and ‘lowflow’ the final 90 to 100 percent. To develop flow durations curves, data were collected at two gauging stations on Boulder Creek. The first gauge station is located at Orodell (BOCOROCO) with historical flow measurements, dating to 1906. This gauging station is located directly upstream of the impaired stretch; however, the location is also upstream of significant diversions that occur upstream of the impaired reach. No historical flow gauge data are available within the impaired reach of Boulder Creek; however, as part of the City’s minimum stream flow monitoring program, City staff began monitoring low flow conditions in 2004 at the site referred to as “Below Broadway”. This monitoring station is located immediately above 13th Street and is therefore, directly above the impaired reach. This monitoring station is also located below the major flow diversions at Broadway and is, therefore, more representative of flow conditions within the impaired reach. Flows at the “Below Broadway” location were typically measured when stream flows have the potential to be below 15 cfs. From 2004 to June 19th, 2006 low-flow measurements were taken by staff once per day. After June 19th, 2006, the City installed an automated flow recorder, expanding the amount of flow data available at this location. Due to the limited amount of data available within the impaired stretch, a relationship was established between the City’s Below Broadway monitoring site and historical data at the Orodell station (BOCOROCO). The steps and assumptions used to estimate flow within the impaired stretch included: Step 1: Flow data are available from 1906 at Orodell; however, the analysis of long term trends narrowed flow data collected at Orodell to dates between 1980 and 2010 to extrapolate the flow conditions at the ‘Below Broadway’ site that are more representative of current conditions. Step 2: Flows within the impaired stretch were estimated based on the relationship between the historical gauge data at Orodell (BOCOROCO) and the flow measurements provided by the City’s low flow monitoring program collected at the ‘Below Broadway’ site from 2004 through the 2010 water year. It can be noted that during the 2010 water year, the City’s monitoring program completed a rating curve based on the stage height to estimate flow at higher conditions. Although data available at ‘Below Broadway’ are limited, a linear regression (Figure 6-1) paired the available data from the City’s sampling with the corresponding daily flow at Orodell. The equation associated with this relationship (y=0.6902x-7.1646), which had an R2 value of 0.85, was used to extrapolate flow conditions within the impaired reach from 1980 to 2010.
33
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Figure 6-1: Regression relationship between flow recorded at Orodell (BOCOROCO) and instream monitoring data gathered by the City at the ‘Below Broadway’ site.
Step 3: To ensure more accuracy under low-flow conditions, extrapolated flow data (for the period 1980-2010) were merged with the available low flow measurements taken at the ‘Below Broadway’ site. In addition, when the extrapolated flow returned a negative number, these instances were replaced with a value of one cubic foot per second (cfs) to account for extreme low flow potential. Step 4: The compilation of extrapolated flow values and actual low-flow measurements at the ‘Below Broadway’ site was considered to be representative of flow within the impaired reach in its entirety. As shown in the flow duration curve, Figure 6-2, significant variability exists between flow conditions. As summarized in Table 6-1, high-flow conditions as defined by flows over 123 cfs were shown to occur less than ten percent of the time; while “moist conditions” as defined by flow between 23 and 123 cfs, occur between 10 and 40 percent of the time; and “low-flow” and “dry-conditions” account for flow under two and 11 cfs, respectively, and are exceeded 60 to 100 percent of the time. Table 6-1 also presents median flows per flow category. These general flow conditions have been used to characterize flow in various locations and are used throughout the USEPA technical guidance document, An Approach for Using Load Duration Curves in the Development of TMDLs (EPA 841-B-07-006).
34
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Figure 6-2: Flow duration analysis of extrapolated flow within the impaired reach of Boulder Creek.
Table 6-1: Range of flow conditions within each flow category. Median flow per Flow Category Flow range (cfs) category (cfs) High Flows Greater than 123 cfs 188
6.2
Percent of time flows equal or greater occur Less than 10 percent
Moist Conditions
23 to 123 cfs
47
10 to 40 percent
Mid‐Range
11 to 23 cfs
16
40 to 60 percent
Dry Conditions
2 to 11 cfs
6.6
60 to 90 percent
Low Flows
Less than 2 cfs
1
90 to 100 percent
Load Duration Curve Methodology
A waterbody’s loading capacity represents the maximum rate of loading of a pollutant that can be assimilated without violating water quality standards (40 CFR 130.2(f)). Establishing the relationship between instream water quality and source loading is an important component of TMDL development. It allows the determination of the relative contribution of sources to total pollutant loading and the evaluation of potential changes to water quality resulting from implementation of various management options. This relationship can be developed using a variety of techniques ranging from qualitative assumptions based on scientific principles to numerical computer modeling. The TMDL for Boulder Creek was developed using the load duration curve (LDC) method to assure compliance with the stream standard of 126 CFU/100 mL at varying flow conditions. As discussed above, for Boulder Creek, a load duration curve methodology was considered to be well suited for the determination of loading capacity based on the need for analysis of extreme seasonal flow variations. Additionally, this methodology provides a sound technique to determine load reductions required to meet the numeric target concentration. Load durations also allow for the analysis of 35
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
monitoring data collected by stakeholders within the watershed to identify potential sources based on flow conditions. A LDC allows for the evaluation of water quality data related to instream flow conditions. According to the EPA 841-B-07-006 document: “The duration curve approach allows for characterizing water quality concentrations (or water quality data) at different flow regimes. The method provides a visual display of the relationship between stream flow and loading capacity. Using the duration curve framework, the frequency and magnitude of water quality standard exceedances, allowable loadings, and size of load reductions are easily presented and can be better understood. The duration curve approach is particularly applicable because stream flow is an important factor in determination of loading capacities. This method accounts for how stream flow patterns affect changes in water quality over the course of a year (i.e., seasonal variation that must be considered in TMDL development). Duration curves also provide a means to link water quality concerns with key watershed processes that may be important considerations in TMDL development…” The load duration analysis utilizes flow duration intervals, as discussed in Section 6.1, to identify flow regimes. Water quality standards can be presented by multiplying instream flow values by the numeric concentration (for E. coli this equals 126 CFU/100 mL) and a conversion factor (Figure 6-3). This step will form a trendline based on flow conditions, which represents the assimilative capacity of the stream at varying flow conditions. Points of observed data that plot above this line represent an exceedance of the standard/assimilative capacity. Load duration curves were used to determine the load reductions required to meet the target maximum concentrations for E. coli as discussed below.
Figure 6-3: Load duration curve used to represent E. coli loading capacity of the impaired reach of Boulder Creek.
36
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Along Boulder Creek, the site ‘Below Broadway’ was selected to represent the flow for the entire impaired reach (refer to Section 6.1) and, therefore, this site also represents the load duration within the impaired reach as a whole. The load duration curve presented in Figure 6-3 was used to assess the monthly geometric mean impairments at sites (BC-13th, BC-CU, BC-30th) monitored by the City between 2004-2010. As shown, five categories of instream flow conditions (i.e. highflows or moist conditions, etc.) are associated with relative loading capacities. The loading capacity, or assimilative capacity, of Boulder Creek is represented in Figure 6-3 by the blue trendline (this line represents the flow multiplied by the numeric target and a conversion factor). This line is in fact, the TMDL, which reflects varying loading capacity based on flow conditions. Flow based loading capacities are further defined in Section 7.
6.3
Loading Assessment of Boulder Creek
To link sources of E. coli to instream exceedances, identified loading sources were evaluated. The Data Assessment, completed in Section 3, generally showed increasing concentrations of E. coli throughout the urban corridor. Additionally, the analysis identified site BC-30th as the location with the greatest degree of impairment. It should be noted the BC-30th location receives runoff and MS4 discharges from primarily City owned land and land owned and maintained by the University of Colorado. To evaluate E. coli loading to the impaired stretch of Boulder Creek, monitoring data were plotted along the duration curve developed for the impaired reach. The remainder of this section presents the water quality duration curve analyses for BC-30th; additional analyses completed for sites BC-Eben, BC-13th and BC-CU can be found in Appendix B. To evaluate annual loading, weekly data were plotted with corresponding flow conditions. Figure 6-4 presents the water quality duration curve for Boulder Creek at 30th Street (site BC-30th). This figure categorizes E. coli concentrations into the corresponding five flow conditions, and includes a ‘Box-and Whisker’ plot to summarize data per flow condition. Box-and Whisker plots are a simple way to summarize the range of data, indicating the 25th and 75th percentile of data by the bottom and top of the box, the median by the band within the box, and the 10th and 90th percentile by the lower and upper tails, respectively. Additionally, the geometric mean is represented on the graphs by a solid blue diamond. From the Box-and Whisker plots, the highest median concentration is found in Dry Conditions followed closely by concentrations within the Mid-Range category. Recognizing that such conditions most often occur during summer months, Figure 6-4 also identifies samples taken during recreational months of May through October (represented by a “plus” within the diamond shaped symbols). The graph clearly indicates that a large majority of exceedances (those above the solid brown line) occur from May through October. Furthermore, this analysis indicates that the majority of exceedances during the months of May through October are also associated with flows corresponding with Mid-Range and Dry Conditions, which are generally less than 23 cfs. Typically exceedances during low flow conditions are related to point sources such as direct dischargers or other sources of pollution that do not include runoff (such as people recreating within the stream). Due to overwhelming evidence associated with exceedances occurring during the recreational period, further analysis was completed on data collected between May and October. Figure 6-5 presents the water quality duration curve, illustrating concentrations rather than loads. This analysis further supports the occurrence of exceedances during the recreational period, especially during Mid-Range and Dry Conditions. It should be noted that, although limited exceedances do occur during the non-recreational season at site BC-30th, the recreation season is identified as the critical condition and for this reason, reductions made to achieve standards during the recreational season, will likely ensure standards are met during the non-recreation season. Additionally, data corresponding to a ‘hydrologic event’ are indicated in red on Figure 6-4. Hydrologic events may be associated with rainfall events that wash pollutants into the stream, or flow diversions that 37
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
could potentially wash pollutants from the steam channel or stir stream-bed sediment. It is important to evaluate such hydrologic events for the implementation of the TMDL.
Figure 6-4. Water quality duration curve of annual trends at site BC-30th.
Figure 6-5. Water quality duration curve of annual trends at site BC-30th.
38
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
7 TMDL Calculations and Allocations The TMDL process quantifies the amount of a pollutant that can be assimilated in a waterbody, identifies the sources of the pollutant, and recommends regulatory or other actions to be taken to achieve compliance with applicable water quality standards based on the relationship between pollution sources and in-stream water quality conditions. The linkage analysis calculated the loading capacity (Section 6) based on flow conditions while this section discusses the calculation and allocation of the TMDL and identified sources as needed. The linkage analysis provides the quantitative basis for determining the loading capacities for E. coli within the impaired reach of Boulder Creek. Because TMDL calculations are based on beneficial uses and associated numeric standards, attainment of the TMDL numeric targets will result in attainment of water quality standards. After the TMDL for a waterbody is calculated, it is allocated to point sources (as wasteload allocations) and nonpoint sources (as load allocations). The TMDL also contains a Margin of Safety, which is described in detail in Section 7.4. Conceptually, the definition of a TMDL is represented by the following equation: TMDL = ∑WLAs + ∑LAs + MOS If the existing pollutant loading from the point and nonpoint sources exceeds allocations, reductions required for individual controllable pollutant sources can be calculated to meet the TMDL, and thus water quality standards. This section describes the process used to determine the loading capacity as well as resulting WLAs and LAs per identified source.
7.1
Establishment of the TMDL
Median flows from each flow category were used to establish a TMDL target and allocate loads that varied with seasonal (fluctuating) flow conditions (Table 7-1). The identification of the critical condition was used to identify needed reductions to ensure protection of beneficial uses year round. Critical conditions identify the period in time in which the most significant load reductions are needed. The critical condition was defined as those months aligning with the recreational season of May through October as discussed in Section 7.5. To ensure protection of beneficial uses throughout the impaired reach required reductions were calculated based on data collected at site BC-30th as this site exhibited the highest concentrations throughout the critical period based on the weekly monitoring data. Existing and allowable (TMDL) loadings were calculated with Equation 1 using the observed geometric mean at BC30th and the water quality standard, respectively. These concentrations are shown in Table 7-1. From the difference between the allowable and existing loads, the percent reductions were calculated. Existing loads at BC-30th, and percent reductions are shown in Table 7-1. Equation 1: Bacteria Concentration * Flow (cfs)* Conversion factor (CF) = Load (CFU) per day Units: (CFU/100 mL) * (1 ft3/sec) *(conversion) = Load Where bacterial concentration equals: For existing loads = Observed geometric means For allowable loads = Numeric target (126 CFU/100 mL) Conversion factor (CF): 3 1 ft =28,317 mL so that CFU/100ml to CFU/day:
((28317 mL/100 mL) * (60 sec/min) * (60 min/hour) * (24 hour/day)) = CF 39
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011 Table 7-1: Identification of E. coli TMDL based on flow conditions within the impaired stretch of Boulder Creek. Loading Calculations Median Flow (cfs) WQS for TMDL (CFU/100 mL)
High Flows
Moist Conditions
Mid‐Range Flows
Dry Conditions
Low Flow
188.069
46.671
15.952
6.639
1.000
126
126
126
126
126
Observed Geometric Mean (CFU/100mL) TMDL (CFU/day)*
88.9
209.3
486.8
546.1
NS
5.80E+11
1.44E+11
4.92E+10
2.05E+10
3.08E+09
Existing Load at BC‐30 (CFU/day)**
4.09E+11
2.39E+11
1.90E+11
8.87E+10
NS
0.00%
39.71%
74.06%
76.92%
NS
Required Reduction (%)
NS = Not sampled. *TMDL is based on 126 CFU/100mL. th **Existing load is calculated with the observed geometric mean at BC‐30 during corresponding flow condition.
Once the TMDL is calculated, and the MOS removed, the resulting loads are distributed as load allocations and wasteload allocations among the nonpoint and point sources in the watershed, respectively (shown in Table 7-2 below). Load allocations are assigned to both the upstream load and the land uses identified as: park, urban, other; open space (including acquired, other, and development rights); and, environmental protection (refer to Section 7.3, for land use discussion) within the watershed. All other land uses were assigned wasteload allocations under MS4 permits (Section 7.2). Point sources identified include MS4 dischargers and permitted facilities. Wasteload allocations for permitted facilities were calculated based on their design capacity and the instream standard (126 CFU/100 mL). The portion of the loading capacity that is allocatable to MS4 permittees was identified by subtracting the MOS and known point sources (i.e. San Lazaro WWTF) and the upstream nonpoint source (load allocation) from the TMDL. This MS4 permittee allocatable load was then allocated to each jurisdiction within the impaired reach. The allocations are identified in Table 7-2 and discussed in detail below.
7.2
Wasteload Allocations
Federal regulations (40 CFR 130.7) require TMDLs to include WLAs for each regulated point source. Each point source within the impaired reach was assigned a portion of the load (after the MOS has been removed) based on discharge limits or jurisdictional area. Within the impaired reach of Boulder Creek, MS4 discharges and WWTFs have been identified as potentially significant sources of E. coli. MS4 permits include the City of Boulder, Boulder County, University of Colorado, and the Boulder Valley School District. E. coli contributions from urban land uses within each MS4 are presented as WLAs. Jurisdictional boundaries were used to assign allocations based on the percent area of jurisdiction coverage within the impaired drainage area for urban land uses. WLAs are also identified for NPDES permitted facilities that contribute E. coli concentrations to the impaired reach.
7.2.1 Wasteload Allocations: MS4 Urban land uses draining to an MS4 system were assigned a WLA based on the allocatable load. The allocatable load is the remainder of the TMDL once the MOS, San Lazaro WWTF, and upstream sources are considered. Table 7-2 presents the MS4 WLAs for each of the five flow conditions. The MS4 loads were delineated based on jurisdiction (as shown in Figure 7-1), resulting in four MS4 WLAs assigned to the City of Boulder, Boulder County, University of Colorado and Boulder Valley School District. The percent area per jurisdiction is shown in Table 7-3. The allocatable MS4 load was distributed based on the area (percent) of land under a responsible jurisdiction. It should be noted that the responsibility of implementation may be further allocated based on ownership within each storm drain subcatchment as discussed below. 40
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Table 7-2: TMDL E. coli wasteload and load allocations (CFU/day) by flow condition. Moist Mid‐Range High Flows Dry Conditions Conditions Flows
Low Flow
CFU/day
TMDL
5.80E+11
1.44E+11
4.92E+10
2.05E+10
3.08E+09
MOS (‐5%)
2.90E+10
7.19E+09
2.46E+09
1.02E+09
1.54E+08
MS4 Permittee Allocatable Load*
4.10E+11
7.92E+10
2.59E+10
7.67E+09
2.40E+09
WLA San Lazaro WLA
5.25E+08
5.25E+08
5.25E+08
5.25E+08
5.25E+08
City of Boulder
2.66E+11
5.14E+10
1.68E+10
4.97E+09
1.56E+09
University of Colorado
6.85E+10
1.33E+10
4.34E+09
1.28E+09
4.02E+08
Boulder Valley School District
5.53E+09
1.07E+09
3.50E+08
1.03E+08
3.24E+07
Boulder County
7.19E+09
1.39E+09
4.56E+08
1.35E+08
4.22E+07
LA Upstream Load Allocation
1.41E+11
5.69E+10
2.02E+10
1.12E+10
0.00E+00
City of Boulder
4.26E+10
8.23E+09
2.70E+09
7.97E+08
2.50E+08
University of Colorado
3.78E+09
7.31E+08
2.39E+08
7.08E+07
2.22E+07
Boulder Valley School District
6.07E+08
1.17E+08
3.84E+07
1.14E+07
3.56E+06
Boulder County
1.57E+10
3.04E+09
9.96E+08
2.94E+08
9.23E+07
*Note: The MS4 permittee allocatable load is the remainder of load after the MOS, the upstream LA, and San Lazaro WWTF are considered.
Table 7-3: Percent jurisdictional WLA and LA. Percent of Area Responsible Jurisdiction
41
City of Boulder
WLA 64.86%
LA 10.39%
Total 75.26%
University of Colorado
16.73%
0.92%
17.65%
Boulder County
1.76%
3.84%
5.59%
Boulder Valley School District
1.35%
0.15%
1.50%
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Figure 7-1. MS4 jurisdictional areas.
42
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Quantification of Known MS4 Sources Existing loads were calculated for each of the regularly sampled storm drain outfalls within the impaired reach (shown in Figure 7-2). For assessment purposes, the discharges from storm drain outfalls were evaluated using the 126 CFU/100 mL numeric target. Actual or observed loads were based on (1) the average outfall flow measured at the specific outfall and (2) the geometric mean of samples collected at the outfall.
30th St
o
de ul
rC
ree
k
ee
k
B
3
# University Av Univ ers ity Av
Arapahoe Av
Arapahoe Av
Cr
9
#
4 # #5 #6
7
#
s Py Foo thill
1 2
##
17th St
Bv
u Bo
r lde
Py
ee k Boulde r Cr
Folsom St
St
on Ca ny
a rl P y
ills o th Fo
t St t ut S Wa ln
St
28th St
l Pe a r
e St
15 t h
c Sp ru
Pe
28th St
t
wa y
9t h S l Pe a r
S 20 t h
d Broa
Ma ple ton Av
Pin
e St
#8 Legend C olorad o Av
Ma jor Str eams/Rivers
TMDL Outfall Subcatchments
27th Wy
oa Br
dw ay
City of Boulder Outfalls and Subcatchments
k
2 3
ar C Be 4
Baseline Rd
NAD_1983_H AR N_StatePlane_Colorado_N orth_F IPS_0501 Map produced 08-18-2011 by E. Moreno
1
Cr ee
y
30th St
9th St
303(d ) Impaire d S egment
Py
wa
ls hil ot Fo
Br oa d
# TMDL O utfalls Ma inRoads
28th St
College Av
an
yo
n
Baseline Rd
5 6 7
Mo U or S H he w ad y 3 Av 6 0 0.1250.25 0.5 Kilometers 0 0.125 0.25 0.5 Miles
8 9
Figure 7-2. Identified storm drain outfalls with concentrations of concern within the impaired reach of Boulder Creek.
Nine regularly sampled outfalls and corresponding subcatchments are identified in Figure 7-2 and are listed one through nine from upstream to downstream. These outfalls consistently had dry weather flow and were identified as a concern by routine monitoring, and in some cases, citizen complaints due to odor and/or visual concerns. The nine drainages associated with the nine outfalls cover predominately City and University of Colorado land. The geometric mean and corresponding loads for each of the outfalls are presented in Table 7-4. Additionally, E. coli loads from outfalls one through seven, directly impact concentrations at site BC-30th (these are located between site BC-13th and site BC-30th) and are totaled in Table 7-4 to represent potential loading at site BC-30th; outfalls eight and nine are downstream of site BC30th and would impact concentrations further downstream (i.e. site BC-47th). Additionally, Table 7-5 shows the sum of outfalls one through seven in relation to the allowable and observed load at BC-30th. This basic analysis shows that the cumulative loads from outfalls one through seven (assuming all are discharging at their average flow and at the geometric mean concentration, and assuming no die off) have the potential to contribute significantly to instream concentrations. Of greatest 43
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
concern, the outfall concentrations have the potential to contribute loads in exceedance of the allowable loads, especially during dry and low-flow conditions. Table 7-4: Observed E. coli loads under dry weather conditions at outfalls identified as a concern within the impaired reach of Boulder Creek. Average Existing Condition Allowable E. Dry Conversion E. coli Target E. coli Geometric Existing E. coli Outfall coli Load Weather factor (CFU/100mL) Mean Load (CFU/day) (CFU/day) Flow (cfs) (CFU/100mL) Outfall 1
0.01
24465888
126
31.03
3.08E+07
7.59E+06
Outfall 2
0.012
24465888
126
2498.53
3.70E+07
7.34E+08
Outfall 3
0.156
24465888
126
85.46
4.81E+08
3.26E+08
Outfall 4
0.038
24465888
126
183.78
1.17E+08
1.71E+08
Outfall 5
0.013
24465888
126
95.50
4.01E+07
3.04E+07
Outfall 6
0.11
24465888
126
1029.68
3.39E+08
2.77E+09
Outfall 7
1.64
24465888
126
714.72
5.06E+09
2.87E+10
6.10E+09
3.27E+10
3.39E+07
1.17E+08
Outfall 9 0.0086 24465888 126 835.22 2.65E+07 Note: E. coli loads from outfalls one through seven, directly impact concentrations at site BC‐30th
1.76E+08
th
Sum of outfalls above BC‐30 (Outfalls 1‐7) Outfall 8
0.011
24465888
126
434.96
Table 7-5: Observed Boulder Creek E. coli load by flow tier at site BC-30th calculated with weekly monitoring data from May through October (considering all data available 6/14/2006-10/27/2010). Moist Dry High Flow Mid Range Low Flow Loading Calculations Conditions Conditions (CFU/day) (CFU/day) (CFU/day) (CFU/day) (CFU/day) Allowable Load
5.80E+11
1.44E+11
4.92E+10
2.05E+10
3.08E+09
Observed Load at BC‐30th
4.09E+11
2.39E+11
1.90E+11
8.87E+10
NS
Observed Loads Associated with 3.27E+10 3.27E+10 3.27E+10 3.27E+10 Outfalls 1‐7* th Percent Loading at BC‐30 8.00% 13.68% 17.21% 36.87% Attributable to Outfalls 1‐7 NS= Not sampled. *Outfall loads represented by geometric mean of all samples and average flow observed From Table 7‐4.
NS NS
7.2.2 Wasteload Allocations: Other NPDES facilities One NPDES permitted WWTF, the San Lazaro WWTF, is located within the impaired reach. In addition, two WWTFs are located and discharge treated wastewater above the impaired reach. These include the Boulder Mountain Lodge and the Red Lion Inn. NPDES permitted facilities are assigned WLAs as discussed below.
7.2.2.1 San Lazaro WWTF The San Lazaro WWTF is a permitted facility located within the impaired stretch, just upstream of the eastern boundary of impairment. Although in compliance with an existing permit, this facility is identified as a potential source of E. coli within the impaired reach, and for this reason the facility is 44
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
assigned a WLA based on the design flow capacity (0.11 million gallons per day) and the instream standard of 126 CFU/100mL. The resulting allocation equaled 5.25 E+08 CFU/day (Table 7-2). This load is assumed to be constant year round.
7.2.2.2 Red Lion Inn and Boulder Mountain Lodge WWTFs The Red Lion Inn WWTF is a small community package treatment facility that discharges treated wastewater to Boulder Creek above the impaired reach. In 2007, enforcement actions were taken on the facility due to illegal discharge of sewage into Boulder Creek in 2000 and 2002. Enforcement included civil penalties and over $30,000 in fines (CDPHE, 2007). It should be noted that the violations at the Red Lion Inn did not coincide with instream monitoring and therefore, the effect of such violations on the impaired reach is unknown. Located on Four Mile Creek, immediately above the confluence with Boulder Creek, the Boulder Mountain Lodge is the second of two WWTFs above the impaired reach. Both the Red Lion Inn WWTF and Boulder Mountain Lodge WWTF are currently compliant with their respective existing discharge permits, however, the potential for these dischargers to increase the level or extent of impairment on Boulder Creek exists. These facilities are not currently assigned a WLA, but should be considered a potential source of E. coli to the upstream load allocation. It should also be noted that if either facility changes the amount or characteristic of wastewater discharged, this TMDL may be reconsidered to include their point source contribution.
7.3
Load Allocations
According to federal regulations (40 CFR 130.2(g)), load allocations are best estimates of the nonpoint source or background loading. Due to indiscrete origins, nonpoint source pollution is difficult to quantify. Additionally, in urban areas, nonpoint source pollution often washes into the MS4 system and is then considered a point source and allocated a WLA. Within this TMDL for the Boulder Creek drainage, load allocations were assigned to (1) the upstream loading and (2) open lands (non-MS4) in the impaired drainage area. The upstream load allocation generally includes loading from septic systems, wildlife and, recreational (or bodily) contact to the stream. This load was calculated based on instream monitoring at site BC-Eben located at Eben G. Fine Park. In addition, open lands within the impaired reach were identified through GIS analysis and included land use categories: park, urban, other; open space (including acquired, other, and development rights); and, environmental protection within the watershed. The acreage of land classified as open lands was allocated a LA (Table 7-3); these loads were further delineated based on jurisdiction, resulting in LAs for the City of Boulder, Boulder County, the University of Colorado, and Boulder Valley School District. Resulting LAs are presented in Table 7-2.
7.4
Margin of Safety
By regulation, TMDLs must include a margin of safety (MOS) to account for the uncertainty in the analysis. There are two ways to incorporate the MOS: (1) implicitly incorporate the MOS using conservative model assumptions to develop allocations and (2) explicitly specify a portion of the total TMDL as the MOS and use the remainder for allocations (USEPA, 1991). In either case, the purpose of 45
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
the MOS is to ensure that the currently impaired beneficial uses will be restored, given the uncertainties in the TMDL analysis. Due to the wealth of sampling, this TMDL was able to calculate actual loads based off of few assumptions. For example, outfalls that consistently exhibited dry-weather flows greater than five gallon per minute (gpm) were monitored, giving actual concentrations and flow measurements. For this TMDL, an implicit MOS was included through the application of conservative considerations throughout the TMDL development. The following describes several key conservative considerations that were used to establish an adequate implicit MOS.
Interpreting bacterial results with geometric means, decreases the variability seen in single sample grabs.
Treating E. coli as a conservative pollutant (one that does not degrade or die-off) over-estimates the impact of storm drains on the stream. In reality, it is likely that the dramatic shift from storm drain to the stream environment forces selection on, and reduces E. coli populations.
Load duration curves ensure that numeric targets are based off of current flow conditions; this ensures that standards align with the assimilative capacity of varying flow conditions and changing seasons.
Use of low flow measurements where actual instream measurements taken by the city were used to develop flow duration curves. In the absence of a stream gage, this ensures low flows within the urban corridor are most accurately represented.
In addition to an implicit margin of safety, a five percent (5%) explicit margin of safety was added to account for any uncertainties within the TMDL development process. A five percent explicit MOS was determined to be sufficient due to the wealth of monitoring data considered within this analysis, thus decreasing the level of uncertainty.
7.5
Seasonal Variations and Critical Conditions
TMDLs are required to consider critical conditions and seasonal variation for streamflow, loading, and water quality parameters. The critical condition is the set of environmental conditions for which controls designed to protect water quality will ensure attainment of water quality standards for all other conditions. The intent of this requirement is to ensure protection of water quality in waterbodies during periods when they are most vulnerable. As discussed above, this TMDL utilizes the LDC methodology to evaluate the assimilative capacity and numeric targets during fluctuating flow conditions. The LDC methodology provides an excellent way to graphically present the instantaneous load and evaluate seasonal flow variations. Utilizing the load duration method ensures seasonal variability is taken into consideration in the calculation of numeric targets, while assessing impairment. In Boulder Creek, the critical conditions for E. coli were identified as those coinciding with the recreational period. This is supported by the Data Analysis (Section 3), the Linkage Analysis (Section 6) and the fact that the greatest contact risk is associated with the recreational period.
8 Implementation and Monitoring Recommendations Although not a required component of TMDLs, this section identifies areas of concern and summarizes potential implementation actions. Implementation of the TMDL will depend on all stakeholders and jurisdictions taking on an active role. Although roles will vary greatly depending on implementation action, a key aspect of implementation success will be collaboration between local jurisdictions. 46
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Jurisdictions with land use authority within the impaired reach of Boulder Creek were identified and assigned wasteload and load allocations by this TMDL. Identified sources are required to meet standards and therefore, must complete implementation actions to ensure beneficial uses within Boulder Creek are maintained.
8.1
Implementation Prioritization
Due to the wealth of monitoring data, implementation planning can be properly prioritized based on needed reductions. For example, Table 8-1 identifies reductions required within the nine outfalls identified as a concern. Required reductions are based on the recreational standard of 126 CFU/100 mL. Although outfalls are not typically held to a Class 1 Recreation standard, setting reductions at outfall locations ensures these flows will not contribute to instream violations. Outfalls of concern were identified based on weekly monitoring, and in some cases, citizen complaints associated with odor and/or visual concerns. Required reductions range from 31 percent to over 90 percent. Table 8-1: Reductions required to ensure outfalls do not contribute to instream E. coli standard violations. Existing Average Condition Allowable Existing Loading Conversion Target Flow Geometric Load Load Calculations factor (CFU/100mL) (cfs) Mean (CFU/day) (CFU/day) (CFU/100mL) 0.01 24465888 126 31.03 3.08E+07 7.59E+06 Outfall 1
Required Reduction (%)
Outfall 2
0.012
24465888
126
2498.53
3.70E+07
7.34E+08
94.96%
Outfall 3
0.156
24465888
126
85.46
4.81E+08
3.26E+08
Outfall 4
0.038
24465888
126
183.78
1.17E+08
1.71E+08
31.44%
Outfall 5
0.013
24465888
126
95.50
4.01E+07
3.04E+07
Outfall 6
0.11
24465888
126
1.03E+03
3.39E+08
2.77E+09
87.76%
Outfall 7
1.64
24465888
126
7.15E+02
5.06E+09
2.87E+10
82.37%
Outfall 8
0.011
24465888
126
4.35E+02
3.39E+07
1.17E+08
71.03%
Outfall 9
0.0086
24465888
126
8.35E+02
2.65E+07
1.76E+08
84.91%
Implementation actions should be coordinated by the jurisdiction(s) managing the land within the subcatchment outfall basins. As shown in Table 8-1 and Figure 8-1, jurisdictions within the subcatchments of concern are within the City of Boulder, the University of Colorado and Boulder Valley School District. Percent reductions per jurisdiction can be calculated based on percent of jurisdictional land within a subcatchment. Resultant reductions for each subcatchment are calculated in Table 8-2. Such reductions may be considered by the State of Colorado within the MS4 permitting process and may be incorporated into renewed permits. It is recommended that additional monitoring and GIS analysis be targeted at better quantifying unknown MS4 contributions and nonpoint source contributions in undelineated drainages. With additional data, it should be noted that required reductions and allocations calculated in this report may be revisited.
47
9t h S
t
Figure 8-1. Outfall subcatchment percent reduction. St
St
* #3
Br oa d wa y
Folsom St
4 5 6 * * # # # *
Arapahoe Av
l Pe a r
NAD_1983_H AR N_StatePlane_Colorado_N orth_F IPS_0501 Map produced 08-18-2011 by E. Moreno
28th St
0
0.125
0 0.1250.25
7
* #
Arapahoe Av
wa
City of Boulder Outfalls and Subcatchments
Baseline Rd
College Av
2
# #* *
1
Bv
University Av
re e k Bou lder C
on Ca ny
t ce S Sp ru
t ut S Wa ln
9th St
15 t h
l Pe a r
St
Ma plet on Av
wa y
17th St
d Broa
28th St
48 t C olora d o Av
#8 *
30th St
0.5 Kilometers 0.25 0.5 Miles
Mo U or S H he w ad y 3 Av 6
#9 *
B
l
u Bo
rC lde
re
Major Streams/Rivers
Su bcatch ment Bou ndaries
303(d ) Imp aired Seg ment
MainRoad s
Lege nd
k ee
Unive rsit y of Colora do
City of Boulder
Bo uld er Valley Schools
95%
88%
85%
82%
71%
31%
0%
Baseline Rd
Total Reduction Req uired
TMDL Outfalls
# * *on # ny a ar C # * Be * # * # * # * #
u
r rC de
ar l Py
Py
k
S 20 t h
Py
o Fo
lls thi
Cr ee
St Pin e
d oa Br
27th Wy
ills o th Fo
28th St
Py Foo thills
30th St
Pe
ek
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
y
o
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Table 8-2: Percent reductions per outfall subcatchment and jurisdictional area. Outfall Subcatchment 1
2
3
4
5
6
7
8
9
Subcatchment Area (Acres) Total reduction required (%)
34.46
191.73
23.35
18.35
14.40
79.26
131.33
56.28
15.50
0%
94.96%
0%
31.44%
0%
87.76%
82.37%
71.03%
84.91%
City Area (Acres)
34.25
191.00
3.27
0.00
0.00
2.82
70.34
55.66
5.09
Percent City Ownership City of Boulder Percent Reduction* University of Colorado Area (Acres) Percent University of Colorado Ownership University of Colorado Percent Reduction* Boulder Valley School District Area (Acres) Percent Boulder Valley School District Ownership Boulder Valley School District Percent Reduction*
99.39%
99.62%
14.00%
0.00%
0.00%
3.56%
53.56%
98.89%
32.87%
94.60%
3.13%
44.12%
70.24%
27.91%
0.21
0.73
20.08
18.35
14.40
76.43
57.05
0.6
10.4
0.61%
0.38%
86.00%
100.00%
100.00%
96.44%
43.44%
1.11%
67.13%
0.36%
31.44%
84.63%
35.78%
0.79%
57.00%
0.00
0.00
0.00
0.00
0.00
0.00
3.94
0.00
0.00
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
3.00%
0.00%
0.00%
2.47%
*Calculated by applying the City of Boulder, University of Colorado and Boulder Valley School District percent ownership to the required reductions presented in Table 8‐1. Table represents available data, additional data may be required to fully characterize outfall streams.
49
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
8.2
Recommended Actions
After TMDL approval, it is suggested that the stakeholders develop a coordinated implementation plan that could include a range of management opportunities. Categories of implementation actions will generally fall into four categories, including: (1) education and outreach; (2) stormwater best management practices (BMP) projects; (3) infrastructure maintenance and upgrades; and, (4) additional monitoring. Each of these categories is summarized below.
Education and Outreach: As a source control technique, education and outreach can function as pollution prevention or the ‘first line of defense’ to reduce or eliminate the amount of bacteria washed from surfaces. Specifically, a targeted pet waste clean-up program on areas of land both adjacent to Boulder Creek and throughout the impaired drainage would reduce loading. Additionally, implementation actions such as municipal incentives can be used to encourage proper irrigation and landscaping that can significantly reduce runoff and overland flow that tends to wash bacteria into the storm system. The City of Boulder and Boulder County are active members in the Keep it Clean Partnership (KICP), a collaborative multijurisdictional effort aimed at protecting water quality. The KICP seeks to educate and engage citizens in protecting water quality. It is recommended that resources be allocated to expand educational programs focused on proper pet waste management. It is also highly recommended that all Phase II permittees, including the City of Boulder, Boulder County, the University of Colorado and the Boulder Valley School District, expand educational programs to ensure maintenance staff is properly educated on waste management and ground maintenance as it pertains to bacterial sources.
Stormwater BMP projects: BMPs include both structural and nonstructural projects that can be implemented to reduce the effects of urban, industrial, and residential developments on stormwater. Structural BMPs can include the incorporation of low impact development (LID) concepts into new or existing sites or along municipal right-of-ways to minimize runoff and enhance pollutant uptake. It should be noted that local ordinances may need to be revised to allow for, or require, the incorporation of structural BMPs in some areas. Nonstructural BMPs largely include education and outreach opportunities (as discussed above).
Infrastructure Maintenance and Upgrades: It is highly recommended that jurisdictions complete an illicit discharge detection and elimination program targeted at lands within the impaired stretch, specifically within those outfall subcatchments identified as a concern. Such a program may include a dye study to identify leaking infrastructure so improvements can be prioritized to areas with the greatest impact on instream loading. Concern is also associated with unapproved or failing septic systems within or above the impaired drainage. Boulder County has an established Septic Smart program that offers guidance and support for home owners in need of replacing septic systems. It is recommended that additional resources be focused on identifying and repairing failing septic systems within and above the impaired stretch. Additionally, jurisdictions should evaluate areas adjacent to the stream for adequate pet-waste disposal and public restroom access.
Additional Monitoring: Additional monitoring could be focused on: source characterization of nonpoint source loading (this may include further development of GIS layers to identify directional storm drainage flow); expanded illicit discharge detection and elimination monitoring programs; extended monitoring on Boulder Creek tributaries; and extended flow monitoring for both outfalls and within the impaired reach. This additional data and information could support revised source assessment, loading calculations, and/or TMDL allocations. 50
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
References CDPHE, 2007.Compliance Order on Consent, Water Quality Control Division, Colorado Department of Public Health and Environment. No: DC-070403-1Available at: http://www.cdphe.state.co.us/wq/enforcement/2007/2007Domestic/Red_Lion_Inn-4-3-07-COC.pdf CDPHE, 2010. Regulation 31- The Basic Standards and Methodologies for Surface Waters. Water Quality Control Division, Colorado Department of Public Health and Environment. Amended 8/9/10. Accessed November 16, 2010at: http://www.cdphe.state.co.us/regulations/wqccregs/. CDPHE, 2010. Regulation 61- Colorado Discharge Permit System Regulations. Water Quality Control Division, Colorado Department of Public Health and Environment. Amended 7/12/10. Accessed November 16, 2010 at: http://www.cdphe.state.co.us/regulations/wqccregs/. CDPHE, 2010. Regulation 93- Colorado’s Section 303(d) List of Impaired Waters and Monitoring and Evaluation List. Water Quality Control Division, Colorado Department of Public Health and Environment. Amended 3/09/10. Accessed November 16, 2010 at: http://www.cdphe.state.co.us/regulations/wqccregs/100293wqlimitedsegtmdlsnew.pdf. CDPHE, 2002. Phase II Muncipal Guide Fact Sheet for Non-Standard MS4s. Available at: http://www.cdphe.state.co.us/wq/permitsunit/POLICYGUIDANCEFACTSHEETS/factsheets/nonstdFS.PDF. CDPHE, 2001. Colorado’s Phase II Municipal Guidance. Water Quality Control Division, Colorado Department of Public Health and Environment. Accessed November 1st, 20102010at: http://www.cdphe.state.co.us/wq/PermitsUnit/POLICYGUIDANCEFACTSHEETS/factsheets/ms4guide.pdf. Frazer, L. 2005. Paving paradise: The peril of impervious surfaces. Environmental Health Perspectives. Vol. 113(7): 456462. Accessed November 1st, 2010 at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1257665/pdf/ehp0113-a00456.pdf Garzio-Hadzick, A., D.R. Shelton, R. L. Hill, Y.A. Pachepsky, A.K. Guber, R. Rowland, 2010. Survival of manure-borne E. coli in streambed sediment: Effects of temperature and sediment properties. Water Research. Vol. 44 (2010): 27532762. Accessed November 4th, 2010 at: http://ddr.nal.usda.gov/dspace/bitstream/10113/42552/1/IND44372489.pdf. Ishii, S., W.B. Ksoll, R.E. Hicks, M.J. Sadowsky. 2005. Presence and Growth of Naturalized Escherichia coli in Temperate Soils from Lake Superior Watersheds. Applied and Environ. Microbiol. Vol. 72(1). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1352292/pdf/1955-05.pdf. Monroe, M., 2009. A multifaceted approach to microbial source tracking in secondary environments. Masters Thesis, Colorado School of Mines. May, 2009. Murphy, S. 2006. State of the Watershed: Water Quality in Boulder Creek, Colorado. U.S. Geological Survey Circular; 1284. Available at: http://pubs.usgs.gov/circ/circ1284/pdf/circ1284.pdf. Stoeckel, D., 2010. Semi-quantitative evaluation of fecal contamination by humans, ruminant, and alternate sources in Upper Fountain Creek, Colorado. Presented at the National Monioring Conference. Denver, CO. April 28th, 2010. Accessed November 2nd, 2010 at: http://acwi.gov/monitoring/conference/2010/I2/I2_Stoeckel.pdf USEPA. 1991. Guidance for Water Quality-Based Decisions: The TMDL Process. EPA 440/4-91-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC. USEPA, 2007. An Approach for Using Load Duration Curves in the Development of TMDLs. EPA 841-B-07-006. Available at: http://water.epa.gov/lawsregs/lawsguidance/cwa/tmdl/techsupp.cfm. USEPA, 1986. Ambient Water Quality Criteria for Bacteria. EPA 440/5-84-002 Available at: http://water.epa.gov/scitech/swguidance/waterquality/standards/library_index.cfm
51
Boulder Creek, Colorado Segment 2b: From 13th Street to the Confluence with South Boulder Creek
Escherichia coli Total Maximum Daily Load (TMDL) Appendices
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Appendix A: Boulder Creek Monitoring Data Boulder Creek monitoring has occurred monthly and weekly since 2003 and 2004, respectively. Available monthly data were used to confirm impairment while weekly data were used to establish loading within the impaired reach. In addition to instream monitoring, outfalls were monitored, in some capacity, since 2007.
A.1 Monthly Monitoring Monthly monitoring occurs along Boulder Creek in its entirety. Data below are specific to monitoring stations immediately upstream of the impaired stretch, locations within the impaired reach, and monitoring locations below the impairment. Monthly data (see table below) were used to confirm the extent of impairment both spatially and temporally. Monitoring locations include:
Boulder Creek above North Boulder Creek (BC-aNBC) Boulder Creek at Orodell (BC-Oro) Boulder Creek at the Canyon (BC-Can) Boulder Creek at the Library (BC-Lib) Boulder Creek near the University (BC-CU) Boulder Creek at 47th (BC-47th) Boulder Creek at 61st Street (BC-61) Boulder Creek above the 75th Street Wastewater Treatment Facility (BC-aWWTP)
Appendix A- 1: Monthly E. coli monitoring data collected by the City of Boulder. Site (CFU/100 mL) Within impaired reach
Above impaired reach Date
BC‐aNBC
BC‐Oro
BC‐Can
BC‐Lib
BC‐CU
Below impaired reach
BC‐47
BC‐61
BC‐aWWTP
2/11/2003
1
10.9
3.1
3/25/2003
1
1
1119.9
43.7
4/8/2003
1
1
151.5
40.8
5/20/2003
1
5.2
14.5
70.8
101.2
5/29/2003
83.9
6/3/2003
37.3
6/10/2003
9.7
6/18/2003
35
6/24/2003
3.1
16
4.1
61.3
72.8
68.3
7/8/2003
3.1
12.2
31.8
58.8
46.4
23.5
7/15/2003
7/22/2003
185
7/29/2003
2602
8.6
61.3
28.2
410.6
52.7
16.3
8/12/2003
172.2
8/19/2003
1203.3
9/9/2003
1
24.3
43.2
1553.1
488.4
8/5/2003
53
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Site (CFU/100 mL) Within impaired reach
Above impaired reach Date
BC‐aNBC
BC‐Oro
BC‐Can
BC‐Lib
BC‐CU
Below impaired reach
BC‐47
BC‐61
BC‐aWWTP
9/23/2003
579.4
10/7/2003
24.6
11/18/2003
17.1
12/2/2003
2
1
3
12
9.7
1/13/2004
11
7.4
8.4
2/10/2004
0
30.9
2
3/9/2004
1
3.1
9.8
14.3
5/11/2004
1
10.9
20.1
172.2
26.2
6/22/2004
6.3
23.1
14.6
80.5
44.6
7/13/2004
3
7.4
9.8
76.8
29.4
8/24/2004
19.7
8.6
18.1
172.5
79.8
9/28/2004
1
6.3
32.3
2419.2
2419.2
10/12/2004
0
3.1
80.1
65.7
29.4
11/9/2004
1
4.1
7.4
30.1
10.9
12/7/2004
1
13
43.5
42.2
1/18/2005
0
0
0
2/22/2005
31.4
139.6
1
3/15/2005
1
2
119.1
8.4
4/12/2005
0
0
0
0
5/17/2005
1
2
2
39.3
95.9
6/28/2005
2
6
13
26
34
7/26/2005
4.1
32.7
45
2419.2
304.4
8/30/2005
13.5
53.7
79.4
58.1
56.9
9/20/2005
8.5
20.1
10.9
28.1
5.2
10/11/2005
2
7
12
649
648
11/8/2005
2
1
66.9
90.6
21.1
2/14/2006
344.1
68.9
9.7
3/28/2006
1
5.2
435.2
30.1
30.5
4/11/2006
1
2
1
44.1
8.6
5/9/2006
1
5.2
191.8
12.1
8.6
6/1/2006
26.2
6/20/2006
24.6
22.6
38.8
190.4
203.5
7/18/2006
3.1
15.8
18.7
235.9
38.8
8/15/2006
11
7.4
101.7
1119.9
166.9
9/12/2006
6.3
5.2
691
20.9
87.6
1
19.3
177.9
10/10/2006
1
9.7
63.1
160.7
980.4
1732.9
1986.3
2419.2
11/14/2006
1
5.2
24
34.1
104.6
98.5
42.6
11/15/2006
307.6
54
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Site (CFU/100 mL) Within impaired reach
Above impaired reach Date
BC‐aNBC
BC‐Oro
BC‐Can
BC‐Lib
BC‐CU
Below impaired reach
BC‐47
BC‐61
BC‐aWWTP
12/12/2006
1
5.2
5.2
35
32.7
28.2
33.5
1/9/2007
18.9
133.3
307.6
74.9
82
2/27/2007
1
22.6
4.1
18.9
31.7
23.3
9.6
3/20/2007
1
6.3
23.8
22.1
79.4
26.2
23.1
10.9
4/17/2007
5.2
2
5.2
35.4
108.1
365.4
461.1
517.2
1
7.3
1
74.4
68.4
153.9
30.9
21.6
6/26/2007
2
8.1
37.4
50.4
40.4
344.8
75.9
172.6
7/17/2007
3.1
8.5
15.8
79.8
62.2
248.9
80.1
23.8
8/14/2007
10.9
3.1
38.9
648.8
488.4
727
78.5
20.9
9/11/2007
5
7
980
119
140
649
91
7
10/9/2007
1
2
16
172.2
365.4
365.4
172.3
86
11/27/2007
6
76
46
66
51
11
12/18/2007
15.8
93.3
108.6
139.6
1/15/2008
20.3
57.3
101.7
52.9
2/12/2008
8.6
145
31.5
63.1
21.3
32.3
3/11/2008
1
52.9
27.2
39.3
63.8
16
10.7
4/15/2008
1
1
9.8
185
43.5
416
15.6
17.3
4/23/2008
16
5/20/2008
1
3.1
178.5
82
71.2
155.3
154.1
133.1
6/24/2008
12.1
37.3
51.2
98.7
178.5
153.9
866.4
80
7/22/2008
8.5
14.5
31.7
23.3
190.4
770.1
68.3
13.4
8/12/2008
1
51.2
25.6
18.5
60.9
238.2
93.3
37.7
9/16/2008
3.1
3
31.5
48.1
206.4
410.6
55.4
45.7
10/7/2008
1
1
60
86
488
921
308
80
11/18/2008
1
1
12.1
1119.9
124.6
387.3
156.5
184.2
12/16/2008
0
648
1/13/2009
3.1
24.1
325.5
344.8
88.2
104.6
2/10/2009
12.2
7.4
48.1
60.2
24.6
5.1
3/10/2009
1
2
5.2
41
35.4
9.6
7.4
4/14/2009
1
1
19.9
6.2
21.6
193.5
6.2
4.1
5/8/2007
5/12/2009
1
2
5.2
18.9
10.9
24.6
152.9
83.6
6/16/2009
8.6
5
47.1
113.7
83.3
98.7
189.2
260.3
7/14/2009
4.1
12.2
6.3
20.1
79.4
178.5
158.5
63.3
8/11/2009
1
3
461.1
1986.3
143.9
461.1
167
18.7
3.1
2
38.9
69.7
214.3
272.3
40.8
33.1
10/13/2009
1
2
25.6
34.1
115.3
172.2
133.4
113.7
11/10/2009
1
1
25.9
26.9
63.1
40.8
22.8
11
12/14/2009
5.2
5.2
41.4
98.5
72.8
38.8
9/8/2009
55
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Site (CFU/100 mL) Within impaired reach
Above impaired reach Date
BC‐aNBC
BC‐Oro
BC‐Can
BC‐Lib
BC‐CU
Below impaired reach
BC‐47
BC‐61
BC‐aWWTP
1/12/2010
1
24.3
38.4
16
2/9/2010
1
90.9
29.5
2
3/16/2010
1
1
1119.9
79.8
17.1
7.4
4/13/2010
1
1
1
30.5
14.8
4.1
5/18/2010
1
1
25.9
108.1
35.4
39.3
43.2
133.4
52
238.2
290.9
7/13/2010
48
53.7
42.8
98.8
135.4
57.3
8/17/2010
5.1
9.8
28.1
290.9
816.4
579.4
9/14/2010
7.5
2
18.3
125.9
93.3
17.3
6/8/2010
A.2 Weekly Monitoring Weekly monitoring within the impaired stretch has occurred, in some capacity, since June of 2004. In total, 228 weekly sampling events occurred. Data gathered during weekly events were used to evaluate the impairment and support allocations. Data are presented in the table below for the following instream locations that are monitored weekly:
Boulder Creek at Eben Fine (above the impaired reach) (BC-Eben) Boulder Creek at 13th Street (within the impaired reach) (BC-13th) Boulder Creek near the University (within the impaired reach) (BC-CU) Boulder Creek at 30th Street (within the impaired reach) (BC-30th)
Appendix A- 2: Weekly instream monitoring data collected on Boulder Creek. BC‐ Eben BC‐13th BC‐CU Date (CFU/100 mL) (CFU/100 mL) (CFU/100 mL) 6/14/2004 58.1 130.1 52 6/22/2004 15.8 40.8 204.6 6/29/2004 20.1 104.6 101 7/12/2004 172.6 658.6 1732.87 7/12/2005 24 54.7 77.1 7/19/2004 22.6 135.4 133.3 7/19/2005 26.2 275.5 1815 7/26/2004 17.5 67.7 139.6 7/26/2005 41.3 104.6 275.5 7/5/2005 8.6 24.3 101.4 8/16/2005 16.1 727 2419.17 8/17/2004 360.9 461.1 2419.2 8/2/2005 20.1 73.3 2419.17 8/23/2005 88.2 435.2 1203.31 8/23/2004 46.4 517.2 488.4 5/31/2006 547.5 154.4 26.2 6/7/2006 13.4 38.8 128.1 6/14/2006 48 98.7 60.2 56
BC‐30th (CFU/100 mL) 172.3 129.6 155.3 133.3 142.1 285.1 178.9 209.8 1413.6 201.4 325.5 220.9 2419.2 1986.21 275.5 40.4 201.4 71.2
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 6/21/2006 6/28/2006 7/5/2006 7/11/2006 7/12/2006 7/19/2006 7/26/2006 8/2/2006 8/23/2006 8/30/2006 9/6/2006 9/13/2006 9/20/2006 10/11/2006 10/18/2006 10/24/2006 11/1/2006 11/8/2006 11/15/2006 11/21/2006 12/6/2006 12/13/2006 1/3/2007 2/7/2007 2/14/2007 2/21/2007 2/28/2007 3/7/2007 3/14/2007 3/21/2007 3/28/2007 4/4/2007 4/11/2007 4/19/2007 4/25/2007 5/2/2007 5/9/2007 5/16/2007 5/23/2007 5/30/2007 6/6/2007 6/13/2007 6/20/2007 6/27/2007 7/2/2007 7/10/2007 7/17/2007 57
BC‐ Eben (CFU/100 mL) 17.1 7.5 18.3 31.8 920.8 18.7 41.4 46.4 2419.6 50.4 2419.6 325.5 27.5 29.5 579.4 6.3 161.6 32.7 12.2 93.2 1 66.3 3 12.1 2 13.1 160.7 30.1 93.9 88.2 16 38.4 46.4 57.3 2 32.7 64.5 10.9 16.1 28.8 40.4 52.1 34.5 55.4 1986.3 268.2 42.6
BC‐13th (CFU/100 mL) 172.2 41.4 28.8 162.4 78 95.9 72.3 387.3 83.9 101.2 93.4 148.3 1986.3 435.2 122.3 34.1 34.5 37.9 166.4 13.5 48.8 43.7 4.1 1 5.2 11.9 68.3 47.1 52 135.4 20.1 33.2 24.1 15.8 30.9 30.5 16.1 43.5 107.1 27.5 75.4 142.1 26.6 67.7 68.3 613.1 156.5
BC‐CU (CFU/100 mL) 47.1 53.7 46.4 218.7 150 178.2 137.6 235.9 248.9 325.5 344.8 920.8 207.5 313 488.4 116 88.4 49.5 93.4 33.6 72.3 21.2 37.9 31.8 32.3 19.9 42.6 79.8 58.1 49.6 7.4 35.5 51.2 186 2419.2 68.9 36.8 10.2 35.9 27.5 59.1 86 86 35.08 410 100.8 325.5
BC‐30th (CFU/100 mL) 42.6 248.9 365.4 137.6 290.9 159.4 435.2 307.6 579.5 816.4 770.1 816.4 547.5 727 1413.6 172.6 57.1 104.6 172 478.6 727 17.3 66.3 49.6 27.5 127 86.2 25.8 40.2 40.2 30.5 125.9 261.3 272 57.6 125.9 98.7 59.6 42 64.4 115.3 151.5 35 104.3 1046.2 275.5 517.2
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 7/25/2007 8/1/2007 8/8/2007 8/15/2007 8/22/2007 9/4/2007 9/11/2007 9/18/2007 9/27/2007 10/2/2007 10/9/2007 10/16/2007 10/24/2007 10/31/2007 11/14/2007 11/20/2007 11/27/2007 12/4/2007 12/18/2007 1/8/2008 1/15/2008 1/22/2008 1/30/2008 2/5/2008 2/13/2008 2/20/2008 2/26/2008 2/28/2008 3/11/2008 3/18/2008 3/25/2008 4/1/2008 4/8/2008 4/16/2008 4/23/2008 4/24/2008 4/29/2008 5/6/2008 5/20/2008 5/27/2008 6/3/2008 6/10/2008 6/17/2008 6/24/2008 7/1/2008 7/8/2008 7/15/2008 58
BC‐ Eben (CFU/100 mL) 36.4 52.9 121.1 1119.9 816.4 235.9 313 93.3 31.1 25.3 16 24.3 17.3 8.5 59.4 25 59.4 18.7 4.1 5.2 72.7 2 2 2 118.7 30.9 9.7 160.7 9.8 7.3 17.1 1 4.1 9.5 5.1 58.3 21.6 38.9 22.8 51.2 12.1 15.6 55.6 65 70.3 123.6
BC‐13th (CFU/100 mL) 79.4 93.3 129.1 119.8 83.6 344.8 114.5 298.7 387.3 93.4 110.6 67 32.8 151.5 6.3 6.3 27.2 20.3 35.5 19.9 133.3 24.9 6.3 36.8 218.7 8.6 866.4 68.3 21.3 5.2 20.1 5.2 7.4 12.1 7.5 15.6 13.2 178.5 75.4 37.9 25.6 18.7 93.3 51.2 114.5 191.8
BC‐CU (CFU/100 mL) 77.1 231 190.4 290.9 365.4 547.5 148.3 2419.6 387.3 218.7 387.3 387.3 261.3 344.8 727 35.9 34.1 34.5 65 56.3 71.2 29.2 8.6 137.4 103.9 18.7 2419.6 42.6 26.2 686.7 53.7 86 62.2 35.9 16 36.4 18.7 124.6 63.1 95.9 21.3 21.3 360.9 82 131.4 64.5
BC‐30th (CFU/100 mL) 344.8 410.6 325.5 488.4 686.7 547.5 547.5 2419.6 1986.3 261.3 435.2 770.1 201.4 613.3 866.4 59.1 39.3 90.9 108.1 88.2 37.7 72.3 8.3 1413.6 35 24.1 870.4 86.2 162.4 71.6 88.8 37.7 44.1 135.4 69.1 224.7 71.2 60.2 86.2 51.2 77.1 248.1 69.7 108.1 218.7 65.7
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 7/22/2008 7/29/2008 8/5/2008 8/12/2008 8/19/2008 8/26/2008 9/2/2008 9/10/2008 9/16/2008 9/24/2008 9/30/2008 10/7/2008 10/14/2008 10/21/2008 10/28/2008 11/5/2008 11/12/2008 11/18/2008 11/25/2008 12/2/2008 12/10/2008 12/16/2008 12/23/2008 12/30/2008 1/6/2009 1/13/2009 1/20/2009 1/28/2009 2/3/2009 2/11/2009 2/17/2009 2/25/2009 3/4/2009 3/11/2009 3/17/2009 3/25/2009 4/2/2009 4/8/2009 4/15/2009 4/22/2009 4/29/2009 5/5/2009 5/13/2009 5/19/2009 5/26/2009 6/2/2009 6/9/2009 59
BC‐ Eben (CFU/100 mL) 17.1 21.6 23.1 16 365.4 35.5 285.1 40.2 36.8 16.8 142.1 48.8 13.5 68.3 47.1 23.1 54.8 2 4.1 9.6 23.1 5.2 3.1 10.9 12.2 16 13.2 3 1 160.7 3.1 3.1 1 9.8 3.1 8.4 98.8 21.3 26.5 1 1 74.9 9.8 35.2 24.9 27.5 14.6
BC‐13th (CFU/100 mL) 48.7 52.1 96 115.3 2419.6 131.7 488.4 72.3 98.7 77.1 43.5 115.3 238.2 166.4 98.8 39.9 13.4 39.9 44.8 37.9 172.2 127.4 31.7 24.6 14.5 74.9 16 23.1 36.8 25.6 13.5 42 167 6.3 29.5 31.3 1 5.2 18.5 13.4 2 81.6 18.1 72.7 20.3 125 56.5
BC‐CU (CFU/100 mL) 307.6 88.8 63.1 172.3 487 139.6 272 162.4 248.1 96 145 235.9 461.1 228.2 272.3 31.8 51.2 90.9 63.1 214.2 1119.9 114.5 172.3 55.7 22.8 307.6 63.8 19.4 37.3 231 68.3 60.9 14.8 98.8 42.6 118.7 23.3 12.1 35.5 12.1 4.1 105 25.9 79.4 24.1 275.5 29.2
BC‐30th (CFU/100 mL) 214.3 579.4 261.3 224.7 3873 416.6 448 770.1 387.3 517.2 201.4 1119.9 866.4 313 228.2 107.1 131.7 103.6 686.7 325.5 2419.6 127.4 101.4 119.8 53.6 285.1 47.3 37.4 25 157.6 365.4 146.7 99 28.8 48.7 435.2 23.3 50.4 48 91 39.9 68.3 29.2 119.8 48 290.9 50.4
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 6/17/2009 6/23/2009 6/30/2009 7/7/2009 7/17/2009 7/21/2009 7/28/2009 8/4/2009 8/12/2009 8/19/2009 8/25/2009 9/1/2009 9/9/2009 9/16/2009 9/23/2009 9/29/2009 10/6/2009 10/14/2009 10/22/2009 10/27/2009 11/3/2009 11/12/2009 11/18/2009 11/25/2009 12/1/2009 12/10/2009 12/15/2009 12/22/2009 12/30/2009 1/5/2010 1/13/2010 1/19/2010 1/26/2010 2/2/2010 2/10/2010 2/17/2010 2/23/2010 3/2/2010 3/10/2010 3/17/2010 3/23/2010 3/31/2010 4/6/2010 4/14/2010 4/21/2010 4/28/2010 5/6/2010 60
BC‐ Eben (CFU/100 mL) 44.8 57.6 19.7 18.3 5.2 12 51.2 24.6 135.4 58.3 517.2 38.4 46.4 77.6 224.7 290.9 45.7 74.4 16.1 38.2 24.6 488.4 11 16.1 5.2 10.8 1 20.1 1 1 1 1 5.2 1 2 1 1 1 6.3 18.9 18.5 148.3 6.3 1 20.1 8.5 8.8
BC‐13th (CFU/100 mL) 57.6 50.4 23.1 148.3 119.8 69.1 75.4 145 83.6 80.9 124.6 88.6 209.8 290.9 307.6 62.4 365.4 58.6 111.2 137.6 61.3 185 39.9 30.9 16 16 27.5 26.6 8.6 10.8 21.6 18.9 19.5 16.1 16 5.2 67.7 4.1 6.1 71.2 29.2 60.2 18.5 4.1 35.9 146.7 14.4
BC‐CU (CFU/100 mL) 83.9 59.4 37.3 142.1 24.1 136.4 178.9 155.3 214.3 257.5 365.4 186 547.5 325.5 727 161.6 613.1 65.7 185 160.7 71.7 60.9 517.2 45.7 133.4 115.3 54.6 39.9 13.5 35 46.4 82.3 30.9 27.9 34.5 24.6 74.9 16.8 1553.1 115.3 39.9 45 238.2 6.3 29.2 51.2 5.2
BC‐30th (CFU/100 mL) 95.9 36.4 33.1 116.2 69.5 344.8 387.3 214.2 235.9 290.9 980.4 686.7 980.4 2419.6 2419.6 290.9 866.4 180.6 275.5 178.5 62.2 105.4 436 56.9 1413.6 110.6 101.7 49.6 86 18.9 50.4 58.1 115.3 143.9 68.3 71.4 83.9 86 185 105 275.5 131.4 344.8 95.9 32.3 42 21.6
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 5/13/2010 5/19/2010 5/25/2010 6/1/2010 6/9/2010 6/15/2010 6/22/2010 6/30/2010 7/7/2010 7/14/2010 7/20/2010 7/28/2010 8/3/2010 8/18/2010 8/25/2010 9/3/2010 9/8/2010 9/15/2010 9/22/2010 9/28/2010 10/8/2010 10/14/2010 10/27/2010
61
BC‐ Eben (CFU/100 mL) 43.5 17.1 5.2 17.3 21.3 14.4 13.2 18.7 17.5 29.2 209.8 59.4 49.6 71.2 34.5 39.9 35.9 235.9 48.8 67 78.9 114.5 22.8
BC‐13th (CFU/100 mL) 75.4 68.3 24.1 33.1 22.3 21.1 14.6 44.1 201.4 52 1299.7 517.2 52 307.6 125.9 70.8 325.5 686.7 86 290.9 142.1 275.5 166.4
BC‐CU (CFU/100 mL) 46.4 28.8 24.6 48.7 36 44.1 53.9 27.2 344.8 143 1732.9 290.9 119.8 727 261.3 209.8 143 224.7 275.5 248.1 435.2 387.3 101.7
BC‐30th (CFU/100 mL) 65 36.4 64.5 48.1 48 45.5 28.8 137.6 816.4 206.4 866.4 648.8 201.4 547.5 1046.2 461.1 920.8 461.1 307.6 328.2 980.4 1553.1 195.6
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
A.3 Storm Drain Outfall Monitoring Outfall monitoring, with a focus on dry weather screening, began in 2007. From 2007 on, monitoring generally occurred in some capacity on a weekly basis. All outfalls with known dry weather discharges were monitored to some degree. Data from outfall monitoring are shown below. Appendix A- 3: Storm drain outfall E. coli monitoring data collected by the City of Boulder. Storm Drain Outfall E. coli Concentrations (CFU/100 mL) Date 1 2 3 4 5 6 7 8 3/12/2007 4.1 2419.2 2419.2 3 261.3 14.6 3/21/2007 1 2419.2 1119.9 1 142.1 3/28/2007 12.1 920.8 980.4 248.9 461.1 4/4/2007 2 410.6 2419.2 9.8 1203.3 4/25/2007 344.8 461.1 8.6 24.6 1046.2 5/9/2007 387.3 1413.6 228.2 4.1 686.7 5/23/2007 3.1 45.7 9.8 42 6/20/2007 52.9 920.8 66.3 387.3 648.8 59.4 6/27/2007 228.2 488.4 191.8 129.1 9.7 10.9 261.3 7/2/2007 107.6 2419.2 328.2 248.1 2419.2 648.8 7/10/2007 135.4 187.2 7.4 98.7 488.4 65.7 7/17/2007 290.9 1413.6 96 25.6 63.3 686.7 7/25/2007 387.3 110.6 365.4 547.5 8/1/2007 29.5 48.7 88.4 920.8 8/8/2007 2419.2 1413.6 8/15/2007 108.6 344.8 8/22/2007 57.3 686.7 686.7 30.5 9/4/2007 2419.2 387.3 579.4 816.4 9/11/2007 133.4 2419.2 104.6 76.6 2419.2 1986.3 2419.2 10/9/2007 13.4 2419.2 2419.2 78.9 727 1732.9 2419.2 11/27/2007 35.4 2419.2 816.4 686.7 12/18/2007 75.9 2419.2 2419.2 31.3 1986.3 1/8/2008 13.4 2419.2 2419.2 9.7 166.9 1/15/2008 104.3 2419.2 2419.2 2419.2 920.8 290.9 1/22/2008 209.8 4838.4 4838.4 344.1 1/30/2008 68.3 6867 41 1374 161.6 2/5/2008 40.5 24192 1313 7270 143.9 2/13/2008 166.4 15531 10 402 1046.2 2/20/2008 110 24192 9804 53 145.5 461.1 2/26/2008 308.8 24192 24192 488.4 1565 2419.2 3/11/2008 56.5 1017 4.1 9804 111.8 74 2419.2 3/18/2008 1553.1 24192 16.8 2755 1732.9 776 3/25/2008 43.2 6893 93.3 880 770.1 4/1/2008 66.3 7701 3.1 272 980.4 4/8/2008 7.4 6867 1 12997 556 4/16/2008 1 265 4106 7.4 2419.2 307.6 4/24/2008 3.1 512 6867 1 359 613.1 4/29/2008 3.1 197 2851 6.3 1333 1413.6 5/6/2008 9.6 426 2014 16 1081 591 5/20/2008 3.1 24192 4.1 2014 21.8 2723 2419.2 62
9 980.4 2419.2 93.2 64.4 56.5 214.3 8.4 1119.9 18.7 770.1 2419.2 2419.2 2419.2 2419.2 2419.2 4838.4 9804 12033 1918 14136 2755 1046 776 3130 173 41 12997 5748 4569 4106 1162
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 5/27/2008 6/3/2008 6/10/2008 6/17/2008 6/24/2008 7/1/2008 7/8/2008 7/15/2008 7/22/2008 7/29/2008 8/5/2008 8/12/2008 8/19/2008 8/26/2008 9/2/2008 9/10/2008 9/16/2008 9/24/2008 9/30/2008 10/7/2008 10/14/2008 10/21/2008 10/28/2008 11/5/2008 11/12/2008 11/18/2008 11/25/2008 12/2/2008 12/10/2008 12/30/2008 1/6/2009 1/20/2009 1/28/2009 2/3/2009 2/17/2009 2/25/2009 3/11/2009 3/17/2009 3/25/2009 4/8/2009 4/15/2009 4/22/2009 4/29/2009 5/5/2009 5/13/2009 5/19/2009
63
1 2419.2 110.6 25.9 6.3 26.2 18.7 11 1 435.2 26.2 325.5 62 127.4 148.3 178.9 920.8 325.5 159.7 6.3 648.8 4.1 866.4 18.5 920.8 65.7 117.8 14.5 85.5 866.4
Storm Drain Outfall E. coli Concentrations (CFU/100 mL) 2 3 4 5 6 7 8 19863 2282 2602 784 6015 259 201.4 45.9 175 1918 1039 457 11 2143 480 9804 455 36.4 11199 420 723 259 30.7 4884 7701 142.1 12.1 3448 1515 10462 201.4 365.4 12033 2419.6 1439 108.6 231 75 620 42.8 15531 33.6 272.3 1631 862 1616 62 290.9 1872 36.9 6131 1046.2 2419.6 1211 459 2282 142.1 613.1 2419.6 805 1664 2481 24196 1333 275 24196 959 4884 1187 391 441 1012 9208 1017 882 10462 1019 3448 52 9.5 3255 31.8 384 345 9804 414 2187 19863 1732.9 3 5172 2419.6 48 24196 1450 2419.6 24196 613.1 7701 26.6 8664 2481 24196 5172 1732.9 24196 5172 4884 2419.6 2723 4352 3282 8664 1259 1670 4352 24196 1860 6131 199 17329 41 2098 4884 410 833 24196 134 1187 5247 14136 638 24196 24196 292 9208 3130 537 9804 2851 350 7701 285 5475 216 17329 3.1 480 7556 794 5247 960 41 1413.6 52 759 754 172.5 1986.3 579.4 32.3 2419.6 2419.6 1211 1112 706 2419.6 6.3 238.2 204.6 2419.6 15531 461.1 980.4 65.7 517.2
9 121 566 10 148 3076 1732.9 2419.6 112.6 24196 14136 1291 576 175 3873 1624 135 6867 4352 24196 12033 5172 3255 520 24196 17329 24196 24196 24196 24196 24196 11199 12997 9804 12997 24196 12997 24196 19863 135 10 1
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 5/26/2009 6/9/2009 6/17/2009 6/23/2009 6/30/2009 7/7/2009 7/21/2009 7/28/2009 8/4/2009 8/12/2009 8/25/2009 9/1/2009 9/9/2009 9/16/2009 9/23/2009 9/29/2009 10/14/2009 10/27/2009 11/18/2009 11/25/2009 12/15/2009 1/5/2010 1/13/2010 1/19/2010 1/26/2010 2/2/2010 2/17/2010 2/23/2010 3/2/2010 3/10/2010 3/17/2010 3/23/2010 3/31/2010 4/6/2010 4/21/2010 4/28/2010 5/6/2010 5/13/2010 5/19/2010 5/25/2010 6/1/2010 6/9/2010 6/15/2010 6/22/2010 6/30/2010 7/14/2010
64
1 1 1 7.5 21.6 2 19.9 2 24.6 27.5 4.1 18.7 24.7 5.2 91 249.5 111.2 1 261.3 18.7 13.2 20.1 46.4 6.3 3.1
Storm Drain Outfall E. coli Concentrations (CFU/100 mL) 2 3 4 5 6 7 8 2419.6 1732.9 2419.6 517.2 41 579.4 41 1354 175 3255 816.4 32.3 1046.2 613.1 325.5 32.7 2419.6 2419.6 461.1 2419.6 1 465 20 4611 5794 214.2 4611 2419.6 344.1 2419.6 1046.2 4884 980.4 3255 617 648.8 663 1046.2 365.4 2359 15531 866.4 2723 2419.6 1246 2419.6 6867 24196 1732.9 1467 1119.9 2419.6 1624 2419.6 1281 2419.6 86 2419.6 686.7 20.3 2419.6 261.3 2419.6 2419.6 2419.6 547.5 137.4 1732.9 38.3 579.4 2419.6 1413.6 387.3 461.1 4.1 2419.6 2419.6 2419.6 686.7 235.9 2419.6 155.3 517.2 145 117.8 2419.6 2419.6 191.8 2419.6 146.7 2419.6 52.9 5.2 55.4 191.8 8.5 33.6 579.4 150 16 24.6 6.3 1299.7 34.1 105 95.9 2419.6 2419.6 2419.6 52.1 8.4 1 36.4 2419.6 12.1 18.7 2419.6 2 27.5 88.4 3.1 27.2 2419.6 1732.9 42.2 365.4 27.2 46.4 1119.9
9 2419.6
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Date 7/20/2010 7/28/2010 8/3/2010 9/3/2010 9/8/2010 9/15/2010 9/22/2010 9/28/2010 10/8/2010 10/14/2010 10/27/2010
65
1 1732.9 4.1 11 11 235.9
Storm Drain Outfall E. coli Concentrations (CFU/100 mL) 2 3 4 5 6 7 2419.6 9.7 13.5 235.9 816.4 29.5 228.2 1732.9 1732.9 8.4 27.9 261.3 2419.6 1 161.6 2419.6 1986.3 1 686.7 2419.6 1986.3 39.5 1299.7 2419.6 2419.6 22.8 2419.6 2419.6 547.5 2419.6 2419.6 24.3 2419.6 1553.1 111.2 344.8 2419.6 240 1553.1 2419.6 344.8
8
9
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
Appendix B: TMDL Analyses The critical period and TMDL were identified and calculated based on weekly monitoring data collected by the City of Boulder (City) and Boulder County (Appendix A). The analyses below included water quality duration curves used to identify the critical period and bi-monthly geometric mean calculations used to support the degree of impairment and identify seasonal variation and the critical period.
B.1 Water Quality Duration Curves To evaluate annual loading, weekly data were plotted with corresponding flow conditions at the four weekly monitoring locations: BC-Eben, BC-13th, BC-CU and, BC-30th. The figures below categorizes E. coli concentrations, in “giga” (or billion) organisms into the corresponding five flow conditions, and includes a ‘Box-and Whisker’ plot to summarize data per flow condition. Box-and Whisker plots are a simple way to summarize the range of data, indicating the 25th and 75th percentile of data by the bottom and top of the box, the median by the band within the box, and the 10th and 90th percentile by the lower and upper tails, respectively. Graphs below include analysis of both (1) all data at each site and (2) data sampled during the recreation period of May-October. Hydrologic events are also colored red and indicate a potential runoff event or a significant increase in flow due to a flow diversion. Hydrologic events indicate a sudden increase in daily stream flow. These events may be associated with runoff events that wash pollutants into the stream, or flow diversions that have the potential to wash pollutants from the channel or stir stream-bed sediment. Hydrologic events are important to evaluate for the implementation of the TMDL. In general, the graphs below show the majority of exceedances occur during the Mid-Range and Dry-Conditions.
66
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
B.1.1 BC-Eben Few single samples collected at site BC-Eben (Boulder Creek and Eben G. Fine Park), above the impaired stretch, were found to be above the bi-monthly geometric mean standard of 126 CFU/100 mL. As shown in the figures below, the majority of those elevated concentrations occurred between May and October.
67
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
68
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
69
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
B.1.2 BC-13th Few single samples collected at site BC-13th were found to be above the bi-monthly geometric mean standard of 126 CFU/100 mL. As shown in the figures below, the majority of those elevated concentrations occurred between May and October.
70
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
71
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
72
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
B.1.3 BC-CU Numerous single samples collected at site BC-CU were found to exceed the bi-monthly geometric mean standard of 126 CFU/100 mL. As shown in the figures below, the majority of those elevated concentrations occurred between May and October, and most often occurred in Mid-Range to DryConditions. Additionally, multiple elevated concentrations during Moist Conditions were associated with a hydrologic event, potentially corresponding to either a rainfall event or an increase in flow due to a change in flow diversions.
73
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
74
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
75
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
B.1.4 BC-30th Numerous single samples collected at site BC-30th were found to exceed the bi-monthly geometric mean standard of 126 CFU/100 mL. As shown in the figures below, the majority of those elevated concentrations occurred between May and October, and most often occurred in Mid-Range to DryConditions. Additionally, multiple elevated concentrations during both Moist Conditions and Dry Conditions were associated with a hydrologic event, potentially corresponding to either a rainfall event or an increase in flow due to a change in flow diversions.
76
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
77
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
78
Total Maximum Daily Load for E. coli – Boulder Creek, Segment 2b 2011
B.2 Summary of Bi-Monthly Geometric Mean Evaluation A bi-monthly assessment included the calculation of annual bi-monthly loading and load reductions required to meet the standard. This analysis was supplemental to the establishment of the TMDL target based on data collected during recreational months. Appendix B- 1: Bi-monthly assessment of annual bi-monthly loading and load reductions required to meet the instream standard (126 CFU/100 mL). Year
Month
2004 June* July/Aug
Ave Flow (cfs)
Allowable load (CFU/day)
156
4.81E+11
Actual load at th BC‐13 (CFU/day) 1.01E+11
% Reduction Required
Actual load at BC‐CU (CFU/day)
% Reduction Required
3.91E+11
Actual load at th BC‐30 (CFU/day) 5.78E+11
% Reduction Required
56
1.74E+11
3.72E+11
53.23%
7.17E+11
75.73%
2.99E+11
41.81%
2005
July/Aug
59
1.82E+11
1.97E+11
7.61%
8.64E+11
78.94%
7.61E+11
76.08%
2006
May/Jun
116
3.58E+11
2.39E+11
1.57E+11
July/Aug
49
1.50E+11
1.16E+11
2.03E+11
26.11%
3.96E+11
62.12%
Sept/Oct
12
3.64E+10
5.54E+10
9.37E+10
61.15%
1.81E+11
79.89%
Nov/Dec
24
7.37E+10
2.51E+10
3.07E+10
7.92E+10
6.94%
Jan/Feb
28
8.55E+10
4.78E+09
2.16E+10
4.27E+10
Mar/April
28
8.74E+10
2.47E+10
5.42E+10
4.94E+10
May/June
133
4.11E+11
1.55E+11
1.37E+11
2.60E+11
July/Aug
34
1.04E+11
1.04E+11
Sept/Oct
13
4.16E+10
4.48E+10
Nov/Dec
21
6.35E+10
7.60E+09
3.65E+10
5.78E+10
Jan/Feb
16
4.82E+10
1.88E+10
2.57E+10
3.16E+10
Mar/April
7
2.21E+10
1.80E+09
9.95E+09
1.54E+10
May/June
99
3.04E+11
1.05E+11
July/Aug
57
1.75E+11
1.80E+11
Sept/Oct
9
2.85E+10
Nov/Dec
7
Jan/Feb
2007
2008
2009
2010
79
34.30%
7.14%
2.58E+11
1.79E+11
41.90%
3.87E+11
73.13%
1.30E+11
68.00%
2.08E+11
80.00%
1.41E+11 2.78%
1.98E+11
1.87E+11
6.42%
4.14E+11
57.73%
2.72E+10
4.88E+10
41.60%
1.04E+11
72.60%
2.14E+10
7.47E+09
1.88E+10
3.74E+10
42.78%
9
2.85E+10
5.89E+09
1.46E+10
2.11E+10
Mar/April
15
4.62E+10
4.06E+09
9.12E+09
2.25E+10
May/June
198
6.12E+11
2.26E+11
2.83E+11
3.13E+11
July/Aug
52
1.60E+11
1.29E+11
1.91E+11
16.23%
3.18E+11
49.69%
Sept/Oct
11
3.54E+10
4.15E+10
7.18E+10
50.70%
1.66E+11
78.67%
Nov/Dec
14
4.31E+10
1.04E+10
2.44E+10
4.47E+10
3.58%
Jan/Feb
6
1.74E+10
2.39E+09
5.62E+09
9.19E+09
Mar/April
35
1.08E+11
1.90E+10
5.26E+10
9.60E+10
May/June
238
7.34E+11
1.73E+11
1.75E+11
2.80E+11
July/Aug
43
1.32E+11
2.12E+11
37.74%
3.60E+11
63.33%
5.49E+11
75.96%
Sept/Oct
5
1.61E+10
2.55E+10
36.86%
2.93E+10
45.05%
6.70E+10
75.97%
14.70%
