GOVERNMENT OF PUDUCHERRY
Public Works Department
ENVIRONMENTAL IMPACT ASSESSMENT STUDY FOR PUDUCHERRY BEACH RESTORATION PROJECT
NATIONAL INSTITUTE OF OCEAN TECHNOLOGY MINISTRY OF EARTH SCIENCES, GOVT. OF INDIA CHENNAI -600 100 JUNE 2016
Public works department Puducherry
EIA studies for Puducherry beach Restoration project
EXECUTIVE SUMMARY Many beaches along East coast of India are subjected to erosion, which threatens habitat, property, public infrastructure, and the tourism industry. Loss of sand can be attributed natural changes (sea level rise, storms, and more recently persistent low pressures due to climate change) and man-made activities (harbors, jetties, seawalls, groins, dredging of tidal inlets and damning of rivers). Puducherry coast is not exceptional and after construction of Puducherry harbour, coast north of harbour is subjected to sea erosion. Initially, sand bypassing was carried out by harbour authorities to prevent downdrift erosion and to maintain channel free from siltation. Later, discontinuing of sand bypassing due to various technical reasons, lead to erosion on Puducherry city. UT Puducherry and Tamil Nadu State Government resorted to short term measures to protect the coast from erosion. Seawall of length 6 km was constructed by UT Puducherry, which covers city of Puducherry and the coastal stretch (2 km) from Sodhanaikuppam to Thanthriyankuppam was protected groin field combined with seawall by Tamil Nadu government. The erosion problem shifted further north, Chinnamudalaiyar Chavadi is experiencing increased erosion and many buildings were lost to sea. Highly eroding fishing hamlet, north of Chinnamudalaiyar Chavadi, and Chinnakalapettai village in UT Puducherry were also protected by seawall. As on date, 8 km length of the coast was protected by seawall and groin field along Puducherry coast by UT Puducherry and Tamil Nadu Government. The above solutions could protect the coast under threat but the authorities and stake holders need an integrated long-term solution for protection of coast and restoration of natural beach. Since, the available information on Puducherry coast is not sufficient for working out suitable strategies; NIOT was consulted by both UT Puducherry and Tamil Nadu government to work out long term / short term strategies for management of coast from erosion and impact of cyclones. NIOT has initiated studies to evolve strategies for protection of Puducherry coast under the project ―Demonstration of Shore Protection Measures through Pilot project", with financial support from Ministry of Earth Sciences. NIOT has taken up task of developing strategies for protection of Puducherry coast with objectives: 1) Assessment of status of existing protection measures and its performance 2) To Understanding the processes responsible for
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Public works department Puducherry
shoreline
changes
EIA studies for Puducherry beach Restoration project
through
monitoring
waves,
tides,
currents,
sediment
characteristics and coastal morphology 3) Analysis of long/short term trends of shoreline along Puducherry coast and 4) Development of shore protection measures through numerical models. The first three activities were completed and documented. The final report with strategies for protection of coast is arrived based on the discussion with the governments of Tamil Nadu and UT Puducherry and stake holders and is attached in annexure. The various dynamical aspects of coast (water level variations, currents & circulation, tides, waves, bathymetric variations, sediment transport, shoreline changes etc) is studied to develop hindcast, nowcast and forecast models on shoreline changes in priority areas for identification of vulnerable areas of erosion/ accretion to arrive at remedial measures for protection of coastline from natural and human perturbations. The study area with coastline length of 18 km was divided into four distinct zones, namely 1) Puducherry harbour and adjoining areas, 2 km 2) Puducherry city, protected by seawall, 6 km 3) Groin field, 2 km and 4) Open coast, 8 km. The shoreline changes in these four zones were analyzed using remote sensing data and field measurements. The result indicate that the average rate of erosion and accretion is 4m/yr and 5m/yr respectively and the coast needs immediate attention for its protection from natural causes or man-made activities. The estimated rate of net drift would be in the order of 0.28 – 0.30 million cum, which needs to be confirmed by detailed shoreline monitoring. Coastal processes responsible for shoreline changes were monitored from 2012, where data on winds, waves, tides, currents, sediments, bathymetry etc were collected between Puducherry Port and Kalapettai village, covering a coastline of 18 km. Seasonal variations on water levels, wave climate, currents and circulation, sediment transport, shoreline changes etc were studied. The measurements made indicated that the tide propagates from south to north. Currents measured upto a depth of 20 m were found to be seasonal, northerly during SW monsoon and southerly during NE monsoon. The average currents during SW and NE monsoon would be 0.3 m/s and 0.5 m/s. The nearshore currents generated by waves follow pattern of coastal currents in Tamil Nadu coast, which is added advantage in 2
Public works department Puducherry
EIA studies for Puducherry beach Restoration project
developing shore protection measures. Wave climate indicate that 70% of the waves approach the coast from SE direction and the remaining 30% from NE direction. Puducherry, known for tourism/recreation, has lost its natural beach due to natural causes or man-made activities. The proposed eco-friendly solution has been arrived based on Detailed Hydrodynamic and Coastal process studies and the solution could be implemented for restoration of beach and ecological functions of the coast. The proposed eco-friendly solution consists of one nearshore reef (at North side), one offshore reef (a South side) and sand nourishment (between northern and southern reef). A northern nearshore wedge reef has been designed for the north of the city foreshore and an offshore reef has been designed for the south of the City foreshore. The goal of the submerged/ northern reef was to provide a mild barrier to sediment losses, thus enabling sand to move naturally to the north while slowing the losses of sand from the City foreshore.The goal of the southern reef design was to create a salient or tombolo which will hold the sand on the city beaches which also acts to prevent sand losses from the City back to the Port. The sand salient/tombolo would provide many public benefits, including a wider beach, a safer beach protected from waves, no construction materials near the shore and minor negative visual impact. The salient will allow the rock seawall to be buried and eventually removed once public confidence is gained. In addition, the sand held in the tombolo could be moved from time to time by mechanical means (normally an excavator or bulldozer) to re-align and re-fill the beach between the two structures.
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Public works department Puducherry
EIA studies for Puducherry beach Restoration project
Table of contents EXECUTIVE SUMMARY
1 7
CHAPTER 1
INTRODUCTION
1.1 GENERAL
7
1.2. PROJECT DESCRIPTION
8
1.3 NEED FOR THE STUDY
9
1.4 OBJECTIVES OF THE EIA STUDY
10 11
CHAPTER 2 2.1 GENERAL
ENVIRONMENTAL BASELINE STATUS
2.2 METEOROLOGY
11 12
2.2.1 Climate
12
2.2.2 Temperature
12
2.2.3 Rainfall
12
2.2.4 Wind
13
2.2.5 Cyclones
13
2.2.6 Rivers
14
2.3 BATHYMETRY
15
2.4 OCEANOGRAPHY
16
2.4.1 Tides and Tidal Analysis
16
2.4.2 Waves
17
2.4.3 Coastal Currents
19
2.4.4 Nearshore currents
20
2.4.5 Suspended sediment characteristics
21
2.4.6 Sediments
23
2.5 COASTAL WATER QUALITY PARAMETERS
26
2.6 BIOLOGICAL PARAMETERS
27
2.6.1 Microbiological parameters
27
2.6.2 Phytoplankton
28
2.6.3 Zooplankton
29
2.6.4 Benthic Fauna
31
2.6.5 Ecological status of the project location
31
2.7 FAUNAL BIODIVERSITY OF PUDUCHERRY
31
2.8 LAND USE PATTERN
32
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2.9 SOCIO-ECONOMIC ASPECT CHAPTER 3
IMPACTS AND MITIGATION MEASURES
32 34
3.1 General
34
3.2 IMPACT ON PHYSICAL ENVIRONMENT
35
3.2.1 Air quality
35
3.2.2 Noise
36
3.2.3 Currents
37
3.2.4 Sediment quality and Quantity
38
3.2.5 Water quality 3.3 IMPACT ON BIOLOGICAL ENVIRONMENT
40 42
3.3.1 Marine biota and habitat
42
3.3.2 Terrestrial biota and habitat
45
3.3.3 Waste management
45
3.4 IMPACT ON SOCIO_ECONOMIC ENVIRONMENT
46
3.4.1 Fishing Activity
46
3.4.2 Navigation
47
3.4.3 Local Land traffic
47
3.4.4 Tourism
48
3.4.5 Safety and human health
48
3.4.6 Livelihoods
49
3.4.7 Accidents and malfunctions
49
CHAPTER- 4 ENVIRONMENTAL MANAGEMENT AND MONITORING PROGRAMME
51
4.1 THE NEED
51
4.2 IMPACTS TO BE MITIGATED
51
4.3 IMPLEMENTATION ARRANGEMENTS ANDRESPONSIBILITIES
51
4.4 ENVIRONMENTAL MANAGEMENT PLAN
52
4.5 MONITORING PROGRAM
53
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EIA studies for Puducherry beach Restoration project
List of Figures Fig 1
Location map of Puducherry
8
Fig 2
Network Connectivity map
9
Fig 3
Location map with buffer of 10km radius
11
Fig 4
Annual wind rose at Puducherry
13
Fig 5
Thane and Nilam cyclone
14
Fig 6
River map of Puducherry
15
Fig 7
Bathymetry map of Puducherry
16
Fig 8
Water level variations
17
Fig 9
Monthly wave climate measured using wave rider buoy at south of Puducherry port at 30 m water depth
18
Fig 10
Wave rose plots during South west monsoon
19
Fig 11
Wave rose plots during North east monsoon
19
Fig 12
Current rose plots during South west monsoon
20
Fig 13
Coastal currents along Puducherry coast, NE monsoon
20
Fig 14
Observed nearshore currents near Gandhi statue
21
Fig 15
Water Sample location and Distribution of Suspended Sediments during NE monsoon period
22
Fig 16
Sediment sampling locations and median grain size
23
Fig 17
Land use map of Puducherry
32
List of Tables Table 1
Sediment Quality 1
24
Table 2
Sediment Quality 2
25
Table 3
Sediment Quality 3
26
Table 4
27
Table 5
Water quality parameters of Puducherry coastal waters (December 2015) Microbial loads in coastal water and sediment at Puducherry coast
Table 6
Phytoplankton densities found in the coastal waters of Puducherry
29
28
Table 7 Zooplankton compositions in the coastal waters of Puducherry
30
Table 8 Summary of the potential environmental impacts due to the Puducherry Beach Restoration Project and the mitigation measures
55
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Public works department Puducherry
EIA studies for Puducherry beach Restoration project
CHAPTER 1 INTRODUCTION 1.1.
GENERAL
The coastline of Puducherry and the neighboring Tamil Nadu coastline is undergoing continuous changes by natural geological agents like wind, wave, tide & currents. Along with these agents, increased urbanized coastal structures along the Puducherry coast have amplified the complexity of the denudation process. Though the structures like groins, seawalls etc have been built to protect the Puducherry coast from coastal erosion and to improve the social economy of the Union Territory, it has been observed that these structures act as an obstruction for the natural littoral drift which have made the sedimentation process more complex. The impacts of these changes started at the time of construction phase of the coastal structures (seawall, jetty, breakwater and Groins) and further extending its effects till today as a continuous process to attain its equilibrium by natural processes. ESSO-NIOT was consulted by both Puducherry and Tamil Nadu Governments to work out long term strategies for restoration of Puducherry coast. ESSO-NIOT has recommended beach nourishment on the north of Puducherry harbor based on the field studies and numerical modeling. Puducherry Government has implemented the beach nourishment scheme, which showed a gain of beach to an extent of 60m. The newly formed beach received positive response from local population. Seeing the success of proposed soft solution, Puducherry Government requested ESSO-NIOT to restore the lost beach near Gandhi Statue of Puducherry. Regional Shoreline management plan for entire Puducherry coast was completed and submitted to Puducherry Government. Based on the learning from experimental beach nourishment, numerical modeling and process based measurements one nearshore reef, one offshore reef and beach nourishment is proposed to restore the lost beach along Puducherry.
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1.2
EIA studies for Puducherry beach Restoration project
PROJECT DESCRIPTION
Puducherry city is the capital of the Union Territory of Puducherry with its main economic activities being small scale industries and higher education. It was the capital of former French India and was also held at times by the Dutch and British. In 1962 it became part of the Union Territory of Puducherry. Puducherry region is situated on the Coromandel Coast between 11°45’ and 12°03’ N latitudes and 79°37’ and 79°53’ E longitudes with an area of 293 km 2 as shown in Figure 1. The existing port of Puducherry (11° 56’ N latitude and 79° 50’ E longitude) is situated between two major ports namely, Chennai and Tuticorin. The port is suitable for lightrage operations during fair weather months (February to September). The coast is of open type with estuaries. Though the regional coastline appears to be almost straight, it is a part of a larger concave coast. The study area is well connected by roadways and railways and the network connectivity map is shown in Figure 2.
Fig 1 Location map of Puducherry
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Public works department Puducherry
EIA studies for Puducherry beach Restoration project
Fig 2 Network Connectivity map
1.3
NEED FOR THE STUDY
Significant erosion has occurred in Puducherry over the last 2 decades, which has threatened development and resulted in substantial protection works. The causes of erosion remain unaddressed by the present rock wall solution. The beautiful historical beach in front of the City has disappeared, leaving only the rock wall which prevents access to the seaside, and is out of harmony with the city’s tourism aspirations. Restoration of the beaches is a top priority for the Puducherry government. The study aims to recreate Puducherry beach near the statue of Gandhi using safe, secure coastal protection methods that allow the beach to be as stable as possible in all weather conditions, with allowances for Global Sea Level rise and cyclones.
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1.4
EIA studies for Puducherry beach Restoration project
OBJECTIVES OF THE EIA STUDY
The main objective of the EIA study is to assess the positive as well as negative environmental impacts likely to accrue as a result of the construction of the proposed project. After identifying the negative impacts, a suitable management plan is to be suggested to ameliorate the adverse impacts. An Environmental Monitoring Programme is also suggested for the parameters which needs frequent observations during project operation phase. Thus, the key objectives of the EIA study are to: Ensure sustainable development with minimum environmental degradation; To prevent long-term environmental negative impacts by incorporating a suitable Environmental Management Plan (EMP); Suggest an Environmental Monitoring Programme, and Estimate budgetary requirements for implementation of the EMP and Environmental Monitoring Programme.
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EIA studies for Puducherry beach Restoration project
CHAPTER – 2 ENVIRONMENTAL BASELINE STATUS 2.1 GENERAL The assessment of baseline environmental setting is an essential component of any EIA study. Assessment of environmental impacts due to the proposed construction of offshore reef along with beach nourishment requires a comprehensive and scientific consideration of various environmental aspects. As a part of the EIA study, a large quantum of related secondary data as available with various departments was collected. Field surveys were conducted for primary data generation on various aspects including water levels, waves, wind, sediments etc. The study area for the EIA study lies in a 10 km radius with the proposed project site as the centre (Figure 3).
Fig 3 Location map with buffer of 10km radius The impacts likely to accrue as a result of proposed activity are expected to occur more on water front i.e. on marine environment. Thus, as a part of the EIA study, specific emphasis has been accorded to marine environment. As a part of the EIA study, the baseline status has been ascertained for the following aspects: 11
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EIA studies for Puducherry beach Restoration project
Meteorology
Oceanography
Landuse pattern
Marine Water quality
Marine Sediment quality
Marine Ecology
Demography and Socio-economics
2.2 METEOROLOGY 2.2.1 Climate Puducherry has hot and humid summer, cool winter and two distinct monsoon seasons (south-westerly and north-easterly). Summer (February) South-West Monsoon (March-September) North-East Monsoon (October to December) Winter (January) 2.2.2 Temperature Climate at the Puducherry is hot and humid. The maximum and minimum temperature recorded at the Puducherry is 35.70 C in the month of June and 20.90 C in January respectively. The average maximum temperature is 31.5 0 C and average minimum temperature is 23.90 C. 2.2.3 Rainfall The rainfall in the Puducherry is influenced by the Southwest and Northeast monsoon. Wet season persists mainly during the north east monsoon period between October and December. The average rainfall received in northeast monsoon is about 1300 mm. Southwest monsoon starts in the month of March and rains still September.
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EIA studies for Puducherry beach Restoration project
2.2.4 Wind During south west monsoon between March and September, the wind blows predominantly from the south. Wind first blows from the coast then changes to northerly direction in December and gradually decreases in force during January and February.
Fig 4 Annual wind rose at Puducherry The direction also changes from northeast to east. Northeast monsoon winds are usually stronger than the southeast monsoon winds. All through the year, wind speed is between 0.2 and 5.1 m/s. 2.2.5 Cyclones Puducherry, being a part of the Indian subcontinent, experiences tropical cyclones which originate from the depression generated in the Bay of Bengal during the northeast monsoon season (October to December). It experiences an average of 2 3 cyclones annually.
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EIA studies for Puducherry beach Restoration project
Fig 5 Thane and Nilam cyclone Highest wind speed of 189 km/hr and the lowest wind speed of 83 km/hr have crossed the Puducherry coast in the past. Cyclone data over the Bay of Bengal since 1891 indicates that on average, a moderate to severe cyclone hits Tamil Nadu and Puducherry coasts every two years. During the cyclone period the winds are around 100 km/hr (Nisha 2008) and 140 km/hr (Thane 2011).The cyclones that hits Puducherry in 2011 & 2012 and the track of the cyclone is explained in the figure 5. 2.2.6 Rivers There are two major rivers draining this region 1) the Gingee River, which traverses the region diagonally from north-west to south-east and 2) the Ponnaiyar (Penniyar) river, which forms the southern border of the region. The river Gingee also known as the Varahanadi or Sankaraparani which has its source in the hills of Malayanur of Villupuram district, Tamil Nadu has a course of 34 km in this region before it confluences with the Bay of Bengal. The river Ponnaiyar originates from the hills of Karnataka and enters the Puducherry region after flowing through the districts of Dharmapuri, Salem, Vellore and Cuddalore of Tamil Nadu.
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EIA studies for Puducherry beach Restoration project
Fig 6 River map of Puducherry 2.3.
BATHYMETRY
Detailed bathymetric surveys were undertaken by NIOT as part of the present study during February 2015. A boat-mounted echo-sounder with heave compensation and a Differential GPS was used. The survey extended 5 km each side of the Gandhi statue and out to 10 m depth. A Real-Time Kinematic Global Positioning System (RTK-GPS) was used for the topographic surveys. The survey data provide near-continuous data from about 6 m above the Chart Datum to 10 m water depth. All the survey data were processed by NIOT to Chart Datum and the data is available in electronic x,y,z form. The bathymetry map is shown in Figure 7.
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EIA studies for Puducherry beach Restoration project
Fig 7 Bathymetry map of Puducherry 2.4
OCEANOGRAPHY
2.4.1 Tides and Tidal Analysis Tides in Bay of Bengal are semidiurnal in nature as the sea level reaches its highest level in November and lowest in March along the south east coast of India, the tidal range in March varied between 0.5 m (neap tides) and 0.7 m (spring tides) whereas in November the range varied between 1.3 -1.0 m. The design water levels for Puducherry are given below: Mean High Water Spring
:
1.3 m
Mean High Water Neap
:
0.8 m
Mean Sea Level
:
0.6 m
Mean Low Water Neap
:
0.5 m
Mean Low Water Spring
:
0.2 m
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EIA studies for Puducherry beach Restoration project
1.4
Water level (m)
1.2 1 0.8 0.6 0.4 0.2 0 26/01
31/01
05/02
10/02
15/02
20/02
25/02
02/03
Date period 2015
Fig 8 Water level variations 2.4.2 Waves The Bay of Bengal experiences three different weather conditions normally fair, southwest monsoon and northeast monsoon. During fair weather season, the sea surface is usually calm and the coastal region is dominated by swells and to a smaller extent by locally generated waves, during this period beach building takes place. Extreme weather events are common during southwest monsoon (JuneSeptember) as well as northeast monsoon (November-January) seasons. SW monsoon is dominated by northerly drift and NE monsoon by southerly drift. Offshore waves Wave measurements were carried out off Puducherry coast by INCOIS, MoES during July 2009 to June 2010 using a Datawell directional waverider buoy in 30 m water depth. Frequency distribution of wave heights show that the waves are approaching from southeast by direction for about 9 months in a year and approaches from east direction for the rest of the year (Figure 9). The wave heights ranges from 0.4 m to 1.2 m during southwest monsoon with SE direction.
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EIA studies for Puducherry beach Restoration project
Fig 9 Monthly wave climate measured using wave rider buoy at south of Puducherry port at 30 m water depth Nearshore waves The characteristics of waves during northeast monsoon (December 2015) off Puducherry coast are measured and analysed. The significant wave height during the NE monsoon period ranges from 0.3 m to 1.50 m with an average value of 0.60 m. Frequency distributions of wave heights show that almost 50% of the significant wave heights are in the range 0.5 - 0.7 m indicating low wave activity during the observation period. The wave rose diagram shows that the wave approaches as the Puducherry from southeast with maximum significant wave height of 1.2 m. The wave periods ranges between 3 - 18 sec at all the locations during northeast monsoon. The frequency distribution shows that more than 50% of the waves have T z in the range of 8-10 sec and 15% of the waves are above 10 s during the deployment period. The wave rose
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EIA studies for Puducherry beach Restoration project
plots of current magnitude and direction for South west monsoon and north east monsoon are shown in Figure 10 and Figure 11 respectively.
Gandhi statue
Pier
Fig 10 Wave rose plots during South west monsoon Gandhi statue
Light House
Fig 11 Wave rose plots during North east monsoon 2.4.3 Coastal Currents Coastal currents are responsible for large scale sediment transport along the open coast. Coastal currents are driven mainly by tide, wind and also by open ocean circulations. Because of tides or local topography, coastal currents are generally irregular. Shankar et al (1996) have studied East Indian Coastal Currents (EICC) and reported that EICC reverses direction twice a year, flowing north-eastward from February till September with a strong peak in March-April and south-westward from October to January with strongest in November. Major diving mechanisms of its variability was attributed to wind in the Bay of Bengal, which reverses with monsoon. It has also been reported that periods of peak monsoon do not coincide with times of maximum current speed.
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EIA studies for Puducherry beach Restoration project
In order to study the variation of coastal currents along Puducherry coast, current measurements were carried out Off Puducherry using the RCM 9 self-recording current meters (Anderaa Data Instruments). Current data was collected at every 10 minutes interval for a period of 15 days for two seasons. The rose plots of current magnitude and direction for South west monsoon and north east monsoon are shown in Figure 12 and Figure 13 respectively.
Fig 12 Current rose plots during South west monsoon
Fig 13 Coastal currents along Puducherry coast, NE monsoon 2.4.4 Nearshore Currents Beach changes result from sediment transport which is controlled by several factors; Near shore currents play major role in driving sediment transport. Nearshore 20
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currents are driven by waves, they are modified at near coast. In order to analyse the along shore variability, nearshore currents (wave induced), were measured by Acoustic Doppler Velocimeter (ADV) with a sampling frequency of 2 Hz at a measuring interval of 20 minutes. The pressure and velocity sensors were located at a distance of 1.1 m from sea bed to measure pressure and wave orbital velocities. The direction of nearshore currents near Gandhi statue follow coastal currents which is southerly during northeast monsoon (Figure 14).
Fig 14 Observed nearshore currents near Gandhi statue The magnitude of nearshore current at S3 is 11cm/s and 13 cm/s at S5. The coastal configuration play dominant role in direction, which is evident from figure, the station S3 is oriented at 100 with respect to north and station S5 parallel to the coast (Figure 46). The intensity of longshore currents is much more than that of on-offshore component except the phase of the sudden bursts of offshore-going currents. 2.4.5 Suspended Sediment Characteristics Knowledge of dynamics of suspended sediments in coastal areas is of great importance in determining the fate and transport of suspended sediment and sediment adherent concentration. SSC in coastal waters is influenced by coastal
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EIA studies for Puducherry beach Restoration project
currents in intermediate water (8m - 20m) and nearshore circulation in littoral zones 0m to 6m. Suspended sediment concentration was monitored from 40 stations along the Puducherry coast (Figure 15). During the survey, samples were collected from Puducherry port to north of Kalapettai village using water sampler from 4 discrete depths (4 to 15 m depth). Relatively high concentration of suspended sediment (40 56 mg/l) was observed along the beach stations and reduced concentrations (24 mg/l ) were observed in the region beyond 13 m water depth (Figure 15).
Fig 15 Water Sample location and Distribution of Suspended Sediments during NE monsoon period
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EIA studies for Puducherry beach Restoration project
2.4.6 Sediments The sediment samples from various locations around the project site were collected and analyzed for grain size (Figure 16) .
Fig 16 Sediment sampling locations and median grain size The sediment samples were also analysed for heavy metals and the results are summarized in Table(1-3). Mercury and cadmium were below detectable limits (BDL) in all the samples analysed. The values of arsenic and lead are comparatively within the permissible range. The higher values of Oil & Grease in sediments from locations near the harbor are noteworthy.
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Table 1 Sediment Quality Parameters
Protocol
Unit
Sam1
Sam 2
Sam 3
Sam 4
Sam 5
Sam 6
Sam 7
Sam t 8
Sam 9
Sam 10
pH @ 25°C
IS 2720 (part:26):1987 Reaff:2007
-
7.57
8.5
7.86
7.65
7.38
7.87
8.32
7.04
7.8
7.9
Heavy metal 1.78 1.35
0.912
1.4
0.81
1.03
1.52
0.67
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
5337
167
5014
5383
4807
Arsenic as As Cadmium as Cd Mercury as Hg
EPA 200.8
mg/Kg
2.15
0.95
EPA 200.8
mg/Kg
EPA 200.8
mg/Kg
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
Chloride as Cl Oil & Grease @ 105°C Sulphate as SO4
APHA 22nd EDI:2012 EPA 9071B
mg/Kg
10121
147
mg/Kg
209
106
10
426
BDL (DL:1.0)
386
BDL (DL:1.0)
76
BDL (DL:1.0)
626
IS 2720 (Part27):1977 Reaff:2006 Walkley & Black Method
mg/Kg
2063
580
1082
848
918
150
620
1038
849
784
%
0.94
0.01
0.14
BDL (DL:1.0)
0.05
0.11
0.01
0.07
0.14
0.05
By GCFID/NWHCID Method
mg/Kg
4339
5051
1309
531
BDL (DL:1.0)
292
BDL (DL:1.0)
796
BDL (DL:1.0)
2396
Total Organic Matter TPH
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
Chemical Parameters 5680 4408 5183
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EIA studies for Puducherry beach Restoration project
Table 2 Sediment Quality Parameters
pH @ 25°C
Protocol
Unit
Sam 11
Sam 12
Sam 13
Sam 14
Sam 15
Sam 16
Sam 17
Sam 18
Sam 19
Sam 20
IS 2720 (part:26):1987 Reaff:2007
-
7.67
8.39
7.59
8.47
7.74
7.67
6.58
8.97
7.57
7.84
Heavy metal Arsenic as As
EPA 200.8
mg/Kg
0.73
0.92
0.91
1.19
1.06
0.86
1.01
0.986
0.937
1
Cadmium as Cd
EPA 200.8
mg/Kg
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
Mercury as Hg
EPA 200.8
mg/Kg
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
BDL (DL:0.1)
Chemical Parameters Chloride as Cl Oil & Grease @ 105°C Sulphate as SO4
Total Organic Matter TPH
APHA 22nd EDI:2012 EPA 9071B
mg/Kg
4856
90
189
71
160
7036
4298
89
5300
3777
mg/Kg
BDL (DL:1.0)
BDL (DL:1.0)
39.98
5
19.2
90
230
69
55.15
386
IS 2720 (Part27):1977 Reaff:2006 Walkley & Black Method
mg/Kg
790
144
259
534
234
1003
1148
106
942
1076
%
0.09
0.03
0.07
0.1
0.09
0.12
0.12
0.12
0.08
0.07
By GCFID/NWHCID Method
mg/Kg
BDL(DL:1.0)
14674
7273
10035
3888
10040
14403
20551
16212
112077
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Table 3 Sediment Quality Parameters pH @ 25°C
Protocol
Unit
Sam 21
Sam 22
Sam 23
-
7.8
7.52
7.8
1.62
1.12
2.18
BDL (DL:0.1) BDL (DL:0.1)
BDL (DL:0.1) BDL (DL:0.1)
IS 2720 (part:26):1987 Reaff:2007
Heavy metal Arsenic as As
EPA 200.8
mg/Kg
Cadmium as Cd
EPA 200.8
mg/Kg
Mercury as Hg
EPA 200.8
BDL (DL:0.1) mg/Kg BDL (DL:0.1) Chemical Parameters
Chloride as Cl
APHA 22nd EDI:2012
mg/Kg
5477
4291
9492
Oil & Grease @ 105°C Sulphate as SO4
EPA 9071B
mg/Kg
708
208
270
IS 2720 (Part-27):1977 Reaff:2006 Walkley & Black Method
mg/Kg
774
705
1728
%
0.24
0.12
0.68
By GC-FID/NWHCID Method
mg/Kg
12528
BDL(DL:1.0)
3451
Total Organic Matter TPH
2.5
COASTAL WATER QUALITY PARAMETERS
Coastal water quality parameters around the proposed sites (Five stations) at Puducherry are provided in table 4. Surface seawater temperature ranged from 28.5 to 29.2ºC in the coastal waters at Puducherry which was normal temperature range observed for the tropical waters. Salinity values recorded ranged from 32.0 to 33.8 PSU around the proposed sites at Puducherry. Dissolved oxygen (DO) values ranged from 4.38 to 5.72 mg/L whereas Biochemical Oxygen Demand (BOD) values ranged from 0.25 to 3.20 mg/L in the coastal waters. The BOD value at station PYD1 was comparatively high which could be attributed to anthropogenic influence in the surrounding environment. Total suspended solids values were from 5.5 to 12.1 mg/L. Nutrients concentrations in all the stations were within the acceptable range for the coastal waters. In general, all water quality parameters were well within the natural variations and characteristics of coastal waters. 26
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Table- 4. Water quality parameters of Puducherry coastal waters (December 2015) S.No. Parameters
Stations PYL 1
PYG 1
PYG 2
PYD 1
PYL 2
1.
Depth (m)
4.5
5.0
9
2.5
10
2.
Transparency (m)
1.6
1.85
2
1.25
4.25
3.
Atomspheric Temperature(°C)
31.5
34.5
33.5
32.2
35.4
4.
Surface Seawater Temperature (°C)
28.6
28.5
28.6
29.2
28.5
5.
TSS (mg/L)
8.8
10.8
5.5
12.1
6.4
6.
Salinity (PSU)
33.5
33.0
33.8
32.0
33.2
7.
pH
8.05
8.07
8.09
7.99
8.05
8.
Dissolved Oxygen (mg/L)
4.71
4.38
5.72
4.63
4.88
9.
BOD (mg/L)
1.43
2.78
2.19
3.20
0.25
10. Chlorophyll ‘a’(mg/m3)
1.16
1.06
1.24
1.05
1.13
11. Phaeophytin (mg/m3)
0.76
0.89
0.76
0.59
0.85
12. Nitrite (µmol/L)
0.43
0.45
0.41
0.97
0.39
13. Nitrate (µmol/L)
0.95
1.05
1.01
2.11
1.07
14. Ammonia (µmol/L)
0.15
1.00
0.55
1.60
0.45
15. Total Nitrogen (µmol/L)
3.93
4.80
3.93
5.24
4.37
16. Inorganic phosphate (µmol/L)
0.51
1.07
1.50
1.59
0.77
17. Total phosphorus (µmol/L)
0.54
1.17
1.53
2.61
0.99
18. Silicate (µmol/L)
1.15
1.25
0.50
3.30
1.85
PYL1& PYL2 - Samples near Light house PYG1 & PYG2- Samples near Gandhi statue PYD1 - Sample near dredging location
2.6
BIOLOGICAL PARAMETERS
2.6.1 Microbiological parameters The fecal coliform (Enterococci) count was high in water sample collected at PYD1, and the concentration was 110 × 101 CFU/100mL. In all other stations the FC was in the range of 2 to 43 × 101 CFU/100mL. However, the FC level was very less in all the sediment samples tested. Escherichia coli were found to be high in water sample collected at PYD1, and the concentration was 44 × 101 CFU/100mL. Interestingly,
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the EC was not detected in all the sediment samples analyzed. Total viable bacterial count didn’t deviate much in all water samples and normal trend was observed. TVC showed two fold increases in its concentration in sediment samples collected at PYD1. Total coliform count was found to be high in the sediments collected at PYD1. Interestingly Vibrio cholera was found to be high in all the sediment samples tested compared to the water samples. Table -5. Microbial loads in coastal water and sediment at Puducherry coast Parameters
PYL 1
PYG 1
PYG 2
PYD 1
PYL 2
TV (CFU/mL)
42 × 107
32 × 107
62 × 107
65 × 107
44 × 107
TC (CFU/100 mL)
133 × 102
84 × 102
94 × 102
162 × 102
68 × 102
FC (CFU/100 mL)
29 × 101
43 × 101
2 × 101
110 × 101
26 × 101
EC (CFU/100 mL)
1 × 101
18 × 101
2 × 102
44 × 101
ND
VC (CFU/100 mL)
112 × 102
66 × 102
78 × 102
86 × 102
24 × 102
TV (CFU/g)
34 × 108
113 × 107
-
226 × 108
25 ×107
TC (CFU/g)
112 × 103
139 × 103
-
149 × 104
92 × 103
FC (CFU/g)
6 × 101
7 × 101
-
12 × 101
5 × 101
EC (CFU/g)
ND
ND
-
ND
ND
VC (CFU/g)
47 × 103
116 × 103
-
81 × 103
77 × 103
Seawater Samples
Sediment Samples
(CFU: Colony Forming Unit; ND: Not Detected) 2.6.2 Phytoplankton A significant difference was observed in species diversity and abundance among the stations at Puducherry. Taxonomic identification indicated the presence of 23 species of phytoplankton, including 19 species of diatoms, 3 species of dinoflagellates and 1 cyanobacterium species. The phytoplankton population ranged from 6574 Nos/L to 26887 Nos./L. The density was inclusive of the dinoflagellate, Noctiluca sp. in high densities observed in all the stations, with the highest intensity at station PYG-1 (17547 Nos./L). The phytoplankton species composition is presented in the table 5.
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Table-6 Phytoplankton densities found in the coastal waters of Puducherry PHYTOPLANKTON S.No.
SPECIES
PHYTOPLANKTON (Nos./L) PYL-1
PYG-1
PYG-2
PYD-1
PYL-2
DIATOM 1 Bacillaria sp.
56
106
53
50
41
1240
1475
1239
8100
732
236
319
212
162
266
4 Diatoma sp.
64
77
106
18
71
5 Fragillaria sp.
84
106
136
58
106
6 Guinardia sp.
72
83
71
65
159
7 Leptocylindrus sp.
172
372
242
180
242
8 Lithodesmium sp.
100
295
77
0
124
9 Navicula sp.
144
289
230
162
94
10 Nitzschia sp.
268
425
319
540
319
11 Odontella sp.
128
136
124
50
136
12 Pleurosigma sp.
236
266
212
180
289
13 Rhizosolenia sp.
288
319
319
900
478
14 Skeletonemacostatum
380
767
283
810
448
15 Planktoniellasol
48
94
71
90
30
16 Thalassiosira sp.
920
2071
797
1620
797
52
71
83
25
71
172
230
136
162
319
28
94
30
112
71
1 Ceratium sp.
2400
2065
767
180
820
2 Noctiluca sp.
9602
17547
6807
1034
908
600
1180
690
194
832
2 Coscinodiscus sp. 3 Cyclotella sp.
17 Thalassionema sp. 18 Thalassiothrix sp. 19 Triceratium sp. DINOFLAGELLATE
3 Prorocentrum sp.
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CYANOPHYCEA 1 Oscillatoria sp. TOTAL Nos./L
64
83
77
32
77
16058
26887
11787
6574
6655
2.6.3 Zooplankton There was a significant difference observed in species diversity and abundance among the stations at Puducherry. The species were segregated into 19 groups coming under 8 different phyla along with larval stages and fish eggs. The zooplankton population ranged from 12933 Nos./100m 3 (PYL-2) to 134525 Nos./100m3 (PYG-1).Copepod was the most dominant group in all the stations, with the maximum incidence (103610 Nos./100m3) at PYG-1station.The zooplankton species composition in each of the stations is presented in the Table 6. The zooplankton samples in all the stations were interfered by the dinoflagellate, Noctiluca sp. bloom. Table - 7. Zooplankton compositions in the coastal waters of Puducherry S.No
Phylum
Groups
PYL-1
PYG-1
PYG-2
PYD-1
PYL-2
Sarcomastigophora Foraminifera
2166
4178
520
144
550
3610
5849
520
431
275
12273
0
0
0
4128
2166
0
0
0
0
Ciliophora Tintinnids Ctenophora Pleurobrachia sp. Cnidaria 1.
Leriopetetraphylla (Hydromedusa)
Chordata 30
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Doliolum sp.
EIA studies for Puducherry beach Restoration project
1444
1671
520
1868
275
0
0
1039
0
0
29599
10361
67554
10918
3027
Chaetognatha Sagitta sp. Arthropoda Copepod
0 Ostracod
0
836
0
0
0
3610
1671
5716
1580
1651
35374
10027
7275
1293
1376
Mysid
2166
0
0
0
0
Lucifer sp.
2166
4178
2598
1580
0
0
0
520
0
0
Evadne sp. (Cladoceran) Penilia sp.
Annelida Tomopteris sp. Larval stages Copepod nauplii
1444
2507
520
718
1376
Polychaete larvae
0
0
0
0
0
Barnacle larvae
0
0
520
0
275
Zoea larvae
0
0
0
287
0
Fish eggs
0
0
2079
0
0
96018 134527 89381
18819
12933
TOTAL (Nos./100 m3)
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2.6.4 Benthic Fauna Benthic species dominance was studied close to the proposed sites. Results indicated the presence of gastropods such as Cerithedia cingulate, followed by Cassidula
nucleus,
Melampus
ceylonicus,
Sphaerassiminea
minuta
and Telescopium telescopium in and around the Site-2. Among bivalves Crassostrea madrasensis was the most dominant, followed by Meretrix meretrix, M. casta, Perna viridis and Anadara granosa along the coast. Six commercially important crab species were reported along the coast of Puducherry. 2.6.5. Ecological status of the project location In order to study the ecological status of project location, all plants located around the site were observed. For this purpose, the flora of the surrounding environment was studied. 1. No true mangrove was observed along the coast of the proposed site. 2. No endemic and threatened flora was observed close to the site. However, detailed study needs to be carried out to document the species level identification of floral composition in the region. 2.7
Faunal biodiversity of Puducherry
Faunal biodiversity in Puducherry coast comprises of small mammals, birds, reptiles and fishes. A large number of birds are sighted in the botanical garden and the two large water bodies namely, Ossudu and Bahour. The wild animals recorded in the U.T. forest are Jackal, Black Napped Hare, Bonnet Macaque, Jungle Cat, Civet Cat, Mongoose, Monitor Lizard etc. whereas dolphins, whales, Olive Ridley Turtle and Leather Backed Turtle are observed in the coastal waters.
2.8.
Land use pattern
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Fig 17 Land use map of Puducherry 2.9
Socio-Economic aspect
The Union Territory of Puducherry is spread over 479 km 2 in area and has a population of 0.9 million according to the 2011 census. The density of population of the Union Territory is 2034 persons/km 2. The rural population is 3, 25,726 persons (33.43%) whereas the urban population is 6,48,619 lack a person which constitutes 66.57% of the total population. At present study area of Puducherry city coastal stretch is covered with extensively important buildings belong to both governments (Secretariat, Customs office, Gandhi Statue, French Light House, etc...) as well as private (resorts). The study area from Vembaikirappalaiyam on south to the Kuruchikuppam village on north covers 2km length of coast has the most historically important oldest French port light house, Gandhi Statue, Dr.B.R.Ambedkar Manimandabam building, French War memorial building etc.. The ambitious beach restoration project of this stretch is most important for the national public development along with the tourist development.
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CHAPTER 3 IMPACTS AND MITIGATION MEASURES 3.1 General Significant erosion has occurred in Puducherry over the last 2 decades, which has threatened development and resulted in substantial protection works. So far, the coastal erosion has severely impacted more than 10 km of the coastline destroying houses and villages and is advancing northwards. The amount of beach land lost has been estimated as 200 acres, a massive loss to the town of Puducherry. This erosion was foreseen when the harbour was designed, so a sand bypassing system was added to regularly shift the accumulated sand from the south to the north. But unfortunately, the required regular dredging and sand-bypassing was hardly ever done since 1995. The degradation is now so severe that natural sedimentation is not anticipated to be adequate for complete reconciliation of the beach erosion. The current seawall protection is not effective in managing the erosion while retaining a beach. Restoration of the beaches is a top priority for the Puducherry government which is in desperate need of a sustainable solution. The pressure to develop alternative coastal protection solutions is intensifying and planning needs to be based on sound scientific knowledge and consideration of the sustainability (environmental, ecological, economic and social) issues. The planning and design studies for Puducherry coastal erosion have included a comprehensive analysis of the causes and extent of erosion. The design studies examined in detail the root causes of the erosion and accommodated coastal processes in the recommended solution rather than simply trying to mitigate the effects. This is a significant change from the traditional piecemeal approach for hard solutions to a more comprehensive one based on planning, better-designed and environmentally friendly coastal protection structure, with the long-term goals of minimizing costs and reaping economic benefits. This Chapter identifies and predicts the potential impacts on different environmental components of the recommended nearshore wedge reef, south reef and beach 34
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nourishment solutions during the pre-construction, construction and operational phase of the project. It details the potential impacts on biophysical and socioeconomic components of the local environment due to the activities and subactivities. The prediction of impacts helps to minimize the adverse impacts and maximize the beneficial impacts on environmental quality during post project completion. 3.2 IMPACT ON PHYSICAL ENVIRONMENT 3.2.1. Air Quality Air quality will be affected during construction by emissions from vessels, equipment, and land vehicles in work activities at work locations. If the conditions at the beach nourishment areas during or shortly after the nourishment are dry and windy, windborne dust may occur. Sediment from the source areas is likely to contain a small proportion of fine sediment. No effects on air quality are expected during the post-construction maintenance of the wedge reef, south reef, and beach nourishment areas, apart from small emissions during short inspection visits by responsible authorities or during the repair of any damage. The visits are expected to be of relatively short duration compared with the initial construction activities. Mitigation measures. Possible mitigation measures include (i) turning off engines and generators when not in use; (ii) ensuring that equipment conforms to international standards; (iii) regularly or routinely servicing all construction vehicles and machinery; and (iv) immediately replacing defective equipment and removing it from the work site. Dust emissions from the beach nourishment site can be controlled (i) by suppressing dust through regular sprinkling (morning and evening) with water; (ii) halting work during excessive onshore winds; and (iii) immediately dealing with social complaints as they are expressed. Residual effects. The effects on air quality are expected to be small in volume and geographic extent. Emissions will occur during most of the construction season, but 35
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will be of relatively short duration in any one location. Potential effects can be minimized through the use of standard mitigation measures. Concentrations of particulates and gases will rapidly return to pre-construction conditions once the activity stops 3.2.2
Noise
Noise will occur when vessels or trucks bring dredged sand to the beach nourishment areas, and equipment or pumps distribute sand along the shore. Vessels and equipment will be used in reef construction, and trucks and equipment will be used in beach nourishment. Additional, though smaller, noise sources will include land vehicles used to move materials and equipment between staging areas and work-area access points. But the noise from the vehicles will be mainly engine noise and not the high-impact noise. The noise will occur during the construction period. Mitigation measures. Possible mitigation measures include (i) identifying work timing windows or appropriate hours of equipment operation acceptable to the community through consultation, (ii) maintaining minimum noise levels near offices and businesses, (iii) checking daily to lessen excessive noise especially out of daylight hours, and (iv) addressing complaints regarding noise immediately. Noise can be minimized by (i) turning off engines and generators when not in use; (ii) ensuring equipment conformity to international standards; (iii) fitting all vehicles used in construction with silencers; and (iv) immediately replacing defective equipment and removing it from the site. Residual effects. Noise will occur at wedge reef’s steel wedge and south reef’s caisson fabrication and construction sites, beach nourishment locations during the construction periods and sand extraction and dredging sites. However, the noise at any single work location will not be sustained and will shift as work is completed. Noise levels can be minimized through the use of standard mitigation measures. The effects on communities can be minimized through public consultation regarding appropriate hours of construction activity. Noise levels will return to pre-construction
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conditions once the activity ends. No significant effects of project-related noise are anticipated. 3.2.3 Currents The wedge reef can alter local current patterns and scour in front of the reef. At the south offshore reef, reduced currents can lead to the formation of salient, which in turn can reduce the amount of sediment transported to downstream beaches. Further, compression of flows between the offshore reef and the shoreline can lead to stronger currents and removal of nourished sand or scour of the seabed in its lee if the reef is placed too close to the beach. Mitigation measures. The effects of the wedge reef and the south reef on currents were considered during the design studies. Detailed numerical modeling was used to evaluate and guide the choice of structure features and placement locations. The factors considered included depth, distance offshore, length, width, shape and placement orientation. A key element of the design studies was avoiding negative effects on the beach system, particularly in relation to beach erosion and unsustainability of beach nourishment. The goal of the southern reef design was to create a salient or tombolo which will hold the sand on the city beaches. The sand salient/tombolo would provide many public benefits, including a wider beach, a safer beach protected from waves, no construction materials near the shore and minor negative visual impact. The salient will allow the rock seawall to be buried and eventually removed once public confidence is gained. In addition, the sand held in the tombolo could be moved from time to time by mechanical means (normally an excavator or bulldozer) to re-align and re-fill the beach between the two structures. The goal of the wedge reef was to provide a mild barrier to sediment losses, thus enabling sand to move naturally to the north while slowing the losses of sand from the City foreshore. The reef should not fully block littoral drift to minimize any downstream impact. The computer modelling was undertaken over 3 years to find the shoreline responses and a detailed sensitivity analysis of the sediment dynamics in typical conditions. Considerable sensitivity testing of the model parameters was 37
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undertaken. A maintenance re-nourishment allowance of up to 50,000 m 3yr-1 is included in the project plan. Residual effects. Significant adverse effects on currents are not expected. Regular shoreline and bathymetric monitoring of the city foreshore and surrounding beaches are planned. Appropriate measures will be considered and taken if significant adverse effects are observed. 3.2.4 Sediment Quality and Quantity Beach nourishment design indicates the use of dredged sediment from the fishing harbour for nourishment. Sediment samples collected from source areas during the project design studies were tested for heavy metals (mercury, arsenic, lead, and cadmium) selected for use as indicators of contamination. The findings presented in the design studies generally show mercury and cadmium to be below detection levels, and arsenic and lead to be below the standards now in use in North America (those standards were used because India has no prescribed standards or levels for the heavy-metal content of sediment). The types of other possible contaminants and the spatial variability of contaminants in bottom sediment within the proposed sand source area are not yet known. Accordingly, the effect of such contaminants on sediment and water quality, ecological conditions, and human health are uncertain. Information about possible contaminants in the dredging area and specifically in the locations where sediment will be extracted will have to be developed in detail to accurately identify the possible effects on sediment and water quality along the proposed beach nourishment areas and downstream areas. The types and concentrations of contaminants in the bottom sediment of harbour mouth are influenced by upstream activities, commercial activities and outfalls, and the uses of the water among the general population. Also, the physical properties of the sediment, such as particle size, influence sediment chemistry. Generally, coarsegrained sediment (such as sand, the target material for beach nourishment) has a lower potential for accumulating contaminants than fine-grained sediment (such as silt). Fine sediment potentially has higher concentrations of, and serves as a sink for 38
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contaminants because a given volume of fine-grained sediment has a relatively greater total surface area for the adsorption of contaminants than coarser sediment. Mitigation measures. Sourcing plans for the extraction of sediment from the harbour mouth to be placed along the proposed beach nourishment areas must incorporate a sampling and analysis program to identify the concentrations of potential contaminants. The sampling program and choice of compounds to be analyzed must be based on a review and synthesis of exisitng data, and potential sources and types of potential contaminants. This is likely to mean an expanded suite of parameters to test, beyond the four metals analyzed in the exploratory sampling during the feasibility studies. Compounds such as oil and grease, additional metals, and pesticides may be included together with additional parameters to support the interpretation of laboratory results for selected contaminants of concern. The program must identify acceptable thresholds based on international standards for each potential contaminant of concern. In concept, high concentrations of potential contaminants may be largely avoided because the design requirements for beach nourishment call for the selection of materials with coarse particle sizes and the avoidance of smaller particles. As noted, high levels of contaminants are usually associated with fine material such as silts and clays, which will be avoided to meet project design needs. Bottom sediment in the proposed sediment source area may contain solid waste material, such as cloths, plastic and bottles. If pre-dredging samples indicate a high concentration of solid waste in selected bottom areas, a strategy will be needed for its removal and proper disposal before the sediment is placed in the beach nourishment area. If such material is observed after the sediment is placed on the beach a beach clean-up may be in order. Residual effects. The quality of the source sediment is known from the initial analysis. If potential contaminants in source sediment are adequately assessed and sediment with high levels of contaminants is avoided, no significant effects on beach sediment quality are anticipated.
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3.2.5 Water Quality During construction, water quality near work areas could be affected by (i)
turbidity during sediment placement in target areas along beaches as fine sediment is flushed from coarser sand material, during possible spills of sediment near the beach nourishment area;
(ii)
contaminants flushed from sediment after it is placed at target locations on the beach; and
(iii)
leaks or spills of operational material such as fuels, oils, or hydraulic fluids.
Turbidity could impair the photosynthesis of phytoplankton and other flora, the feeding and migratory behavior of fish and invertebrates, and aesthetic attributes potentially important to tourist activity at the beach areas. By design, the project will select bottom sediment that is made up largely of coarser sand material. Increased turbidity is expected after the initial sand placement and possibly after the first period of heavy waves as fine sediment is removed from coarser fractions. The increased turbidity is expected to be of short duration, however, with concentrations of fine material declining as those particles settle out of the water column in lower-energy areas away from the immediate shoreline. Sediment having high concentrations of potential contaminants will not be used for placement on the beach. Currently, the types of contaminants that may be present in sediment to be used for beach nourishment are not fully known. In general, contaminants have the potential to be toxic to organisms, to interrupt food webs and the migration of fish and other organisms, and to affect human health. If present in sediment placed on the beach such compounds are likely to be rapidly flushed from the sand material together with fine sediment. Fuels, oils, and hydraulic fluids also have the potential to affect ecological resources and human health. Their effects would depend on the amount of material released and the degree of exposure of organisms and humans. Mitigation Measures : The selection of sediment to be used for beach nourishment will be based in part on the identification of potential contaminants and the acceptable limits for allowing the use of sediment containing those contaminants. 40
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Further, the selection of sediment will also be based in part on the presence of mainly larger particle sizes and small proportions of fine material such as silt and clay. Equipment inspection and repair will be undertaken and documented routinely before and during sediment transfer from the dredge or sediment stockpile site to the nourishment site. Fuels, oils, and hydraulic fluids. Protocols for routine equipment inspection, repair, maintenance, and fueling will be required before the start of work, and practices during work must be documented. Contingency plans to be used in the event of spills will also be required beforehand, and spill containment and clean-up equipment must be present during all fueling and fluid replacement or top-up activities. Vessels and equipment should be fueled at shore mooring locations where spill containment equipment is present before the start of fueling. Routine discharges are unlikely because of the nature of the project. If there are accidental spills, contingency plans should be initiated immediately. Residual Effects: Water will be temporarily turbid along the nearshore after dredged sediment is placed in the beach nourishment areas. Periods of high turbidity are expected to be of relatively short duration and alongshore extent, with a return to background levels dependent on the amount of fine material in the sediment, and prevailing water or climate conditions. Periods of high wave activity could induce additional flushing of fine material at that time. Possible contaminants in sediment should be identified before extraction by dredging or other means from source areas. No effects should be evident if sediment having contaminants is avoided during dredging or extraction. Standard measures for preventing, containing, and cleaning up possible leaks or accidental spills of fuels, oils, or hydraulic fluids are available and should be in place before the start of construction. The effects on water quality are not expected to be significant if the proposed mitigation measures are used.
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3.3 IMPACT ON BIOLOGICAL ENVIRONMENT 3.3.1 Marine Biota and Habitat The placement of sediment for beach nourishment will smother intertidal and subtidal benthic biota and temporarily impair food-web relationships and possibly local food production of harvestable species. However, due to the presence of the seawall, intertidal and sub-tidal benthic population is very limited. The effect on beach nourishment areas will be short lived as the benthic population will begin reestablishing once the sediment placement stops., Baseline information has not been collected to characterize fish and invertebrate use of the proposed project area for breeding or other purposes. The presence of rock seawalls suggests that the areas are not a unique habitat for breeding or other lifestage activities. The areas comprise exposed, rough environments with bottom sediment being highly abrasive sand to gravel in some areas. Taxa that move inshore seasonally to breed or rear is likely to avoid areas influenced by wave breaking, as eggs deposited on the sea bottom could be damaged. At the locations of nearshore wedge and offshore caisson reef are proposed sanddwelling benthos will be smothered and the sand-bottom habitat will be replaced by a potentially reef-like habitat. Reef structures have been shown to provide shelter from the impact of waves and currents, as well as substrata for the growth of epiflora and fauna. The structures offer the potential to enhance marine life with the increase in surface area provided by the rocks and the creation of reef habitat suitable for breeding by some species, and will form the basis for new fish and invertebrate assemblage, possibly strengthening local fisheries. The effects of benthic smothering are expected to be short lived considering the short generation times of these organisms and the prevailing littoral transport of larvae of these organisms. Recolonization of the benthic fauna is expected within a few months. Effects of water quality changes. The temporary increase in turbidity has the potential to reduce photosynthetic activity and impair plankton production, feeding activity, and migration and behavior patterns. These effects could cause a short-term 42
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reduction in the production of harvestable species. However, the zone of high turbidity is expected to extend less than 1–2 km. The project activities could cause the release of chemicals along the beach, including contaminants in sediment from dredging locations, fuels, oils, and hydraulic fluids. Measures that will minimize the potential release of these compounds are described above. These materials could be directly toxic to organisms and could interfere with food webs, migration and behavior patterns, and the catch of harvestable species. Effects of sediment dredging and extraction. Details of the proposed methods and timing of sediment dredging and extraction are not yet known. The dredging will remove sediment from bottom areas in the harbour mouth and create temporary sediment plumes. The activities will involve the movement of vessels and equipment to and from work sites over the work period. Dredging will remove benthic biota and temporarily impair food-web relationships and possibly the local food production of harvestable species. The effect will be short lived, however, as the reestablishment of the benthic population will begin with the cessation of sediment removal. Dredging activities include underwater noise and surface lighting that could affect the seasonal use of the dredge area for activities such as breeding or migration. As noted above, the temporary increase in turbidity may reduce photosynthetic activity and impair plankton production, feeding activity, and migration and behavior patterns, and cause a short-term reduction in the production of harvestable species. Sediment plumes moving with prevailing tidal cycles could affect habitat and organisms elsewhere in the coastal area. The dredging activities could cause the release of chemicals, including contaminants in sediment at dredging locations or in fuels, oils, or hydraulic fluids. These materials have the potential to be directly toxic to organisms and to interfere with food webs, migration and behavior patterns, and the catch of harvestable species.
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Mitigation measures. Measures that will minimize the release of sediment and chemical compounds during the placement of sediment in the beach nourishment areas and during the construction are described above. Fish and invertebrate taxa using the beach areas are not known. The characterization of the fish and invertebrate communities, especially mobile species, would enable the types and timing of likely use to be identified, and the timing of construction activity refined to minimize possible effects. Additional information on the proposed dredging activities at the harbour mouths is needed for the development of mitigation measures. The project activities are to be completed as quickly as possible. At the reef locations, the sand-bottom habitat will be replaced by a potentially reef-like habitat and invertebrate assemblages. The reefs, if deemed no longer necessary, lend themselves to decommissioning through floating the steel caissons and the removal of the caissons. All this suggests that the benthic smothering effects would be reversible if the steel caissons were removed. Residual effects. The project is likely to cause the localized reduction of benthic and planktonic production in the beach nourishment areas during the construction period, with effects lasting for several months, after which the benthic biological conditions typical of sand habitats are anticipated to be re-established. The benthic habitat in relatively small areas under the proposed offshore reefs will be replaced by a reeflike habitat as biological colonization of the reefs takes place. Follow-up studies to verify that reefs are providing the expected habitat, fish and invertebrate assemblages, and possible fisheries enhancement will require the collection of preconstruction baseline data. Measures can be applied to minimize the potential effects of dredging and other construction activities. Long-term significant effects are not anticipated if appropriate mitigation measures are developed and adhered to. If measures to prevent the release of potentially harmful chemicals are implemented, adverse effects on marine life are not likely. Adverse effects on marine life in the beach areas are expected to be limited to the duration of the construction activities 44
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and to occur over the relatively small construction area, with turbidity temporarily affecting a broader area. Significant adverse effects on marine life are not anticipated. 3.3.2 Terrestrial Biota and Habitat Small areas of land are likely to be needed during construction for equipment access points or material and equipment storage or staging and steel caisson fabrication. The project needs are as yet uncertain; they will be identified on the basis of the contractors’ proposals during tendering. The projects are mainly located in areas of human habitation and business activities, including tourism. Adverse effects on terrestrial habitat are unlikely. Mitigation measures. The conditions in the project area indicate that any disturbance of local habitats is likely to be rectified. Stabilization of the environment is therefore possible. Residual effects. Land needs for the construction activities are limited and hence the effect on terrestrial habitat is minimal. No significant adverse effects are anticipated and effects can be mitigated if needed. 3.3.3 Waste Management Throughout construction, the workforce will generate general refuse comprising food scraps, waste paper, empty containers etc. The storage, handling and disposal of general refuse have the potential to give rise to some environmental impacts if not properly managed. These include odour if waste is not collected frequently, windblown litter, water quality impacts if waste enters water bodies, and visual impact. Mitigation measures: Rapid and effective collection of site wastes and disposal of it without any adverse impact on the environment. Residual effects. With good waste management practice, no long-term effect is anticipated.
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3.4 IMPACT ON SOCIO_ECONOMIC ENVIRONMENT 3.4.1 Fishing Activity Small fishing vessels moving along the shore from other areas would be subject to navigational effects during construction and after construction, of the offshore reefs. Larger trawl vessels that fish off Puducherry do so mainly in deeper water but would have to avoid the reefs during construction and after construction if they were to operate closer to shore. During the construction of the reefs and beach nourishment, some disturbance to the navigation of fishing boats may occur mainly because of the harbour entrance dredging activity, floating of caissons to the reef site and when bringing rocks to the offshore reef site. The floating of the caissons and its placement will cause only localised and short-term disruption of fishing activities. The installation of offshore reef including placement of rocks should take less than 60 days, excluding weather downtime. The area of the offshore reef is very small compared with the length of the beach. As the wedge reef works are in the littoral zone, unlikely to have any impact on the fishing activities. In general, fishing vessels are not likely to be disrupted by activities in the project areas. Mitigation measures. During construction, some areas will have to be restricted to ensure the safety of the local people and site workers. The offshore reef areas will be visible to fishing vessels while work vessels and equipment are present. Consultation meetings will be held before construction to inform stakeholders of planned activities and to discuss the type and scheduling. After construction, the potential effects on fishing activity relate mainly to vessel operation near the offshore reef. Residual effects. Significant adverse effects on fishing activity are not anticipated. The locations of the offshore reef and the effects on fishing activity will be included in further consultation sessions to be held during project implementation.
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Navigation
During construction, the navigation of small vessels could be affected by the movement of vessels or barges bringing rocks to be placed as scour protection, pipelines conveying sediment from vessels carrying dredged sediment to land or deposition areas along the beach, vessels used for reef placement, once they are installed. There is wide sea space around the proposed work areas so risks of collision or impaired movement of local boats are low. There is potential for disturbance to the navigation of fishing boats near offshore reefs. But there is ample space, and most coastal traffic would move outside the line of the reefs and impairment of local boat traffic is not likely. Mitigation measures. Navigation aids such as buoys could be used to show the location of offshore reef but have not been used in other areas where artificial reefs have been installed. In those locations, wave breaking signal the presence of a structure including the rocks just below surface (similar to a natural reef). This topic will be discussed in future public meetings including those to be held before the start of construction. Future consultations will involve awareness building so that stakeholders know the final locations of the proposed reefs and associated construction activities, and they can give their input regarding the need for markers such as buoys. Residual effects. Significant adverse effects on navigation are not anticipated. The locations of the reefs and their effects on navigation will be included in further consultation sessions to be held during project implementation. 3.4.3 Local Land Traffic During construction there will be periodic movement of trucks, equipment and supplies by land to storage and site-access areas. The main material to be used during these activities—sediment for beach nourishment and rocks for wedge reef and offshore scour protection —will be transported by trucks or barges. The number of vehicles and trips required during construction will be identified during the tendering; however, these requirements and their effects on land traffic are not expected to be large. 47
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Mitigation measures. Construction-related activities, including the movement of equipment and supplies, will be discussed with stakeholders during consultations before construction. Project needs related to access points, staging areas, and land traffic will be discussed at that time, together with community input regarding the timing of activities and any local traffic control needs. Residual effects. No significant adverse effects on local traffic are anticipated. 3.4.4 Tourism During construction, local tourist entities may be periodically affected by air quality changes, noise, local traffic, and water quality changes (high turbidity) along the shoreline noting that there is no beach present now and hence no beach tourism at present. These effects will be temporary. The beach nourishment will bury most of the rock seawall and provide a beach for recreation. Further, the sand salient/tombolo in the lee of the south reef would provide many public benefits, including a wider beach, a safer beach protected from waves, Mitigation measures. Consultation meetings will be held before construction to inform stakeholders of planned activities and to discuss their type and scheduling. Measures that will mitigate the possible effects of high turbidity and degraded water quality are described above. Residual effects. The main residual effect on tourism will be periods during construction when truck movement along the foreshore road, sound and dust from the construction activities. These effects are only during the construction stage and significant adverse effects on tourism along the beach are not anticipated. Benefits to tourism will accrue once the project is completed with wider, safer and more accessible beaches. 3.4.5 Safety and Human Health Factors that could affect human health during construction include reduced air quality, noise, accidents or malfunctions, and reduced sand and water quality. Factors that could affect safety are accidents or malfunctions, increased land traffic,
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navigational mishaps, and equipment activities at the beach nourishment areas, as well as in the reef work areas. Mitigation measures. During equipment operation and construction, work areas will have to be restricted and clearly marked to ensure the safety of local people and site workers. Possible measures that will mitigate the potential effects on air quality, noise level, sand and water quality, land traffic, and navigation are described in preceding subsections. Mitigation related to accidents and malfunctions is described in section 3.4.7 below. Residual effects. Measures must be implemented to protect human safety and health. Significant adverse effects are not anticipated if the measures are adhered to. 3.4.6 Livelihoods The project is not expected to adversely affect livelihood during or after construction. Possible local effects during construction on fish production (the short-term reduction in benthic and planktonic food organisms is not likely to be detectable in the catch), and tourism are not likely to be manifested in loss of livelihood. Mitigation measures. Additional mitigation measures to protect livelihoods do not appear necessary. Residual effects. Any negative effects on livelihoods are not anticipated. 3.4.7. Accidents and Malfunctions Possible accidents and malfunctions that could have adverse environmental effects during construction include fuel, oil, and lubricant spills; fires or explosions; sand spills; and vessel collisions. Fuel, oil, or lubricant spills could affect water quality, ecological resources, and human health. Fires and explosions could affect air quality and human health. Spills of sediment could affect water quality mainly by increasing turbidity along the shore. Vessel collisions could lead to economic losses and human injury or fatality. 49
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Mitigation measures. Measures can be taken to prevent these accidents and malfunctions. In addition, contingency plans can be prepared to contain and clean up spills of fuels, oils, lubricants, and sediment if an event occurs Residual effects. Significant adverse effects of accidents or malfunctions are not anticipated as long as preventive safeguards are in place and contingency plans prepared and implemented if found necessary.
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CHAPTER- 4 ENVIRONMENTAL MANAGEMENT AND MONITORING PROGRAMME
4.1
The Need
Environmental Management Plan (EMP) is required to meet specific needs at the project location. The EMP aims to ensure that adverse impacts are prevented or properly mitigated, and identifies mitigation, monitoring, and institutional measures to be taken during the project implementation and operation. The EMP also identifies the parties responsible for implementing each action.
4.2
Impacts To Be Mitigated
The environmental impact that could occur during the pre-construction, construction, and post-construction stages (operation and maintenance) and the measures that would mitigate the potential impact are presented in Chapter 3. Potential adverse effects during the construction stage include temporary and localized effects on air quality, noise levels, beach sand quality, water quality, nearshore biota and habitat, terrestrial biota, fishing activity and navigation, vehicle traffic, tourist activity, and safety of beach users. Measures have been identified to prevent or minimize these effects. Potential adverse effects during operation and maintenance include the erosion of nourished beach (if the structures do not perform as planned or unexpected events occur), as well as effects on the marine habitat and biota, fishing activity, and navigation. These possible effects were important considerations during the design stage and are mitigated mainly through detailed coastal process studies, numerical modeling and site-specific design features such as placement location, depth, size, and shape.
4.3
Implementation Arrangements and Responsibilities
The Puducherry Public Works Department (PWD) with technical support from the National Institute of Ocean Technology (NIOT), Chennai will be responsible for implementing the environmental mitigation measures and monitoring programs The 51
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PWD also will include local representatives from the Puducherry Port Department, Environment Department, Fisheries Department, PondyCAN and other interested groups
NIOT will provide technical support, including field surveys and monitoring as required. A senior scientist of NIOT will be assigned to supervise the implementation of the EMP, monitor compliance with planned mitigation measures and monitoring programs, and coordinate other environmental aspects of the project.
4.4
ENVIRONMENTAL MANAGEMENT PLAN
An environmental management plan (EMP) is presented in Table 8. The EMP identifies potential impacts to be mitigated, monitoring plan, and institutional measures to be taken during key project activity stages. The EMP identifies the parties responsible for implementing each action.
Potential adverse effects during the construction stage include temporary and localized effects on air quality, noise levels, beach sand quality, water quality, marine biota and habitat, terrestrial biota and habitat, nearshore fishing activity, vehicle traffic, tourist activity and safety of beach users. Measures are identified to prevent or minimize these effects.
Potential adverse effects during operation and maintenance stage include erosion of nourished beach if structures do not perform as planned or unexpected events occur, marine habitat and biota, fishing activity.
These possible effects were
important considerations during the design stage and have been mitigated mainly through detailed studies and site-specific design features such as construction material selection, structure placement locations, depths, size and shape.
The EMP is to be revised once construction and operational activities are well defined. Additional information will be necessary during the early stages of project implementation to support development of final mitigation measures.
These are
outlined below. 52
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Sediment tests should be conducted to refine selection of sediments to be used for beach nourishment; parameters to be tested are arsenic, cadmium, lead, mercury, oil/grease, hydrocarbons such as PAHs, or pesticides based on assessment of potential contaminants of concern in bottom sediments. Methods regarding how dredged sediment or sediment stockpiled on land will be transported to the beach nourishment. Methods of how rocks would be transported to the site and placed both for the wedge reef rock base and offshore reef’s scour protection Information on benthos, fish and larger invertebrate taxa using the nearshore areas,
should
be
characterized
using
existing
published/unpublished
information to aid identification of possible refinements to work activities and schedules. Information should include possible seasonal/migratory species and timing of occurrence and habitat use in near-shore areas.
4.5
MONITORING PROGRAM
Environmental monitoring plans that identify the impact to be monitored and the planned monitoring activities have been prepared and presented in Table 8. Monitoring is planned for the construction period, to monitor pre-construction and construction activities, and for the post-construction stage, to monitor the effectiveness of the structure designs and locations and prevent impact on relevant environmental features such as sand loss from the nourished beach, and adverse impact on fishing activity, navigation and tourism. Detailed bathymetric and shoreline surveys, sediment sampling need to be conducted before the construction at the project site and adjacent coasts for baseline data. Following construction, the beach nourishment and the reefs performance need to be monitored to evaluate the project performance and to regularly assess the condition of the nourishment and any adverse impact on adjacent coasts. These include bathymetric surveys, shoreline and berm positions, total volume, and the response of the beach to a storm. Bathymetric surveys, beach sediment sampling, shoreline surveys, and wave, current and 53
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water level monitoring would provide an accurate and objective measure of the coastal protection project’s response. Without physical monitoring data, it is difficult to estimate how well the project is performing in comparison to the design. The monitoring program should involve an early phase of more intensive data collection of bathymetric surveys, beach profiles, sediment and marine ecology to evaluate project performance. After the project performance is established, data collection can be scaled back to focus on monitoring project condition. Environmental monitoring data will be used to evaluate: (i)
Extent and severity of environmental effects against predicted effects;
(ii)
Performance of environmental protection measures or compliance with pertinent rules and regulations;
(iii)
Overall effectiveness of the EMP
(iv)
Any additional remedial actions need to be considered.
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Table 8 Summary of the potential environmental impacts due to the Puducherry Beach Restoration Project and the mitigation measures Project Stage
Potential Activity
Preconstruction
Site preparation: material and equipment staging areas and beach access location
Possible removal of terrestrial habitat
Wedge reef and offshore reef construction and beach nourishment:
Physical
Construction
Transport of sediment, rock and construction materials to the project site
Potential Environmental Impact
Proposed Mitigation Measures Sites rehabilitated and stabilised before contractor leaves the site upon completion of the construction activities.
Air quality
Adherence to national air quality standards
Increase in exhaust fumes
Engines and generators turned off when not in use
Equipment conforms to international standards. Possible dust emission
Fabrication of steel caissons
Dust suppression by regular sprinkling (i.e., morning and evening) or other means. Halt work during excessive onshore winds.
Fabrication of the
Verbal social complaints dealt with immediately and efficiently.
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wedge
Noise
Adherence to national noise standards
Temporary pipeline installation, operation and removal during dredging
Increased noise levels from:
Engines and generators turned off when not in use
Sediment placement and leveling at the beach nourishment site
Wedge reef rock base construction
Offshore reef’s rock scour protection
steel caisson fabrication including loading, unloading, welding, and other works
Equipment conforms to international standards.
Vehicles and engines fitted with silencers Truck movements, crane and bulldozer operations, vessels operate nearshore
Daily checks and remedy of potential sources of excessive noise especially out of daylight hours.
Complaints regarding noise dealt with professionally and with respect Sediment quality
Chemical contaminants in sand used to nourish beach sand
Adherence to international sediment quality standards
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Chemical testing of sand source before use—compounds to be tested are to be based on initial assessment of potential contaminants of concern (e.g., oils and grease, PAH compounds, pesticides from upstream locations, heavy metals)
Solid waste in dredgedmaterial Removal of solid waste if present in dredged sediment Water quality
High turbidity during sediment placement for beach nourishment
Adherence to national water quality standards
Supervision of all operation procedures to minimize spillage of chemicals oil or fuel Possible turbidity from onshore activity Ensure sediment grain size requirements as per the design Oil discharge during vessel and equipment operation
Minimise the fines (silt and clay) in the borrow sand.
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Contaminants in sand
Sediment is to be screened for potential contaminants and not used if present above thresholds identified in international standards
Possible spills of fluids (e.g., oils, fuels) and sediment
Accidental spills contingency plans should be initiated immediately
Biological Terrestrial biota and Habitat :
Any disturbance to local habitats should be rectified before contractor leaves site..
Onshore biota or Habitat
Removal of habitat for site access or material and equipment staging
Sand piles or protruding abnormalities to be leveled
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Marine biota and Habitat :
Develop mitigation components on the basis of a review and characterization of fish and invertebrates that occur in nearshore areas including seasonal or migratory species and sensitive times and locations.
Sediment for beach nourishment could cover soft sediment benthic habitat and biota
Newly placed sediment and rocks are expected to be colonized by benthic biota and return to pre-nourishment /construction condition within a few months.
Rock placement for wedge reef and scour protection could cover benthic habitat
Minimize sediment release during construction to reduce affected area outside sites of beach sand nourishment and reef construction
High turbidity and sediment settlement temporarily impair photosynthesis and biological production in adjacent offshore areas
Implement contingency plans if spills of sediment /oil or contaminants occur
Social, economic, and cultural Navigation
Local navigation and
Barge and boat movement, reef construction and rock dumping operation may be carried out in consultation with stakeholders to avoid interference with regular fishing
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fishing Public consultation to identify times, and types of potential safety risks, and develop site-specific advisories and safety measures Tourism All equipment, waste, and construction materials debris must be removed daily from the site or safely stored without any adverse impact on the promenade users
Safety and human health
Public consultation to identify times, and types of potential safety risks, and develop sites-specific advisories and safety measures
All equipment, waste, and construction material debris must be inspected and/or removed daily from site or safely stored without any adverse impact on the promenade users. Fishing activity
Disturb nearshore fishing activity Operation and Maintenance
Beach maintenance and effectiveness
Public consultation to identify locations, times, and types of potential conflict, and develop site-specific measures to minimize disruption of nearshore boat use
Physical
Erosion of nourished
Detailed modeling was used during the design stage to
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sand
determine location and design features
Beach formation— sand loss from the nourishment site
The wedge reef is design to break waves offshore and drive currents shorewards which acts to reduce the approaching longshore currents and ensures that sand is carried towards the beach
The offshore southern reef is designed to reduce wave energy in its lee, which slows longshore drift and causes sand to be trapped at the shoreline.
Annual re-nourishment using 50,000 cu m sand is planned as a mitigation measure Change in effectiveness of retention structures
Induces erosion or diminishes storm buffer of beaches
Structures are designed to be effective for improving conditions at the site without diminishing storm buffer along other beaches
No further mitigation is planned, but possible change in effectiveness to be monitored
Social, economic, and cultural Storm buffer effectiveness
Results of numerical modeling to support design and location decisions are expected to improve conditions at Puducherry
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without diminishing storm buffer along other beaches Buffer diminishes along beaches as a result of erosion, resulting in structural and economic loss Navigation
Long-term effect on nearshore navigation
No further mitigation is planned, but possible downstream erosion to be monitored
Regular stakeholder meetings to discuss social and environmental concerns including navigation issues
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