DEMOCRATIC SOCIALIST REPUBLIC OF SRI LANKA

MINISTRY OF TRANSPORT AND HIGHWAYS

OFFSHORE SAND MINING FOR THE

COLOMBO 7<ATUNAYAKE EXPRESSWAY PROJECT

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ROAD DEVELOPMENT AUTHORITY

"Sethsiripaya", Battaramulla

SRI LANKA

DECEMBER 2000

PREPARED BY:

^\\, Lanka Hydraulic Institute Ltd.

OFFSHORE SAND MINING FOR THE

COLOMBO KAiUNAYAKE EXPRESSWAY PROJECT

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ROAD DEVELOPIVIENT AUTHORITY

"Sethsiripaya", Battaramulla

SRI LANKA

DECEMBER 2000

OFTMIOHE I)U[JX;IN(; RIR C()U)MR() KATUNAVAKE EXPRESSWAY PROJECT

Eiiviromiiciilal lnip;)Ct Asscssiiicnl Ucpoil

TABLE OF CONTENTS

1.0 Introduction 1

1.1 Background 1

1.2 Extent and Scope of the Study 2

1.3 Brief Outline of the Conlentsand Methods Used 2

2.0 Description of the Project 4

2.1 Nature, Aims and Scope of the Project 4

2.2 Justification of the Project 4

2.3 Methodology of Operation 5

2.4 Evakialion of Alternatives 7

2.5 Workforce 10

2.6 Programme 10

3.0 Borrow Area and Dredging 11

3.1 Location and Size of Proposed Borrow Area 11

3.2 Volume and Type of Material 11

3.3 Method of Dredging 11

3.4 Timing, Rate and Zoning of Production 12

3.5 Vessel Numbers and Movements 12

3.6 Control of Dredging 12

3.7 Notification and Liaison 12

3.8 Onshore Destination 12

3.9 Alternative Sources of Material 12

4.0 Borrow Area and its Environment 13

4.1 Physical Environment 13

4.2 Biological Environment 13

4.3 Human Environment 15

4.3.1 Fishing Activities 15

4.3.2 Other Activities 17

5.0 Sand Storage Sites and Their Environment 18

6.0 Anticipated Environmental Impacts 19

Ün>iHORKDRi:D(;iN(; R)RCnU>MH() ICVTIINAVAKE EXPRIiSSWAY I * R 0 J E C T

Eiivironmciilal Impacl Assessment Rcjwrt

6.1 Physical Effects 19

6.2 Biological Effects : 20

6 3 Effects on the Human Environment 21

7.0 Proposed Mitigatory Measures 22

7.1 Royulaiiüii/'Müiiitoiiny ufDicdging Activity 22

7.2 Protection of Borrow Areas 22

7.3 Coastal Stability 22

7.4 Navigational Hazards and Interference with Fishing Activities 22

7. 5 Pipeline on Land and Crossing Hamilton Canal 23

7.6 Sea Water Impacts on Surface Water and Groundwater 23

8.0 Monitoring Programme 24

8.1 Dredging Activities 24

8.2 Pumping/Drainage Activities 24

8.3 Long Term Monitoring of Dredge Site 24

9.0 Conclusions and Recommendations 25

ANNEXES ANNEX 1

ANNEX 2

ANNEX 3

ANNEX 4

ANNEX 5

ANNEX 6

ANNEX 7

ANNEX 8

Terms of Kcfcrciice

Bathyntctric Survey Plan

Construction Programme

Mincralogical Analysis

Seismic SuiTcy Report

NARA Report on Fisheries and Marine Habitat

Boreholes Investigation Report

Section 5,4.1.1 Dredging and Transport of Sand to

Stockpiling Area (ElA Report of Colombo-Katunayake

Expressway RDA 1997)

IÄFSIIOREDREDGINC FOR COLOMBO KATUNAYAKE EXPRESSWAY PRO.TECT ^T

Fnviroiimciilal Impact Assessment Report

LIST OF HGURES

Figure 1 - Location Map fui Dreilging

Figure 2 - Location of Stockpiling Areas

Figure 3 - Proposed Trace of tlie Express Highway

Figure 4 - Typical Cross Section of the proposed Highway

Figure 5 - layout of the Submerged Pipeline

Figure 6 - Layout of Boreholes

Figure 7 - Resource Map (Isopatch Chart)

OFFSHORE DRF.IK;IN<; FOR COUIMROKATUNAYAKE EXPRESSWAY PROJECT I-

Environmental Inipact Assessment Report

1.0 INTRODUCTION

1.1 Background

The need for a high speed transport link between the City of Colombo and Katiinayake has

been long recognised. The proposal to build such a highway between the Katunayake

International Airport and the City of Colombo was approved by tlie Cabinet of Ministers in

1998 (Cabinet Paper 98/1307/22/075 dated 26.06.1998).

The Project Proponent is the Road Development Authority (RDA). The RDA has studied

several traces of the proposed Colombo-Katmiayake Expressway (CKE) and a final trace was

selected. The Hnvironmental Impact Assessment Report (RDA, 1997) on the main project was

submitted in August 1997 and approved, in terms of Regulation 13, National Environmental

Regulation No. 1 of 1993, by the Central Environmental Authority (CEA) by its letter No.

08/05/16/20/96/Vol V dated 28 January 1998. The EIA was based on the sand being collected

using a trailer suction hopper dredger and transported to a nearshore point, where tlic sand is

pumped via a floating pipeline to tlie storage area. This methodology was covered by the EIA.

However, the EIA did not cover the exploration for and mining of off shore sand.

Tlie Terms of Reference for "Environmental Impact Assessment of Offshore Dredging for

Colombo Katunayake Expressway Project" was finalised by the CEA and sent to the RDA on

30 December 1999. This report has been prepared in response to these Terms of Reference

(TOR), which are reproduced in Annex 1.

Prior to preparing this report, the Consultant carried out field investigations to obtain data on

the physical and biological environment in (he prospective borrow area, with a view to

satisfying the requirements of the TOR. These investigations were also to satisfy the

requirement of the Geological Survey and Mines Bureau (the Licensing Autliority for s ind

mining) to establish that sufficient sand of the required quality was available.

To quote the TOR, "The signiftcance and extent of (he effects of aggregate eximction on the

sea bed will depend upon a range of factors including the location of the licensed area, the

nature of the surface and underlying sedimera, the method of extraction, the sensitivity of tlie

habitats and fisheries in that locality." This report is intended to enable the organ] salion(s)

responsible for licensing to establish whether the dredging will have

• any impact on the adjacent coast

• any potential impact on fisheries, local or regional

• areas of marine conservation

• other marine environmental issues

OFFSHORE DREDGING FOR COLOMBO KATUNAYAKE EXPRESSWAY rROjECr Environmental Impact Assessment Report

1.2 Extent and Scope of the Study

Tlie EIA is to evaluate the impacts of removing a volume of approximately five million cubic

metres of well graded medium to coarse sea sand from the grid units designated 093203,

093204, 094203, 094204, 095203 and 095204 (see Figure No. 1). The area is located

approximately 3 km offshore of Kerawalapitiya. just north of Colombo. The average sea

depth at the location is 16m below LWOST. The area of dredging is 6 sq. km. and the

average depth of excavation will be approximately 1 .Om.

The scope of the study is to evaluate the aviulability of the required material and the effect of

removal on the wave climate, ajid Impacts on fisheries, shoreline stability and natural resources

of the area.

The methodology for pumping sand to a stockpiling area (also shown in Figure No. 2) and the

arrangements made for the return of saline water to the sea was to follow the practices adopted

for the Kerawalapitiya sand fill {see EIA Report, SLLRDC 1993). Originally the stockpile

was to be made within the Kerawalapitiya sand fill (see EIA Report - RDA 1997, and Relevant

Section in Annex 8). This methodology had already received clearance from the CEA.

However, the an alternative site , adjacent to the Kerawalapitiya and fill has now been reserved

for the stockpile. The methodology for sand fill and evacuation of drainage water remains

/ neariy the same. However, the impacts of filling this area and the return of saline water from

this area have also to be included in the study.

1.3 Brief Outline of (he Contents and Methods Used

The EIA Is formatted to follow the Terms of Reference (TOR) provided by the CEA. It

provides a description of the project, a site description and a description of the existing site

environment, a description of the anticipated environmental impacts, proposed mitigatory

measures and the monitoring programme to be followed.

TTiere have been two dredging projects implemented in the area immediately adjacent to the

site. These were for the purpose of obtaining approximately one million eubJc metres of sea

sand for filling purposes for the JA YE Container Terminal Project In the Colombo Harbour,

and for obtaining approximately 4.8 Million cubic metres of sea sand for the Kerawalapitiya

Reclamation Project. The Queen Elizabeth Quay Expansion Project has recently received

environmental clearance to obtain 1.69 million cubic metres of sea sand from an adjacent area.

An EIA and an lEE (Initial Environmental Examination) were carried out respectively for the

On->"HORF. T)RFDf;iN(; FOR COLOMBO KATIINAYAKF, EXPRESSWAY PROJECT 3 Enviroimiciilal Impact Assessment Report

the purpose of this EIA. The additional field investigations carried out for the present study are

described later in this report. All available information on the fishery and the reefs in the area

were studied.

The results of these investigations, studies and assessments are presented in tliis EIA.

OiTsiiORE DREDGING FOR COLOMBO KATUNAYAKE EXPRESSWAY PROJECT 4 Environmental Impact Assessment Report

2.0 DESCRIPTION OF TlIE PROJECT

2.1 Nature, Aims and Scoi>e of tlie Project

The need for a high speed link between Colombo and the International Airport and Export

Processing Zone in Kalunayake has been recognised from the I980's. The consirnction of the

Colombo-Kafunayake Hxpnsssway (CKE) along a final trace (see Figure No 3) was finally

approved by the C^inet of Ministers on 26* June 1998, after a prolonged planning process

which included extensive public consultations. The Environmental Impact Assessment Report

on this project was approved by the Central Environmental Authority on 28 January 1998.

The final design of the expressway (as shown in Figure No 3) has the following main

jiaramelers:

Lengtii (km)

Width of reservation (m)

Width of eadi carriageway (m)

Number of Inter changes

Southern Terminus

Northern Terminus

25.10

30-100

27.20 (Four Lanes)

02 (Peliyagoda and Ja-Ela)

New Keiani Bridge Intersection

Airport Intersection

Figure 4 shows the typical cross section of Ihe road.

The CKE trace runs through significant extents of marshy land witli peaty under-layers. The

proposed methodology for pre-loading and draining these layers has been considered in the

previous EIA. The metliodology requires the use of 5 million cubic metres of sand obtained

from offshore as fill material. The original CKE proposal was to mimic the procedure adopted

for the Muthurajawcia sand fill and environmental clearance was therefore granted. The new

proposals suggest the use of a storage area (see Figure No. 2) on the eastern side of the Dutch

Canal (Old Negombo Canal). This proposal has thus been included in this present EIA,

TTie originally proposed borrow areas are no longer available to this project. Thus it has been /

necessary to explore tlic availability of sand in new, adjacent areas and carry out a full

environmental impact asst ssment of dredging and tmnsporting Ihe sand from these new areas

and to satisfy the Geological Survey and Mines Bureau (GSMB) licensing procedure for

exploration and mining.

2.2 Justification of the Project

The justification for the CKE Project has been deaJt with exhaustively in the main EIA Report

(RDA, 1997). The need for the expressway has been established and the choice of a road link,

OFI^IIÜRE DREDGING POR COLOMBO KATUNAYAKE EXPRESSWAY PROJECT 5

Environmental Imjincl Assessment Report

the actual road trace, the environmental and social impacts and the economic feasibility etc has

already been established. No attempt will be made to repeat the justification for the entire

CKE in this EIA report.

The reasons for tlie selection of the particular source of sand, selection of borrow areas and

melhudology of opcratiuii will be described in sections 2.3 and 2.4 lliai fulluw.

2.3 MeÜïCMJology of Operation

As successfully employed in previous projects, the dredging (sand mining) will be carried out

using a trailing suction hopper dredger. The area to be dredged are bounded by tiie Sri Lanka

Grid Eastings between 93000 E and 96000 E and Northings betwt^n 203000 N and 205000 N.

This area, for wlüch an Industrial Mining Application has been made, comprises the following

kilometre squares according to the GSMB grid reference':

093203, 093204, 094203, 094204, 095203, 095204

The areas to be dredged will have an average water depth of 16m and remain outside the active

longshore and cross-shore sediment transport' zone that influences coastal stability. Tlie

positioning system on board the trailing suction hopper drctlger will be a Differential Global

Positioning System (DGPS) {with a positional accuracy of less than 1 metre) wliich will enable

the vessel to maintain precise positioning and restrict tlie dredging within tlic licensed area.

There will be an intermittent increase in turbidity at site during the dredging. However, as the

site even otherwise has very high turbidity, and the additional turbidity will clear between

dredging ojKrations, any impact on marine organisms will be williin acceptable limits.

The sand/walcr mixture will be pumped from die sea bed into tlie hopper. Once the hopper is

full, tlie vessel will sail to the seaward end of the floating pipeline and connect up with the

pipeline. The contents of tlie hopper will be pumped ashore along an approximately 2 km long

pipeline. A length of 150m of this pipeline is floating while the rest is submerged. The

floating pipeline will consist of flexible elements and will be connected lo a submerged

pipeline, which will in turn connect to the onshore pipeline, (see Figure 5). The floating

pipeline {of 80 to 90 cm diameter) will be anchored to the seabed by ten ton weights each

fitted with three anchors. The weight will be attached to the pipeline by chains.

The submerged pipeline will be laid through the same gap in the reef tliat was used in the

Kerawalapitya Reclamation project (see Figure 5), and at the safe distance from the existing

' Tlie firsl Itircc digits refer lo Uic casting (in kin) and (he next Uirce digits refer lo llie nonliing of tlie soulliH'CSt corner of Itic kiloiiiclre by kilometre grid square.

On-'siioRE DREIX;IN(; FOR COUJMBO KATUNAYAKE EXPRESSWAY PROJECT 6 Etivironnientiil Iinp:ict Assessment Rcpoil

Shell gas pipeline, that generally follows tlic same direction. The submerged pipeline will be

laid on the seabed so that it would not affect movement of fishing boats. It is envisaged that

one or two 2500 kW booster pump stations would have to be used in the pumping pipeline to

carry the material the total distance required. The booster station will be located in tlie sea as

was done previously and/or on land near Hamilton Canal. 71ie Kerawalapitiya Reclamation

Project EIA Report (SLUU^C, 1993) considers these as the most suitable places for the

booster station, provided it is located so as to minimise unacceptable noise levels reaching

residences.

Stockpiling of sand will be carried out in the area marked in Figure 2. The stockpile area is

adjacent to and cast of the Old Dutch Canal and next to the Kerawclapitiya sandfill and The

area used for stockpile would be around 32 ha (80 acres). The maximum height of sand

s(ocki)iIe would be around lOm and tlie average around 6 m.

The sand/sea water mixture (which will be about 80 percent water by volume) will be

delivered to the stockpiling rrca. An outer embankment, perimeter canal and other drains will

be constructed to collect the drainage water and direct it to a specially excavated and prepared

reach of the Old Dutch Canal, which will function as the receiving pond. The seepage water

will be pumped out of the Old Dutch Canal into tlie sea, eitlicr by way of the Kerawalapitiya

Siindfill drainage system or directly using the same pipeline that was used for pumping sand

from the sea. Water levels in selected wells surrounding tlic area will be monitored during tlie

entire operational ix:riod to ensure that their level always remains above that in the perimeter

canal. The stockpile will be built up of sand layers varying in height from 2.5m to 3m

approximately. Tlie sand-water mixture will flow out of the pipe, the sand will settle in the

neighbourhood and the water vill flow off towards the ditches. Bulldozers will level the sand

in front of and behind the pipe end lo the required levels. ITiis process will be continued until

final level of that particular layer is reached over the whole of the stockijile area.

Simultaneously, on tlie outsidcs of the area of the layer, excavator will set up a dike to contain

the next layer.

The sea bed at site is completely flat and does not contain any reefs or other fish habitats such

as sea grass beds as evinced by the detailed bathymetric survey carried out by the National

Hydrographie Office. A copy of this bathymetric survey plan is submitted as Annex 2 to this

Report.

O F F S H O R E D R E D G I N G F O R C O L O M B O K A T U N A V A K E E X P R E S S W A Y P R O J E C T 7

Eiivi ronmental Impact Assessment Repor t ^ ^

A det^Ied seismic survey has already been carried out to quantify the total sand reserve

available within the licensed area. The seismic survey report is included as Annex 5 . The

results of the boreliole investigation are given in Annex 7. These results have already been

submitted to tlie GSMB as per the conditions of tlie Industrial Mining l i c e n c e .

During the dredging a detailed dredging log will be maintained.

2.4 Evaluat ion of Alternatives

fk Offshore Sand,Extr?>ct'Qn Sc Borrow Site Selection

The extraction of sand from offshore regions for the purpose of artificial nourishment of

beaches and reclamation and landfill in nearsliore regions is an accepted practice, which has

been successfully implemented both in the developed and developing world. The extraction

of sand as a mineral from the sea bed is in many cases more feasible, and environmentally

less disruptive, than using fill material from inland sources. This is particularly relevant when

a large quantity of material is required for the purpose of filling. The removal of materials on

a large scale from inland borrow pits lias had a greater impact on the environment than

offshoie mining. The extraction of sand from a considerable distance offshore of the wave-

breaking zone does not have any impact on the nearshore sediment budget, which is the vital

to the stability of the shoreline.

The sdeclion of the borrow sites, within a reasonable disiance {up to 10km) from the proposed

stockpiling site was constrained by iJie fact that a significant number of one square kilometre

blocks off the coas'lii ^ adjacent to Kerawalapitiya had already been rescived by other agencies

of the Government. The six blocks selected had actually been reserved for exploration by

Soulh Asia Gateway Terminals Ltd for obtaining sand for expansion of the Queen Elizabeth

Quay expansion and subsequently released for use by the RDA.

After bathymetiic survey and on the results of the seismic surveys that were carried out, the

project proponent has identified the proposed borrow region (Figure I) as being th^ï nio.st

suitable for the following reasons:

(a) These areas have not been dredged before;

(b) Tliey were well clear of any reefs or ecologically sensitive areas;

(c) The six blocks have a completely fiat sandy bottom free of any coral or reef patches or

other fish habitats.

OFFSHORE DREDGING POR COLOMBO KATUNAYAKE EXPRESSWAY PROJECT 8

Environmental Iiiipact Assessment Repoit

In accordance to the regulations of the Coast Conservation Department sand mining is not

permitted within the 5 fathom contour or 1,000 meter seawards from the low water mark.

Sand mining in the ncarshore regions very close to the shoreline would have a severe Impact

on increasing erosion and hence cannot be considered as a viable alternative, extraction of

sand from very deep areas and pumping to the shore is extremely costly and such an exercise

will be economically unviable. The navigation channel of the Port of Colombo is a declared

restricted area and hence dredging cannot be carried out in the channel.

For offshore sand mining to be a viable option, from both an economical and engineering point

of view, it is important lliat dralging is carried out as close as possible to the shore, but at a

sufficient distance offshore from tlie slioreline so that it does not have an impact on the

longshore drift and the onshore-offshore sand movement coni])onenls of the coastal salinient

budf.et for the given region. Research and practice in coastal engineering indicates that

extraction of sand, well beyond the wave breaking zone, has no impact upon coastal erosion or

accretion. Coastal engineers have established that extraction of sand beyond the -12mMSL off

the west coast of Sri Lanka is safe from the point of view that it would have no impact on

ncarshore processes that contribute to coastal erosion or accretion. In view of the above

observations the site chosen by the project proponent for borrowing of sand is acceptable.

The alternatives that were available for the extraction of sea sand could be classified as

follows:

(t) Extraction/dredging of sand from ncarshore;

(?) Extiaclion/diïdging of sand in deeper areas beyond the proposfxl borrow area;

(3) Extraction/dredging from the navigation channel.

Removing sand from the ncarshore area is not acceptable because of interfeience willi coastal

sedimentation processes. Extraction of sand from deeper areas or from the navigation channel

would make the operation uneconomical because of the distances involved.

Fill material from land or river based sand sources is normally an alternative. It should be

noted that the volume of fill material required is very large, viz. up to 5 million cubic metres.

No large land based sand sources have so far been discovered. Furlliermore, the

environmental consequences of mining such a large amount of sand in the densely populated

Western Province are likely to be unacceptable. The two possible rivers sources are the Kelani

Ganga and the Maha Oya. Both rivers are already subject to over-mining and the increased

coastal erosion resulting from the ongoing sand extraction has been severe. Any further

extraction of sand from these rivers would eventually have the same (or worse) adverse impact

OfTsiiORE DREDGING FOR COLOMBO KATUNAYAKE EXPRESSWAY PROJECT 9 Environmental Impact Assessment Report

as the removal of sand from the nearshore region. Thus, the supply of 5 million cubic metres

of sand from land or river sources is completely non-viable.

Hence, it is concluded that the only possibility is to obtain the required fill material from tlie

proposed offshore borrow site, which is llie only available site at a reasonable dislanee, wiiich

has not been reserved by other users.

hi PellvervofSenSand

There is no practical method other than a pipeline for delivering (he sand to the stock-pile.

Dcllvcnng the sand at Colombo port and tlicn tniclcing it from there to the stockyard wil! both

be extremely slow as wdl as disruptive and expensive. There is also no practical method for

unloading the sand directly on the beach from a vessel. Tlie proposed methodology allows for

the sand to be pumped ashore from the trailer suction hopper dredger. Pumping the sand to an

intermediate .stockpile on the beach is also not economical because of the need fur double

handling. TTius the only viable solution is to pump the sand/water mixture all tiie way to the

final stockpile area(s). As I'lis would require a length of pipeline exceeding three kilometres, it

is necessary to install at least one booster pump station to overcome pipe resistance.

The methodology adopted by the Kerawalapitiya Reclamaüon Project was for the dredger,

once tlie hopper was full, to s^l up to the end of tlie pipeline and connect up. The pijx-Iine had

one booster station in the sea, which r llowed the sand to be pumped direct to the fill area. The

same methodology will be employed in Ihc present case.

The pipeline axis is to some extent pre-determined by the existing break in tlie reef which must

be used as the crossing point for the submerged portion of tlie pijjeline. The pipeline must

cross above Hamilton Canal leavin.' sufficient headrcK)ni for a 3.5 Tonne fishing vessel to pass

under it. In the altem; five it is also pos;-ible to lay a submerged pipeline across the Hamilton

canal and the lord, as done i cviou-sly di'nnf the dredging operations for the Kerawlanitiy

landfill.. The proposed pipelines trace is shown in Figure 5. The floating pipeline will be

assembled on water and dragged into position by tugboats. The submerged pipeline will be

similarly assembled afloat and sunk in position by filling with water. The mooring of the

pipeline will be by chains attached to ten Tonne iron weights.

OFTSIIORE DRFJXnNG FOR COLOMRÜ KATUNAYAKE EXPRESSWAY PROJECT 10 Environmcnl.'il Impact Asscssnicnl Report

c. Ix>c;ilion nnd Type of Booslcr Station

The booster station will be located at sea (as shown in Figure 5) inside the reef.

d. Returning Sca\v.itcr from Stockpile Site

The pumped sand/water mixture would contain about 80 percent or more seawater by vohinie.

That means that approximately 20 million cubic metres of scawaler have to be pumped back

into the sea during the filling operation. There are two stages to this operation. The first is to

gather die excess water in the de-watering ditch around die storage area and die other is to

pump it back into the ocean via a suitable pipeline. The possibility of returning the water by

gravity flow into Hamilton Canal has been considered by die KRP and found to be

unacceptable because it would have caused too much contamination of groundwater and also

because the flow rates would have been insufficient.

Thus a separate return water pipeline would have to be laid. The main operational criterion is

that the canal water levels are always maintained below the level of the surrounding

groundwater table. An alternative methodology would be to use the same pipeline for the

return water. In this case a new set of pumps is still required at die stockpile site (die booster

station can still be used) and the two pumping activities have to be carried out alternately.

Care has to be taken to ensure that the drainage pond has sufficient storage to hold the return

water from one hopper load 5,400 m* of sand, ie., 21,600m' of water.

2.5 Workforce

The workforce will be the dredger crew, and they will be housed in the dredger. All

occupational safety procedures recommended for operation of such dredgers will be followed

as the dredging work will be carried out by an internationally experienced dredging contractor.

The stockpile area will be manned by die workforce of die main contractor and this is covered

by die previous EIA Report.

2.6 Programme

The Construction programme for the dreading operation is given in Annex 3.

OFFSHORE DREOGINÜ FOR COLOMBO KATUNAYAKE EXTRI-SSWAY PROJECT I i

Etiviroiiiiienl.'il ïnipiict Asscssmoiit Itcporl

3.0 BORROW AREA AND DREDGING

3.1 Location and Size of IVoposcd Borrow Area

The baüiyiiiclry of the sea bed in and around the proposed borrow site is given in tlie

bathyinetric survey plan prepared for the project by Lanka Hydraulic Institute, given as Annex

2. V : area is also shown in Figure I. In the 6 sq. km block proposed as the borrow site the

sea bed slopes gently to the west from 13 m in the east to 19 m depth in the west. Tlie

echographs do not show the presence of any reefs, rock outcrops or seagrass beds. Tlie

bottom is sandy.

3.2 Volume and Type of Material

The types of loose material available above the base rock were identified as follows after

interpretation of the seismic survey could be divided into three classes (see Annex 5) as

follows:

Unit 1; Comprising sand on top giving way to fine material at the bottom

Unit 2; Channels (cutting tlirough unit 3 and occasionally through unit 1) filled with well

laminated sediment probably fine sand and silt/clay.

Unit 3: Near surface sands, mainly medium sands to gravel widi some finer fractions at lower

levels.

Unit 2 cannot be used in tlie project. The main resource to be mined is unit three which lies

either on the surface or very close to it. Although a part of unit 2 might also be used, only unit

3 has been taken into account in quantifying the available resource. The volum.e of material

required for the road filling is 4.8 million m*, and a further 0.5 million m' will be required for

filling the stockpile area. Tlie available volume of unit 3 is conservatively estimated to be 8.34

million cubic metres.

3.3 Method of Dredging

The trailer hopper suction dredger to be deployed will cause the minimum disturbance to the

sea bottom. The main source of turbidity will be the overfiow water from the hopper.

Maximising the transport density into the hopper can reduce tlie amount of overfiow water.

Spillage during can be minimised by not overfilling the hopper.

OFFSHORE DREIÄING FOR COLOMBO KATIINAVAKE EXPRESSWAY PROJECT 12

Etivirotinu'iilal Impact Assessment Rcpoi!

As only one dredger is being used, and it has to sail to the end of ilie pipeline to discharge each

load, tlic dredging ojx;raiion will not be continuous. The estimated cycle time of dredging,

transportation and pumping into stockpile will be approximately 6 hours. Thus in every six

hour cycle, there will be about two hours for the turbidity raised by each dredging operation

to settle down

3.4 Timing, Rale and Zoning of Produclion

Tlie area to be dredged will be carefully regulated using DGPS position fixing. The dredging

plan and schedule will be submitted to RDA two weeks prior to commencement. The

dredging plan shall take into account the recommendations made for mitigation of impacts. The

dredging and stockpiling will be conducted in two campaigns. One before the 2001 monsoon

and one thereafter. Each campaign will take approximately 4 months.

3.5 Vessel Numbers and Movements

A plan containing vessel numbers and movements will be filed with the naval autliorities and

the Fisheries Department well before implementation of the dredging plan.

3.6 Control of Dredging

The dredging plan will be executed by the dredging contractor and a representative of the

Client shall be permitted to come on board to monitor progress.

3.7 Notification and Liaison

The dredging plan and schedule should also be notified to a designated officer of the Fisheries

Department to ensure tliat tlie fishing community is kept aware of the movements of the

dredger. The plan will also receive formal clearance from the Western Naval Command.

Tliese contacts will be facilitated through the good offices of the RDA.

3.8 Otishore Destination

This is discussed in section 2.4.

3.9 Altoninlive Sources of Material

This is discussed in section 2.4.

OKl>^^ORF.DRF:tx;IN(;RlRC()U)MlM) KATIJNAYAKE Exrut-isswAY pRojFxrr 13 1'JLviromnctUal liii|iacl Asjjcssmeiit Reporl

4. RORROW AREA AND ITS ENVIRONMENT

4.1 Itiysical Environrneiil

The baUiynietry of Ihe sea bed in and around the proposed borrow site is given in Ihe

bathymctric survey plan prepared for the project by Lanka Hydraulic Institute, given as Annex

2. The area is also shown in Figure 1. In the 6 sq. km block proposed as the borrow site the

sea bed is perfectly flat over much of the area, and is at a depth of 13 m to 19.5 m. The

echographs do not show the presence of any reefs, rock outcrops or seagrass beds. The

bottom is sandy with patches of finer deposits.

A seismic survey of the area was carried out by LHI in association with the Danish

Geotechnical Institute. Four boreholes were drilled to provide calibration data. The

interpretation was also assisted by some vibracore samples taken in an adjacent area for a

previous project. The area surveyed, the positions of tlie boreholes and vibracores are shown

in Figure 6. The seismic and geotechnical work is described in Annex 5. The results of this

investigation indicates that the sea bottom is sandy (except for a few small patches of finer

material) and that there is a sand layer of 1 to 2 m thickness available for extraction. The

isopach chart (Figure 7) shows tlie distribution of the exploitable layer.

The geological history of the area indicates a general recession of the coast. The appearance

of beach rock on the beach is identified as a sign of recent erosion because it had been formed

within the sand body of the beach ridge. In the stretch north Dikkowiia near the Pegasus Reef

Hotel the coast has receded behind the beach ridge. Due to excessive sand mining in the

Kelani Ganga, there is insufficient river borne sand to nourish this beach segment. This deficit

contributes to increasing coastal erosion in the area.

The wave climate in the area is characterised by two simultaneous wave systems. These are

tlie long period (12 seconds) swell waves from south-southwest (wave direction 200E to 240E

from the nortli) all year, and a shorter period (5 seconds) sea wave system with the majority of

waves projiagaling almost normal to the shore line. The sea wave system is generated by the

South West Monsoon trade winds.

4.2 Biological I'.nviroiiiiU'nt

NARA undertook a study of tlie biological environment, where a short-term survey has been

conducted to determine the impacts on marine ecology and fisheries.

, The key areiis of study are;

OFFSHORE DRFIMUNG FOR COUÏMRO KATUNAYAKE EXPRESSWAV PROJECT 14

Enviioiiiiieiilni liiipacl Asütasiiiciil Repotj

• Borrow site and adjacent area

• Fishing activities

• Socio-economic conditions

• Extent of shrimp trawl grounds

• Impacts of removing sand on marine ecology and fisheries

The detailed report is given in Annex 6. The findings of the report are used in the descriptions

that foUow.

The Borrow Site and Adjacent Area

The borrow site is a rectangle with the longer (3 km) side running east-west. The area does

not contain any reef formations or any rock outcrops. However, the eastern half of the

rectangle lies within the trawling grounds of the local fishery. The area is a part of tlie

spawning grounds for shrimp and the habitat for several species of fin fish and crustaceans.

The subject of fisheries is dealt with in the section 4.3.

Impacts on iVIariiic F^cology

The magnitude of impacts rendered will depend on the following three key factors:

• Metliodology employed

• Frequency of sand removal

• Duration of the borrowing operations

The need to minimise the impact of the above three activities will guide the selection of best

practice in planning and carrying out the dredging activities.

The possible negative impacts are:

• Disniption of the shrimp larvae, eggs etc in the water column

• hicreased turbidity will reduce primary protluciion which is the foundation of a sustainable

marine ecosystem

• Removal of Ihe bentliic fauna and flora during dredging

OFF^HORI' DRFIXJNC; FOR CoixiMito KATIINAVAKE EXPRESSWAY PROJECT 15 LuviroiiiiiL'iilal Iiiipact AssesMiioiil Repoil

• The borrowing activity would impact seagrass beds and coral reefs (if any exist in the area

aiid on juvenile prawns.

4.3 Ilimiaii Fiivironnicnt

4.3.1 Fisliiiig Aclivities

The major fishing activities have been categorised into three main groups. They are

a) Nearshore fisliing witli log rafts and fibreglass rafts (0.5 km to 4.0 km from shore)

b) Nearshore fishing with 17-23 ft FRP boal-s (0.5 km to 12 km from shore)

c) Nearshore trawling with 3.5 ton inboard engine boats

Fishermen between Dickowita and Uswetakeiyawa operate approximately 200 theppams on a

normal fishing day. The total number of boats operated during the monsoon (May-Sept) is

iiuich higher than the number operated in the non-monsoon (Oct-Apr) period. The number of

theppams operated, however, declines during the monsoon because of rough seas. Further

details are to be found in Annex 6.

Studies carried out by NARA (Annex 6) indicate that fishing activities take place on the eastern

half of the sand mining area. The studies also show that shrimp trawling is the most important

fishing acüviiy in this area. All the fishing activity is very seasonal and a very large

percentage of the fishing income is obtained during the southwest monsoon, ie May-September

each year. The shrimp fishery is connected with the production of the Negombo Lagoon, and

it appears that the minimum disruption of the shrimp life cycle would take place if dredging is

done in the period December to April.

The prtxluctivity of the shrimp fisheries of Hendala presented in Annex 6 have been processed

to show the percentage of the total value of production in tlie off monsoon season is indeed

very low (see Table 1). The figures for Hendala should be very similar to the area under

consideration. It should be noted that the totals given in Table 2 applies to a much larger area

of fishing ground than the 6 square kilometres under study. On the other hand, most Theppam

fishermen operate mainly outside the monsoon period, thus dredging activity during the off-

Enonsotin period would affect these fishermen more than the average shown in the overall

statistics.

There could be adverse impacts on small scale fishermen unless care is taken to confine the

extraction of s;ind to tlie western half of the designateti area. The overall fisheries impact will

OFFSIIORK DRIIIXÏINC VOR Coi»Mi«) KATIFNAVAKK EXPRFSSWAY PROJECT 16 Environmental Impact Asscssnicnl Rcpoil

bc small if Üie dredging operalions are carried out mainly in the period from December to

April. The removal of a sand layer would have an impact on the productivity of the dredged

area, which would recover fully over a period of time.

ITie NARA report (Annex 6) states that " Tlicppam Fishemien go out fishing around 3.30a.m

and return around 7.30a.m ". TTiis means tlmt they would be Fishing for a period of about 3

hours at the fishing grounds Oess travel time). As far as possible dredging could be planned to

be outside this four hour period to cause minimum disruption. The dredging operation could

be organised so the deloading the hopper takes place as far as possible during this period.

Moiitli (1999) Effort CPUE TP NI (Rs) % I n c o m e

January 12 18.24 5,36 571 0.98%

February 12 17.77 5,22 198 0,31%

March 7 8.35 1.46 250 0.25%

April 9 12.95 2.79 787 0.98%

May 37 15.03 13.25 1075 5.70%

June 49 28.17 33.29 1985 13,50%

July 71 36.31 61.87 1785 18,18%

Auj^iist 77 30.46 56.10 2952 32.60%

September 51 22,49 27.66 1712 12.12%

October 46 22.86 25,37 1322 8.72%

November 39 23.11 21.63 1118 6.05%

December 12 19.00 5.73 349 0.60%

Table 1 Catch/EfTort Statislics for Shrimp Trawl Fishery in Hendala Effort = Average boats operated/day CPUE = Mean Catch in kg/boat/day TP "Tola! fish "roductivity NI = Mean net income/operation

Information regarding the boat population, species of fauna, fishing gear, the mean monthly

income of persons engaged in fishing activity etc, are given in Annex 6.

Over the past several years, fishermen of the area have observed a gradual declining trend of

the fisheries resources. This is partly tlie result of more people entering into fishing activities

in the area.

Fishermen in tlie area, particularly the smaller local fishermen have already been adversely

affected by restriction of access and movement enforced because of security concerns (Port

Security Zone, Gas Terminal etc). Any further restriction of fishing activity, however

temporary, should be avoided as far as possible or compensated.

OFFSHORE DREDGING FOR COLOMBO KATTTNAYAKE EXPRESSWAY PROTECT 17

Envirointtciilal Impact Assessment Report

4.3.2 Other Activities

Existing Inf rast nicture: The nearshore area just north of Colombo has an increasing number

of inslallalions connected with the import of i)elroiciim prmhicts and the disposal of waste.

These are tlie Shell gas terminal and pipeline, the proposed CPC terminal and pipeline, the

Colombo North Sewage Outfall etc. This has increased security concerns and tlie resulting

measures have adversely affected exisüng users. The environmental hazard has also increased.

Mililary Exercises: The security zone of the Port of Colombo is well outside the area of

activity and as such the dredging activities will not impact on any ongoing security exercise.

Nevertheless, in compliance with current regulations, tlie dredging activities would be

commenced after obtaining clearance for the vessels and crew from Naval Headquarters.

Recreational activities: The area under consideration is not used for any regular recreational

activity. The tourism activities which are shore based will not be impacted.

OFFSIIORK I)KFJX;IN(; IX)R COIX)MIIO KATUNAYAKE EXPRESSWAY PROJECT 18

Environmental Impact Assessment Report

5.0 SAND STOIUGE SITES AND THEIR ENVIRONMENT

The sandfill site is a marshy low lying area which is bounded in the west by the Old Dutch

Canal and in the east by a small number of homesteads which are located at a higher elevation.

The Old Dutch Canal is in a state of complete disrepair to an extent that weeds and aquatic

plants cover tlic entire water surface.

The land will be acquired by the state and does not perform any economic function at present.

Neither has it been included in the Muthurajawela Conservation Area. The land presently

drains into the Old Dutch Canal. It has been proposed that a part of the canal could be re-

excavated and used as the collecting basin for the seepage water, which could then be pumped

out. It is also proposed tlial a peripheral canal be along the eastern boundary to connect up to

the Old Dutch Canal.

Due to the pre-loading of the site by the storage of sand, the previously marshy land will be

improved (from the point of view of building construction) for later development. The

settlement of the site would invariably cause a certain loss of sand during transit. The creation

of the storage site will, to an extent, temporarily reduce the flood retention capacity of that

area. This could easily be overcome if the return flow pumps could be operated during every

storm.

OFTSIIORK I)KI:IX;IN(: FOR COLOMEÏO KATTINAYAKK KXI-RE-SSWAY PROJECT 19

Knvironmoiilal Impact Assessmciil Rcpoil

6. AN IICII'A I Cl) ENVIRÜNMICNI AL IMPACTS

6.1 Physical Kffects

* Transpon and Settlement of Fine Matetial Suspended by the Dredging Activity:

The dredging method adopted utilises a trailing suction dredger. Unlike in tlie case of a cutter

suction dredger, a grab or a bucket dralger, the increase in turbidity is less in the use of a

trailing suction dredger. The absence of any cutting or excavating action will reduce the

amount of turbidity generated at the point of dredging. There would however be an outwash

plume resulting from hopper overflow. This will be controlled by limiting the dredging

activity to areas of sandy bed. The sediment plume from tlie Kclani Ganga outflow makes this

a high turbidity area under norma! conditions. The contribution to turbidity from this dredging

activity is not expected to contribute significantly. There will, however, be some increase in

turbidity during dredging operations. Only a single dredger will be deployed. The dredger

will make four trips a day for de-loading. The dredging operation is discontinuous and will

allow time for some settlement of turbidity between trips.

* Implications for Coastal Erosion:

As the dredging operation is taking place at 17 meter depth at a distance in excess of 3 km

from the coastline, tliere will be no impact on coast erosion. The temporary increasing in

depth will be around one metre and will be spread over the entirety of the 6 grid squares. This

increase in depth will have no impact on the wave regime at this depth and consequently have

no impact on the sediment transport processes on shore. The waves experience^l along this

coast line are also not capable causing any measurable movement of bed sediment at a depth of

17 metres. Thils the sediment being removed from the bed does not form a part of the

sediment budget of the shoreline which delermines whether the beaches are stable.

* Implications for Local Water Grculationi

There will be no removal or creation of any other topographical features on the sea bed such as

pumping stations, booster stations or pipelines. The dredging is completely self-contained.

OFT^IIÜRE DRL:IK;ING FOR COLOMBO KATUNAVAKE EXPRESSWAY PROJECT 20

Enviroiinicntnl Impact Assossincnl Itcpoit

* Ukely liffects on Oiatises in Wave and Tidal Conditions:

The dredging is spread over a 6 square kilometre area and the average depth of removal is less

than 1 m. The sea bed topography is such tliat there will be no measurable impact on wave

and tidal conditions.

* Likely mfects on the Local Coastline.

The magnitude of the dredging operation is too small and the dredging site has been so selected

as to have no likely impact on the shoreline.

• Water Quality Impacts:

No new soil type will be exposed as a result of dredging. The only impact wilt be a marginal

and temporary increase in turbidity at site. Any impact will be insignificant and of a

temporary nature. (Impact of seepage will not exceed 1 km and the effect is temporary until the

next rainy season.)

* Cumulative effects of Dredging:

At present there is one other dredging project underway adjacent to this area, as described in

section 4.3.2 ^ove. Mining rights in the 6 km grid squares under consideration will be

exclusive to this project during tlie dredging period. A post-dredging baUiymetric survey will

be carried out and il'ie baUiymetric survey plan deposited with the GSMB.

6.2 Biological Effects

The main biological impact will be the short term impact on the productivity of the dredged

area. The following mitigating factors must however be kept in mind. Firstly, tlie

predominantly sandy bed in the area to be dredged indicates a relatively low productivity,

when compared with other nearby areas with fine sediment on the surface. Pivvided the

dredging activity docs not expose the undcrlayers, the sea bed would recover to nearly its

original state witliin a relatively short time. The temporary increase in turbidity will also effect

a reduction in productivity. This again could be minijnised by llie intermittent use of tlie trailer

suction hopper dredger, which must be regulated to dredge a given area only once.

OFFSHORE PRKIK;ING FOR COU>MBO KATUNAYAKE EXPRESSWAY PROJECT 21

Enviroiimcnial Impacl Asscssniciit Rcpoil

The impact on the fisheries productivity could be minimised using best practice during the

dredging operations. In the context of the total area of nearshore area available for fisheries

productivity, the affected area is only a small fraction. Nevertheless, impacts could be reduced

even further if the sand could be extracted from the smallest possible area within the

designated 6 square kilometres.

6.3 EfTects on the Human Environment

The area selected for tlie extraction of sand lies partly within the area used for shrimp trawling.

The rectangular area lies between 3km and 6km from the shore, while fishing activities take

place to a distance of about 4 km or 4.5 km from the shore in tliis area. Thus it would be very

beneficial if the dredging activities could be carried out only in the western half of the reserved

area. By a happy coincidence, tiie available sand layer is thicker in the western part and the

full requirement of 5 million cubic metres can be extracted from the area lying outside the

trawling limit, (see Annex 6).

Nevertheless, the presence of a working dredger, which sails towards the shore every four

hours, and the presence of a length of floating pipeline would be both a hindrance and a hazard

to fishing craft. Thus, very close liaison must be established between the dredging contractor

and the local fishing community to avoid any conflict.

OFI'-SHOIU: DKIIIX.IM; FOR COUIMHO KAHINAVAKE EXPRESSWAY I*R(JJECT 22

Kiivii-dimn-iilal Iriijwcl A.ssessnierit Rcpnil

7.0 FUOrOSKD M1IIGATORY MEASURES

7.1 Regiilalioii/Moniforing of Dredging Activity

Tlie dredging programme will be submitted to the harbour authorities, and the defence

establishment will be kept informed of dredger movements. The dredger will be in regular

radio contact with the Pilot Station in the Colombo Harbour.

Frequent contact will be maintained with Fisheries Officers of the area, and the fishing

community will be kept informed of dredging operations, timing, etc.

7.2 IVolcclinii of Borrow Ai-eas

It is necessary that tlie dre lging programme proceeds according to the pre-set schedule to

ensure that the impact of increased turbidity is felt intermittently and in a limited area at a

given time. The dredging will be controlled to ensure that lower strata are not exposed after

on no account exposed after a given area is dredged out, so that the disturbed sea-bed

ecosystem is given the best chance of re-estabUshing itself in the shortest possible time.

The use of a trailing suction hopper dredger for minimising turbidity has been specified. No

otlier type of dredger is permitted.

7.3 Coastal SlabiUty

The prescribed borrow area is such that the act of dredging, and the consequent small increase

in water depth is sufficiently far away not to have any impact on coastal stability.

Laying of the submerged pipeline (80-90 cm diameter) on the sea bed would only form a very

minor obstruction to littoral sediment transport. However, it is recommended that the pipeline

should be buried under the sand where it crosses the beach zone. It is specified that tlie

pipeline will cross the offshore reef (see Figure 5) through an existing gap. Under no

circumstances will this assessment cover the impacts resulting from making a new opening in

the reef.

7.4 Niiviynlioiiiil Ihizards and Interference with Fishing Activities

111 order to prevent collisions between fishing vessels and the floating pipeline, it is

recommended that warning lights/buoys indicating the presence of the pipeline. The presence

of tlie submerged pipeline in the gap in the reef should also be clearly sign-posted. The

pipeline should be laid in a manner that fishing vessels that also use this gap are not obstructed.

OiTNMORE DRI:IK;IN(; FOR COMJMIM) KATIJNAVAKK EXPRESSWAY PROJECT 23 Envirciiiiiiciil;i[ lm|i;icl AssessiiiPiil Ropnrl

In onier to ensure nnnimiim impact on fishing activities and on productivity, the dredging

activity should be as far as possible be confined to the western ha(f of the area reserved for

dredging. Deloading activities should, as far as possible, he timed to coincide with peak

fishing activity to cause minimum inconvenience to fishing crqft. If any disturbance to the

fishery community in the dredging area is encountered compensation will be paid after

negotiation with the dcpailmenl of IHsheries under their recommendation.

A formal liaison and a grievance handling procedure sliould be set up to forestall the possibility

of disputes with tlie fishing community.

7. 5 Kpeline on Ijind and Crossing Ilaniillon Canal

The laying of the pipeline on land should be done in a manner that causes minimum disniption

to the environment and minimum inconvenience lo local residents and road transport.

Crossing Hamilton canal should be done ensuring sufficient headroom for 3.5 Tonne fishing

boats to pass witliout hindrance. The location of all pumping stations should be made in such

a way that minimises the disturbance to local residents caused by noise.

7.6 Sea Water Impacts on Surface Water and Groundwater

Evacuation of seawater from the sand storage area must be carried out in such a way that

leaves no possibility of contamination of surrounding surface water bodies or the groundwater

table. The preparation of storage site would require the excavation of a peripheral canal and

otiicr drainage canals and the re-cxcavation and cordoning off of the Old Dutch Canal to serve

as the sump for collecting seawater. If the same pipeline is to be used both for pumping in die

sand/waier mixture and for pumping out seawater alternately, sufficient storage must be

provided to ensure that the sea water level does not exceed the surrounding groundwater

levels. This would also ensure that the presence of the storage site would not increase the

tlood hazards in the adjacent homesteads.

OFI'^HORI' I)RI;IX;IN(; FOR CoutMito KATIINAVAKE EXPRESSWAY PROJECT 24 Envirotinu-nliil IIIIJ);K1 Asa'ssmeiil Repoil

8. MONITORING PROGRAMME

8.1 Drodgiiiß Activities

A dredging log will be maintained ai ail times during the dredging operation. An online record

will be maintained of all dredger movements. This log will include the navigation lines on

which the dredger is moved, the volume of material dredged, times of dredging, the site to

which materia! was being puniiKd, etc.

On completion of dredging, a detailed bathymetric survey of the licensed area will be carried

out and the post-dredging balhynietric plan submitted to the GSMB.

8.2 Piiinping/I>niiiiagc Activities

A pumping log will be maintained at every pumping station, in which times, pumping rates

and hourly water levels in the inflow pond/canal would also be recorded. In order to ensure

that excessive seepage does not occur, a record will be maintained of water levels in each canal

system (Sites A and B taken at the start and end of drainage pumping) and daily groundwater

levels at selected points in the adjacent populated at ea. Weekly sampling of groundwater

quality should be carried out at selected wells.

8.3 Long Term Monitoring of Dredge Site

As far as the Consultant is aware, pre- and post-project monitoring of the borrow area has not

been systematically undertaken at any previous sand borrow site. Thus the speed of recovery

of the seabed ecosystem has been the subject of informed speculation. Particularly as sea bed

sand mining is expected to increase rapidly in the near future, it is imperative that a strong,

long term monitoring programme is undertaken as soon as possible, The frequency and

intensity of observations and sampling have to be determined by the respective regulatory

agencies.

Ol Fsnourc I>Ri:rx;iN(; R)R COUIMKO KATIINAYAKE EXPRESSWAY PROJECTT 25 Envii'onmeiilnl Impact Assessment Report

9.0 CONCLUSIONS AND RECOMMENDATIONS

The offshore saiid borrow method is the most environmentally acceptable method of obtaining

the required fill material.

The site is selected with a view lo achieving the smallest and least persistent environmental

impact as is possible. The methtxl of drwlging, the area of dralging and times of the dredging

operations have all been selected with this in view.

The impact of removal of 1 m of betl form in the 6 sq km block is not expected to create a

significant physical impact, as it is from a high turbidity de|X)sitional area for the .sediment

plume from the Kelani Ganga. The maximum impact will be from the temporary raising of the

turbidity levels during dredging operations. The loss of productivity in tlie dredged area will

be temporary. The inconvenience and restrictions imposed on small scale fishermen have to

be minimised.

The distance and depth at which dredging takes place will ensure that this activity will in no

way have an impact on coastal stability.

The pollution of surface and groundwater by the release of saline water during fdling is prevented by collecting drainage water and pumping it directly to the sea.

OFi"sn()ki:Diu:ix;tN(; FORC()U)Mm) KATIJNAVAKK EXPRESSWAY PKOJKCT 26 Knviroiimoiitiil hn[)!ict AssfssniciH Roport

LIST OF REM!:itENCES

1. South Asian Gateway Terminals (Pvt.) Ud/Lanka Hydraulic Institute, Ltd

Colombo Port Development Project - Phase 1

Expansion of QEQ - Environmental Assessment Report

(Submitted to World Bank/ADB - December 1998)

2. SLRDC/Engineering Consultants, Ltd.

Kerawalapitiya Reclamation Projei. t

Environmental Impact Assessment Report - December 1993

3. Atiiapaitu Anton R. Jayakody, D.S.; De Alwis, T.L.

Report on the short term survey conducteti to investigate different fisheries around ilie borrow site at Hcndala and lo Determine the impact of Sand Borrowing at these Fisheries - May 1995

4. ADB - Environmental Evaluation of Coastal Zone Projects

Methods and Approaches - ADB Environmental Paper No. 8, June 1991

5. World Bank - Guidelines for Environmental Impact Assessment - 1989

6. World Bank - Environmental Considerations for Port and Harbour Developments Technical Paper 126(1990)

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" — Proposed Expressway (W)

Main Road {A3}

IC Interchange B.I.A. Bandaranaike Inlefnalional

Airport A1 Colombo - Kandy Road A3 Colombo (Peliyagoda) - PuHalam Road i n

Peliyagoda > < i

'X-

P I P E LINE SYSTEM TO THE STOCKPILING AREA

Colombo •- Kat;unayake Expressway |w* i i * r n Troe») Cons t r u c t i o n ' P r o j e c t

S o u r c e - S .S . -L .H .D .C . and R . D . A .

Figure 5 - Layout of the Submerged Pipeline

?h\OJF.CT

T- < ff>

• CKE z.

• CK E 3

CK? 2 «

CKt - 1 CKE: - 2 CKE - 3

CKE - 4

94,656 95,610 94,352 95,583

203000N

203,059

203,064

203,560

204,560

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SURVEY AREA AND LOCATION OF VIBRACORES

Ftguro 6 - Layout of Boroholos

Mi • ' ':W,-mMß:-'M^^m^'^

H M O O O

M a o o A O»

H

205000 N

204000 N SAND RESOURCE CHART,

ISOPACH CHART CKE AREA

DEC ; 1999

Cl . : 0.5 MEIERE

SCALE . 1:15,000

PROJECTION TM

ELLIPSOID EVEREST 1830

DGl JOB NO 161 17 343

EXEC HLR

203000 N Area with seismic uni t 2 exposed at surface

CKE SAND SEARCH STUDY

Figure 7 - Resource Map (Isopatch Chart)

lanka hydraulic Insti tute Ltd Danish Geotechnical Insti tute Executed HLR Checked : INS

Approved : JBC

Dale Date Date

2000-01-09 2000-01-24

2000-01-24

Subject : ISOPACH CHART

OrfNiioRE I)RFrx;iN(; FOR COLOMBO KATimAVAKF. EXPRÜSSWAV PROJKIT

EiivironriK'iilul liiipiicl A.ssessiiK-'iil Krpoil

ANNEX 1 - TERMS OF REFERENCE

TERMS OF REFERENCE

[•OR THE

ENVIRONMENTAL IMPACT ASSESSMENT (EIA) REPORT

PROJECT TITLE

PROJECT PROPONENT

PROJECT APPROVING AGENCY

OUTLINE OF THE EIA REPORT

Summary Chapter I Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9

Off-Sliorc dredging for CK[- Project

Road Development Authority

Central Environmental Authoriiv

Introduction Description of the Project Borrow area and Dredging Borrow area and its Environment Dump site and its Environment Descnption of the Anticipated Environmental Impacts Proposed Mitigatory Measures Monitoring Program Conclusion and Recommendations

Annex I

n in rv

Executive Summary

Sources of Data &. Information References List of preparers including their work allocation Comments made by ihc public, NGOO and other agencies, A brief statement of tlie analysis of such comments should al;o be included.

The summary should be a brief non-lcchnical siiinniar>' of the salient features of the proposal, alternatives, existing environment, environmenia! impacts and mitigalori' measures adequately and accurately covered The summary should also mdicatc in brief the responses to tlic issues raised by the public and other agencies.

CHAPTER I:

(NTRODUCTION

Tlic signiTicancc and extern or llic cffccis of agt;rcg;ilc cxtracUoii on the scii bed \\ ill depend upon a range of factors including llie location of tlic Lccnsalarea, Uic nature of ihe surface and imdcrlyiny sedmicn!. llic mcUiod of cxiriiction, and Uic scnsiliviiy of kabilats and fislicries in tJic localily Tlie ElA/lEE aims lo enable llie organizaiion{s) responsible for licoisint; lo establish whctlier Uic dredging \MII have

• any significani impact on tlicadjaceiMcoast.

• any potential impact on fislieries. local or regional

• areas of marine conserNation

• other marine environmcmal issues

CHAPTER 2:

DESCRrPTÏON OF THE PROJECT

•%A Nature Aims and Scope of Project

A descriptioti of the tnajor featurts. location and layout of tlic project. Mode of operation and time-table for development coiitemplated expansion of the project at the proposed location.

2.2 Justification of tlic Proiecl

2.3 Methodology of operatton

Special reference should be made to the nature and type of any structures envisaged under this project within the coastal zone with special emphasis on Ihe foieshore/nearshore reaches of the coast line.

2A Evaluation of Alternatives

a. Burrow site selcaion Discuss the alternative burrow sites for the dredging operations (sea sand)

b. Delivery of lill material (sea sand) Describe the alicrnaüve methodology for dclivei y til till material to intermediate booster station (if any) Describe the alternalivcs for (he siting of tlie proposed pipeline and method of mooring and laying.

C. Describe ttie aliemaiives for liKation and type of intermediate Iviostfi Station.

d. Proposed altcrrialive methodology für pumping sea water from ihe isolated till area back into ttie sea.

This section should briefly state the basic criteria for evaluali.in of alternatives and should recommend tiie environmentally suitable alternative lor each option mentioned above.

2.5 Work force

Labour requirements Availability of labour Occupational health and safely Facilities rc<iuircd or provided

2.6 Time Schedule

CHAPTER 3 :

BORROW AREA AND DREDGING

3.1 Location and stzc of jiroposcd barron area

The location of llie proposed borrow area should be specified by a list of co-ordinates together with a map showing its location in relation to the surrounding sea area and adjacent coastlines, Tlic size of the area should also be q)ccuïed.

3.2 Volume and type of material

Tltc volume of materia! in the bomnv arcc should be slated along with a desci iption of the type of material e.g. sand, gravel. Representative data on die particle size consument of die deposit should be provided, including tlie fine fraction < 2 mm in size, as Ulis will be important in assessing the potential environmental iiÈipacls of dredging.

3.3 Method of dredging

TIic type of dredgers to be used should be described e.g. trailer sucdon hopfcr dredger, togcdicr Willi details of vessels load capacity, overflow arrangements and operating m^lliods. It should be made clear whellicr screening (i.e. rejection of fine or coarse fractions) is to be employed to meet required sand : gravel ratios as tlic process waicr generaled can be significanr when assessing die poleniial environmental impacts of dredging. 71ie depth of material tliat is to lie removed from llie deposit should be specified.

3.4 Timing, rate and zoning of produclian

Any proposals for seasonal or episodic extraction operations sbould be stated, as should be proposed extraction rates and Uic lifetime of the deposit. Tlie applicant should explore tlic possibihlics for zoning the proposed extraction area to reduce llie surface are;, affecied at any one time in order to nuainiizc interference with oilier users of the sea and to allow recover ' of the seabed fauna

3.5 Vessel numbers and movements

Eslimalcs should be provided of llic likely miuibcr of shipping niovcnienis on an annual, seasonal cic. basis, as appropiialc, and tlic numbers of vessels hkcly to use Ihc area ;il any one lime. The routes hkely lo be taken by dredgers u> and from tlic proposed borrow areas sitould be specified.

3.6 Control of dredging

The applicant should detail their proposed opcralional control procedures to ensure lliat dredging only lakes place in tJic pcmiitted area and iliai interference with oilier users of the sea area minimized both within the wiilioul tlic proposed extraction area Accurate position fixing sucli as DGPS (Differcnlial Global Positioning System) is recommended logctlier with suitable plottjng devices, to facililate accurate dredging operations Masters of dredging vessels should keep accurate rccordsof loading operations and vessel movcmcnls

3.7 Notification and liaison

Applicants should consider appropriate noltfication and liaison arrangements with oilier relevant users of the sea (e.g. fislicmien) to ensure liamionious working relationships between the different parties.

3.8 Onshore destination

Details siiould be provided of ihc wharves/ports or reclamations where (he exlraacd marine aggregates arc lo be landed.

3.9 Alternative sources of material

Within llic EIA/iliH it is necessary to demonstrate the need to exploit tlic resource in question tlirough consideration of Uic local, regional and national need for the material, cspecialh m relation to llie impacts of the proposal, and tiic relative en\'iroimicntal and social costs of pro\ision from other sources.

CHAPTER 4:

4. BORROW AREA AND ITS ENVIRONMKNT

Tiic physical and biological aspects, and human cnviromnenl of tlic potential borrow area and its surrounds should be described in suflicienl detail lo enable a subsequent assessment lo be made of tlie proposed dredging activity. Topics to be considered arc described first .ind litis is followed by a brief discussion of tlie potential impact of the dredging on these topics.

4.1 Physical aspects

Tlic pliysical aspects i!uu need lo be considered when the cnvironmcnl is described area

• tlie baüiomeio' of Ihc sca bed in and around llic poicnlial cxiraciion area logcllicr Willi any BoCablc features and indicators of lidal currcni slrcngih and directions.

• tiic geological hi Msy of the site and its surrounds with particular relevance to ihc resource body

• the geology and ^omorphology of the nearby coast especially its modem evolution and ciiaqgc

• tliecliaracicrislicsflf Ilic seabed sediments in and around Uic site based on side-scan sonar and s irnptc daia.

• lite aggregate rcso«cc cliaraclerisiics including its panicle size and lilliology, origin and coniposüon. tlückness. and nature of undcrlyi ig deposits

• the hydrography of ihc area including tidal regime, wave conditions and residual water movemenls

• Uic csliniatcd voluac and nature of likely overflow, if necessary based on data from an actual dii:i!|ging operation in similar material.

• seabed mobility and sedimcnl iranspod palliways based on direct observations, numerical modeling studies, or inferred from bcdform asymmetry and type

• water quality pn<» fo dredging obtained from an appropriate goverruncni agencies, witJi an Mdu3Uon of likely seasonal variations.

4.1 Biological Environment

• Survey of marine fauna and flora

4.2 Human environment

Aspects of the human cnvimnienl thai need consideration include

.• The active fishing in tlie potential extraction area, including landing statistics, and number of iioaiscd fishing vessels; tlie data niay be obtained from tlie fishing autliontics but local fishennen sliould be consulted for more deiailed infomialioa

• Otlier dredging actniiics in tlie area and their possible cumulative effect.

• Waste disposal by dumping or pipeline in llic region

• Offshore oil or gasaclivities wfiich might impact or limit dredging

• Marine archaeology c g. wrecks and tlic need for a safety zone to protect tJicm from dredging.

• Shipping and naviption Iia7.ards, logcilicr with an indication of shipping frequency.

• Location of any militiry exercise arc a wliich may limit dredging.

• Location and niagnjiKic of recreational activities such as yachting or angling

* Locationof pipelines,cables and oliicrsucli features, especially iliosc vulnerable to dredging.

* Location orconsctvaüonandhciilage areas, and tiicir vulnerability.

CHAPTER 5:

DUMP SITE AND ITS ENVIRONMENT

Describe the ejcisdn[; environmem of tlic .• elecicd dump site succinctly widi ilie help of maps/skeiclies. Show die existing drainage pailis and waier bodies in ilic vicinity. Indicate die quality of water from representative surface and underground poiius.

CHAPTER 6:

DESCREPTION OF THE ANTIdPATCD ENVKONMENTAL (MPACTS

ASSESSMENT OF POTENTIAL EFFECTS

When evaluating [lie overall impact, it is necessary to identify and quantify the environmental consequences of iJie proposal, and ihis should be summarized as an inipaa hypothesis lliat will draw on the results of earlier studies of environmental cliaraaenstics and iheir variability. Tlie assessment of some of the potential impacts requires predictive locfaiiques. and it may be necessary to use appropriate maüicmatical modeis. Where such models arc usat there should be sufficient explanation to enable an assessment of llicir suitability for tlic paniailar «odclhng cvcrcisc.

A concise summary of these effects should be produced.

0.1 Physical effects of dredging

To assess Uic physical impact ofaggi^jh: extraction aaiviiics on the hydrograpluc and seabed environments, information should be puvidcd on:

* transport and settlement of tla maicrial suspended by the dredging activity.

• dispersion of an outwash pliwc resulting from hopper overflow or on-board processing and its relationship to llic notaal and maximum suspended load pioduccd by the dredger.

temporarily)

implications fro coastal crosi» to (iic nearby coastline.

implications for local water orculation resuiling from removal or creation of (at least

lopograpiiical features on tlic seabed

llie likely effects on the sea bed of removing maicrial in particular, the grade of sediment and topography left aflcr dredging {c.g furrows and ridges) and ihc predicted cfFccis on any colonial animals (e.g coral tcefs and sabeltona). Tlie choice of dredging method will largely delerminc the iiat«cofihc impact on the seabed.

• the efrccls of cMtaciion on Ilic nalutal scdimciu Uaiisporl palliways should be predicted, possibly wiili the aid of a computer mode, Tlicsc models aided by field observation will indicate Ütc direction of net scdimcnl tiansport byt the change in sediment flux due to dredging will be more difficuU lo quantify.

• the likely effects of changes in lite wave and lidal conditions around tlic extraction site. This \vill be particularly important in assessing effects on iJie coast.

• tlic likely effects on local coastlines. This would involve consideration of beach draw down and also the possible disruption of the supply of sediment lo llic coast.

• the likely crfccts on water quality mainly through increases in ihe amount of fine material in suspension, potentially producing effects beyond the borrow area.

• cumulative effects of exliactions, i.e. lliccnccts of dredging in otlicr, nearby areas as well as llic proposed dredging application should be assessed as such multiple operations may have a substunlial impact on the wider marine cavironnicnl.

6.2 Biological effects of dredging Tlic principle biological impacts of dredging include disiutbancc and removal of bents and alternation of ilic substrate upon which colonisation depends. Tliis affects the suitability of the seabed as a fish or shcUfish food resource or habitat.

Where the remnant substrate is identical lo the undisttnbcd superficial sediments, disturbance is unlikely lo be permanent and the cxuaaion are will be rccoloniscd, although Uie ume-scale will vary depending of the nature and location of llie deposit. It may also cause fish to mo\'C away from ihc area (probably temporarily) because of Ihc noise of dredging activity or increased suspended load.

Specific topics lo nolc are;

• an assessment of the lemponi and spatial vahabilit)' of the bcntliic assemblages along with Ihc prediaed case and rate of rccolonisation of ihe denuded seabed. Information on predatof/prey relationships between llic bcnihos and demersal fish species may also be appropriate (e,g. by stomach content investigations).

• Uic potential impact on tlic fish and shellfish resources; it may be sensible to assume the worst case scenario i.e. that the fish and didlfisli resources of ihe poteniial extraction area will be totally dcsiroyed. It will then be necessary to conccnlrati: effort on assessing tlic impacts on llie fish and sitellfisli resources outside the potential i:xtraction area with particular attention lo spaivning and nursery areas for ovigerous crustaceans and known routes of migration.

• an assessment should be made of scabirds, manne mammals, sliarks, tunics Uiat frequent or migiatc througli Ilic potential extraction based on consultatiun wiili experts in conservation agencies, universities etc Marine manuiials and sliarks may be particularly sensitive to Üic noise created during dredging

6.3 Kffccts on (lie human environment

Tlic effects on llic human environmeni include:

• loss ofcommercial fisheries and shell fisheries, and if migratory fish ar spawn ing/nurser>' areas are involved, tlicn tlie area tliat could potentially be impacted might be very large. U will usually be necessary lo estimate iherfTcct on the economics of the fisheries in and around the potential extraction area.

Üic cumulative cffccls on fisheries or other vulnerable biological resources.

ihc effects of the dredging waste, for example, significant deposition of sediment from aggregate dredging at waste disposal sites or silting up of discliar;;c outlets or even abstraction nüeis,

there niay be sonic impiici, such as increased sillntion on iiurinc arclia':oIogy. wrecks and was graves, but tlie material LS lilicly to be tciiiovcd in ilic long-ienn by tidal and/or wave action.

tlie dredging may increase stupping traffic and routes and buoys may need to be changed during the dredging

tlie dredging may interfere with recreational activities eg angling yachting and diving and appropriate zoning or tiiumg restrictions may need to be dc\-iscd

safety zones will need to be established around cables, pipelines and otiicr constructions on llie sea bed. Direct impacts such as siltalion are unlikely to cause long term damage and are likely be to short lived

dredging is unlikely to be allowed adjacenl to sensitive conservation and heritage areas When dredging is furtJier afield, sillation from tlie sediment plume or to clianges in sediment transport as a result of dredging may lead to unacceptable effects on the siteCs) concerned.

CHAPTER 7:

MITIGATORY MEASURES

Tlie EIA/IEE should include consideration of the practical steps tliat might be taken to mitigate thi effects of extraction activities. These should include:

• modification of dredging depth to limit changes to hydrodynamics and sediment transpon of the surrounding region

* agreed sliipping and navigation approach routes to and from the potential extraction area so as to minimize interference wjUi shipping, fistiing and otiicr users oi the sea.

• the zoning of the area lo bo licensed or scheduling extraction tamfwigns may be introduced to protect sensitive fisheries or lo respect access lo iMditional fislicries. Seasonal restrictions on drcd);ing can be a useful approach to nti'iiniize impacts on migratory fish stocks or on vulnerable parts of an animal's life cycle.

• zoning tiie extraction area may be introduced to protect sensitive bcnlhic assemblages or timing dredging operations to limit impact upon \iilnerablc life history stages.

• iniporlanl archaeological wrecks, war gnives or otJier marine arcliaeology sites will usually need a safety zone around llicni it they arc to be proiccicd from the cfTccts of dredging.

* effective liaison between dredging operators and other users of Ihc sea can minimize conflicts bciwccn the different activiiics.

I

consullaüon mlli appropriate apcris in conscr\'aüon agencies uiiivcrsilics cic, will usually be necessary lo devise ncasurcs lo proicci seabirds. marine nijimiiuils, sharks, tunics cic.

C H A P T E R S :

MONITORING

Aggregate dredging by its very nature causes dbairbancc to llic marine environment Tlic extent of the disturbance and its cnviroruiiental significance will depend on many factors Conditions attached lo licences are aimed at minimizing these eiïccis by conlrolling tlic operation of iJic dredging activity However, in many cases it is not possible a( the outset to predict all liie environmental efTccts, and a monitoring programnic will need to be establisltoil to assess whctJier llie licence conditions arc leading lo unacceptable effects on the marine environment Monitoring is here defined as the repeated measurement of an effect ulicllicrdiicci or indircaon the marine environment.

When developing a monitoring programme a miidxr of questions should be addressed:

1. Wliat arc die cnvironmcnial conccn;s th^ the monitoring programme seeks to address?

2. What measurements are necessary lo idc^ify the significance of 3 particular effect?

3. Wliat arc liie most appropriate locationsst which to take samples for assessment?

4 How many ntcasurcmcnis are required?

5. How often and for how long should measurements be made?

Monitoring operations arc expensive, as Uicy rcqnre considerable resources both a' sea and in subsequent sample and data processing. It is important, ilicnforc. to ensure that a monitonng programme is properly designed so that it meets its objectives. Tlie results should be reviewed at rcgulw intervals against the stated objectives and the monitoring exercise shonld then be continued, revised or c\cn terminated

It is also important tliat account is taken of natural variability in tlie parameter or process being measured. This can be achieved by comparing tlie physical w biological status of the areas of interest with reference sites located away from tlic influence of dredging cfTca. Suitable sites should be idenlificd as part of the EIA's/IEE's Impact Hypothesis.

He spatial extent of sampling should take account of ilie area designated for extraction and areas outside whicii may be affected In most cases tiierc shtmld also be a region monitored arnund the sampling area where no cfTccl is expected. This would be for reassurance purposes and would ensure tluit llic true limit of effect is detected In some cases it may be appioprialc lo monitor (reassurance monitoring) more distant sites wliicb arc important for ilieir fishery or conscivation interest even where it is tliought unlikely to be affected, (o ensure predicUons of nil effects arc justified Tlic mobility of fine inaierial, for example. brought into suspension by the dredging activity can travel long distances before settling out.

Tlic frequency of monitoring will depend upon Clic scale of extraction activities, Uic sensilivitj' of Uie environment and tlic anticipated period of consequential environmental clianges tlial may extend beyond tlie cessation of extraction activities.

Concise statements of monitoring activities should be prepared Rcporis should detail tlic measurements made, results obtained their imerprctation and liow (licsc data relate to die monitoring objectives.

8.1 Coni[ili.incc moniloring

Marine dredging activity should be monitored on a conlinuous basis to provide a pcrrnancni record, wliich should be available lo (Jic regulatory auUioritics. Tlic i[ifomia(ion provided will allow Uic regulator lo monitor tlic acliviucs of ihe dredger lo ensure compliance wiili speciTic conditions williin iJie dredging licencc/pcmiii and lo investigate liiird party allegations or illegal dredging activities i( may be appropriate 10 install Elccironic Monitoring Devices (EMD) on extraction vessels to facilitate the monitoring of dredging aciiviiy. The minimum data collected and stored should include

• The position of Ihe dredger on a 24 hour basis to an agreed level of accurac>'.

• Tlie timing of dredging equipment dcvclopmeni.

• The timing of drcdgmg operations.

Tlie frequency of recording will vary depending on tiic status of tlie vessel (e.g. inf cqucni records when laid up at lt)e dockside, but frequent records wlicn dredging) The position should be recorded in latitude and longitude or other agreed co-ordinates using GPS or DOPS.

CHAPTER 9:

CONCLUSION AND RECOMMENDATIONS

The acceptability of the proposed project and the alternatives to be analysed through an enviroiunental cost/bcnef« analysis.

Urt»i\ck«or.doc

OFFSHORE DREDCIN« FOR COU>MB() KATIJNAYAKE KXPKKSSWAY fttojixT EnvironiiifiU;!! lnii>!icl Assessment Rc-poil

ANNEX 2 - BATIIYMETRIC SURVEY PLAN

The estimated mean catch for the investigated area are as follows;

Transect A 213.73 l<g/km^

Transect B 494.95 kg/km^

On the 2 km line from the coast 157.89 kg/km^

4.General Conclusions

Present study indicated the presence of more than 20 species oi" fin fish and more

than 10 species of crustaceans of commercial importance in the close vicinity of

the sand burrowing area. Fishes and crustaceans have adapted to a wide range

of habitats. I t is extremely important to note that the exploited species make up

a relatively small proportion of the total number of species available.

The fish community of the area is dominated by Sciaenids and Leiagnathids

where as the crustacean community Is dominated by Metapenaeus dobsonf.

Some of the most abundant species and their seaward distribution is shown in

Table 4.

Analysis of the monthly fish and crustacean production figures for the period

1998 and 1999 (Information obtained from Fisheries inspectors) indicate that

near shore shrimp resource is the most attractive income source to the local

fishermen of the area. Small pelagic fishery and rock fish fishery also contribute

significantly to the economy of the small scale fishing community of the area.

Theppams (log rafts) constructed of wood or fibreglass are the highest number of

fishing crafts owned by the fishermen of the Taladiyawatta to Uswetakeiyawa

area. Fare amount of 3.5 ton inboard engines boats used for prawn trawling and

small FRP boats used for small meshed gillnet fishing are also operaated in the

area.

There are around 900 fishing families living in the area with a fishing population

of around 3700.

It was noted that not only the local fishermen, but also outsiders (Fishermen from

Colombo & Negombo) also use the proposed sand burrow site and adjacent

waters for various fishing activities such as gillnetting, trammel netting and

bottom long lining.

There are about 25 species of fish and 10 species of crustaceans of economic

importance commonly occur in the area and are used for commercial exploitation.

Though highly seasonal, Prawn trawling by 3.5 ton boats Is the highest income

generating fishing activity of the area.

5. Impact of removing sand on marine ecology and fisheries

Magnitude of the impact due lo sand burrowing will be ciependent on the

mechanism, frequency and the duration of burrowing operations. As the above

details were not available for the analysis, impacts are not ([uantified but the

present status of the marine ecology and the fishery resources are given and also

the area for concern is indicated.

• A possible impact of sand burrowing in nearby area of the shrimp trawling

ground may relate to habitat modification. It is important to investigate the

effect of burrowing sand on sea grassbeds, coral reef areas and also on

juvenile prawns in the vicinity.

6.Recommendations

• As these critical and sensitive habitats exist in the vicinity of the proposed

sand burrowing site, high priority has to be given to ensure that all possible

steps are taken to minimise the chance of degrading the habitats or other

deleterious effects from sand burrowing.

• The dredging operation to be conducted beyond 4.5 km from the shoreline to

minimise effects on the shrimp grounds.

• Fisherman affected during the operation period of dredging need to be

compensated as most of them are solely dependent on flshirg in the area.

Project proponent could use the socio-economic statistics presented in the

report in deciding on such compensation.

• Project proponent should allocate a reasonable amount of funds to monitor

long term effects of dredging operation on the ecosystem.

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Table 4 : Fish and Crustacean species commonly caught around the proposed

sand burrowing area.

Common Name

Salaya

Sudaya

Lagga

Moralla

Karalla

Mondali

Pannawa

Halmessa

Thottawa

Keeli

KDSsa

Karattaya

Nagariya

Kumbalawa

Wenganawa

Kalanda

Jeelawa

Kalawa

Orawa

Anguluwa

Kalawa

Meevetiya

Pulunna

Thora

Crustaceans

Kiri issa I

Kiri Issa II

Kurutu issa

Kal issa

Mai Issa

gal issa

Lagoon crab

Sea crab

Spiny lobster

Scientific Name

Sardinella sp.

Sardinella albella

Thryssa sp.

Hemiramphus sp.

Leiognathus sp.

Johnius sp.

Otolithes sp.

Stolephorus sp.

Opisthopterus tardoore

Terapon sp,

Epenephelus sp.

Hilsa kelee

Upeneussp.

Rastrelliger kanagurata

Pellona sp.

Sillago sihama

Sphraena sp.

Eleutheronema sp.

Siganidae sp.

Arius sp.

Polynemus sp.

Lutjanus sp.

Lactarius lactarius

Scornberomorus commersoni

Penaeus indicus

P. merguiensis

P. semisulcatus

P. monodon

Metapenaeus dobsoni

M. monoceros

Scylla serrata

Portunus pelagicus

Panulirus sp.

Family

Clupeidae

Clupeidae

Engraulidae

Hemiramphidae

Leiognethidae

Scienid.3e

Scienid.3e

Engraulidae

Clupeidae

Terapon Ida e

Serranidae

Clupeidae

Mul]ida<>

Scombiidae

Clupeidae

Sillainidae

Sphyrai^ntdae

Plynemidae

Siganu;.

Arildae

Polynernidae

Lutjanidae

Lactariidae

Scombridae

Penaeidae

Penaeidae

Penaeidae

Penaeidae

Penaeidae

Penaeidae

Portunidae

Portunidae

Palimunidae

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Environmciilal Inipiicl Asscssiiienl Report

ANNEX 3 - CONSTRUCTION PROGRAMME

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OFFSHORE DREIKJING FÏJR COLOMBO KATDNAYAKF. KXI-RESSWAV PROJECT Enviroiinicntiil Inipiui As,scs.snieiit Rcpoil ^

ANNEX 4 - MINEHALOGK AL ANALYSIS

OFF SHORE SAND MINING

MINERALOGY - R E P O R T

The scope of study is based on disturbed samples collected offshore in the Onagala area, within the exploration grid system. These samples representing 04 different locations are identified as CKE-1, CKE-2, CKE-3 and C:KE-4,

These specific samples will be as reported below.

The mineralogy of the sea bed sediments down to the level of proposed dredging is relevant for an ElA evaluation. Therefore the sea based stratigraphy for a

mineralogical assay is as given below for such relevant samples, based on a binocular microscope study, for grain examination, and for a percentage of mineral constituents.,

A representative selection of 07 samples based on the seabed surface and below is given for the mineralogical assay The depth referred to in these samples is from the seabed.

Borehole

Sample Depth

Description -

Mineralogy

CKE-1 (E94656N 203059).

0 . 0 0 - 2.00m.

Pale brown fine grained sand with medium grained sand. Poorly graded sub-angular grains of quartz Taccs of shell fragments No clay fraction.

Fine Quartz sand - 70% Medium Quartz sand - 28% Shell fragments - 2%

Borehole

Sample Depth

Description -

Mineralogy -

CKE-1 (E 94656 N 203059)

3.50-4.50m.

Brownish medium grained to fine grained sand Poorly graded with angular to sub-rounded grains Some yellowish brown clay. Traces of shell fragments.

Medium Quartz sand Fine Quartz sand Yellowish brown clay Shell fragments

- 70% - 25% - 5% - < ] %

Boreil ole

Sample Depth

Description -

Mineralogy -

CKE-2 (E 95610 N 203064)

2,30-4.70m,

Yellowish brown very fine silty sand with yellowish brown slightly plastic clay. Poorly grade fine quartz sand. Traces of shell ft-agments.

Fine silty sand - 75% Yellowish brown clay - 25% Shell fragments - <1%

Borehole

Sample Depth

Description

Mineralogy -

CKE-2 (E 95610 N 203064)

4.70-5.30m,

Greyish brown fine grained to silty sand. Poorly graded with angular to sub-rounded grains of quartz. Some fine biotite mica. Traces of shell fragments.

Fine Quartz sand - 80% Silty Quartz sand - 17% Biotite mica - 3% Shell fragments - <1%

Borehole

Sample Depth

Description -

Mineralogy

CKE-3 (E 94352 N 203560)

2.20-4.50m.

Yellowish brown medium grained sand and fim; grained sand. Some coarse sand Poorly graded sand, angular to sub-angular grains of quartz. Traces of shell fragments. No clay fraction.

Medium Quartz sand - 45% Fine Quartz sand - 45% Coarse Quartz - 10% Shell fragments - <1%

Borehole

Sample Depth -

Descrinlioii -

Mineraloev

CKE-4 (E95583 N 204560).

0 . 0 0 - 2.20m.

Pale brown fine grained sand Some medium grained sand. Poorly graded angular to sub-angular grains of quartz. Traces of shell fragments. No clay fraction

Fine quartz sand - 80% Medium Quartz sand - 20% Shell fragments - <1%

Borehole

Sample Depth

Descriplioii -

Mineraloev -

CKE-4 {E95583 N 204560).

5.50-6.50m.

Pale grey fine silty sand with greyish brown soli clay Poorly graded fine quartz fraction. Traces of shell fragments / mica.

Fine silty sand - 75% Grey clay - 25% Shell fragments/mica - <1%

D.Priyalal Dias M.Sc Geologist

OFFSHORE DREDGIW; FOR COLOMBO KATIINAYAKF EXPRESSWAY PROJÜCT Eiiviroimiünlal liiipacl Assessment Repoil

ANNEX 5 - SEISMIC SURVEY REPORT

Seismic Survey for the CKE Development Project

Contents

1. Introduction 2 2. Scope of Work 2 3. Operations 2

3.1 Equipment 2 3-2 Survey Grid 3 3.3 Weather 3

4. Results 3 4.1 Seismic Sun/ey 3

5. Assessment of Resources 5 5.1 Quality 5 5.2 Volumes 6

6. ReconiniendatJons 6

Enclosures Isopach Chart

Danish Geotechnical Institute

Summary

A seismic mapping project was ceirricd out oß'the Colombo Harbour. Sri Lanka. ThisfKir-ticular area was examinated with pinger and boomer shallow seismic equipment. Three seis­mic units have been identified and (he occurrence of sand mapped. The remits of the inter­pretation are shown in a sand/gravel resource chart, aiid estimated volumes of sand/gravel have been calculated.

1. INTRODUCTION

In connection with the Colombo Katunayake Expressway (CKE) Development Project, a seismic mapping survey was carried out off the Colombo Harbour.

The Danish Geotechnical Institute (DGI) was contracted by the Lanka Hydraulic Institute (LHl) to supply seismic equipment including operator of the equipment. Oceanic Resources Charting (CRC) was subcontracted by DGI to deliver on site quality control of seismic data as well as interpretation of the seismic records and reporting of events and findings.

The field work was carried out from the vessel "Puffin" owned and operated by Master Divers, Colombo.

2. SCOPE OF WORK

The specifications included the following ten 1 km^ blocks : 91203, 92203, 93203, 94203, 95203, 91204, 92204, 93204, 94204 and 95204

The purpose of the sui 'ey was to map sand and gravel resources necessary for the construction of the CKE.

A nominal grid with a line spacing of 250 metres was laid out. Two types of seismic equip­ment were used as no previous experience of suitability of a given seismic source was held.

3. OPERATIONS

3.1 Equipment

Two types of shallow seismic equipment with different transmission frequencies were used;

Finger. Four transducers in a square array deployed on a pole suspended from a bracket welded to the boat. The equipment was mn with a centre frequency of 3,5 kHz. A heave com­pensator was used to remove vertical ship movement from the records. The heave compensa­tor delays the signal by 4.5 milliseconds, this must be taken into acctiunt if the device is used for depth mapping.

Boomer. A single source transmitting at 1-2 kHz mounted on a surfboard towed 20 metres be­hind the boat. An 8 element hydrophone towed behind the suriboard (on either side of the

Danish Geotechnicat Institute 3

boat's wake, approximately 5 metres between source and receiver). No heave compensation was applied to this equipment.

The data was recorded digitally usiny the Elics Delph II software package. Both channels were sampled at 16 kHz and stored using tiic Elics compressed format and successively printed. Processing prior to printing was limited to band pass filtering: Highpass 640 Hz and lowpass 6400 Hz for the pinger and highpass 480 Hz for the boomer. In addition a 3-shot stack was ap­plied to the pinger data to reduce the diffractions caused by near seabed coarse material.

Differential GPS navigation was supplied by LHI. The navigation string was send to a laptop PC and reconditioned for input into the Delph system. Events were numbered consecutively and issued every 30 seconds (i.e. 40-50 metres apart, survey speed 3-4 knots). Only one navi­gation string designed for the pinger setup was sent to the Delph system, i.e. if the boomer data is used a layback of 30 metres must be applied to the positions i:i the records.

3.2 Survey Gr id

The line spacing was specified as 250 metres, tie lines were planned in the field and in total 5 tie lines were run. The main grid was laid out in an east-west direction for meteorological rea­sons; the main grid comprised 9 lines. Four tie lines were run north-south and one was run southwest-northeast. A total of 48 line kilometres were run excluding run-ins/run-outs and overlaps from the westwards extension of the survey area.

3.3 Weather

The weather conditions during the survey period were not ideal. The wind was usually quite calm in the morning (06.00), the waves consisting mostly of a southerly swell. Mid morning (09.00-10.00) the wind would start picking up and around noon the survey had to be termi­nated, as the data grew progressively more noisy.

4. MSULTS

4.1 Seismic Survey

Both pinger and boomer were run throughout the survey. Penetration from the pinger proved to be sufficient for the purpose of the survey and as the level of detail obtained from the pinger is far better than from the boomer, only the pinger data has been used for mapping the near surface sand and gravel resources. Only where the bedrock is deeper than about 10 metres be­low the seabed is the boomer superior to the pinger, i,e, for mapping the bedrock the boomer would probably be the better choice.

Three distinct seismic units are noted (Figure 4,1): l/nil I: Units dipping westwards, the dip decreasing progressively to the west. The unit com­prise sands at the top giving way to finer sediments towards the base. These units overlap each other and are tentatively interpreted as regressive sand units.

Danish Geotechnical Institute 4

Unil 2: Channels cutting through unit 3 and occasionally unit 2 The fill consist of well lami­nated sediment, probably fine sand and sill/clay. The unit is displayed in the resource chart as hatched circles indicating where on the pinger profiles it is seen. No altempt to correlate be­tween lines has been done.

Unit 3: The near surface sands (resource) characterised by abundant diflractions in the upper metre of sediment stemming from the coarse fraction. The surface reflector is sharp with little ringing, only where a thin surface layer of different composition is present, some ringing can be seen. Normally the thickness of the surface layer if present cannot be resolved, and is con­sequently less than 0.5 metres thick. Internally the sand displays short, weak, chaotic internal reflectors, This pattern gradually gives way to a more ordered internal parallel laminated pat­tern with depth, testifying a gradual change to more clayey sediments as described in the vi-brocores taken in this area. The unit caps unit 1 but the boundary is commonly very diffuse and gradual, in particular where the more sandy parts of unit 1 grade into unit 3. Table 5.1 be­low displays the variability of the sand resource: medium sand to gravel with some clay is ex­pected.

Figure 4.1 Pinger profile showing seismic units, approx. 9 m from top to bottom of picture, 65 m from left to right.

Laterally the units often display fuzzy gradations into one another, i c. picking the base of the near surface sand is occasionally somewhat difficult. Often the underlying sands have been in­cluded in the resource map, as the provenance of the sand is probably less important than the amount of useable sediment. This problem becomes more pronounced in the western half of the area, where picking the base of the unit is sometimes impossible. In this latter case a con­servative approached has been used: The first occurrence of the faintest continuous reOector has been picked as the base of the resource, possibly rendering the resource smaller than it is in reality.

Danish Geotechnical InstKute

5. ASSESSMENT OF RESOURCES

5.1 Quality

A number of vibrocores have been drilled to the south of this area. The lilhology of the sedi­ment immediately below the seabed is detailed below, for full description please refer to the relevant report.

Core Easting Nor­thing

I.ithology

VC 15 93 041 201 422 0.74 metre of gravelly coarse sand overlying a 0.51 metre sandy transition zone into the underlying heterogenous gravel/sand/si it and clay

VC 16 93 722 201 310 1.12 metre of medium to coarse sand overlying peat and mud

VC lóbis 93 317 201 200 0.64 metre of gravel/sand and coarsely sandy clay VC 17 94 661 201 234 1.78 metres of sand and gravel changing gradually into a

sandy clay with gravel VC 19 93 061 202 104 1.08 metre of medium to coarse sand overlying a gradual

transition into clay VC 20 93 669 202 323 1.40 metres of medium to coarse sand overlying clay VC 21 94 608 202 137 No recovery VC 23 93 173 203 117 1 metre of sand/clay overlying a gradual transition into

mud Note: There is some confiision about which ellipsoid has been used in positioning these vibrocores, i.e. the location of the cores may be wrong.

Table 5.1 Vibrocores to the south of this area, near seabed lithology

Additional coring was undertaken to assess the quality of the resource

u o o o n 09

O o o •w

H

s O o o o»

205000 N

204000 N SAND RESOURCE CHART, ISOPACH CHART CKE AREA

DEC : 1999

Cl . : 0.5 METERE

SCALE : LI 5,000

PROJECTION TM

ELLIPSOID EVEREST 1830

DGI JOB NO 161 17 3-.3

EXEC HLR

203000 N Area with seismic uni t 2 exposed at surface

CKE SAND SEARCH STUDY

Resource Map (Isopatch Chart)

lanka hydraulic Institute Ltd Danish GeoLechnical Institute Executed HLR Checked : INS

Approved : JBC

Dale Date Date

2000-01-09 2000-01-24

2000-01-24

Subject : ISOPACH CHART

OFFSHORE DREDGING FOR COLOMBO KATUNAVAKK KXPRKSSWAV PUOJECT

EiivLi'oiiiiicii<;il Impact A.ssessiiiciil Rcpoil

ANNEX 6 - NARA REPORT ON FISHERIES AND MARINE HABITAT

Report on the short-term survey conducted to investigate different fisheries around Taldiyawatte to Uswetakeyyawa area to determine the impact

of sand burrowing on marine ecology and fisheries

For

I n v e s t i g a t i o n of Sand Bu r row Area fo r Co lombo - Ka tunayake Expressway

Pro jec t

National Aquatic Resources Research and Development Agency Crow Island Colombo 15 June 2000

Contents

Page No.

1. Introduction 1

2. Methodology 1

3. Results 2

Burrow Site and adjacent area

Fishing Activities of the area and socio-economic conditions

Extent of shrimp trawl grounds

4. General Conclusions 5

5. Impact of removing sand on marine ecology and fisheries 6

6. Recommendations 7

7. Annexes 8

1 . Introduction

On the request of Lanka Hydraulic Institute Ltd. (LHI) NARA undertool< a study to

assess the impact of removing of about 5 million cubic meters of sand from the

proposed 6 km^ area off Uswetakeyyawa on marine fauna and the fisheries of the

area. This sand will be used for the construction work of the Colombo-

Katunayake express way project. The study was carried out using the expertise

available at Marine Biological Resources Division, Fishing Technology Division and

Socio Economic and Market Research Division of NARA. Special attention was paid

to identify the impact of sand extraction on the near shore coastal environment,

artisanal fisheries and also on the impact of fishing communities.

2. Methodology

Initially the research team has contacted the LHI to obtain the details of the sand

removing process, especially the duration and security restrictions (restricted

areas) going to be implemented during the operations. As they were not available

to the study team the investigation was carried out in three main areas to fulfil

the task.

They are,

(i) Fishing activities of the proposed sand burrowing area.

Fishing gear types, craft types craft-gear combination etc.

(ii) Fish species and their bio-diversity

(iii) Socio-economic aspects

Information was collected in the following manner,

(i) Using available information -

Data available on bathymetry of the area and coral distribution. In

addition information was available on two short-term studies done by

NARA at the same area, one during the period 1983/84 and the other

during 1995.

(ii) Visiting the area and interviewing fishermen - A rapid appraisal of the

socio-economic conditions of the stretch of Taldiyawatte to Uswetekeiyawa

was conducted.

(iii) Collecting catch statistics from commercial fishing crafts of the area

During the survey period information/statistics on the following parameters

were collected.

Fishing population of the area

Fish production of the area

Number & types of fishing crafts operated in the area

Types of fishing gear used

Species composition off ish catches

Income levels

Seasonality of the fishing activities

(i) Experimental fishing with community participation A resources

experimental trawl survey was carried out in the proposed site for the

assessment. The survey area was divided into 3 transects (A, B and C

showing in Fig 2) parallel to the shore which in turn were divided into

three stripes perpendicular to the former making 6 squares. The Trawl

operations were conducted on 9'" and 11" ' of May 2000. Six travi/l

operations were conducted at transects A and B. Transect C was excluded

due to unfavourable bottom conditions for trawling. The total catch of

each species, the total length of shrimps and fish caught v^ere measured.

The trawling lines were recorded using a differential GPS and depth of the

tracks were recorded.

3. Results

3.1 Burrow site and adjacent area - The length and the breadth of the

proposed area is approximately 02 and 03 km respectively (93000-96000

E and 203000-205000 N) shown in Fig 1. The bathymetric data available

with National Hydrographie Office of NARA does not indicate any high

points, which reveals that no reef formations within the identified area.

Previous studies and recent observations revealed the existence of five

main near-shore reef areas outside the identified site- There locations and

names are given below and Fig. 0 1 .

Near-shore reef areas

Name of t h e reef App rox ima te depth ( m )

Wave breaking near 0.5 - 1.0

shore reef

Kalapu Gala 2.0 - 3.0

Ona Gala 5 . 0 - 7 . 0

Thamba Gala 8.0 - 12.0

Wetiya Gala 20.0 - 35.0

A p p r o x i m a t e d is tance f r o m the coast ( m ) 15 - 20

400 - 500

800 - 1000

2500 - 3000

5000 - 6000

3.2 Fishing Activities of f / ie area and socio-economic conditions

Major fishing activities of the area can be categorised into 03 main groups. They

are;

(a) Near-shore fishing with log-rafts and fibre glass

(b) Near shore fishing with 17 - 23 feet FRP boats

(c) Near shore trawling with 3.5 ton FRP inboard engine boats

Fishermen of the area off Dickowita, Uswetakeiyawa area operate approximately

200, Theppams (log rafts) on a normal fishing day. There <ire two types of

Theppams - wooden theppams and fibre glass theppams. Numbar of these crafts

operated in a normal fishing day during the non-monsoon (Sepi:. - April) is very

much higher than the south-west monsoon period. During the south-west

monsoonai moths Theppam fishing comes less important and during the mid-

monsoon period this fishery comes to a hold due to rough sea conditions.

Theppam fishermen go out for fishing around 3.30 am and return around 7.30

am. Fishing area of Theppams are the area between 0.5 km - 4.00 km from the

coast line. Table 01 shows the fishing gear used, gear specifications and target

species for the Theppam fishery. Mostly two people are involved in the operation

of the Theppam but there are instances where a single fishermen is involved in

the operation.

Fibreglass (FRP) boats operate their gillnets between 0.5 km - 12 0 km from the

coast line. Various fishing gear types operated by FRP boats are also shown in

Fig. 02. These boats are geared by 8 to 15 Hp engines.

Prawn trawling is the major income generating fishing activity in this area. Catch

rates were low during the non-monsoon period and hence the number of boats

operated was few. With the onset of the south-west monsoon Ic'irge number of

3.5 t boats engage in shrimp trawling. Results of a recent study done by NARA

reveals that the mean number of trawlers operated/day varied from 39 - 93

during the period June to November and from 12 - 37 during December to May.

Information collected on the shrimp trawl fishery off Hendala is shown in Table

02. Results indicate that the catch rates are higher during May to November.

Percentage composition of major finfish and crustaceans caught in trawl catches

are shown in Table 03.

A list of commonly occurring fish and crustaceans around the proposed sand

burrowing area are given in Table 04.

I t was noted that local fishermen of the Hendala, Wattala and Uswetakeiyawa

area as well as fishermen from Negombo and Colombo also visit this area for

various fishing operations. A seasonal calendar of fishing gear operations carried

out in and around this area is shown in Table 05.

Table 06 shows the income levels of craft owners and crew members of the area.

3.3 Extent of Shrimp trawl grounds: Near shore areci off Handala,

(Uswetakeyyawa) is a rich shrimp ground. It has been used for shrimp trawling

and it's a part of the shrimp stock in Negombo lagoon and Ntgombo coastal

waters.

In this area shrimp trawlers are operated from about 50 m from the shore up to a

distance 5 km. Survey conducted by NARA revealed that about 50% of the

proposed dredging area is comprised of the trawlable grounds. Over 25 fin fish

and crustacean species were recorded at site during the survey (table 5 and 6) .

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Etivirotiiiicnlal Impact Assessment Report

ANNEX 8 - SECTION 5.4.1.1 DREDGING AND TRANSPORT OF SAND TO STOKPILING AREA

(EIA Report of Colombo-Katunayake Expressway RDA 1997)

»rrvisioH—Bmkimg-

This IS a two sioreycd building wKich in addiuon to being 3 monitoring and unpiemcnling loil collattion. scn'es as the Central Adm Office for the expressway Facilities at this supervision buildin direction and support for the whole afperation The main functions are

a. Administration b Maintenance c. Traffic control and cmerafncy telephone communication d. Pohce enforcement ( st^ï not directly employed by the

cei

)A)

tre for strati on provide

The ground floor of the sut/er\ision buildmg accommodates ffnance / cash and security rooms located closc/co each other with easy access fiiom to!! gates and are separated from the rest/of the activities of the building for security reasons.

5.4 Methodology' of Constriction

The methodology of construction and the sequenced of events have been indicated by the RDA. (where appropriate, reference is/made to Japanese EIA Reports of the Eastern Trace 1992 and Kerawalapitiya Reclamation Project 1993)

5.4.1. Raw Material Remiirfd

It has been estimated that for the CFCE following m/ierials will be required.

Sand for sand/blanket Sand for conc/ete and road works Gravel Aggregate

(ill ion

(000 XOOO

ni

m

m-

3

Sand fo/ the sand blanket has to be obtained from offshore dredging Sand for concrete/ and road works is to be purchased locally from contractors over a period ''of foiif vears.

5.4.1.1. Dredging and Transport of Sand to Stockpiling Area

The methodology recommended for dredging, mooring, pipeline laying, installation of booster pumps, stockpiling of sand cic is as follows ( Kerawalapitiya Reclamalion Project El/\ repoil 1993 and SLLRDC sources)

t32

I) Dredging üpenit ion

The methodology adopted in the extraction of sand is by dredging in an area located at a minimum distance of 3 km offshore since [his is beyond the wave breaking zone, it will not have an effect on the near shore sediment budget Dredging is al a depth of 15 m below the sea level which is safe from coastal engineering considerations. The depth of dredging wil! be limited to 2 m below the existing sea bed level since it would not acate hydraulic and geotechnical problems Dredging will be carried out parallel to the shore line in linear channels, avoiding scattered deep holes in the sea bed. The quantity of sand to be extracted IS ÜB million m-'

For dredging operations for the excavation of offshore sand, self-propelled ocean-going suction hopper dredgers have been found to be the most suitable as they can operate in rough and open seas without creating too much turbidity. Experience by SLLRZ>C and others have confirmed this,

ii) Pipeline Lajing Operation

A system of pipelines with floating, submerged and onshore sections having 80-90 cm diameter will be used for pumping.

The floating pipeline consisting of flexible elements will be connected to the submerged pipeline. This fully welded pipeline will be connected to the onshore pipeline ( Fig, 5.7)

The pipeline w!l be laid through the same gap in the reef that was used by SLLRDC for Kerawalapitiya Reclamation Project C Fig. 5. 8) The route of the onshore pipeline of length 4.87 km will be selected in order to minimize adverse impacts on people and property As such the route followed upto the road crc"ssj.".3 by the Kcrawalapiliya Project is. suggested. Beyond which it will follow the northern boundary of the sand filled area (Fig. 5. 8).

iii) Transpoii of Dredged Material

The dredged sand is transported through the pipeline system where the dredged material is pumped to the stockpiling area A booster station is necessary to supplement the capacity of the pumps and is located at a place where cooling water is available . C Fig 5.8 ) Tlie power for the booster station is 2500 kw ( SLLRDC)

133

I 14

»35

The material pumped to the stockpiling area is a mixture of sand and sea water in the ratio of lO: 0 by volume Hence for 3 5 million m^ of sand 4.4 million m-' of water will be pumped from the sea. which will drain from the stockpiling area leaving sand in the pile. The drainage water will be pumped back • to sea by a drainage pump via another pipeline laid adjacent to the in­coming pipeline.

iv) Mooring System

The same anchoring system used by the SLLRDC for sand pumping will be used. It comprised a sunken heavy wei^t held fast by three anchors of ten ton weight and two chains attached to the heavy weight. One chain would hold the floating pipeline while the second will be connected to the dredger when dischargir^ sand. ( Fig. 5.9)

v) Stockpiling of Sand

For easy construction RDA has proposed to stockpile sand in Kcrawalapitiya area which is convenient for transporting to all five sections of the CKE, RDA considers two alternative sites for stockpiling purposes. First, it hopes to negotiate an arrangement with the SLLRDC to obtain about 100 Acs from the area already reclaimed. (see the fig. 5.8). On the alternative, a land bordering the Old Negombo Canal has been identified by the SLLRDC as a possible stockpiling area. (Fig. 5.8), This land is already earmarked for development by the SLLRDC.

5.4.1.2 Aggrcgqtgs — ƒ -

Approximate quantity/ of aggregates and crushed stones required for the project is 160,000 m3.

Quarry sites thet are already in operation at / Koratota , Yakkala and Koladeniyawa will be used. Quarry site at NawagamiJSva is close to the southern section of the project, quarry site at Yakkala is clasc to middle section of the project and the/site at Kotadeniyawa is close to ihtf northern section. Access from the quarr>' sites to the project sites will be along Xhc existing "B" and "C" class roads as indicted in Fig, 5.10.

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OFFSHORE DRE:IK;IN(; FOR COU)MB() KATUNAYAKE EXPRI-SSWAV PROJECT Environmental Impact Asscssinciil Rcpoij

ANNEX 7 - BOREHOLES INVESTIGATION REPORT

REI*ORT OF THE BOREHOLE INVESTIGATION FOR THE SAND SURVEY OFF-SHORE OF COLOMBO PORT

1.0 INTRODUCTION

1.1 A request was received from Lanka Hydraulic Institute to conduct a borehole drilling investigation off-shore, off the Port of Colombo.

A total of 04 Nos. locations were selected for drilling and sampling, identified after an earlier Geophysical Survey.

1.2 The purpose of this survey is to identify the thickness of sand along a sandbar located off-shore.

In addition to proving the sand beds by sampling, a quantification of sand resources is earmarked for future exploitation.

1.3 This Report covers an area of units of the Grid System, which is the official Licensing Control System of the Geological Survey and Mines Bureau (GSMB).

The area of investigation is shown in Figure 1 with the positions of 04 Nos. boreholes identified as CKE-1, CKE-2, CKE-3 and CKE-4.

The positions of the boreholes off-shore were identified by Lanka Hydraulic Institute using DGPS.

1.4 The off-shore drilling investigations were carried out from 9th January 2000 to 16th January 2000.

Althoueh the drilling time per borehole was between three to five hours in durafion, the positioning time off-shore entailed more time.

2.0 OFFSHORE RIGGING

2.1 The drilling rig, water pump and equipment were transported to each off-sliore location by a water barge provided by Master Divers.

The water barge also carried the off-shore Trestle which can be assembled on four legs to suit the different water dqiths.

- I -

2.2 On re;iching each drilling location, ihe barge was anchored in position by anchors operated by an Electric Generator. A crane, mounted and fixed onto (lie barge, placed the Trestle in the sea at each position. A working deck was provided atop the Trestle on which the Drilling machine/water pump and accessories were placed using the barge crane.

A ladder was provided for personnel to reach the working platform from the sea.

2.3 All drilling operations of the seabed were carried out from the Trestle platform.

3.0 INVESTIGATIONS

3.1 A hydraulically operated Rotary Drilling Rig was used for the drilling operations. NX size casings (78mm0 ), as a free casing run was used to reach the level of the seabed from the working deck.

For wash boring of the seabed sediments 'B' size drilling rods were introduced within the NX casings to reach the seabed.

3.2 Wash boring was carried out by a centrifugal pump jetting water via the 'B' size Rods, so that the sediments were collected in an apron on the working platform.

Advancement of the borehole was by rotation of the casings, where the rods also followed the casing depth by jetting of water.

By this process the sediments of the seabed were jetted out from the annular space between the casings and the rods.

3.3 On reaching the hard strata below the sediments, either a chop bit or a diamond bit was used to recover material of the hard strata.

3.4 The depths of the different horizons of sediments were recorded from the deck by recording the casing and rod depths below the bed.

3.5 Continuous sampling was possible along the entire profile of sediments. These samples were collected on deck, and sealed in polythene for storage, with the depth records.

-2-

4.0 LOCATION

4.1 The area covered by this Report is located approximately 3 Km to 5 Km from the coast off-shore North-West of the City of Colombo.

Along the Western Coast. North of Colombo, the area is between Palliyawatte (North of the Keiani River mouth) and Uswetakeiyawa. This vicinity is called ONAGALA.

4.2 Figure 1 shows the location of the 04 Nos boreholes drilled within the Grid System, which have the following coordinates:

Location Easting Noilliing CKE-1 94656 203059 CKE-2 95610 203064 CKE-3 94352 203560 CKE-4 95583 204560

4.3 The MSL of the seabed at each borehole location is indicated in the annexed borehole logs.

5.0 GEOLOGICAL SETTING

5.1 The Island of Sri Lanka is underlain by complex metamorphic rocks which are divided into series. The largest and the oldest of these series is the Highland Series (see annexed Geology Map).

The metamorphic rocks of this series are of the Precambrian Age and well over 600 million years old. They are hard, gneissic rocks whose principal constituents are quartz, feldspar, mica, amphiboles and pyroxenes.

This Highland series belt is seen to project into Hie sea North of Colombo. Therefore, in the area of investigation, the basement lard rock will be the Highland Series Belt.

5.2 The major rock type of the Highland Series are Biotite Gneiss, Biotite Homblende Gneisses, Charnockites, Crystalline Limestones, Quartzites. and Garnet Sillimanite Gneisses. In these rock types the principal unweathercd constituent will be quartz.

Thereby, from the catchments of major rivers, large quantities of quarts sand will be discharged into the sea at ilie river mouths. Clay and silt are also discharged as weathered products of other minerals.

-3-

5.3 Sitting unconforniabty on the basement gneiss arc stjdiments of Quaternary Age.

In this area, former bathymctric surveys have revealed the existence of a sand bar parallel lo the coast.

5.4 The existence of this sandbar was evaluated by a Vibrocore Survey, the locations of which arc shown in Figure 2. A subsequent Geophysical Survey carried out by Lanka Hydrauhc Institute in December 1999 provided an L-S profile indicating the thickness of sediments and the dqjth of hard strata.

The selection of drilling positions for this survey was based on the Geophysical profile.

5.5 It is believed that this off-shore sandbar had developed as a result of the Kelani Ganga sediments, deposited for thousands of years.

The sorting of sediments and accumulation parallel lo this coast off-shore will be the results of wave action and current patterns.

5.6 It is known that hundreds of tons of river sands, clays and weathered rock material are annually discharged from the Kelani River moulh.

Therefore, the sediments of the sandbar should represent the weathered products of the rocks within the Kelani River Catchment.

6.0 LABORATORY TESTS

6.1 Representative samples from each layer of sedimente from the boreholes were subject to particle size distribution analysis.

Since the materials were mainly granular in composition, Sieve Analysis was carried out.

The results of the tests are annexed along with (he particle size distribution curves.

7.0 SEA BFI) STRATIGRAPHY

CKE Buriiigs

7.1 In CKE-1. the surface horizon of the seabed is a medium quartz sand to 2.00ni depth, and from 2.00m to 3.50m the medium sand is mixed with coarse quartz sand. From 3.50m to 4.50m the medium to course quartz sand has about 20% - 30% clay.

-4-

In all the above horizons liiere is a minor clay content with traces of sea-shell fragments.

From 4.50m to 4.70m is the highly weathered basement rock disintegrating to medium/coarse sands, with mica. Below 4.70m is hard, weathered rock.

7.2 In CKE-2 the surface horizon of the seabed is a fine to very fine sand with almost 50% clay down to 0.40m depth. From 0.40m to 2.30m the fine sands have a lower clay content [20% to 30%]. From 2.30m to 4.70m a similar content of clay is observed in the fine sands.

From 4.70m to 5.30m highly weathered bascincnt rock disintegrates to fine/medium sands with Mica. Below 5.30m depth is hard weathered rock.

7.3 In CKE-3 the surface horizon of the seabed is medium quartz sand, having traces of shell fragments/clay to a depth of 2.20m. From 2.20m to 4.50m is medium to coarse quartz sand with fine sand with a clay content up to 10%. From 4.50m to 5.60m is a greyish medium sand with coarse quartz sand.

At this location the sands directly terminate on hard weathered rock at 5.60m depth, which is resistant to chopping.

7.4 In CKE-4 the surface horizon of the seabed is medium quartz sand with about 10% clay/shell fragments to a depth of 3.05m. From 3.05m to 5.50m is a black layer of sand containing medium quartz sand with about 2% organic matter, and decayed wood.

From 5.50m to 6.50m is a layer of yellowish fine to very fine quartz sand with about 20% to 30% clay.

At this location the sands directly terminate on hard weathered rock at 6.50m depth, which is resistant to chopping.

7.5 In all CKE profiles the granular sediments, which is mainly quartz sands, terminate in the in-siiu basement.

The basement is a gneiss as indicated by the presence of mica in the washings when the hard strata is chopped during drilling.

-5-

In all the CKE boreholes tliis basement gneiss is encountered. A summary for the sand thickness and MSL for bedrock will be as follows;

Borehole Sand Tliiekiicss(m) MSL(m) to Bedrock

CKE-1 4.70 -22.10 ' CKE-2 5.30 -21.20 CKE-3 5.60 -23.20 CKE-4 6.50 -21.70

7.6 From the above table it is noted that the thickness of Ihc sandbar is variable from a minimum 4.70m to a maximum 6.50m.

Uie bedrock profile is also variable and undulating from a minimum of -21.20m MSL to a maximum of -23.20m MSL.

8.0 QUALITY OF SANDS

8.1 The predominant material of the sandbar is quartz sands of varying colours and grain sizes. In a few beds (as described in Section 7-0) a clay cogent of 10% to 30% is observed.

In an overall concept the material of this sandbar will have a quartz sand content in excess of 90%.

8.2 The horizons of sands vary in grain sizes from very fine, fine, medium, to coarse. However, most horizons have medium quartz sands.

A few horizons show fine gravel, when coarse quartz sands exist. Considering grain angularity, most sand beds show angular quartz grains. A few horizons show sub-rounded to rounded grains.

8.3 Traces of sea shell fragments, organic matter, Ilmenite and Mica are observed in some horizons (see borehole logs).

-6-

b U H t fUJUC L O U

Foundation & Waterwell Engineering (Pvt) Ltd. PROJECT

OFFSHORE SAND SURVEYS.

LOCATION E94&56 N 2 0 3 0 5 9

CLIENT L . H . I .

OOnEHOLE

CKE-1

DRtLUNGMACHINE R o t a r y H y d r a u l i c

ORIUUNGTVPE Wash B o r i n g

CASING SIZE 7Smin0

DEPTH OF HOLE i . 70in

GROUND LEVEL Sea bed l e v e l t a k e n as Ze ro

iNCLiMATiON V e r t i c a l

DATE STARTED .15/.0.1/2009OMPLETED.15/01/2000

LOGGED 8YC.N..Thi lakacat l ine/ . '^r . . .D..P.Dias

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D E S C R I P T I O N OF M A T E R I A L

STANDARD PENETRATION TEST

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Yellowish Brown

medium sand.Traces

of ;ShelI. fragments/

Clay.

Yellowish medium

quartz sand with

coarse sand.Traces

of clay.

Yellowish medium to

coarse sand.with

Clay.Traces of fine gravel.

KEY R - Rock : W f - WÄaltiered Rock

HS - Hammgt haboundng - (SPT) WOR - Woighl of Rods (SPT) WOH - Weigh! of Hammer (SPT)

U/S - 60 mm dia undisluited Samplo CIS - DisturOed Sample

V - water Level W.^ iOn i

Weathered rock

disintigrating to

Brownish medium sand

with coarse sand.

Some fine gravel-•

Traces of sea shells

/Biotite.

Borehole completed

at the depth of 4.7C|n.

• ' . "

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REMARKS

Weathered Basement rock at i.50m depth.

SCALE 1:50 SHEET 01 OF 01

, J

i jkJUL- in-zut ; u'w'ij

Foundation & Waterwell Engineering (Pvt) Ltd. PROJECT

OFFSHORE SAND SURVEYS.

LOCATION.E95656 N203O64

aiEMT: L.H.I ,

0O«EHOLE

CKE-2

DRILLING MACHINE R o t a f y H y d r a u l i c

DRIUINGTYPE Wash B o r i n g

CASING SIZE 78iiim0

DEPTHOFHOLE 5.30m

GROUN0LËVELSea bed leve l taken as Zero

iNaiNATiON Ver t i ca l DATE STARTED I 7 / 1 / 2 0 0 0 C O M P L E T E D 1 7 / Ö 1 / . 2 Q O O

LOGGED BYC.N.Thilakarathne/Mr.J)..P.Dias

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D E S C R I P T I O N O F M A T E R I A L

STANDARD PENETRATION TEST

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18,20 .2.L2Ü

SC

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20.60

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Dark Greyish f ine to

very f ine sand and

Clay.

Brownish f ine tovery

f-ine sand with c l a y .

SP Yellowish Brown fine

sand..with clay. .

Tr-ace S pf shell-

fragments.

Weathered rock

di •Jintjioratrns to Greyi'Sh f ine t o ' ' medium sand.Wibht', c lay . i ; race5.J l£ .?hel l f ragments /Bio t i t e .

Borehole completed at

the depth of 5,30m.

'•'••'i

KEY R • Rock ; WR • WaaUiered Hock

HB - HammefRebouncing-(SPT) WOR • Wcighio(Rods(SPT) WOH - Weighl of Hammer (SPT)

U'S • 50 mm dia undisturbed Sample CVS • Disturöed Sample

V • : waiof Level 1 5 . 9 0 i n

REMARKS

Weathered rock a t 4,70m depth.

SCALE 1 : 5 0 SHEET 01 OF 01

Foundation & Waterwell Engineering (Pvt) Ltd, PROJECT

OFFSHORE SAND SURVEY.

LOCATION. E94352 N203560

CLIENT L,H. I .

DORE HOLE

CKE-3

DRILLING MACHINE Ro ta ry H y d r a u l i c

DRILUNGTYPE Wash B o r i n g

CASING SI2G 78miii0

DEPTH OF HOLE 5.60m

GROUNDLEVEiSea bed leve l taken as zero iNO-iNATiON V e r t i c a l

DATE STARTEOl6/01/2000:OMPLETED 1 6 / 0 1 / 2 0 0 0

LOGGED 8Y C.N.Thilakarathne/Mr.D.P.Dias

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2.30

5.60

SP

Yellowish Brown

medium sand.Traces

of Shell fragments/

Clay.

SP

White to Greyish

medium~co::coarse

quartz sand with

fine sand. Some ClayJ

1.10 ot'

Greyish medium sand.

Some coarse sand.

' > • / > • ' •

Borehole completed

a t the depth of

5.60m.

TTT-

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H Rock WH-WeameredRock H8 - Hammer Rebounang-(SPT)

WOR • Weight of Rods (SPTJ WOM • Wcigfir ol Hammof (SPT)

U/S ' 60 mm di3 undisturCed Sample 0 ^ ' Disturbed Sample t

V - waier Level

17.60/^;

REMARKS

Hard dense S t r a t a a t 5.SDm depth.

SCALE 1 : 50 SHEET 01 OF 01

BORE HOLE LOG

Foundation & Waterwell Engineering (Pvt) Ltd. PROJECT

OFFSHORE SAND SURVEYS.

LOCAKON. E95583 N20^560

CLIENT: L . H . I . CKE-4

DRILLING MACHINE R o t a r y H y d r a u l i c

ORlLLINQTYPEUash ß o r i p g

CASING SIZE 7801010

DllPTilOFiiOiE 6 . 5 0 n l

GROUND LEVEL Sea bed l e v e l t a k e n a s z e r o

fNCUNATiON V e r t i c a l

DATE STARTEd7/Ql./.2D00COMPLETED .17./.0.1./2PPO

LOGGED BYQ.^^*^Tt?i.l.a.^^.a^a,c!?.^.?/M?.^P.^?.^Pi^^

o

[ i l

LU O m

in in UJ ILI

O ? Si

D E S C n i P T I O N OF M A T E R I A L

STANDARD PENETRATION TEST

w 'ë(y

ILl

g 0 ZO 40 GO SO

O O _ j

O

>-

BTTC-OTW

SI*

Yellowish Brown

medium sand.Some

Shel l"fragments/^lay

18.2^_Uli JLÜ'

20.7Q -1^ 2.45

21.7C 6. 0 1.00

SP

SP

Blackish medium sand

with fine sand.

Some organic matter/

Decayed wood.

1 • V

Yellowish fine and

very fine sand.With

Clay.

KEY R - Rock . WR • Weaiflered Rock

HB • Haminef ReDouncitig • (SPT) WQR . Woighl Ol Roos (SPT) WOH • Weigh! ot Hammer (SPT)

U/S - 60 mm dia undisturbed Sample Ü ^ • DiSlufOedSanipIo

V • w.ilof Level I ^ . 20m

Borehole completed

at the depth of 6.50m. J

+ -Y-

REMARKS

Hard dense S t r a t a a t 6.50m,not p o s s i b l e t o CHbp and Wash bore.

SCALE!: 50 StfET 01 OF 01

-O Ca W o n

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BO'OffE Bl'Off «•Off

, Simplified geological map of Sri Lanka

BOREHOLE LOCATIONS OF THE OFFSHORE SAND SURVEYS

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