1. Metro Colombo Urban Development Project

Public Disclosure Authorized

Environmental Screening Report for Public Disclosure Authorized 1. Improvements to Mutwal Outfall (box drain, tunnel inlet and outlet) 2. Reconstruction of Aluth Mawatha culvert 3. Embankment protection along selected locations of the Main Drain

Final Report

December 2011

Public Disclosure Authorized Uni‐Consultancy Services University of Moratuwa

Table of Contents

1. Project Identification 3

2. Project Location 3

3. Project Justification 5

4. Project Description 8

5. Description of the Existing Environment 11

6. Public Consultation 19

7. Environmental Effects and Mitigation Measures

7a. Screening for Potential Environmental Impacts 21

7b. Environmental Management Plan 29

8. Conclusion and Screening Decision 51

9. Screening Decision Recommendation 65

10. EMP implementation responsibilities and costs 66

11. Details of Persons Responsible for the Environmental Screening 69

Annexes

1. Photographs of some of the important locations along project roads

2. Detailed drawings of project components

URBAN UPGRADING WORK

Metro Colombo Urban Development Project

Environmental Screening Report

1. Project Identification

Project title 1. Improvements to Mutwal Outfall (box drain, tunnel inlet and outlet) 2. Reconstruction of Aluth Mawatha culvert 3. Embankment protection along selected locations of the Main Drain

Project Sri Lanka Land Reclamation and Development Corporation Proponent

2. Project Location

Location Location of the project is depicted in the Fig. 1.

Definition of The project area is the (i) culvert across Aluth Mawatha, (ii) the canal banks of Project Area the Main Drain from St. Sebastian North Canal through Prince of Wales Avenue and to Port Access Road up to the culvert at Aluth Mawatha, (iii) Mutwal tunnel and the outfall

(The geographical extent of the The geographical extent is shown in Fig. 1. project & areas affected during construction)

Adjacent land See “Other features” in Section 5. and features

Figure 1. Location map showing the Main Drain and the Mutwal Tunnel Outlet

3. Project Justification

Need for the project The Colombo Drainage System comprises a network of large open drainage canals, smaller tributary canals and low-lying marshes functioning as natural retention basins. It functions to serve the drainage needs of the Greater Colombo area and reduces incidence (What problem is the of flooding and thereby protects the urban community, particularly project going to solve) the urban poor who inhabit low-lying regions of Colombo.

The system could be broadly divided into two, with canals to the north of Sri Jayawardenepura Mawatha as Colombo North system and that to the south as the Colombo South system (see Figure 1. The system has four outlets and three of which Dehiwala and Wellawatte Outfalls and Mutwal Tunnel directly discharging in to the sea, while the North Lock discharges in to the Kelani River. There is a fifth outlet for the spill waters of the Beira Lake, via a circular weir near the old Parliament; the canal system is no longer connected to the lake to prevent highly polluted canal waters entering the lake. When the Kelani River level is high, the gate at the North Lock outlet to Kelani River is closed, so that reverse flow (from the river into the system) cannot take place. This operation is now carried out by the Department of Irrigation. Mutwal Tunnel of diameter 1.8 meters, functions as the outlet of the Main Drain. The head of the canal system could be considered as Parliament Lake, to the East of Kotte Lake. Under dry weather conditions the North Lock, Wellawatte and Dehiwala outfalls are the major outflow points. In a flood situation, with the North Lock closed due to high water level in the Kelani River, the system has to rely mainly Wellawatte and Dehiwala sea outlets. Also the Mutwal Tunnel helps ease the drainage problems of North Colombo to a great deal at times when the North Lock is closed.

Aluth Mawatha Canal, Mutwal Tunnel and Outfall The Main Drain takes off the flow from St. Sebastian North Canal through a culvert crossing Prince of Wales Avenue and it runs mostly parallel to the Port Access Road and crosses the canal at two locations.

Then the canal changes its direction to the North and enters Aluth Mawatha area by crossing the Railway Track to the Colombo Port. At Aluth Mawatha the Main Drain connects to the Mutwal Tunnel through Aluth Mawatha Culvert (of which the existing capacity is not adequate) followed by a box drain (3 m x 3 m; L = 82 m). There is an urgent need to increase the capacity of this culvert. Mutwal Tunnel is approximately 1.8 m diameter horse shoe type tunnel of which the length is 570 m. The Mutwal Tunnel outlet is the only outlet that discharges storm water from the Colombo North area canal system directly into the sea. The inlet to the tunnel is at a dilapidated state at the moment that needs urgent rehabilitation. Thus the enhancement of the conveyance capacity of the Mutwal Outfall is essential and accordingly rehabilitation & upgrading of the system is required.

Purpose of the project The purpose of the project is to: - Increase the capacity of the culvert across Aluth Mawatha (what is going to be achieved by carrying out the - Accommodate improvements to Mutwal Outfall (box drain, project) tunnel inlet and outlet) - Embankment protection along selected locations of the Main Drain The purpose of the project is to derive the following benefits and the beneficiaries are listed below: Benefits ∗ Enhancement of flood control. ∗ Reduction in allocations for flood relief for the Government. ∗ Increased in land values in adjacent areas. ∗ Improved health conditions & reduction in health expenditure. ∗ Reduction in annual operation & maintenance cost to the central government. ∗ Increased use of the canal system for recreational purposes & waterfront development.

Beneficiaries ∗ People residing close to the Main Drain and with the combined effect, the entire Colombo Metropolitan area. ∗ The Government and the agencies managing the storm water drainage.

Alternatives considered No other alternative is considered for the project as it is envisaged that there are no any technically feasible and economically viable (different ways to meet the engineering interventions that could be accommodated in place of project need and achieve the proposed option. the project purpose)

4. Project Description

Proposed start The tender documents are expected to be ready by December 2011. Awarding of date the tender will take place only after the 16th of March 2011. Construction period is estimated to be one year.

Proposed It will take minimum 12 – 15 months to finish the project from the date of opening completion date bid documents.

Estimated total Estimate: 3.34 US$ million cost

Present land Entire project lies in areas belonging to SLLRDC. ownership

Description of The detailed drawings of the project are given in Annex 2. the project

(with supporting List of Proposed Activities material such as 1. * Rehabilitation of Main Drain Bank Protection maps, drawings New Gabion walls - 1450 m etc attached as New sheet pile walls - 57 m required) Rehabilitation of gabion walls - 778 m {Total length of Main Drain = 1650 m} ∗ Reinstatement of storm water drainage connections (hume pipe) to Main Drain through gabion walls and introducing catch-pits wherever required. 2. Aluth Mawatha Culvert Improvement ∗ Demolish and reconstruct 3.0 x 3.5 x 12 m reinforced concrete box culvert ∗ Connection of box culvert to existing 3.0 x 3.0 mm box drain leading to Mutwal Tunnel. ∗ Reinstatement of Aluth Mawatha at culvert locations ∗ Temporary shifting & relocation of service lines (electricity, water, telecom, sewer) 3. Renovation of existing box drain (covers of the openings - 6 Nos.) connecting Aluth Mawatha culvert & Mutwal Tunnel and anticipated catch-pits carrying storm water.

4. Replacement of covers of Mutwal Tunnel manholes (03 Nos.) a). Stream lining of inlet area to suit the transition ∗ Introducing a trash screen ∗ Formation of 2 Nos. new storm water manholes at Mutwal inlet and connection of the above two to inlet areas. ∗ Construction of boundary fence around the inlet areas a (with a gate) as a safety measures. 5. Stream lining the Mutwal Outfall

In addition to the above, operation and maintenance of the drainage system is needed. The main drain, Mutwal box drain, & tunnel are under the custody of SLLRDC. Hence it will be maintained by Colombo North Regional Office; Drainage Division of SLLRDC. Following are the activities done under regular maintenance. a). Regular observations b). Surface clearing c). Canal dredging d). De-silting of box drain, tunnel & catch-pits.

Project Agency: Management Team The agency responsible for design and implementation is the SLLRDC and the organization structure for the project is given in Figure 2

Contact person: Ms. A.H. Thushari

Assistant General Manager (Special Projects) Sri Lanka Land Reclamation & Development Corporation

Nature of the consultation and input received:

Meeting and consultation at design office and site were done. Design drawings, master plans and other relevant information were too gathered.

Figure 2. Implementation arrangements for MCUDP under SLLRDC

PROJECT MANAGER

DEPUTY PROJECT MANAGER

Environmen Social Consultant Planning Design Accountant Consultant (Land Project Project talist Planner Engineer Engineer Engineer Acquiring) Engineer Engineer (Contracts (A) (B) & Claims) Land Officer AO/Clerk Draughtsmen Quantity Computer Project Project Project Project Surveyors Operators super‐ super‐ super‐ super‐ Office Driver visor visor visor visor Aide

5. Description of the existing environment

5.1 Physical features – Ecosystem components

Topography and terrain The topography of Sri Lanka is marked by great diversity caused by long years of faulting and erosion of the landscape. The central mountainous region with the highest elevations covered by virgin forests and grasslands rises up to about 2,500 m above mean sea level. The surrounding plains, which rise to about 50 to 100 m above sea level, are largely used for agriculture and homesteads, but still have virgin scrubland where the population distribution is lower. This general topography of the country can be divided into three distinct geographical areas or well marked peneplains featuring the coastal belt, the plains, and the central highlands.

The Colombo district which incorporates the project area falls into the so called lowest peneplain of Sri Lanka (after P.G. Cooray – Geology of Sri Lanka, 1984). The elevation variation of Colombo district situated in this coastal peneplain ranges to a maximum elevation of 150 m from sea coast. The terrain in Colombo largely consists of gently undulating plains and low-lying flatlands with a high density of drainage paths formulating a geography consisting of a mix of land and water. The city has many canals and the 65-hectare (160-acre) Beira Lake situated in the heart of the city is one of the most distinctive landmarks of Colombo.

Mutwal is part of the Colombo Core Area and lies about 3 km north-east to the Colombo commercial hub. The Mutwal sea outfall which has a 5 m3/s capacity is one of the five outlets of Colombo drainage system and it drains the low-lying catchment and accumulated runoff in the connected drainage canals directly to the sea through 6 feet diameter tunnel constructed through underlying rock.

The general topography of the project area in Mutwal and Aluth Mawatha where drainage improvement, embankment rehabilitation and culvert expansion works have been proposed consists of largely flat or mildly sloping low-lying terrain. Elevations vary only from 0 m MSL (at sea level) to 6

m MSL in high areas. Therefore, the slopes encountered in the project area are flat to mild (<0.8 %) and gently slope in seaward direction while the contour lines are aligned approximately parallel to the shoreline.

Soil (type and quality) The geology of Colombo is representative of the geology of the western coast of Sri Lanka and has existed for much of the Quaternary era. Bore holes drilled in central Colombo City show that this area once formed an estuary of the Kelani River and the Kalu Ganga River, the two main rivers that drain into the sea on the western coast. A few kilometers upstream in the inland valleys, there is a high-level gravel formation consisting of quartz pebbles embedded in a matrix of laterite separated with pebble- free layers of laterite. The floodplains along the rivers consist mainly of alluvial deposits. The floodplains of Kelani River also provide thick alluvial profiles for unconfined aquifers, in addition to the productive overburden along tributary banks.

Vast area (over 90%) of Sri Lanka is underlain by metamorphic crystalline rocks of Precambrian age, which includes the project area, which cover a variety of Gneisses. The geology of Colombo is representative of the geology of the western coast of Sri Lanka and has existed for much of the Quaternary era. This is shown in the 1:10,000 and 1:50,000 geological maps of Colombo region produced by the Geological Survey and Mines Bureau. The typical rock types of this basement include Biotite gneiss, Hornblende Biotite gneiss, Charnockites, Charnockitic gneisses, Quartzite and undifferentiated Meta sediments. The floodplains along Kelani River and the Kalu Ganga rivers consist mainly of alluvial deposits. The floodplains of Kelani River also provide thick alluvial profiles for unconfined aquifers, in addition to the productive overburden along tributary banks. According to Survey Department soil maps (Figure 3) the main soil types in the project area are as follows. • Red Yellow Podzolic soils with soft or hard laterite and undulating terrain • Bog and Half bog soils: flat terrain • Alluvial soils of variable texture and drainage: flat terrain • Regosols on recent beach sands: flat terrain

Field surveys and observations carried out using trial pit holes have indicated that the local geology in the proposed project area is characterized by organic clays with sand and deep bedrock while the soil types include peaty and sandy clays with clayey laterite types sporadically distributed in patches. It is presumed that these site-specific features are the most important ones as the environmental impact is considered.

Figure 3. Soil Maps of the Study Area (Source: Greentech)

Surface water Sources (sources, distance from the site, local uses and quality) The most prominent source of surface water in the vicinity is the Main Drain and the surface water drainage canal network that is connected to it.

Distance from the site

Project area includes the Main Drain, Aluth Mawatha culvert, banks of the canal and Mutwal tunnel and the outfall.

Local uses

The canal plays an important role in conveying surface drainage and flood waters. Although the local people do not derive other benefits than diverting their surface drainage into these canals, the intrinsic function is vital and most important in draining the flood waters of the area. There are numerous illegal discharge points of grey water from residences, commercial establishments and warehouses located adjoining the canal, and due to appalling level of water pollution, no other local uses can be derived from the water body.

Quality

Recently measured data is not available for water quality of the Main Drain.

It is visible that the turbidity and total suspended solid content are very high in the water. It is highly likely that dissolved oxygen, and pH are too not in the range that is amenable for biological activities but conducive for anoxic conditions to prevail mainly due to the lack of dissolved oxygen. Nutrient enrichment is apparent in the canal due to disposal of domestic and industrial wastewater and solid waste into the canal over time.

Ground water Sources (sources, distance from the site, local uses and quality) According to the Land Use Division of the Irrigation Department, the project area falls within the local or discontinuous moderate to low aquifer in fractured rock. Only available source of ground water is abstracting water from shallow wells. Distance from the site

The ground water table is very shallow and is about 0.5 m on average close to the Canal, and can be at a level from almost at surface up to 2.0-3.0 m.

Local uses

Only a handful of households use shallow wells to abstract water. Even those who have shallow wells do not use water for daily consumption; they use the wells only occasionally for bathing and washing of clothes.

Quality

There are no data available for quality of ground water. However, it can be assumed that dissolved solid levels including salinity to be high as the project area is located very close to the coastal belt. The ground water can get contaminated due to dilapidated state of sewer connections due to leakages.

Flooding The downstream areas in Mutwal, especially the area surrounding Aluth Mawatha Road, has suffered from intermittent flooding in the recent past presumably. This is mainly due to unfavorable downstream conditions caused by inadequate capacity of the culvert at Aluth Mawatha that does not facilitate additional flow as a result of elevated flood levels and in part due to temporary blockage of existing storm water drainage system by debris, solid waste disposal and siltation. Recorded flood levels in Aluth Mawatha Road and adjacent localities are in the range of 0.3 ~ 0.6 m during monsoon months.

Air quality Heavy vehicle movements along Aluth Mawatha in the project area lead to high levels of air pollutant

(any pollution issues) emissions, such as dust including particulate matter, smoke including CO, CO2, NOx, SOx etc. Such air pollution episodes can aggravate during peak hours when traffic movements are impeded. Construction sites in the vicinity and within the project area affect the air quality in the area immediately surrounding such construction activity. Fugitive dust particles could escape into the atmosphere during such construction activities and during transportation and subsequent storage and handling. Emanation of foul odors from the canal, especially during dry weather when water levels are low, could take place from rotting solid wastes thrown in the water and sewage discharges.

Noise level and vibration Existing ambient noise and vibration levels in the area are consistent with highly urban and light (Any anticipated issues) industrial and businesses. There is also heavy traffic noise from major roads such as Aluth Mawatha, St. Andrew’s Road and Elli House Road. Intermittent high levels of noise and vibration levels are observed due to train operations of Petroleum Corporation. Industrial activities and commercial activities of most of the major roads mentioned above contribute to high levels of noise. Noise and vibration levels in the area would increase slightly due to the proposed construction activities.

5.2 Ecological features – Eco-system components

Vegetation Main Canal, Aluth Mawatha

(trees, ground cover, The canal embankment is highly affected by human interventions. Therefore, no trees can be found aquatic vegetation) along the canal stretch from the railway line to the Aluth Mawatha Canal. Some trees were recorded upstream of the railway line and within the vicinity of the project area viz, Terminalia catappa (Kottan), Ficus religiosa (Bo), Cocus nusifera (Pol), Mangifera indica (Amba).

Culvert

There is a Bo tree (Ficus religiosa) located on top of the culvert and its roots have penetrated through the canal and the culvert.

Mutwal outfall

The outfall is area also dominated by man-made activities including settlements, commercial establishments and industrial activities and no trees were found. However, ground cover of Bim thambaru (Ipomoea asarifolia) and Elephant's ear (Colocasia esculenta) were found near the sea outfall.

Presence of wetlands There are no wetlands found within and vicinity of the project area.

Fish and fish habitats Fish sampling was not carried out. However, schools of small fish can be found plenty in the canal.

Birds (waterfowl, migratory Other than the common birds observed during the rapid screening survey such as Saxicoloides fulicata birds, others) (Indian Robin), Copsychus saularis (Oriental Magpie Robin), Acridotheres tristis (Common Mayna), Streptopelia chinensis (Spotted Dove), Pelecanus philippensis (Spot Billed Pelicon), Ardeola grayii (Indian Pond Heron) no endemic or threatened animal species were recorded.

Presence of special habitat There are no such special habitats demarcated as protected areas within and immediate surroundings of areas (special designations the project area. & identified sensitive zones)

Other features

Residential/Sensitive Areas Throughout the study area on either side of the canal is occupied by underserved settlements. No (Eg, Hospitals, Schools) sensitive land uses such as schools, hospitals were recorded. The Mutwal tunnel outlet traverses the Colombo Fishery Harbour Corporation before it discharges to the sea.

Traditional economic and Most of the households of the area are involved in informal sector activities. cultural activities No traditional economic or cultural activities recorded.

Archeological resources No Archeological resources are located in the project area.

6. Public Consultation

Public consulted Consultation Date Details/Issues raised method

Mr. Ramkumar Informal 19.12.2011 Before the widening of the canal, they had a good access to the canal bank, but (Left Bank near Interviews after the widening, the access road gradually eroded. During the proposed the culvert) improvements it is necessary to provide access to these premises. (Only one house)

Mr. Siriniwasan The community on the left bank had got access from a road on the rear boundary (Left Bank near and that was closed by the owner and therefore the canal bank is the only access the culvert) they have. It is important to make the canal bank road available for these two

families.

Ms. Pilamina Construction of the gabion wall is a good option as it will prevent encroachments. (President / After previous improvements, the area did not go under water. Community Leader of the right bank)

Mr. Sinnathambi The cover slabs of the tunnel are broken at many places creating a big danger for (On the tunnel children who play on this trace. trace)

Mr. Perera (On The canal trace (the covered section) is the access road to this settlement. Children the tunnel trace) play on this trace and always there is a danger due to collapse of cover slab. If the project can upgrade this stretch as a good access road the community will benefit

largely.

Sashi Kumar 09.12.2011 The project is a positive initiative. However, the traffic situation during the (Resident of construction of the culvert need to be planned properly as this road is heavily used Aluth Mawatha by containers and trucks headed for the port. and Three Wheeler Driver)

M.H Wilfrida, 09.12.2011 It is expected that the project will ease the flood risk in the area and reduce water Mary Isabel, Ajith stagnation. Temporary cutting off access to the Garden is not a major issue when

Kumar (residents the box drain is open for rehabilitation as there are two main alternative routes. of 321 Garden – along the Mutuwal box drain trace linking with the tunnel inlet

7. Environmental Effects and Mitigation Measures

7a. Screening for Potential Environmental Impacts

Screening question Yes No Significance of the effect Remarks

(Low, moderate, high)

1 Will construction and operation of the Yes Low Project involve actions which will cause physical changes in the locality Most of the interventions are carried out along the canal hence no physical changes in topography and landform is anticipated other than strengthening of the canal banks with gabion structures, landscaping, paving of foot walks and road surfaces.

2 Will the Project involve use, storage, Yes Low transport, handling or production of substances or materials which could be Transport of material and construction activities, harmful to human health or the environment including excavation, demolition of the existing or raise concerns about actual or perceived culvert and material piles will emit dust and fugitive risks to human health? particles which may pose a health hazard to vulnerable persons in the immediate surrounding on temporary basis. The wind will be the triggering factor for such impacts though it is sporadic in nature.

3 Will the Project produce solid wastes during Yes Moderate construction or operation?

During construction:

There will be small amounts of construction debris produced during demolition of existing culvert across the road, structures and pavements, excavation of trenches.

During operations:

There will be street sweepings, solid waste collected at garbage bins and dump areas which need regular collection and disposed appropriately. In addition, debris and sediments, floating matter and other solid waste carried by surface drainage which can collect at manholes, catch pits etc. that needs proper disposal. Regular cleaning of side drains and road will too generate such material. Culverts will also generate spoil material.

4 Will the Project release pollutants or any Yes Low hazardous, toxic or noxious substances to air? There will be bituminous material used during overlay and re-surfacing of Aluth Mawatha, bituminous patching, crack sealing, carriageway edges and shoulder repairs.

5 Will the Project cause noise and vibration or Yes Low release of light, heat energy or The project activities will cause noise and vibration

electromagnetic radiation? during demolition of the existing culvert, asphalt overlay, excavation of trenches, and during compaction, construction of gabion walls, transport of material etc. These impacts are temporary in nature and will cause inconvenience to the neighboring people only.

6 Will the Project lead to risks of Yes Low contamination of land or water from releases of pollutants onto the ground or into The canal where the base of the gabions will be surface waters, groundwater or coastal placed will need to be excavated to remove the soft wasters? surface sediment layer. Such excavated material should be disposed of safely. Stock piling of excavated sediment material, soil, debris and other material may release pollutants back into surface waters, groundwater or coastal waters. If the excavated bottom sediment is contaminated with heavy metals, and if those removed materials are not properly handled and disposed, they might pose a significant environmental and health risks to the residents and downstream marine ecosystems.

7 Will the project cause localized flooding Low and poor drainage during construction Temporarily blocking of existing drainage flows Is the project area located in a flooding may be required during constructional activities for location? the proposed tunnel improvement works in Mutwal, culvert and bank restoration/ rehabilitation works

along the Main Drain leading to localized flooding.

Raised embankments and raised finish levels, stock piling of construction debris and other materials may block existing drainage flow paths, causing flow stagnation and poor drainage leading to temporarily flooding effects.

Aluth Mawatha Road in the proposed project area is an identified flood prone area and the ensuring of proper construction practices like provision of improved drainage network, maintaining naturally stable slopes, vegetation replanting/turfing, etc. will improve drainage conditions, reducing flood risk during the construction phase and in the aftermath of project completion. Additional pumping and dewatering should be arranged during the construction phase, if the alternative flow diversions provided are not adequate.

8 Will there be any risks and vulnerabilities to Yes Low public safety due to physical hazards during construction or operation of the Project? Excavation for Gabion wall construction may cause the adjoining properties to collapse causing destruction to accessibility. (Particularly the family staying close to the culvert)

Safety issue in terms of injuries caused by construction material, machinery and falling into

excavated trenches by neighbors and commuters could be anticipated.

9 Are there any transport routes on or around Yes Low the location which are susceptible to congestion or which cause environmental Due to the closure of Aluth Mawatha for problems, which could be affected by the construction of the culvert and asphalt overlay, project? traffic would be diverted through the main Mattakuliya road which by-passes Aluth Mawatha but connect the same destinations. It is likely that Aluth Mawatha can be operated for one-way traffic while the construction of the culvert is in progress. The traffic on the Mattakuliya road will be increased as Aluth Mawatha is used by traffic headed to the port. However, this will be a temporary impact.

10 Are there any routes or facilities on or Yes No Low around the location which are used by the public for access to recreation or other There are no significant recreational, or similar facilities, which could be affected by the facilities located on or around the project area. project?

11 Are there any areas or features of high No Since project mainly deals with work along the landscape or scenic value on or around the canal and roads, no impact is anticipated. location which could be affected by the project?

12 Are there any other areas on or around the Yes Low location which are important or sensitive for reasons of their ecology e.g. wetlands, No such sensitive areas are found in the project area watercourses or other water bodies, the other than the coastal area. coastal zone, mountains, forests which could be affected by the project?

13 Are there any areas on or around the No No such areas are found. location which are used by protected, important or sensitive species of fauna or flora e.g. for breeding, nesting, foraging, resting, migration, which could be affected by the project?

14 Is the project located in a previously No The project area and the surrounding is fully undeveloped area where there will be loss of developed and one of the high density residential green-field land areas in the city of Colombo.

15 Will the project cause the removal of trees Yes There is a Bo tree (Ficus religiosa) which has in the locality? grown on the culvert that has to be removed during construction.

16 Are there any areas or features of historic or No There are no cultural/religious places which are cultural importance on or around the located along the roads which are affected during location which could be affected by the construction. project?

17 Are there existing land uses on or around Yes Low the location e.g. homes, gardens, other The land use of either side of the project area is

private property, industry, commerce, dominated by high density residential development recreation, public open space, community (underserved settlements). A few retail commercial facilities, agriculture, forestry, tourism, establishments are found on Aluth Mawatha road. mining or quarrying which could be affected From the Aluth Mawatha culvert towards the by the project? railway a few industries and stores are located on the left bank area. At the Mutwal out fall a large extent of land is covered by the Fisheries Department fishery facility and flour milling industry. However impacts of the project on these land uses are negligible as the construction activities of the project are limited to a very narrow strip that will not have any connection with the aforementioned land uses.

18 Are there any areas on or around the Yes Low location which are densely populated or built-up, which could be affected by the The adjacent areas of the project are heavily built project? up as this is an area of concentration of underserved settlements. The impacts would be mostly disturbance to pedestrian movement which is of short duration nature.

19 Are there any areas on or around the No No such sensitive areas are found. location which are occupied by sensitive land uses e.g. hospitals, schools, places of worship, community facilities, which could be affected by the project

20 Are there any areas on or around the No The fisheries development facility of the Fisheries

location which contain important, high Department is located at the Mutwal canal out fall. quality or scarce resources e.g. groundwater, However there is no fishing activities carried out at surface waters, forestry, agriculture, this location. Its main functions are collection of fisheries, tourism, minerals, which could be fish that are brought by boats and distribution by affected by the project? lorries. Thus there is no impact by the project.

21 Are there any areas on or around the Yes Aluth Mawatha canal is highly or moderately location which are already subject to polluted depending on the seasonal effects. There is pollution or environmental damage e.g. a continuous leak from petroleum pipelines causing where existing legal environmental oil pollution close to the railway track. standards are exceeded, which could be affected by the project?

7b. Environmental Management Plan

Key project activities Potential Environmental Mitigation Measures Effects

Site preparation including Physical: Physical: provision of access roads, material storage yards Emission of dust Clearing of the canal bank for on-site material storage and access has to be carried out with the minimum use of machinery and sprinkling of water should be done appropriately.

Social: Social:

Disturbance to pedestrian One house on the left bank near Aluth Mawatha culvert is the movement, accessibility to most affected as its current access is very narrow located on the houses. canal bank. This access road should be incorporated into the canal reservation so that it can be used as a good access road also.

Ecological: Ecological:

No impact N/A

Temporary shifting & relocating Physical: Physical: of utility posts (electricity, water, sewer & telecom). No impact N/A

(This is only for re-construction of Social: Social: Culvert across Aluth Mawatha

Key project activities Potential Environmental Mitigation Measures Effects

Road) Disturbance to pedestrian and Provide adequate de-routing facilities and keep the pedestrians vehicular movement. and drivers well informed by fixing sign boards on appropriate locations. Ecological: Ecological: No impact N/A

Canal bank/bottom excavation, Physical: Physical: dewatering and disposal of bottom sediments Excavations of the canal Sediment quality in the proposed sections of the Main Drain banks and the canal bed should be established to understand the risk of contamination where the base of the gabions involved and to determine the suitable disposal method for the will be placed will be needed excavated sediments and waste. If contamination is established during proposed construction according to accepted reference criteria, disposal must be activities to provide the base planned properly, as indicated below. layer for embankment and gabion wall construction/ (a) given the small volume of exvated sediments that will be rehabilitation and for generated from this stretch of the canal (300m) the project maintaining the required should explore the possibility of using the two existing (and design depths in the existing only) small semi engineered landfills in Sri Lanka at Mawanella canals. These activities would ad Nuwara Eliya. Since the anticipated volume of excavated degrade water quality by matter in this case would be small, the project would be able to mixing of fines and negotiate with the Central Environmental Authority and the potentially contaminated relevant Pradheshiya Sabhas for using their facility or (c) dispose to Holcim industrial incinerator as alternative fuel.

Key project activities Potential Environmental Mitigation Measures Effects

material into downstream There will, however, be a cost involved in incinerating the areas of the canal and ground material at Holcim which is presumably not significant given water. Dewatering may cause the small quantities. surface ponding of removed water if proper drainage is not Proper and adequate dewatering should be ensured either using allowed, especially when the a proper monitoring schedule or using an automated upper soil layers are saturated submersible pump system with float device to ensure site due to recent storm events. activities are uninterrupted due to seepage water. Excessive dewatering may cause water table to decline Proper surface drainage and retention-detention capacity should rapidly, lowering soil pore be provided to safely remove pumped-up water from the site to pressure and sinking and a natural drainage to avoid in site ponding effects. localized land subsidence effects adjacent to existing Construction activities can be planned during the periods of low load bearing structures. water table to avoid excessive dewatering requirements and save costs while reducing risks of slope failures, increased Stock piling of excavated erosion, etc. material, soil, debris and other material may block The construction materials intended for temporarily storage surface drainage paths should be properly stockpiled in most appropriate areas in the causing localized flooding site to avoid disturbance to site mobility, traffic and stored during constructional and away from drainage paths and suitably covered to avoid operational periods. washout.

Silt traps and catch pits should be used during construction period where necessary to avoid excessive mixing of fines and

Key project activities Potential Environmental Mitigation Measures Effects

potentially contaminated material back into canal and downstream water bodies. All collected fines, excavated materials should be properly stored until safe disposal at suitably selected, adequately isolated disposal grounds.

Social:

Odour of this nature is of very short term duration and thus is Social: negligible. However if excavated material causes odour to emanate, removal of such material as practical as possible Odour problems would be undertaken. The handling of such material must be done only after the sediment quality testing has been carried

out and according to its conclusions.

Ecological:

Depending on the disturbance of the first few cm of the benthic layer, fauna that inhabit the top layer could be temporary

disturbed. Hence disturbance must be made to the minimum Ecological: level so that they could once again establish soon.

Smothering of benthic fauna

Removal of temporary structures, Physical: Physical: debris, demolition waste and other The demolished materials and debris intended for temporarily

Key project activities Potential Environmental Mitigation Measures Effects solid waste along the banks Emission of dust and noise storage should be properly stockpiled in most appropriate areas in the site to avoid disturbance to site mobility, traffic and Disturbances to traffic and stored away from drainage paths and suitably covered to avoid pedestrians during storage of washout. material and debris. Demolition has to be carried out with the minimum use of machinery and sprinkling of water should be done appropriately.

Suitably arranged barge may be used where access through existing roads is not available.

Construction debris management plan must be worked out prior to construction begins.

Social: Social: Fixing warning signs at appropriate locations and proper Inconvenience to present fencing are needed as safety measures. Also, avoidance of residents and pedestrians. slippery conditions along roadsides and pavements and walking surfaces have to be ensured.

Ecological: Ecological: N/A No impact

Key project activities Potential Environmental Mitigation Measures Effects

Excavation for the gabion wall Physical: Physical: construction and coffer damming The construction of gabion Vertical and near vertical soil embankments and excavation walls along the canal faces in saturated, sandy/peaty soils in the area should always embankment for bank be protected by shoring or installation of sheet piles/coffer strengthening and damming. stabilization would require substantial excavation close Coffer damming is required to contain and divert movement of to the existing earth canal water, to prevent slope failures at soil embankments/ near embankments. Such deep vertical excavation faces and to provide a reasonably dry excavations in saturated week construction area for the laying of screed concrete base (if soil would result in required by design) and interlocking rubble work arrangement collapsible vertical soil faces during gabion wall construction. The excavations in saturated and increased susceptibility to soil may lead to failure for collapsible soil faces erosion and liquefaction leading to bank failures. Minimum driving power should be used where the installations are located close to sensitive/load bearing structures to avoid Excessive vibration during differential settlements, cracks and other undesirable hydraulic driving of sheet deformations in soil subsurface structure. piles for coffer damming may weaken adjacent soil layers Excavated material from trenches and side faces for the erection while it may also affect of gabion walls should be properly stored and disposed at nearby foundations and other selected safe disposal locations. structures.

Key project activities Potential Environmental Mitigation Measures Effects

Social: Social:

Inconvenience to present Ensure that the present access on the canal bank to some houses residents and pedestrians. be not disturbed. Present access on the canal bank should be incorporated into the canal reservation so that it could be used for canal maintenance as well as the access to the houses.

Fixing warning signs at appropriate locations and proper fencing are needed as safety measures. Also, no slippery conditions along roadsides and pavements and walking surfaces have to be ensured.

Ecological: Ecological: This effect is temporary in nature. Ensure not to leave any Temporary distraction of fish material, chemical or any other substance that will eventually get washed away into the drain that could create toxic effects particularly to fingerlings.

Material transport and storage Physical: Physical:

Emission of dust and noise The construction materials intended for temporarily storage due to transport of material should be properly stockpiled in most appropriate areas in the site to avoid disturbance to site mobility, traffic and stored away from drainage paths and suitably covered to avoid

Key project activities Potential Environmental Mitigation Measures Effects

washout.

Dust emissions should be controlled by wet spraying of construction sites and roads which are used for transportation of construction materials at regular intervals.

Dust barriers should be erected if there are houses nearby stockpiles and tarpaulin covering is mandatory on trucks / lorries which are used for transporting materials.

Vehicles should be maintained in good condition and regularly maintenance in good conditions so that noise generating from wear and tear will be minimal.

Suitably arranged barge may be used for access if existing roads are not available.

Social: Social:

Inconvenience to the Construction vehicles and equipment should be parked at neighbours suitable locations without hindering the day to day

residential and urban activities.

Warning signs at appropriate locations and proper temporary

Key project activities Potential Environmental Mitigation Measures Effects

fencing are needed as safety measures.

Ecological: Ecological: No impact N/A

Physical: Physical:

Construction of flow guidance Improper alignment of flow Lined-concrete flow guide walls designed following appropriate walls for Main Drain bank guidance walls will lead to design guidelines and correct construction methodologies protection diverted flows, increased should be used where it is necessary to control bottom and side flow velocities causing erosion when the gabions walls are expected to get exposed to New Gabion walls: 1450 m significant erosion of soil adverse flow regimes at bend locations, changing sections, drop embankments adjacent to points, etc. New sheet pile walls: 57 m important structures, loosening bank support and All excavated and excavated materials arising from additional Rehabilitation of gabion walls: weakening of the interlocking work should be properly stored and disposed at selected safe 778 m of rubble used causing disposal locations as per recommendations given above. immature failure of gabion

structure before its intended design life. {Total length of Main Drain = Social: 1650 m} Additional excavation and dredging if required will lead On the left bank where new gabion walls are proposed there are

to undesirable environmental a few houses located, getting the access from canal bank. In such locations make sure that the present access on the canal

Key project activities Potential Environmental Mitigation Measures Effects

consequences. bank to those houses be not disturbed. Present access on the canal bank should be incorporated into the canal reservation so Social: that it could be used for canal maintenance as well as the access to the houses. Inconvenience to present residents and pedestrians. Ecological:

N/A

Ecological:

No impact

Reinstatement of storm water Physical: Physical: drainage connections (hume pipes) to Main Drain through gabion Erosion of soil from adjacent Strom water connections across the gabion walls should be walls and introduction of catch structures leading to provided using hume pipes or box culverts of adequate size pits wherever required. loosening of bank support according to pre-determined design storm events and return will lead to weakening of the periods. interlocking of rubble used causing immature failure of Catch pits should be provided at suitable spacing to remove gabion structure before its excessive fines through settlement. Catch pits should be

Key project activities Potential Environmental Mitigation Measures Effects

intended design life. regularly cleaned and maintained in proper order. Fines Blockage due to removed should be properly disposed to avoid them joining accumulation of fines due to flow paths again. cross drainage flows will lead to pore pressure build-up behind the gabion structure, leading to unbalanced pressure forces, making the structure susceptible to failure by toppling. Social: Social: N/A No significant impact Ecological: Ecological: N/A No impact

Backfilling of banks behind the Physical: Physical: gabions, turfing and planting of trees Selection of below grade fill Backfill materials should be selected after proper analyses of materials will not attain soil characteristics. Adequate compaction should be applied to required soil strengths after attain required soil strengths in banks and embankments. compaction and will lead to differential settlements The construction materials intended for temporarily storage

Key project activities Potential Environmental Mitigation Measures Effects

causing the gabion walls to should be properly stockpiled in most appropriate areas in the misalign and fail. site to avoid disturbance to site mobility, traffic and stored away from drainage paths and suitably covered to avoid washout.

Social: Social:

Inconvenience to present Close supervision by the field technical staff is necessary to residents and pedestrians and make sure that no accidents to people and damage to existing potential accidents if the houses happen. heavy equipment are not handled with great care. Suitably arranged barge may be used where access through existing roads is not available. Ecological: Ecological: No impact N/A

Reinstatement of maintenance Physical: Physical: road (width: 3 m) on left bank and construction of road side drain and Lack of side drains and toe Side drains and toe drains of adequate design sizes should be cross drainage to the canal. drains of adequate sizes provided alongside of the maintenance roads and proper cross alongside of the maintenance drainage structure should be provided where necessary to divert roads will lead to localized accumulated flows to the main drains. ponding in road pavements and weakening of soil sub- The construction materials intended for temporarily storage

Key project activities Potential Environmental Mitigation Measures Effects

base underneath. should be properly stockpiled in most appropriate areas in the site to avoid disturbance to site mobility, traffic and stored away from drainage paths and suitably covered to avoid washout.

Suitably arranged barge may be used where access through existing roads is not available.

Social: Social:

Inconvenience to present This activity would be a social benefit to the people as the residents and pedestrians maintenance road will also become access road to their houses.

Close supervision by the field technical staff is necessary to make sure that no accidents to people and damage to existing houses happen.

Ecological: Ecological:

No impact N/A

Aluth Mawatha Culvert Physical: Physical: Improvement: Temporarily blockage to Construction should be carried out during dry weather periods

Key project activities Potential Environmental Mitigation Measures Effects

- Demolish and reconstruct 3.0 x cross drainage flows may when the canal flow is low and almost stagnant to minimize the 3.5 x 12 m reinforced concrete occur during construction need for pumping and/or adequate flow diversions, dewatering, box culvert activities. De-watering and pumping should be arranged to maintain required cross - Connection of box culvert to diversion of flows may be drainage flows and to provide required dry conditions for existing 3.0 x 3.0 mm box needed to maintain construction activities while avoiding flooding and temporarily drain leading to Mutwal undisturbed canal flows and ponding issues. Tunnel. establish required dry - Reinstatement of Aluth conditions for construction Construction debris should be properly handled, stored and Mawatha at culvert locations purposes. eventually disposed, minimizing undesirable environmental consequences at all times. Material recycling is promoted to Construction debris arising minimize debris generation and wastage. from the demolition of pavement layers and existing Proper backfill materials should be selected after carrying our reinforced concrete culvert required field/laboratory tests and optimum compaction may cause adverse conditions should be maintained to attain maximum possible environmental effects like soil strengths after compaction of cover layers. blockage of surface drainage and site mobility, washout of Catch pits, drain inlet sediment traps/barriers, turbidity curtains fines, dust and increased should be used to minimize washout of fines and silting effects accident risk, if not properly in the downstream. Energy dissipaters and drops should be used handled, stored and disposed. where necessary to reduce flow velocities to reduce erosion and cavitation risks. If the connection between the newly constructed culvert and Minimum flow velocities required flow self cleansing of existing box drain leading to drains/structures should be maintained by providing required design gradients in drains, toe drains to minimize siltation.

Key project activities Potential Environmental Mitigation Measures Effects

Mutwal Tunnel is not Regular maintenance and cleaning of sediment traps, catch pits properly designed, the cross is highly recommended. drainage flows will be disrupted due to inadequate Checking of compaction achieved for backfill material would gradients while turbulence be done on regular basis. due to drops/humps may cause erosion and cavitation Frequent cleaning must be undertaken in order to keep the effects. effective areas devoid of such materials.

Inadequate backfill cover above culvert apex level may lead to inadequate load distribution and excessive

loads on the box frame. Selection of below grade fill

materials that would not attain required soil strengths after compaction and will lead to differential settlements in cover layer above box culvert causing the pavement layers to develop differential settlements and fail.

Key project activities Potential Environmental Mitigation Measures Effects

Sediment deposit leading to excessive siltation may reduce expected design flow capacities during operational phase.

Social: Social: Disturbance to vehicular and pedestrian movement. Provide adequate de-routing facilities and fix sign boards to efficiently re-direct the traffic towards their destinations. St. Andrew’s Road, Mattakuliya Road and Ellie House Road can be use as alternative routes. Ecological: Ecological: No impact N/A

Renovation of existing box drain Physical: Physical: (covers of the openings - 6 Nos.) connecting Aluth Mawatha culvert Temporarily blockage to Adequate flow diversions, dewatering, pumping should be & Mutwal Tunnel and anticipated cross drainage flows may arranged to maintain required cross drainage flows and to catch pits carrying storm water. occur during construction provide required dry conditions for construction activities while activities. De-watering and avoiding flooding and temporarily ponding issues. diversion of flows may be needed to maintain Construction debris should be properly handled, stored and

Key project activities Potential Environmental Mitigation Measures Effects

undisturbed canal flows and eventually disposed, minimizing undesirable environmental establish required dry consequences at all times. Material recycling is promoted to conditions for construction minimize debris generation and wastage. purposes. Proper backfill materials should be selected after carrying our Construction debris arising required field/laboratory tests and optimum compaction from the demolition of conditions should be maintained to attain maximum possible pavement layers and existing soil strengths after compaction of cover layers. reinforced concrete culvert may cause adverse Catch pits, drain inlet sediment traps/barriers, turbidity curtains environmental effects like should be used to minimize washout of fines and silting effects blockage of surface drainage in the downstream. Energy dissipaters and drops should be used and site mobility, washout of where necessary to reduce flow velocities to reduce erosion and fines, dust and increased cavitation risks. accident risk, if not properly handled, stored and disposed. Minimum flow velocities required flow self cleansing of drains/structures should be maintained by providing required If the connection between the design gradients in drains, toe drains to minimize siltation. newly constructed culvert and Regular maintenance and cleaning of sediment traps, catch pits existing box drain leading to is highly recommended. Mutwal Tunnel is not properly designed, the cross drainage flows will be disrupted due to inadequate gradients while turbulence

Key project activities Potential Environmental Mitigation Measures Effects

due to drops/humps may cause erosion and cavitation effects.

Inadequate backfill cover above culvert apex level may lead to inadequate load Checking of compaction achieved for backfill material would distribution and excessive be done on regular basis. loads on the box frame. Selection of below grade fill materials that would not

attain required soil strengths after compaction and will

lead to differential settlements in cover layer above box culvert causing the pavement layers to develop differential settlements and fail.

Sediment deposit leading to excessive siltation may reduce expected design flow capacities during operational Frequent cleaning must be undertaken in order to keep the

Key project activities Potential Environmental Mitigation Measures Effects

phase. effective areas devoid of such materials.

Social: Social:

Disturbance to the movement This activity will be carried out section by section and the box of people and potential drain covers are pre-cast (no in situ construction will take place accidents when the box drain other than small repairs) and thus removal and replacing will covers are replaced as the take very short period of time and thus impact would be access to the settlement lies negligible. Access to the settlement along the box drain will not on this box drain. be an issue as two alternative routes are available.

Ecological: Ecological:

No impact N/A

Replacement of covers of Mutwal Physical: Physical: Tunnel manholes (03 Nos.) If the transition is not well Proper design and construction of the transition using precise aligned and properly alignment and correct dimensions following related guidelines designed, excessive and specification is needed to avoid undesirable environmental Stream lining of inlet area to suit turbulence causing erosion consequences listed as above. the transition and cavitation risk, either reduced flow velocities Installation of trash screens and manholes will reduce - Introducing a trash screen causing siltation or increased accumulation of debris while allowing ease of access to regular - Formation of 2 Nos. new flow velocities causing maintenance activities. storm water manholes at erosion/cavitation, spilling

Key project activities Potential Environmental Mitigation Measures Effects

Mutwal inlet and and overtopping due to Frequent maintenance of all blocking areas needs to be connection of the above inadequate capacity may undertaken. two to inlet areas. occur. - Construction of boundary fence around the inlet areas If the trash screen is not a (with a gate) as a safety properly installed using measures. correct dimensions and proper alignments, trash may not be adequately trapped lading to debris accumulation inside the culvert area and

flows may be disrupted leading to overtopping and

localized ponding.

Lack of adequate accessibility for maintenance activities may lead to blocking of the system reducing design capacity. Social: Social: Frequent removal of material getting stuck in front of screen Blockage of solid waste in the needs to be undertaken. Pesticide application for mosquitoes trash screen will lead to temporary ponding where

Key project activities Potential Environmental Mitigation Measures Effects

water quality could get must be done on regular basis. degraded causing inconvenience to people particularly with the threat of mosquito breeding.

Ecological: Ecological:

Open pits and drains may This is a very temporary impact and such locations where allow animals, particularly animals can creep in could be covered to avoid any potential domestic ones, to creep into accidents to animals. the tunnel and get trapped inside

Stream lining the Mutwal Outfall Physical: Physical:

If the streamlining of the Streamlining should be carried out ensuring that the required structure at sea outfall is not gradients to maintain design hydraulic flows are not altered or carried out properly, disrupted. excessive turbulence causing erosion and cavitation risk, Adequate concrete cover should be provided to ensure that the either reduced flow velocities reinforcements are not constantly exposed to saline water. causing siltation or increased flow velocities causing erosion/cavitation may occur.

Key project activities Potential Environmental Mitigation Measures Effects

Exposure of reinforcements due to deterioration of the concrete cover will lead to the disruption of the structural performance of the outfall.

Social:

Unsound walls may cause Social: inconvenience to the neighbours Sound construction should be guaranteed through proper supervision. Ecological:

No Impact Ecological:

N/A

8. Conclusion and Screening Decision

Summary of environmental effects: Assuming that all mitigation measures are implemented as proposed, the following effects can be predicted

Key project activities Potential Environmental Effects Significance of the environmental effect with mitigation in place

NS- Effect not significant, or can be rendered insignificant with mitigation SP - Significant positive effect SN - Significant negative effect U - Outcome unknown or cannot be predicted, even with mitigation NA – Not applicable

Site preparation including Physical: provision of access roads, material storage yards Emission of dust NS

Social:

Disturbance to pedestrian movement, accessibility to houses. NS

Ecological: NS No impact

Temporary shifting & relocating Physical: of utility posts (electricity, water, sewer & telecom). No impact NS

(This is only for re-construction Social: of Culvert across Aluth Disturbance to pedestrian and vehicular Mawatha Road) NS movement.

Ecological: NS No impact

Canal bank/bottom excavation, Physical: dewatering and disposal of bottom sediments Excavations of canal banks and excavation of the canal bed close to the sides may be needed during proposed construction activities to SN provide the base layer for embankment and gabion wall construction/ rehabilitation and for maintaining the required design depths in the existing canals. These activities would degrade water quality by mixing of fines and potentially

contaminated material into downstream areas of the canal and ground water.

The low water table may cause dewatering a

crucial issue to reduce pore pressure build up,

slope instability and transport of fines.

Dewatering may also be needed to carry out SN construction activities without interruption in canal embankments especially for gabion wall construction and widening, and for other excavated areas during the periods of high groundwater table.

Dewatering may cause surface ponding of removed water if proper drainage is not NS allowed, especially when the upper soil layers

are saturated due to recent storm events. Excessive dewatering may cause water table to

decline rapidly, lowering soil pore pressure and sinking and localized land subsidence effects adjacent to existing load bearing structures.

Stock piling of excavated material, soil, debris and other material may block surface drainage NS paths causing localized flooding during constructional and operational periods.

If not properly stored and adequately covered, SN fine material washout may significantly degrade groundwater and surface water quality in canals, inland reservoirs and sea outfalls, while increasing risk of slope failures, siltation and blockage of structures.

Social:

Odour problems NS

Ecological:

Smothering of benthic fauna NS

Removal of temporary Physical: structures, debris, demolition waste and other solid waste Emission of dust and noise NS along the banks Disturbances to traffic and pedestrians during NS storage of material and debris.

Social:

Inconvenience to present residents and pedestrians. NS

Ecological:

No impact NS

Excavation for the gabion wall Physical: construction and coffer damming The construction of gabion walls along the NS canal embankment for bank strengthening and stabilization would require substantial

excavation close to the existing earth embankments. Such deep excavations in saturated week soil would result in collapsible vertical soil faces and increased susceptibility to erosion and liquefaction leading to bank failures.

Excessive vibration during hydraulic driving of NS sheet piles for coffer damming may weaken adjacent soil layers while it may also affect nearby foundations and other structures.

Social: NS Inconvenience to present residents and pedestrians.

Ecological:

NS Temporary distraction of fish

Material transport and storage Physical:

Emission of dust and noise due to transport of NS material

Social:

Inconvenience to the neighbours NS

Ecological:

No impact NS

Physical:

Construction of flow guidance Improper alignment of flow guidance walls will NS walls for Main Drain bank lead to diverted flows, increased flow velocities protection causing significant erosion of soil embankments adjacent to important structures, New Gabion walls: 1450 m loosening bank support and weakening of the interlocking of rubble used causing immature New sheet pile walls: 57 m failure of gabion structure before its intended design life. Rehabilitation of gabion walls: 778 m Additional excavation and dredging if required NS will lead to undesirable environmental consequences.

{Total length of Main Drain = Social: 1650 m} Inconvenience to present residents and NS pedestrians.

Ecological: NS No impact

Reinstatement of storm water Physical: drainage connections (hume pipes) to Main Drain through Erosion of soil adjacent structure leading to NS gabion walls and introduction of loosening of bank support will lead to catch pits wherever required. weakening of the interlocking of rubble used causing immature failure of gabion structure before its intended design life. Blockage due to accumulation of fines due to cross drainage flows will lead to pore pressure build-up behind the gabion structure, leading to unbalanced

pressure forces, making the structure susceptible to failure by toppling.

Social:

No significant impact NS Ecological:

No impact NS

Backfilling of banks behind the Physical: gabions, turfing and replanting of trees Selection of below grade fill materials will not NS attain required soil strengths after compaction and will lead to differential settlements causing the gabion walls to misalign and fail.

Social:

Inconvenience to present residents and NS pedestrians and potential accidents if the heavy equipment are not handled with great care.

Ecological:

No impact NS

Reinstatement of maintenance Physical: road (width: 3 m) and construction of road side drain Lack of side drains and toe drains of adequate NS and cross drainage to the canal. sizes alongside of the maintenance roads will lead to localized ponding in road pavements and weakening of soil sub-base underneath.

Social:

Inconvenience to present residents and NS pedestrians

Ecological:

No impact NS

Aluth Mawatha Culvert Physical: Improvement: Temporarily blockage to cross drainage flows

- Demolish and reconstruct 3.0 may occur during construction activities. De- NS x 3.5 x 12 m reinforced watering and diversion of flows may be needed concrete box culvert to maintain undisturbed canal flows and - Connection of box culvert to establish required dry conditions for existing 3.0 x 3.0 mm box construction purposes. drain leading to Mutwal Tunnel. Construction debris arising from the demolition - Reinstatement of Aluth of pavement layers and existing reinforced NS Mawatha at culvert locations concrete culvert may cause adverse environmental effects like blockage of surface

drainage and site mobility, washout of fines, dust and increased accident risk, if not properly

handled, stored and disposed.

If the connection between the newly constructed culvert and existing box drain NS leading to Mutwal Tunnel is not properly designed, the cross drainage flows will be disrupted due to inadequate gradients while turbulence due to drops/humps may cause erosion and cavitation effects.

Inadequate backfill cover above culvert apex level may lead to inadequate load distribution NS and excessive loads on the box frame. Selection of below-grade fill materials that would not attain required soil strengths after compaction and will lead to differential settlements in cover

layer above box culvert causing the pavement layers to develop differential settlements and fail.

Sediment deposit leading to excessive siltation NS may reduce expected design flow capacities during operational phase.

Social:

Disturbance to vehicular and pedestrian NS movement.

Ecological: NS No impact

Renovation of existing box drain Physical: (covers of the openings - 6 Nos.) connecting Aluth Mawatha Temporarily blockage to cross drainage flows NS culvert & Mutwal Tunnel and may occur during construction activities. De- anticipated catch pits carrying watering and diversion of flows may be needed storm water. to maintain undisturbed canal flows and establish required dry conditions for construction purposes.

Construction debris arising from the demolition of pavement layers and existing reinforced NS concrete culvert may cause adverse

environmental effects like blockage of surface drainage and site mobility, washout of fines, dust and increased accident risk, if not properly handled, stored and disposed.

turbulence due to drops/humps may cause erosion and cavitation effects.

Inadequate backfill cover above culvert apex NS level may lead to inadequate load distribution and excessive loads on the box frame. Selection of below-grade fill materials that would not attain required soil strengths after compaction and will lead to differential settlements in cover layer above box culvert causing the pavement layers to develop differential settlements and fail.

Sediment deposit leading to excessive siltation NS may reduce expected design flow capacities during operational phase.

Social:

Disturbance to the movement of people and NS potential accidents when the box drain covers are replaced as the access to the settlement lies on this box drain.

Ecological: NS No impact

Replacement of covers of Physical: Mutwal Tunnel manholes (03 Nos.) If the transition is not well aligned and properly NS designed, excessive turbulence causing erosion and cavitation risk, either reduced flow velocities causing siltation or increased flow Stream lining of inlet area to suit velocities causing erosion/cavitation, spilling the transition and overtopping due to inadequate capacity may occur. - Introducing a trash screen If the trash screen is not properly installed using NS - Formation of 2 Nos. new correct dimensions and proper alignments, trash

storm water manholes at may not be adequately trapped lading to debris Mutwal inlet and accumulation inside the culvert area and flows

connection of the above may be disrupted leading to overtopping and two to inlet areas. localized ponding. - Construction of boundary fence around the inlet Lack of adequate accessibility for maintenance NS areas a (with a gate) as a activities may lead to blocking of the system

safety measures. reducing design capacity.

Social:

Blockage of solid waste in the trash screen will NS lead to temporary ponding where water quality could get degraded causing inconvenience to people particularly with the threat of mosquito breeding.

Ecological:

Open pits and drains may allow animals NS particularly creepers to enter into the tunnel and get trap inside

Stream lining the Mutwal Physical: Outfall If the streamlining of the structure at sea outfall NS is not carried out properly, excessive turbulence causing erosion and cavitation risk, either reduced flow velocities causing siltation or increased flow velocities causing erosion/cavitation may occur.

Exposure of reinforcements due to deterioration NS of concrete cover will lead to disrupt structural

performance of the structure.

Social:

Unsound walls may cause inconvenience to the NS neighbors

Ecological: NS No Impact

9. Screening Decision Recommendation:

Final Majority of the potentially adverse effects can be classified as general recommendation construction related impacts and are mitigatable with good construction and site management practices. The public is generally supportive of the project and their concerns do not warrant further assessment. Therefore, a stand- alone Environmental Assessment is not required and, the Environmental Management Plan provided with this report would be sufficient to mitigate the identified impact.

However, the following specific recommendations given in the EMP are of utmost importance to be implemented.

A sediment quality testing for toxicity and the quantification of excavated material that will be removedl must be undertaken by the SLLRDC. This is the only potentially significant issue identified. Depending on the results of the sediment quality testing the excavated material should be disposed as specified in the EMP. If not the excavated material can be stored in a suitable site and subsequently used for refilling once the construction of gabion wall is done or even disposed to a municipal waste dump.

Safe handling of the excavated material with a proper plan for disposal including transport must be finalized prior to commencement of the project. Although the draft tender documents would be ready by 31/12/2011, they should be updated based on the results of the sediment testing and subsequent requirements, prior to being advertised.

Construction debris management plan must be worked out and implemented.

Heavy vehicles i.e., large trucks, should not be allowed for material transport. Only small vehicles such as tractors, carts will be promoted particularly in the areas of underserved settlements.

Restoration of existing gabion walls must be done with extreme care so as not to make any collapse of remaining portions by ensuring proper state of art engineering applications.

Sheet pile portion must be done with minimal damage to nearby infrastructure. However if damage is inevitable, compensation should be paid appropriately.

Construction activities should be encouraged during dry season so that impacts due to water levels will be minimal.

At the Mutwall outfall outlet structure, extreme care must be taken in the case of sea water intrusion for the purpose of promoting flushing of pollutants as the lining of the tunnel or open channel may not be fully water tight. If the lining is not water tight, concrete structures could be corroded and nearby groundwater could go brackish or saline casing foundations be perished due to corrosions. Hence water tightness of the conveyer system in areas where concrete cross sections are available must be tested and guaranteed for.

Transport of materials for sections of gabions where there is no access, head transport must be allowed with a slightly higher rate.

10. EMP implementation responsibilities and costs

The overall responsibility of ensuring compliance with safeguard requirements for the sub- project lie with the SLLRDC. Specifically, it will be responsible for undertaking sediment quality testing in selected locations of the Main Drain where the project interventions are proposed for, estimation of excavated material quantities generated and guiding the contractor on suitable disposal methods. The contractor will be responsible for implementing all other provisions in the EMP that relate mostly to good construction planning, site management and public safety practices with no additional costs involved.

The SLLRDC will also be responsible for taking into consideration all recommendation in the EMP relating to designs and ensure they are revised, if necessary, to address the concerns raised.

The additional cost involved in implementing the EMP relate to (a) undertaking sediment quality tests and (2) disposal of excavated material if contamination is established. Environmental monitoring will be carried out largely through compliance monitoring using the checklist provided in the EMF by the Environmental Officer of the CMC and the contractor jointly.

As such, the only additional costs envisaged are explained below:

Item Cost (Rs) Implementation Responsibility

Sediment quality testing – 180,000 SLLRDC 3samples

For following physical and chemical parameters

Particle size distribution, pH, Sulphate, Chloride, Total Organic Carbon, Fe, Cd, Ni, Zn, Cu, Cr, Al, Pb, Mn, Ca, Mg, Hg, As and leachability test for heavy metals

The testing will be done in early January 2012

Disposal of excavated material The cost of mitigation is hard to Contractor estimate at this stage as the quantities of material, quality of pollutants/substances, and sites for disposal etc. are undecided. The consultant will work with the SLLRDC for estimating the mitigation cost once results of the sediment quality test

Screening report completed by Date

Dr. Mahesh Jayaweera, Team Leader

University of Moratuwa

Tel: 0777320590 email: [email protected] Signature

Name/Designation/Contact information

Screening report reviewed by Date

Name/Designation/Contact information Signature Approved by Date

Name/Designation/Contact information Signature

11. Details of Persons Responsible for the Environmental Screening

(1) Dr. Mahesh Jayaweera, PhD, BSc in Civil Eng (Hons.), MIE (SL), CEng. – Team Leader (Overall coordination and planning) Experience: Team Leader/Consultant/Expert for more than 60 EIA and IEE studies during the past 15 years

(2) Professor Mrs. Niranjanie Ratnayake, BSc in Civil Eng (Hons.), MSc, FIE (SL), CEng. – Environmental assessment specialist Experience: Team Leader/Consultant/Expert for more than 40 EIA and IEE studies during the past 20 years

(3) Dr. Jagath Manatunge, PhD, MSc, DIC, BSc in Civil Eng (Hons.), MIE (SL), CEng. – Environmental Engineer (Noise, Water, Wastewater, Vibration, Air) Experience: Team Leader/Consultant/Expert for more than 40 EIA and IEE studies during the past 12 years

(4) Dr. Lalith Rajapakse, PhD, MEng, BSc in Civil Eng (Hons.), MIE (SL), CEng. – Civil Engineer (Hydrology, Geology, other civil engineering aspects) Experience: Consultant/Expert for more than 20 EIA and IEE studies and assignments mainly related to hydrological during the past 6 years

(5) Mr. Hemantha Jayasundara, BA (Hons.), MSc (Town and Country Planning), PG Dip in Urban Development, PD Dip in Environmental Sci. –Urban Planner Experience: More than 20 years as a Consultant/Expert on Urban and Regional Planning, Urban Design, Disaster Management, Environmental Management, Projects Management etc.

(6) Dr. Anusha Kasige, PhD, MSc, BSc in Zoology – Ecologist (Flora, Fauna, Ecosystems) Experience: more than 15 EIA and IEE studies and ecological studies during the past 5 years

References

Cooray, P.G.(1984). An introduction to the geology of Sri Lanka (Ceylon), with a foreword by John Sutton, National Museums of Sri Lanka Publication, Colombo, Sri Lanka.

Greentech (2011). Environmental Assessment Final Report for Metro Colombo Urban Development Project, Vol. 1, Greentech Consultants (Pvt) Ltd., Colombo 5, Sri Lanka.

Annex 1:

Photographs of some of the important locations along project roads

Aluth Mawatha and Mutwall outfall

1. Canal embankment

0 0 Fig.A‐ 1 Lat‐6.957060 Lon‐79.863720 Fig.A‐ 2 Lat‐6.95727 Lon‐79.86338

Fig.A‐ 3 Lat‐6.957820 Lon‐79.862740 Fig.A‐ 4 Lat‐6.957660 Lon‐79.862850

Fig.A‐ 5 Lat‐6.95623º Lat‐79.86483º Fig.A‐ 6 Lat‐6.956460 Lon‐79.864670

Fig A‐1. General view of the canal and the right bank

Fig A‐2. General view of the canal and the right bank

Fig A‐3, General view of the canal and the left bank

Fig A‐4. General view of the canal and the left bank

Fig A‐5. View of the canal from the railway bridge

Fig A‐6. Canal near the railway bridge. 2. Outfall (Ceylon Fisheries Corporation)

0 0 Fig.A‐ 7 Lat‐6.961970 Lon‐79.857930 Fig.A‐ 8 Lat‐6.96193 Lon‐79.85802

Fig.A‐ 9 Lat‐6.961970 Lon‐79.858020 Fig.A‐ 10 Lon‐6.958220 Lat‐79.861750 Fig A‐7. Mutwal outfall

Fig A‐8. About 40 m upstream of the outfall

Fig A‐9. Outlet from the tunnel

Fig A‐10. Outlet from the tunnel 3. Culvert at Aluth Mawatha

0 0 0 0 Fig.A‐ 12 Lat‐6.95761 Lon‐79.86284 Fig.A‐ 11 Lat‐6.95782 Lon‐79.86274

Fig.A‐ 13 Lat‐6.957810 Lon‐79.862680 Fig.A‐ 14 Lat‐6.957820 Lon‐79.862740 Fig A‐11. Culvert at Aluth Mawatha

Fig A‐12. The Bo Tree located very close to the culvert

Fig A‐13. View from the Aluth Mawatha towards canal upstgream

Fig A‐14. Gabion walls near the culvert which need rehabilitation

Annex 2: Detailed drawings of project components

Main Drain

Proposed bank protection Proposed bank protection Proposed bank protection Proposed bank protection