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1. Metro Colombo Urban Development Project    

                      

   

Environmental Screening Report for  Micro‐drainage improvement in Marine Drive development from 

Dehiwala Bridge up to Bambalapitiya Station Road  in sub‐catchment 2, 4 and 5  

   

Draft Final Report  

December 2011   

Uni‐Consultancy Services University of Moratuwa 

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Table of Contents

 

1. Project Identification 3

2. Project Location 3

3. Project Justification 6

4. Project Description 7

5. Description of the Existing Environment 10

6. Public Consultation 23

7. Environmental Effects and Mitigation Measures

7a. Screening for Potential Environmental Impacts 26

7b. Environmental Management Plan 34

8. Conclusion and Screening Decision 45

9. Details of Persons Responsible for the Environmental Screening 51

Annexes

1. Photographs of areas of flooding

2. Detailed drawings of project components

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Metro Colombo Urban Development Project

Environmental Screening Report

1. Project Identification

Project title

Micro-drainage improvement in Marine Drive development from Dehiwala Bridge up to Bambalapitiya Station Road – in sub-catchment 2, 4 and 5

Project Proponent

Colombo Municipal Council

2. Project Location

Location

(relative to the nearest town, highway)

Location of the project is depicted in the Fig. 1. Sub-catchment 2 of the proposed project includes the area demarcated by the Colombo-Galle Road (A1) and Marine Drive in the stretch from the by-roads International Buddhist Centre (IBC) Road and Boswell Place (Fig. 1).

Definition of Project Area

(The geographical extent of the project & areas affected during construction)

The entire project lies in and around Marine drive road in between Wellawatta Canal and Dehiwala Canal. The project area is primarily divided into 3 sub-catchments namely 2, 4 and 5 respectively. Sub catchment 2 covers wholly or partly International Buddhist Centre Road, Vaverset Place, Fernando Road, Moor’s Road and Boswell Place and the connecting line along the Marine Drive Road. The line collecting storm water from the above-mentioned roads then cut across the Marine Drive Road and joins the existing sea outfall. However there is a doubt whether the existing outfall will be sufficient for the new network and if in any case designs manifest a need for a new one, another outfall will be proposed. This decision is yet to be taken.

Sub-catchment 4 mainly runs along the Marine Drive Road but does not go into connecting roads. Connecting roads that cover this sub-catchment include Frances Road, Alexandra Road and Charlemont Road respectively. The above-mentioned network running along the Marine Drive Road finally joins the Wellawetta Canal through an outfall.

Sub-catchment 5 too mainly runs along the Marine Drive Road but goes into connecting roads with maximum distances of approximately 20 30 m. It is

URBAN UPGRADING WORK 

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required that this inter connection along the by roads up to the valley which is found couple of meters from the Marine Drive Road. Connecting roads include St Peter’s Place, Ridgeway Place, Kinross Avenue, Mary’s Road, Castle Lane, Sagara Road and Clifford Place respectively. The above-mentioned roads are connected to a one network running along the Marine Drive Road and finally join the Wellawetta Canal through an outfall.

The existing drainage network is shown in Figures A-12, A-13 and A-14.

Adjacent land and features

See “Other features” in Section 5.2 (Page 16)

The land use pattern in Colombo Municipal Council area is given in Table xx below. Table xx. Land use pattern in Colombo Municipal Council area.

According the data presented, the region is highly built up (over 84%) and the locality under the proposed project is predominantly residential.

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Figure 1. Location map and the project boundary

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3. Project Justification

Need for the project

(What problem is the project going to solve)

The main problems causing recurrent localized flooding in the CMC area can be identified in a combination of (i) unauthorized constructions on and along drainages, (ii) dumping of waste in the drainages, obstructing/blocking free flow, (iii) backwater from the main canals system during major floods impeding the drainage, (iv) lack of regular maintenance and cleaning of the drainage system and (v) current under-dimensioning of micro-drainage infrastructure not enabling to cope with increasing rainfall frequency and intensity, possibly due to climate changes. CMC has identified 45 of such flood prone areas where localized flooding is regularly taking place, out of which 15 have been selected as priority for micro-drainage improvement sub-projects to be financed under Component 1.

Purpose of the project

(what is going to be achieved by carrying out the project)

The main purpose of the project is to relieve the sub-catchment 2, 4 and 5 from localized flooding following rainfall events by providing a new storm water drainage network with a view to providing proper maintenance to some selected geographical areas.

The proposed drainage network is shown in Figures A-12, A-13 and A-14.

Alternatives considered

(different ways to meet the project need and achieve the project purpose)

No any other alternative is considered for the project as it is envisaged that there are no any other technically feasible and economically viable engineering interventions that could be accommodated in place of the proposed option.

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4. Project Description

Proposed start date The opening of bid documents will be done by 29th February 2012 and 6 months will be taken for selection of a contractor. The construction period for each sub-catchment will be 8-10 months.

Proposed completion date It will take minimum 14 – 16 months to finish the project from the date of opening bid documents.

Estimated total cost Each sub-component will be around 60 - 80 Million rupees.

Present land ownership Entire project lies in areas belonging to CMC. However, sometimes small sections particularly bordering Wellawette Canal belonging to private owners will be acquired for laying the underground pipes.

Description of the project (with supporting material such as maps, drawings etc attached as required)

Location of the project is given in the Fig. 1. The entire project lies in and around Marine drive road in between Wellawatta Canal and Dehiwala Canal. The project area is primarily divided into 3 sub-catchments namely 2, 4 and 5 respectively.

Sub catchment 2 covers wholly or partly International Buddhist Centre (IBC) Road, Vaverset Place, Fernando Road, Moor’s Road and Boswell Place and the connecting line along the Marine Drive Road. The line collecting storm water from the above-mentioned roads then cut across the Marine Drive Road and joins the existing sea outfall.

Sub-catchment 4 mainly runs along the Marine Drive Road but does not go into connecting roads. Connecting roads that cover this sub-catchment include Frances Road, Alexandra Road and Charlemont Road respectively. The above-mentioned network running along the Marine Drive Road finally joins the Wellawatta Canal through an outfall.

Sub-catchment 5 mainly runs along the Marine Drive Road but goes into connecting roads with maximum distances of approximately 20 30 m. It is required that this inter connection along the by roads up to the valley which is found couple of meters from the Marine Drive Road. Connecting roads include St Peter’s Place, Ridgeway Place, Kinross Avenue, Mary’s Road, Castle Lane, Sagara Road and

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Clifford Place respectively. The above-mentioned roads are connected to a one network running along the Marine Drive Road and finally join the Wellawatta Canal through an outfall.

Key project activities identified are as follows:

– Site Surveying, Testing & Data Collection – Negotiations with land owners – Land acquisition – Land Clearing – Temporary parking lots – Traffic diversion/Generation of additional traffic due to

construction – Demolition of existing structures – Pavement demolition – Excavation of trenches and shoaling (cross sections of

trenches are given in Annex 2) – Dewatering and site drainage – Stockpiling of material – Transport of construction material – Trenching, construction of pipelines, filling and re-

surfacing/overlay (see drawing provided in Annex 2) – Construction of structures such as gullies, manholes, catch

pits etc. (see drawings provided in Annex 2) – Compaction & Soil Stabilization – Spoilage disposal – Maintenance of catch pits, manholes, gullies etc. and

removal of material and disposal The existing and the proposed drainage network is shown in Figures A-12, A-13 and A-14.

Project Management Team

Agency:

CMC will be responsible for the implementation of this proposed project. Nevertheless, A Project Management Unit (PMU) has been established under the Ministry of Defense and Urban Development (MoDUD) to implement the Metro Colombo Urban Development Project. The PMU will operate under the oversight of a Steering Committee, chaired by MoDUD’s Secretary and composed by

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SLLRDC, UDA, the PLAs, the Ministry of Provincial Councils and Local Authorities, the National Water Supply and Drainage Board and the Ministry of Irrigation. Other ministries and agencies will be identified as stand-by members, to be called when relevant issues need to be dealt with (e.g. Central Environmental Authority). While the PMU will remain responsible for the overall implementation of the project, responsibilities will be decentralized to the Project Partner Agencies (PPAs = SLLRDC and UDA) and to the Project Local Authorities (PLAs), assisted by consultants for construction supervision.

Contact person:

Mr. Chandrapala, Maintenance Engineer; Tel: 0777514627

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.

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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 general topography 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 so called lowest peneplain of Sri Lanka (.G.Cooray – Geology of Sri Lanka 1984). This coastal peneplain rises to a maximum elevation of < 500 feet from sea coast. Elevation in sub-catchment 2 in the proposed project area varies from 2 m – 6.2 m, with mild slope in the seaward direction. The slope in the upper catchment up to about 210 m from Marine Drive is slightly steeper (~ 1.0%) while the slope in the seaward segment is only about 0.5%. The contour lines are aligned approximately parallel to the shoreline. The topography of the area is slightly undulating with alluvium on surface of the terrain. There is a valley area located towards the mid-section of International Buddhist Centre Road in Sub-Catchment 2. Most of the roads in sub-catchments 4 and 5 are clopping towards the seaward side.

Soil (type and quality)

A 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. 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. According to Survey Department soil maps (Fig. 2) 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

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The soil types were verified during the field visits to the project site and by a trial excavation pits (Fig.3 ).

Fig. 2. Soil Maps of the Study Area (Source: Greentech)

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Fig. 3. Excavated trial pit and dug soil from upper surface layer

Surface water (sources, distance from the site, local uses and quality)

Sources

The only sources of surface water in the vicinity are the two surface water drainage canals: Kirillapone canal and the Dehiwala canal (Map **). These two canals drain surface runoff of areas such as Kirillapone, Havelock town and Southern Colombo suburbs.

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Distance from the site

The Kirillapone canal is adjoining Charlemont Road in sub-catchment 4 and St. Peter’s Road in sub-catchment 5. The canal is the division between these two sub-catchments and is located about 300 m North of sub-catchment 2. The Dehiwala Canal is about 1.5 km from the site.

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 of grey water from residences located adjoining the canal, and due to appalling level of water pollution, no other local uses can be derived from the water body.

Quality

The water quality measured on 22nd August, 2011 at a location about 700 m upstream of canal from the sea outfall is given in Table 1 and measured on 15th August, 2011 is given Table 2.

The salinity levels as shown in Table 1 should be much higher in the canal water near the site area, as the location is almost at the sea mouth and salt water intrusion makes the water mixed with a lot of sea water. Also, BOD, turbidity and total suspended solid content are very high in the canal water. Dissolved oxygen, and pH are within the normal range. Fecal coliforms levels are very high that indicate sewage contamination.

Nitrate and Phosphate concentrations are also relatively high which indicate nutrient enrichment due to disposal of domestic and industrial wastewater into the canal over time.

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Table 1. Water quality of Kirillapone canal near Havelock city during neap and a spring tide

During a Neap Tide During a Spring Tide Parameter Morning Afternoon Morning Afternoon Temperature ͦC) 24.1 25.3 23.4 25.5 pH 7.36 7.98 6.90 6.98 DO (mg/l) 6.09 7.18 5.91 6.60 Conductivity (dS/m) 7.03 4.50 4.39 14.43 Turbidity (NTU) 28.9 16.5 28.8 18.8 TDS (g/l) 4.9 3.9 0.2 4.7 TSS (mg/l) 108.2 75.1 52.3 83.4 BOD (mg/l) 30.1 32.4 26.7 30.0 Fe l Coliform (MPN/100 ml)

> 104 > 104 > 104 > 104

Table 2. Water quality fluctuations of the canals at Galle Road during 1997-2009

Parameter Wellawatta Canal

Dehiwala Canal

pH 6.2-7.2 6.1-8.3 Conductivity (dS/m) 1-14 1-12 Turbidity (NTU) 8-16 10-40 Ammonia (mg/l) 1.2-5.3 1.1-6.3 Nitrates (mg/l) 0.1-1.6 0.1-1.7 Phosphates (mg/l) 0.8-3.0 0.3-3.2 DO (mg/l) 1-3.5 0.8-6.7 BOD (mg/l) 8-32 10-34

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COD (mg/l) 10-90 18-00

Ground water (sources, distance from the site, local uses and quality)

Sources

Only available source of ground water is abstracting water from shallow wells. 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.

Distance from the site

The ground water table is very shallow and is about 0.4-0.5 m on average and can be at a level almost at surface up to 1 m. (see Figure 3)

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.

Quality

There is no data available for quality of ground water. However, it can be assumed that salinity levels 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 existing drainage system in the area follows a trellis pattern and drains the catchment to the sea through a network of secondary drains laid perpendicular to the by-lanes across the lower most elevation area in the middle part of sub-catchment 2 and a main drain aligned along the Moor Road to direct accumulated storm water to a baffled sea outfall across Marine Drive. See Annex 1 for Photographs of areas subjected to flooding (Figs. A4-1, A4-2 & A5).

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Fig 4. Existing drainage network in sub-catchment 2 However, after heavy storm events the flood water movement concentrates to the middle part of the area due to the sloping ground from both directions and causes temporary flooding in the adjacent localities, causing inconvenience to residents and damage to homesteads and properties. The elevated

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groundwater table, saturated subsurface soil layers, highly built up localities with less permeable paved areas and blocked and in adequate drainage lines with lack of proper maintenance are the main causes contributing to those flash (See Figs. A2-1, A2-2, A3-1 and A5). Raised floors and entrance locations were seen (Figs. A4-1 and A4-2) to avoid flood water coming into residential units. Flood events which frequently occur during monsoon and inter monsoon seasons apparently last for several hours until the downstream conditions are favorable for gravity drainage or until blocked drainage paths are cleared and normal flows are restored.

Air quality (any pollution issues)

Heavy vehicle movements along Galle Road and Colombo Plan Road (Marine Drive) lead to air pollutant 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 is prevalent along many of the roads where blockages of gullies, manholes and drainage canals are a common occurrence (Figs. A-1, A2-1, A2-2, A3-1 and A3-2).

Noise level and vibration (Any anticipated issues)

Existing ambient noise and vibration levels in the area are consistent with urban residential and light industrial businesses, hotel and restaurants. There is also heavy traffic noise from Galle Road and Colombo Plan Road (Marine Drive), both of which carry heavy traffic during peak hours as well as during the night time. Intermittent high levels of noise and vibration levels are observed due to train operations along Coastal Railway line, which is also one of the busiest rail lines of the country. Noise and vibration levels in the area would increase due to construction activities mostly high rise building where operation of construction equipment and machinery.

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5.2 Ecological features – Eco-system components

Vegetation

(trees, ground cover, aquatic vegetation)

Sub-catchment 2

The five cross roads and the marine drive road stretch comes under sub-catchment 2 of this project is predominantly a human settlement consist with home gardens, Buddhist / Hindu temples, hotels/ restaurants and by roads. Therefore the entire area is a man made environment and no ecological sensitivity. Common home garden plant species, Mangifera indica (Amba), Cocos nucifera (Pol), Terminalia catappa (Kottan), Acacia melanoxylon, Gliricidia sepium (Weta Mara), Leucaena leucocephala (Ipil Ipil), Azadirachta indica (Kohomba), Artocarpus heterophyllus (Kos), Musa x paradisiaca (Kesel), Tabernaemontana divaricata (Watu Sudda), Filicium decipiens (Pehimbiya) are dominant in the home gardens in the area. Sea is the marine aquatic habitat present parallel to the marine drive and there is no beach vegetation due to human interferences. No endemic or threatened plant species recorded during the rapid screening survey.

Sub-catchment 4

The three cross roads (Frances Rd, Alexandra Rd and Charlemont Rd) of this project is predominantly a human settlement consist with home gardens, restaurants, private/ public/commercial buildings, and by roads. Therefore the entire area is a man made environment and no ecological sensitivity. Common home garden plant species, Mangifera indica (Amba), Areca catechu (Puwak), Cocos nucifera (Pol), Terminalia catappa (Kottan), Acacia melanoxylon, Gliricidia sepium (Weta Mara), Leucaena leucocephala (Ipil Ipil), Azadirachta indica (Kohomba), Artocarpus heterophyllus (Kos), Musa x paradisiaca (Kesel), Tabernaemontana divaricata (Watu Sudda), Plumeria obtuse (Araliya), Filicium decipiens (Pehimbiya) are dominant in the home gardens in the area. Sea is the marine aquatic habitat present parallel to the marine drive and there is no beach vegetation due to human interferences. Wellawatta canal exist next to Charlemont Rd which flows down to sea across the marine drive. No endemic or threatened plant species recorded during the rapid screening survey.

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Sub-catchment 5

The seven cross roads and the marine drive road stretch is a commercial area and a human settlement consist with home gardens, school ( St Peters College at Galle Rd), hotels/ restaurants and residential apartments. Therefore the entire area is a man made environment and no ecological sensitivity. Common home garden plant species, Cocos nucifera (Pol), Terminalia catappa (Kottan), Azadirachta indica (Kohomba), Artocarpus heterophyllus (Kos), Musa x paradisiaca (Kesel), Tabernaemontana divaricata (Watu Sudda), Filicium decipiens (Pehimbiya), Spondias dulcis (Amberella), Psidium guajava (Pera), Areca catechu (Puwak), Plumeria obtuse (Araliya) are dominant in the home gardens in the area. Sea is the marine aquatic habitat present parallel to the marine drive and there is no rich beach vegetation due to human interferences. No endemic or threatened plant species recorded during the rapid screening survey.

Presence of wetlands There is no wetland habitats within or in the vicinity of proposed project area

Fish and fish habitats

Sub-catchments 2 & 5

There is no aquatic habitat other than the sea within and immediate surroundings of the proposed project area. The fish sampling was not carried out due to limited time.

Sub-catchment 4

Wellawatta canal exist close to Charlemont Rd which flows down to sea across the marine drive. The fish sampling was not carried out due to limited time availabity.

Birds (waterfowl, migratory birds, others)

Sub-catchments 2 & 5

Acridotheres tristis (Common Myna), Eudynamys scolopacea (Asian Koel), Columba livia (Rock Pigeon), Copsychus saularis (Oriental Magpie Robin), Turdoides affinis (Yellow-billed Babbler),

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Dicaeum erythrorhynchos (Pale-billed Flowerpecker), Corvus levaillantii (Large-billed Crow), Corvus splendens (House Crow), Nectarina zeylonica (Purple-rumped Sunbird), Orthotomus sutorius (Common Tailorbird), Pycnonotus cafer (Red-vented Bulbul), Dicrurus caerulescens (White-bellied Drongo), Streptopelia chinensis (Spotted Dove) are common birds observed during the rapid screening survey and no endemic or threatened animal species was recorded.

Sub-catchment 4

In addition to above birds, Halcyon smyrnensis (White-throated Kingfisher) and Bubulcus ibis (Cattle Egret) were observed associated with Wellawatta canal.

Presence of special habitat areas (special designations and identified sensitive zones)

For all three Sub-catchments There are no such special habitats demarcated as protected areas within and immediate surroundings of the proposed project area other than Sea.

Other features

Residential/Sensitive Areas (Eg, Hospitals, Schools)

Sub-catchment 2 International Buddhist Centre Road A Buddhist Institute and a Hindu temple are located close to the Marine Drive. Land use is predominantly residential mostly with single and two story houses. Land use is changing from residential to institutional and single low density housing to high density housing. 34 pedestrians and 07 vehicles were recorded on the road during the inspection time (30 minutes) No sensitive land uses. Vaverset Place The land use is very mixed predominantly residential and institutional. Many houses have been converted into institutional uses. Low density housing is has changed to high density housing in the

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recent past with high-rise apartment buildings. 24 pedestrians and 14 vehicles were recorded on the road during the inspection time (30 minutes) No sensitive land uses were found. Fernando Road The land use is predominantly residential – close to the Galle road and Marine drive middle income housing and at the centre low income housing. A small Hindu temple is located near the low income settlement. 12 pedestrians and 2 vehicles were recorded on the road during the inspection time (20 minutes) No sensitive land uses were found. Since the road is very narrow road side drains have been damaged due to vehicular damaged. Boswell Place The land use is predominantly residential – close to the Galle road commercial. Two high rise apartments (6 stories and 8 stories) are located. Land use has changed from low rise residential to high rise residential in the recent past. A Catholic Church (Trinity Reformed Presbyterian Church) is located. and Marine drive middle income housing and at the centre low income housing. A small Hindu temple is located near the low income settlement. 12 pedestrians and 2 vehicles were recorded on the road during the inspection time (20 minutes) No sensitive land uses were found. Since the road is very narrow road side drains have been damaged due to vehicular damaged. Sub-catchment 4 This sub-catchment consists of three roads namely, Frances road, Alexandra road, and Charlemount road. Predominant land use of these roads is residential and commercial office uses. The current project does not intend to undertake any construction on these roads as they do not experience flooding problems similar to other roads. The main project activity here is construction of the main drain on the shoulder of the Marine Drive. Main land uses along this stretch along the Marine Drive are commercial mostly hotels and restaurants. Sub-catchment 5 St. Peters Place The land use of this road is predominantly residential

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Ridgeway Place The land use of this road is predominantly residential, changing from low rise residential to high rise apartments. Movement of 11 vehicles and 16 pedestrians were recorded during the 20 min of study. Kinross Avenue The land use of this road is predominantly residential, fast changing from low rise residential to high rise apartments. Environment of this road is different to others as half the road from Galle road has a medium size tress on either side. Mary’s Road The land use of this road is predominantly residential and mostly single to two story housing. Castel Lane This road is wider than the other roads in the study area and the land use is predominantly residential with a few institutional buildings. Sagara Road The land use is predominantly residential mostly low rise buildings and two high rise apartments. Movement of 14 vehicles and 28 pedestrians were recorded during the 15 minutes of study period. Clifford Place Land use is predominantly low residential. The vehicular traffic is mostly dominated by three wheelers – 9 of them were recorded during the 10 min of study. A Catholic church is located.

Traditional economic and cultural activities

No such activities were found within the three sub-catchments. The roads are very narrow (about 12 feet wide). The garbage along the road has become the main issue of the flooding issue as they block the catch pits during rainy seasons.

Archeological resources

No such activities were found within the three sub-catchments.

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6. Public Consultation

Public consulted Consultation method

Date Details/Issues raised

Mr. Asmin

A Resident of International Buddhist Centre Road, Sub-catchment 2

Informal discussion

14.12.2011 The road surface over the time has been raised by overlaying of bitumen without scraping the original surface which has caused most of the properties to locate below the road level. This has increased the vulnerability of these properties to flooding.

Disposal of garbage is a key issue as storm water carries them and blocks the drainage paths. People need to be educated in regards to handle garbage properly.

Many people have built structures on the drain path that intersects their properties and therefore maintenance has become increasingly difficult.

Disturbances created during construction of new drain are manageable as it will bring more benefits and is of short term in nature.

Dr. Rajeev

A Resident of International Buddhist Centre Road, Sub-catchment 2

Dr. Rajeev is a new resident to the area. When he purchased the property he was unaware of the flooding problem. After experiencing flooding during the recent rainy seasons he had partly constructed a structure along the entrance to prevent flood water being entering into his property.

He is very positive and supportive for the proposed project.

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Engineer Gamini Perera

A Resident of Vaverset Place, Sub-catchment 2

If the set back of the road is in accordance with the Municipal street line and if it is maintained by all, and if the solid waste is managed properly many issues can be resolved, without much effort.

Mr. Vincent

A Resident of Fernando Road, Sub-catchment 2

The key issue it ignorance of people in handling solid waste. Maintenance of the drains by CMC is very poor that has led to deterioration of the system very fast.

Although the road is narrow, many vehicles use this road for through traffic due to easy connection to the Marine Drive. This increased traffic flow has damaged side drains.

Mr. Anil Fernando

A Resident of Fernando Road, Sub-catchment 5

This householder is one of the worst affected by flooding. The residents of his house showed the damaged furniture due to recent floods and how they have kept the furniture to prevent further damage. They have placed furniture on bricks to avoid flood damage.

Some houses in the vicinity are adversely affected as storm water is contaminated with wastewater. Although the road is narrow this road has now become a through road and has damaged almost all the drain covers in front of houses.

Inconvenience during construction of a new drain is negligible compared to the hardships they face due to flooding and the agony that they are undergoing now.

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Mr. Nagaraj

A Resident of Mary’s Road, Sub-catchment 5

They are frequently affected by floods when flood water inundated the frontal portion of the house beyond their car porch.

The only reason for flooding is improper handle of garbage by the residents and dumping garbage along the roadside. The garbage bags are washed away and completely cover the top screens of catch pits, thereby not allowing surface runoff to flow into drainage canals. This occurs very often and blocks the storm water entering the drainage lines, and also blocks the man holes.

The most important aspect that has to be considered to mitigate the problem is to educate the people.

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7. Environmental Effects and Mitigation Measures

7a. Screening for Potential Environmental Impacts

Screening question Yes No Significance of the effect

(Low, moderate, high)

Remarks

1 Will construction and operation of the Project involve actions which will cause physical changes in the locality

No Most of the interventions are carried out underground hence no physical changes in topography and landform is anticipated.

2 Will the Project involve use, storage, transport, handling or production of substances or materials which could be harmful to human health or the environment or raise concerns about actual or perceived risks to human health?

Yes Low

Transport of material and construction activities, including excavation, and material piles will emit dust and fugitive particles which may pose a health hazard to vulnerable persons on temporary basis. The wind blowing with the sea breeze will be the triggering factor for such impact though it is sporadic in nature.

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

Yes Moderate

During construction:

There will be spoilage (Construction debris) produced during demolition of existing structures and pavements, excavation of trenches.

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During operations:

There will be debris and sediments, floating matter and other solid waste carried by surface drainage collected 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 hazardous, toxic or noxious substances to air?

Yes Low

There will be bituminous material used during re-surfacing the trenches, bituminous patching, crack sealing, carriageway edges and shoulder repairs.

5 Will the Project cause noise and vibration or release of light, heat energy or electromagnetic radiation?

Yes Moderate

The project activities will cause noise and vibration during excavation of trenches, and during compaction, transport of material etc. These impacts are temporary in nature and cause only inconvenience to the neighboring people only.

6 Will the Project lead to risks of contamination of land or water from releases of pollutants onto the ground or into surface waters, groundwater or coastal wasters?

Yes Low

Stock piling of material will lead to washing away of soil and may increase turbidity and TSS in road side drainage and the nearby canal temporarily during construction period. During operation, some

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debris, sold waste and domestic wastewater (both gray and black) could be brought in to the canal through the proposed network.

It is anticipated that additional land clearing, leveling and other land preparatory activities may be needed prior to and during the construction of proposed additional drainage structures. The surface soil and the topmost layers of subsoil in the proximity of proposed site areas are either Red Yellow Podzolic soils with laterite or sandy clay in subsurface layers. Laterite soils consist of reasonable grade distribution and are relatively more stable than typical clayey soils while clayey and sandy soils with their smaller grain sizes are less resistant to erosion and washout. Therefore, once exposed due to removal of land cover, loosened due to excavation and harrowing or heaped and left uncovered, these soil layers will pose threat to the environment by causing washout of fine material degrading water quality, removing soil fertility, silting downstream catch pits and canals, degrading soil stability and risking slope and bank failures.

Construction activities in the proposed project site may also involve soil and some rock excavation (if any), storage, and removal or replacement of parts

29  

of the existing land features, and digging borrow pits which might increase erosion risk of top soil layers and cause siltation, if proper mitigation measures are not adopted.

On the other hand, proper construction practices like soil compaction and stabilization, turfing, maintaining naturally stable slopes, reforestation, etc. will improve soil stability, reducing erosion risk and siltation effects during the construction phase and in the aftermath of project completion.

7 Will the project cause localized flooding and poor drainage during construction

Is the project area located in a flooding location?

Low Raised embankments and raised finish levels, stock piling of construction debris and other materials may block existing drainage flow paths, causing flow stagnation and localized flooding effects. Increased soil formation levels in large area extents may occupy significant volume of retention capacity previously available for flood detention and retention, causing flash flood events in the long run. The middle section of the proposed project area where the terrain sags with a mild slope from both sides is a flood prone area where flood depths of 1-2 ft have been recorded frequently during heavy rain events.

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However, ensuring proper construction practices like provision of improved drainage network, maintaining naturally stable slopes, reforestation, etc. will improve drainage conditions, reducing flood risk during the construction phase and in the aftermath of project completion.

8 Will there be any risks and vulnerabilities to public safety due to physical hazards during construction or operation of the Project?

Yes Low

Disturbance to pedestrians during night time, safety issue in terms of falling into excavated trenches by neighbors and commuters could be anticipated.

9 Are there any transport routes on or around the location which are susceptible to congestion or which cause environmental problems, which could be affected by the project?

Yes Low

Due to the closure of the road for construction the traffic would be diverted to other nearby roads making the traffic volume of those roads increased. However there are many connecting roads so that impact would be marginal. Only very few dwelling units will be affected depending on the time of excavation. Such locations will be carefully handled with the provision of temporary car parks with security arrangements to ease such problems.

10 Are there any routes or facilities on or around the location which are used by the public for access to recreation or other

Yes Low

Use of road to access the beach may be temporary

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facilities, which could be affected by the project?

affected but not completely cut off.

11 Are there any areas or features of high landscape or scenic value on or around the location which could be affected by the project?

No Since project mainly deals with underground work no impact is anticipated.

12 Are there any other areas on or around the location which are important or sensitive for reasons of their ecology e.g. wetlands, watercourses or other water bodies, the coastal zone, mountains, forests which could be affected by the project?

No No such sensitive areas are found in the project area.

13 Are there any areas on or around the 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?

No No such areas are found.

14 Is the project located in a previously undeveloped area where there will be loss of green-field land

No No such green field is encountered.

15 Will the project cause the removal of trees in the locality?

No No tree is planned to be uprooted or cut or pruned.

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16 Are there any areas or features of historic or cultural importance on or around the location which could be affected by the project?

Yes Low

Access to religious places (Methodist Memorial Church, Hindu Kovil and the International Buddhist Centre along IBC Road, Trinity Reformed Presbyterian Church at Boswell Road may be temporarily affected but not completely cut off.

17 Are there existing land uses on or around the location e.g. homes, gardens, other private property, industry, commerce, recreation, public open space, community facilities, agriculture, forestry, tourism, mining or quarrying which could be affected by the project?

Yes Sometimes small plot of private land bordering Wellawatte canal may be acquired for the purpose of constructing an outfall. This decision is not yet taken as the designs are not yet finished. Once the underground line is done the owner can be able to use the land without any hindrance.

18 Are there any areas on or around the location which are densely populated or built-up, which could be affected by the project?

Yes Low

Residents of the area would not be able to travel by their vehicles only for couple of days till the trenches are completed.

19 Are there any areas on or around the location which are occupied by sensitive land uses e.g. hospitals, schools, places of worship, community facilities, which could be affected by the project

Yes Low

Places of worship only that are not used on regular basis: Methodist Memorial Church, Hindu Kovil and the International Buddhist Centre along IBC Road, Trinity Reformed Presbyterian Church (Boswell Road)

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20 Are there any areas on or around the location which contain important, high quality or scarce resources e.g. groundwater, surface waters, forestry, agriculture, fisheries, tourism, minerals, which could be affected by the project?

Yes Low

Coastal habitats are affected due to sea outfalls bringing additional loading of BOD and COD rich waters together with oil and grease content.

The low lying marshes, bordering canals, retention areas have led to a near surface groundwater table, which during drought periods can be at a depth of 1.5 to 2.5 m. In the interior (away from the coast) sector of the project area fresh water resources exist. However, most of such resources are today polluted due to a high concentration of urbanization, with poor waste disposal practices. No significant additional impacts are expected due to proposed project components and intended construction activities.

21 Are there any areas on or around the location which are already subject to pollution or environmental damage e.g. where existing legal environmental standards are exceeded, which could be affected by the project?

Yes Wellewatta Canal and near shore sea are said to be slightly or moderately polluted depending on the seasonal effects. However the addition from the project seems to be very marginal or perhaps negligible.

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7b. Environmental Management Plan

Key project activities

Potential Environmental Effects

Mitigation Measures

Site Surveying, Testing & Data Collection

Obstructions to vehicular movement

Use modern surveying equipment and carry out the work during non – peak hours of traffic.

Detailed design Impacts due to design failures, inadequate capacities, difficulties in maintenance, shortened life spans, structural failures

If suitable structures like gullies, manholes, and catch pits are not provided at appropriately calculated spacing along the alignment of channels/ducts, the drainage network may not function as per the intended design criteria.

If gullies are not provided at certain regular spacing, surface runoff may not diverted properly to the designed channels. Irregular spacing of

This is the only potential significant impact and therefore, mitigation should be carefully planned.

Design parameters have to be carefully and accurately estimated. For example, design for accurate rainfall intensity (I) needs to be re-validated as the valley area gets flooded even now with slightest rainfall event. Appropriate design return period should be assumed following guidelines, and design storm event should be carefully decided to estimate a reasonable rainfall intensity value (i mm/hr; i.e. either estimated from existing IDF curves or based on past climatic records) to reflect climatic, regional, land use and terrain characteristics in the target project area.

The slopes (gradients of pipelines), cross sections and location and sizing of man holes, catch pits etc. have to very accurately determined. The connections of different slopes must be through proper catch pits where provision must be made available for periodic silt and debris removal.

Estimation of required design capacity of the drainage lines and other structures need to be carried out according to specific guidelines while allowing adequate free board for possible variations in available data and

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manholes and catch pits may lead difficulty in carrying out regular maintenance operations leading to excessive silt accumulation in the drain network causing loss of capacity provided in the design.

methodologies.

Suitable slope should be maintained in channel/duct alignments to maintain minimum required self cleansing velocities while sections and slopes should be properly designed to minimize erosion and cavitation risk especially when channel slope changes from relatively steeper section to a milder one according terrain layout in the project area.

Use of accepted commercially available software for sewer deigns will be encouraged taking into account the infiltration component and backwater curve generation. Periodic maintenance schedule for debris and silt removal will be recommended. All the structures should be provided following specifications and guidelines to ensure proper functioning of the system and maintenance of the drain network is ensured.

Negotiations with land owners

No potential impacts No measure is required.

Land acquisition None (as no land acquisitions) or perhaps small area

It has not yet decided to acquire private lands for the project. If the need arises, it will be done without affecting the structures.

Land Clearing Disposal of spoilage Disturbance to native flora and fauna

Any spoilage should be disposed appropriately of without stockpiling along roadside. Clearing in vegetation should be kept to the minimum required to safely construct the road and meet other environmental requirements (e.g. spoil storage).

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Generation of cleared vegetation stockpiles Potential for the spread of weeds

Cleared vegetation should be stockpiled outside of watercourses (Sea) and must be disposed in an environmentally sustainable manner at a location agreed upon with local government authorities. The invasive species Lantana camara (Gandapana) was recorded during the rapid screening survey, and spreading of weeds such as Mimosa pudica (Nidikumba) can be controlled by arranging proper disposal of cleared vegetation.

Temporary parking lots

Impediment to traffic flow along Marine Drive Reduction of on road parking for other users

Proper signage is necessary together with traffic diversion and control by contractor’s personnel. Parking lots should be aligned away from existing road boundary. It is planned to implement the construction work section by section so that only a few number of temporary parking would be necessary.

Traffic diversion/Generation of additional traffic due to construction

Obstruction to vehicular movements

Disturbances to day-to-day activities of residents due to traffic diversions and restricted entry to by-roads

Increased traffic on alternate roads

Construction vehicles and equipment should be parked at suitable locations without parking along road sides.

Appropriate signage should be posted on affected roadways, and residents should be informed of any traffic diversions and restriction of entry during construction.

Turning of vehicles should not cause obstruction to other vehicular traffic along the Galle Road and Marine Drive and other by-roads.

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Provision of adequate signaling to keep the drivers well informed of the construction so as to divert the traffic among several parallel roads to minimize impacts on few adjacent roads should be carried out.

Demolition of existing structures

Demolitions are very minimal and small in volume and no re-settlement or loss of business is involved. Minor impacts are possible due to:

Emission of dust

Generation of noise

Demolition has to be carried out with the minimum use of machinery and sprinkling of water should be done appropriately.

Pavement demolition Emission of dust

Generation of noise

Demolition has to be carried out with the minimum use of machinery and sprinkling of water should be done appropriately.

Excavation of trenches and shoring

Closure of roads for traffic If the sea outfall has to be re-designed and re-constructed for sub-catchment 2, then excavation across the Marine Drive is necessary, which will cause severe obstruction to traffic movement Emission of dust during excavation

Provision of alternative routes for vehicles, temporary parking lots for residents with security facilities should be done. Alternative traffic management plan has to be devised in consultation with Police Department; Appropriate signage has to be adopted for any diversions; Single lane alternative traffic movements should be provided by constructing only a part of the road at a time. Dust barriers during excavation in front of residences, and sensitive locations such as religious places should be places if the wind blowing dust becomes a nuisance. Such dust barriers should be made mandatory

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Emission of air pollutants from equipment and machinery Generation of high levels of noise and vibration Disturbance to pedestrian movement

The surface soil and the topmost layers of subsoil in the proximity of proposed site areas are either Red Yellow Podzolic soils with laterite or sandy clay in subsurface layers. Laterite soils consist of reasonable grade distribution and are relatively more stable than typical clayey soils while clayey and sandy soils with their smaller grain sizes and uniform distribution are less resistant to deformation and slope failures.

The high soil saturation and shallow groundwater table especially during monsoon and inter-monsoon seasons may loosen soil structure and further

for excavation along the Marine Drive as strong winds from the sea would spread the dust in a wide area. Construction equipment, and machinery should be maintained in good condition and regularly maintenance in compliance with National Emission Standards (1994). Use of heavy construction equipment and plants should be discouraged. All equipment and machinery (such as compacters and vibrators) should be operated with exhaust silencers to limit generation of noise not to exceed 75 dB. Regularly maintenance of all construction vehicles and machinery to meet National Emission Standards (1994) and noise control regulations stipulated by the CEA in 1996 (Gazette Extra Ordinance, No 924/12). The use of high noise generating pneumatic construction equipment should be restricted. It will be ensured that the levels of intermittent vibration (in ppv) would be less than the 2.25 mm/sec at 1 Hz to avoid human discomfort and inconvenience as per the Interim Standards for Vibration of the Operation of Machinery, Construction Activities and Vehicle Movement & Traffic. Working time should be restricted for noise generation activities and carried out only from 6.00 am to 6.00 pm. Construction related activities near sensitive places have to be scheduled in consultation with the relevant authorities; For example, places where religious activities are carried out.

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weaken soil stability.

For the laying of underground in-situ or precast concrete drainage ducts and canals, it may be required to excavate soft soil up to about 1.0 ~ 1.5 m. Subsurface soil layers may be susceptible to collapse and fail under outward seepage flow in excavated areas, if proper mitigatory measures and safe construction steps are not adopted.

Adequate space at least on one side of the road for the use of pedestrians, adequate sign boards to educate the pedestrians to use adjacent parallel roads should be provided. Adequate shoring at a predetermined spacing should be provided for any excavation beyond safe open excavation depth (approximately > 2 ft) for sandy soil layers. Dewatering should be carried out to avoid build-up up of pore pressure in the soil structure and transport of fine grains.

Dewatering and site drainage

The low lying marshes, bordering canals, retention areas in the project area may lead to near surface groundwater table, especially during rain seasons. Even the dry period water table depths can be as high as 1.5 to 2.5 m during drought periods. This 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 construction

Proper and adequate dewatering should be ensured either using a proper monitoring schedule or using an automated submersible pipe with float device to ensure site activities are uninterrupted due to seepage water.

Proper surface drainage and retention-detention capacity should be provided to safely remove pumped-up water from the site to a natural drainage to avoid in site ponding effects.

Construction activities can be planned during the periods of low water table to avoid excessive dewatering requirements and save costs while reducing risks of slope failures, increased erosion, etc.

40  

activities in excavated areas without interruption during the periods of high groundwater table.

Dewatering may cause surface ponding of removed water if proper drainage is not allowed, especially when the upper soil layers are saturated due to recent storm events.

Stockpiling of material

Emission of dust

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

If not properly stored and adequately covered, fine material washout may significantly degrade groundwater and surface water quality in canals, inland

All construction materials (sand, gravel, aggregates, cement, bituminous products) should be stored with proper cover.

Fugitive dust particles could escape to the atmosphere during construction activities and during transportation and subsequent storage and handling.

Disturbance to the soil, cutting & filling, and storage of construction material within the site could potentially contaminate the surface runoff, notably increasing the turbidity during construction. Erosion control practices should be implemented during construction to limit turbidity and silt transport off site. Safe handling of construction material would minimize the potential contamination of surface runoff and thereby prevent affecting the quality of the water bodies nearby.

Rainy season should be avoided as practical as possible. If any case rainy period is unavoidable, it is necessary to make sure to have temporary

41  

reservoirs and sea outfalls, while increasing risk of slope failures, siltation and blockage of structures.

drainage so as to drain off the rain water.

Proper storage of material and handling of construction material is essential.

Material recycling and proper scheduling of ordering and disposal should be promoted to avoid unnecessarily maintaining material/debris stockpiles for extended periods.

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

Transport of construction material

Emission of dust due to transport of material

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 nearby public sensitive locations and tarpaulin covering are mandatory on trucks / lorries which are used for transporting materials.

Vehicles should be maintained in good condition and regularly maintenance in compliance with National Emission Standards (1994)

Trenching, construction of pipelines, filling and re-surfacing/overlay

Emission of air pollutants during re-surfacing and overlay

Open excavation of deep trenches in loose sandy soil may

Mitigation is similar to above.

Deep excavations in trenches should be adequately supported when surfaces are vertical/near vertical. Proper shoring should be provided to

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cause slope failures in vertical faces. If adequate capacities, required minimum slopes, and proper aligning of pipelines are not properly addressed, undesirable ponding, spilling and excessive siltation or erosion/cavitations may lead the drainage network to fail before its intended design life.

Establishment of weed species in the project area due to introduction through imported raw material. construction equipment, or unplanned dumping of cleared wed species

avoid risks of slope failures. Dewatering should be adapted to lower water table if necessary.

Proper construction techniques should be used to lay precast concrete ducts/ canals, while necessary precautions should be taken following design standards and guidelines when insitu concreting is carried out.

Suitable surface finishing (paving or turfing and concrete/asphalt cover where necessary) should be provided to minimize erosion of new formations and also to ensure ease of access to regular maintenance activities.

Appropriate washing facilities and locations for vehicles and equipment need to be provided. All vehicles, plant and equipment (including hand tools such as shovels) will be inspected by nominated personnel before being certified clean. Equipment and vehicles will be cleaned in designated cleaning-up sites before leaving weed infested areas or entering weed free areas.

Construction of structures such as gullies, manholes, catch pits etc.

Minor impacts due to transport of material

Mitigation is similar to above.

Compaction & Soil Stabilization

High noise and vibration levels No high noise generating machinery is encouraged. Extreme precautions should be taken on compacting or vibrating machines which will be

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If excavated trenches are not properly back-filled using suitable material and compacted adequately, uneven settlements may cause leakages, deformation leading to cracks and eventual failure of anchorages and pipelines.

operated only during day-light hours.

Suitable back-fill material (soil) with required grading and strength characteristics should be used either from on-site burrow areas or outside. Proper compaction to achieve reasonable strength should be adopted to avoid differential settlements and fissures/cracks

Spoilage disposal Contamination of surface runoff

Construction of the proposed facilities would not generate hazardous or toxic waste and therefore do not create any potential hazard to human health due to contamination. If accidental spills do occur (if any) during construction of materials such as paints, solvents, bituminous material or any other hazardous or toxic constituents, the contractor should take appropriate measures to clean up such spills immediately and waste material should be disposed appropriately. The contractor should take precautionary measures to minimize and control spoilage of material during storage and handling and during construction processes. There should be provisions for proper storage of construction materials to reduce the amount of waste caused by damage or exposure to elements.

Maintenance of catch pits, manholes, gullies etc. and removal of material and disposal

Emanation of foul odor due to stagnant water Collection of floating matter and blocking catch pits, gullies and manholes Contamination of water due to

Regular maintenance of gullies, pipelines and manholes is essential. Proper disposal of debris is necessary.

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improper disposal of debris and sediments

If the catch pits, manholes, gullies etc. are not properly maintained and if accumulated silt and debris in catch pits are not periodically removed, the design capacity of the drainage system may be affected by excessive and undesirable accumulation of silt and debris.

Proper disposal of removed material is required to ensure that they are not trapped in the catchment and transported back the drainage paths and also to avoid undesirable nuisance, odor, and health risks etc.

Regular maintenance of drainage structures is needed while additional routine checks may be needed during monsoon seasons and after heavy storm events.

Accumulated silt and debris should be properly removed and disposed appropriately following guidelines and local regulations to avoid any further nuisance.

Proper silt traps, measures to reduce erosion like turfing, paving, diversions, etc., should be adopted if siltation is unacceptably high in the project area.

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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 Surveying, Testing & Data Collection

Obstructions to vehicular movement NS

Detailed design Impacts due to design failures, inadequate capacities, difficulties in maintenance, shortened life spans, structural failures

SN

Negotiations with land owners No potential impacts NA

Land acquisition None (as no land acquisitions are involved) or perhaps small area

NS

Land Clearing Disposal of spoilage NS

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Disturbance to native flora and fauna Generation of cleared vegetation stockpiles Potential for the spread of weeds

NS NS NS

Temporary parking lots Impediment to traffic flow along Marine Drive Reduction of on road parking for other users

NS NS

Traffic diversion/Generation of additional traffic due to construction

Obstruction to vehicular movements

Disturbances to day-to-day activities of residents due to traffic diversions and restricted entry to by-roads

Increased traffic on alternate roads

NS

NS

NS

Demolition of existing structures Demolitions are very minimal and small in volume and no re-settlement or loss of business is involved. Minor impacts are possible due to:

Emission of dust

Generation of noise

NS

NS

NS

Pavement demolition Emission of dust NS

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Generation of noise NS

Excavation of trenches and shoaling

Closure of roads for traffic If the sea outfall has to be re-designed and re-constructed for sub-catchment 2, then excavation across the Marine Drive is necessary, which will cause severe obstruction to traffic movement Emission of dust during excavation Emission of air pollutants from equipment and machinery Generation of high levels of noise and vibration Disturbance to pedestrian movement

NS NS NS NS

Dewatering and site drainage Surface ponding if proper drainage is not allowed

NS

Stockpiling of material Emission of dust

Erosion of material during rains

NS

NS

Transport of construction material

Emission of dust due to transport of material NS

Trenching, construction of Emission of air pollutants during re-surfacing NS

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pipelines, filling and re-surfacing/overlay

and overlay Establishment of weed species in the project area due to introduction through imported raw material. construction equipment, or unplanned dumping of cleared wed species

NS

Construction of structures such as gullies, manholes, catch pits etc.

Minor impacts due to transport of material NS

Compaction & Soil Stabilization High noise and vibration levels NS

Spoilage disposal Contamination of surface runoff NS

Maintenance of catch pits, manholes, gullies etc. and removal of material and disposal

Emanation of foul odor due to stagnant water Collection of floating matter and blocking catch pits, gullies and manholes Contamination of water due to improper disposal of debris and sediments

NS NS NS

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Screening Decision Recommendation:

Final recommendation

All potentially adverse effects can be classified as general construction-related impacts and are mitigatable with known technology. Public concern does not warrant further assessment. Therefore, stand alone Environmental Assessment is not required, an Environmental Management Plan would be sufficient. However, design for accurate rainfall intensity (I) needs to be validated as the valley area experiences frequent local flooding even now with slightest rainfall events. The connections of different slopes must be through proper catch pits where provisions must be made available for periodic silt and debris removal. Use of accepted commercially available software for sewer deigns will be encouraged taking into account the infiltration component and backwater curve generation. Periodic maintenance schedule for debris and silt removal will be recommended.

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Screening report completed by Dr. Mahesh Jayaweera, Team Leader

University of Moratuwa

Tel: 0777320590

email: maheshjayaweera@gmail.com

Name/Designation/Contact information

Date Signature

Screening report reviewed by Name/Designation/Contact information

Date Signature

Approved by Name/Designation/Contact information

Date Signature

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9. 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

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Annex 2

 

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Annexure 1 

 

Fig. A‐1: Partly blocked storm water drain  in  International Buddhist Centre Road where the flood height was 1.5 ft during recent flood events in May 2011 (Lat‐6.8693º  Lon‐79.85990º ) 

 

  Fig. A‐2‐1 & Fig. A‐2‐2: Totally blocked storm water drainage lines due to silting and    improper construction activities in International Buddhist Centre Road  

Fig. A‐2‐2: Lat‐6.86936º Lon‐79.86002º   Fig. A‐2‐1: Lat‐6.86954º Lon‐79.86075º

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  Fig. A‐3‐1 & Fig. A‐3‐2: Gully overflowing due to blockage and a totally blocked    drain line due to improper constructions and lack of maintenance in International Buddhist Centre Road  

 Fig. A‐4‐1 & Fig. A‐4‐2: Flood height in International Buddhist Centre Road in sub‐catchment 2 (200 m from Marine Drive).  

 

Fig. A‐4‐2: Lat‐6. 86990 º   Lon‐79.85990º Fig. A‐4‐1: Lat‐6.86942º   Lon‐79.86001º º  )º)

Fig. A‐3‐2: Lat‐6.86957 º Lon‐79.86085ºFig. A‐3‐1: Lat‐6.87028º   Lon‐79.86211º  

Flood height  

Flood height  

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Fig. A‐5: Flood locations in Moor’s Road where flood heights were up to 1.5 feet  

(Lat 6.86960º, Lon 79.85931º) 

 

 

Fig. A‐6: Blocked drainage in Section in International Buddhist Centre Road 

  (Lat‐6.86968º  Lon‐79.86143º)  

 

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Fig. A‐7: Household downpipes directly drained to the road in Fernando Road 

  (Lat‐6.87007º  Lon‐79.85883º) 

 

 

Fig. A‐8: Blocked drains in Fernando Road (Lat‐6.8720º  Lon‐79.85939º) 

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Fig. A‐9: Starting point of drainage improvement works in Fernando Road 

  (Lat‐6.87028º  Lon‐79.8584º) 

 

 

Fig. A‐10: Residence in Fernando Road affected by recent flood in May 2001 (flooded depth 1.5 ft) (Lat‐6.87031º  Lon‐79.85994º) 

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Fig. A‐11: Blocked drainage pit in Fernando Road, silting effect. 

  (Lat‐6.87027º  Lon‐79.85982º) 

 

 

 

 

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Fig A‐12 Existing (Red/Blue) and Proposed (Blue/Green and Pink) Drainage Network Improvements in Section 2 

 

 

Fig. A‐13 Existing (Red/Grey) and Proposed (Green) Drainage Network Improvements in Section 4 

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Fig. A‐14 Existing (Red) and Proposed (Green) Drainage Network Improvements in Section 5