Eia-water,land And Noise.docx

JOMO KENYATTA UNIVERSITYOFAGRICULTURE AND TECHNOLOGY Civil, Construction and Environmental Engineering Department

TITLE:

ENVIRONMENTAL IMPACT ASSESSMENT OF PROPOSED CONSTRUCTION OF SUSPENSION BRIDGE .

WATER, LAND AND NOISE POLLUTION

WATER ENVIRONMENT

INTRODUCTION. The name of the river in question is River Loboi. It separates the greater Loboi region from the Loboi Town Centre. It is a semi-permanent river with consistent flow (ground flows during the dry season).The river serves the following functions: it is a habitat for various forms of aquatic life e.g. algae and fish, it is a source of water for the residents, it is a source of water for the Loboi-Lakwar Irrigation scheme and recreational activities for the residents e.g. swimming. The physical and chemical characteristics of the water in the river are as follows: temperature (200c-250c), low turbidity (--), pH (6.5-7.0), low salinity (--), adequate dissolved oxygen to support aquatic life effectively, clear, colourless and odourless.

BRIDGE CONSTRUCTION ACTIVITES. Excavation for the foundation in-situ Excavation of borrowed material from borrow pits. Diversion of river water Concrete works for the superstructure and substructure Bituminous works for the substructure Transportation of materials from the Origin to Destination

EFFECTS OF BRIDGE CONSTRUCTION ACTIVITES ON WATER ENVIRONMENT. Excavation of the foundation in-situ leads to instability that results in land subsidence thereby affecting the quality of ground water. The excavated material may also fall into the river thereby contaminating it. Excavation of borrowed material from a borrow pit may affect the ground water in an area with a shallow water table. During construction, these pits are left open and collect run-off which reduces volume of surface run-off which in turn reduces the volume of the river due to reduced recharge capability. The pits could also act as a breeding ground for mosquitoes and water-borne diseases making the water unfit for use. Diversion of water in order to obtain a dry working surface leads to the death of aquatic life in the area. This also lowers the river regime due to induced meandering.

During construction of the superstructure, concrete and asphalt may spill into the water during casting of slabs and beams thereby contaminating it with chemicals harmful to aquatic life. The completed substructure may undergo scouring on the foundation and piers over time causing the eroded material to contaminate the water with harmful chemicals.  Workers on the site may dump plastics and other waste materials into the river thus contaminating the water Solid waste such as leftover nails and binding wires may find their way into the river during construction contaminating it with metals Transported material form the borrow pits may accidently be dumped on the river channel thereby reducing its width.

PROPOSED MITIGATION MEASURES. Geo-exploration should be to determine the depth of the water table thereby allowing the determination of effective depth of (---) When excavating material, the pits created should be covered with a suitable material within the shortest time possible to prevent water accumulation. The bridge construction site should be located in an area with minimal presence of aquatic life to reduce deaths. Polythene material maybe be used to cover the working area in order to prevent contamination by spillages from concrete and bituminous works. The plant operators e.g. excavator operator should increase precision to prevent spillage of material during excavation. Formulation and implementation of site rules and regulations against waste disposal. Waste bins should also be provided on site to prevent dumping of solid waste into water bodies while enhancing recycling of materials.

NOISE ENVIRONMENT INTRODUCTION. Noise/Sound pollution is the propagation of noise with a harmful impact on the activities of human or animal life. The source of outdoor noise on the construction site is through the use

of construction machinery and by propagation and transportation vehicles. The rural area of Loboi generally has low noise levels, lower than those prescribed as limiting by the WHO Guidelines (50db).The main source of noise pollution is through traffic movements and is detrimental in the following ways: high noise levels can lead to cardiovascular effects in humans as well as increased incidences of coronary artery disease. In animals, the noise may alter the predator/prey detection or avoidance abilities and interfere with their reproduction and navigation activities. Noise also poses a physical and psychological threat to children’s’ learning and behavioral patterns.

EFFECTS OF BRIDGE CONSTRUCTION ACTIVITES ON SOUND ENVIRONMENT. Excavation of material for foundation in-situ and from the borrow pit make use of excavators to cut material resulting in the production of noise from the engine, hydraulic arm, drill bit and the chains and wheels Diversion of water by using coffer dams to retain water generates noise during construction of the sheet piles which have to be driven into the river bed using a pile driver that has a noisy engine. Pumping of water also pollutes the environment with noise from the water pump engine. Concrete works produce noise from the assembly of formwork and use of mechanical vibrators during compaction e.g. poker vibrator. Bituminous works produce noise from mechanical pavers, graders and rollers during compaction of the AC layer that produce noise from their engines as well as their movements. Workers produce noise during curtailment through activities such as bar bending, hammering and use of hack saws. Transportation vehicles produce noise from their engines and movement when loading and off-loading construction materials.

PROPOSED MITIGATION MEASURES. When carrying out excavations, the operator should wear ear muffs to protect themselves from excessive levels of noise. The type of machinery used should also be very efficient by producing minimal noise.

During construction of the coffee dam, the workers and residents close to the area should be provided with ear muffs and the chosen method of driving the piles to produce minimal noise. When compacting, the operator of the mechanical vibrator should be equipped with ear muffs to prevent ear damage When carrying out bituminous works, the machinery should be efficient enough to produce little to no noise at all and operators equipped with ear muffs. Laborers should be provided with ear muffs during cutting and bending of bars for use in curtailment During transportation, the vehicles should be well maintained, have efficient engines, driven at low speeds and not overloaded to minimize noise pollution LAND ENVIRONMENT INTRODUCTION. Pollution of the land affects all ground surface components such as slope, soil type, and vegetation among others. The soil type that exists around the proposed site is alluvial silt with smooth texture lying on a fairly flat ground surface(slope<10%). Land animals and vegetation are likely to be affected tremendously through the suffocation of living organisms and disruption of habitats of land animals and natural vegetation found on the surface among others.

EFFECTS OF BRIDGE CONSTRUCTION ACTIVITES ON LAND ENVIRONMENT. Excavation of material for the foundation in-situ loosens the existing ground top surface exposing it to soil erosion. It also disrupts the natural habitat of the existing land animals and causes soil loss around the proposed site.  Excavation of borrowed material will change the existing ground slope thereby affecting the aesthetics of the area. It also causes soil contamination from exposing the surface to contaminants from heavy machinery and solid waste. In a case whereby the existing soil characteristics do not meet the required standard, filling of excavated land will lead to soil contamination and change in the soil structure Land clearing will expose the land surface to increased soil erosion leading to the loss of biodiversity

Diversion of water will cause a change in the soil characteristics e.g. contour and texture. This will affect the soil structure on the site by reducing the strength of the soil in the area Construction of sub-structure will cause the contamination of soil in case of spillages Construction of super-structure lead to soil contamination resulting in the change of soil characteristics Transportation of construction materials causes changes in the soil structure due to repeated compaction by heavy machinery. It also enhances erosion of the top soil due to loosening of the surface and contamination in the case of accidental deposition of solid waste. Waste disposal will arise to contamination of soil surface altering its chararcteristics. It also causing suffocation of land animals in the earth’s surface. Approach roads construction lead to change in soil structure of the adjacent area and may also cause change in slope and alter the site aesthetics. Dredging for soil slope. This clearly alters the ground slope in the proposed site.

PROPOSED MITIGATION MEASURES. Avoid overtopping of construction materials into trucks during transportation to avoid spillages Avoid spillage of bituminous and concrete materials during construction by using an appropriate cover material e.g. polythene During construction, ensure the soil compaction is within the acceptable limits to avoid damaging the soil structure Use human methods of land clearing e.g. slashing as opposed to machines to avoid excessive disruption of soil structure Diversion of water to be carried out on a well-structured soil area to avoid disintegration of soil layers around the area Use of human methods of excavation as opposed to machine methods to minimize effects on land surface Using filler materials of similar characteristics to ensure maximum bonding with existing soil thereby improving soil strength Creating specific pathways for heavy machinery Creating a proper waste disposal and management system

Compacting areas with loose soil Providing soil erosion control measures on steeper slopes Controlling speed and operation of construction material Regular maintenance of machinery

IMPACT ASSESSMENT: LEOPOLD MATRIX METHOD Bridge Construction Activities

Water Environment

Noise Environment

Land Environment

Excavations for the foundation in-situ -7

-7

7

-7

8

9

Excavations from borrow pits -8

-7

7

2

8

8

Filling of excavated pits 2

5 Diversion of water -6

-5

9

-2

9

9

Concrete works for superstructure -3

-3

8

-4

8

8

Concrete works for substructure -5

-6

8

-1

8

4

Transportation of Construction material -2

-2

7

-5

5

9

Waste disposal -6

5 Land clearing -7

8 Dredging for soil slope -4

6

REFERENCES. Wikipedia.org/wiki/noise-pollution Wikipedia.org/wiki/water-pollution Wikipedia.org/wiki/land-pollution WHO Guidelines 2009 Republic of Kenya Water Quality Regulations (2006)

Environmental Impact Assessment for the Construction of a Bridge in Bangladesh by Md. Faisal Environmental Impact Assessment Fever Creek bridge replacement by Analissa Merrill, Western Washington University. Environmental Impact Assessment-Study Report by Westland Syke Development, December 2015.