IMPACT OF SAND AND GRAVEL DREDGING ON THE ENVIRONMENT

CHAPTER TWO

REVIEW OF RELATED LITERATURE

2.1 INTRODUCTION

Soil is an important source of raw materials such as clay, sand, gravel and minerals. It is a non-renewable natural resource with potentially rapid degradation rates and extremely slow formation and regeneration processes (Mwangi, 2007). Sand is a cheap and heavy resource consisting of very small pieces of rocks and minerals, a result of weathering that forms beaches and deserts. Gravel is a heavy and cheap commodity made of small weathered stones used to make surface for paths and roads. The resource’s compressibility, plasticity and textural properties have been valued in construction for hundreds of years. The ability of soil to be moulded and its cohesion properties were the basis for using it to build the earliest houses (Goddard, 2007). Saviour (2012) defined soil as a mineral which protect the environment, buffer to strong tidal waves and storms, habitat for crustacean species and marine organisms. The mining of pit sand and gravel can be done on open areas, beaches, inland dunes, mountain sides while river sand is extracted from riverbeds and banks. Unscientific mining has led to degradation accompanied by subsistence and consequential mine fires, severe ecological imbalance around mining areas (Saviour, 2012). The practice is becoming an environmental issue as the demand for sand as an important mineral resource is increasing in the construction industry. Goddard (2007) realised that decisions on where to mine, how much and how often requires definition of reference state and sand budget. Reference state is the minimal acceptable physical and biological condition of a channel (Goddard, 2007). Though reference state is difficult to determine, a general knowledge of fluvial processes is necessary to minimise detrimental effects of mining. A sand budget for a particular extraction area for example a stream or open area should be done to first determine the amount of sand that can be removed without causing degradation and erosion. Before doing a sand budget, consider mining methods to be used, particle size, characteristics of the sand, riparian vegetation and magnitude as well as frequency of hydrologic events after disturbance.

Therefore minimisation of the negative effects of sand and gravel mining requires a detailed understanding of the response of site to these disturbances (Goddard, 2007). Hill and Kleynhans (1999) discussed various methods of mining sand and gravel. Dry pit mining is a method used when sand is extracted above water table from a dry stream bed and exposed bars using conventional bulldozers, scrapers and loaders. Wet pit mining involves extraction of sand and gravel from below water table stream channel or a perennial river using hydraulic excavator or dragline. Dewatering can be done in advance to allow easy excavation though this depends on deposit thickness, permeability of the ground as well as after use and restoration requirements. Bar skimming or scalping is a method used when only the top layer of soil is removed by scraping without excavating below summer water table which is the level of underground water in summer season (Hill and Kleynhans, 1999).

Our focus in this chapter is to critically examine relevant literature that would assist in explaining the research problem and furthermore recognize the efforts of scholars who had previously contributed immensely to similar research. The chapter intends to deepen the understanding of the study and close the perceived gaps.

Precisely, the chapter will be considered in two sub-headings:

• Conceptual Framework
• Chapter Summary

2.2 SAND AND GRAVEL DREDGING IN THE WORLD

Sand mining and gravel extraction are a worldwide activity in both developed and developing countries as was realised by Draggan (2008). Industrial sand and gravel are produced, processed and used in construction and industry all over the world. The leading nations in mining and processing sand and gravel are United States of America, Australia, Austria, Belgium, Brazil, India, Spain, Nigeria, Kenya and South Africa. As a cheap and readily accessible resource many companies are involved in its mining both legally and illegally without considering the damage they are causing to the environment (Draggan, 2008). Soil mining and gravel extraction is a common activity in United States of America. A publication by Schaetzl (1990) showed that historically, from 1920s many states in USA relied on mining of gravel and sand for road and cement aggregate. The uses had doubled by 2008 to date. Sand and gravel are mined more than all other minerals in most States in America. According to Draggan (2008), USA is the largest producer and consumer of sand and gravel in the world as well as the leading exporter of silica sand to every region of the world. This is because it has extensive high quality deposits of the resource combined with technology to process it into any product. Construction sand and gravel are produced in all 14 fifty states. The highest producers are California, Texas, Michigan, Minnesota, Ohio, Arizona, Utah, Colorado and Washington. They all produce about 52% of total amount of construction sand and gravel. More than a billion tonnes of sand and gravel are produced and used annually. Due to high demand in these States, some sand and gravel are still imported from Canada, Mexico, Bahamas, and Australia (Draggan, 2008). Schaetzl (1990) realised that in California and Michigan, many prime sources of sand and gravel are glacial deposits, eskers, deltaic deposits and old lake beds. These states have an abundant of sand and gravel which are well distributed. Many minerals are mined but sand and gravel are extracted most. Sand and gravel have been exhausted, and the area is now covered by housing developments and farmland. Schaetzl (1990) further noted that river sand, pit sand and gravel are mined around large expanding urban areas. The most urbanised and largest states have greatest areas of sand and gravel pits. The chart below shows that about 58000 acres of land is used to mine sand and gravel which is more compared to all other minerals mined Stebbins (2006) highlighted that in State of Maine, sand and gravel deposits cover up to five percent of the land. The resources are mainly used in construction and pumping drinking water which had increased demand so there are many sand and gravel pits. Approximately two hundred and sixty acres of land is used for mining by both companies with and without licences. Construction grade sand and gravel has high volume, hence the resources cannot be transported over long distance. Large trucks are used as transport for up forty eight kilometres, therefore most pits are near the consumer as these bulky commodities normally cannot economically stand costs of long distance transportation. Most mining is done near the consumer in USA. The once abundant supply of gravel and sand is rapidly diminishing in areas surrounding cities (Stebbins, 2006). Schaetzl (1990) noted that there are four basic operations used to extract sand and gravel from open pit mines in USA. The operations include site clearing to remove vegetation, then mining, processing and finally reclamation of the mined area. Machinery commonly used for mining includes bulldozers, tractor scrapers, front end loaders and stone crushers. The mining is done almost twenty four hours in order to keep up with the high demand internally and externally for sand and gravel (Schaetzl,1990). According to Goddard (2007) soil mining operations began in 1930s in Australia to supply the expanding Sydney building market and continued into 1990s with an estimate of seventy million tonnes of sand removed. Most important commercial sources of sand and gravel are river floods, river channels and glacial deposits. Goddard (2007) further noted that soil extraction and processing have significant impacts on scenic landscapes. Excessive extraction intensifies coastal and exposed hillside erosion, causing accumulation of seawater upstream of rivers, leaving the coasts more vulnerable to extreme weather conditions. Soil mining contributes to construction of buildings and development but can cause permanent loss of soil as well as major habitat destruction (Goddard, 2007). 16 Kuttipuran (2006) reviewed soil mining in Indian communities and explained that as urban areas grow, less wood is used with more concrete structures being required leading to demand for low cost sand. Sand and gravel are most accessible cheap and basic raw materials for construction industry in India. There is a business of indiscriminate sand mining in public spaces in India. Soil mining is an environmental issue in India and public awareness of illegal extraction in states of Maharashtra and Goa is going on (Pereira, 2012). Bagchi (2010) supported Kuttipuran (2006) on that construction boom fuelled the demand for sand and gravel facilitating uncontrolled extraction which threatens existence of river systems. Illegal mining of minerals resources is rampant in India such that the country’s natural resources are destroyed as forests are clean felled. Pereira (2012) researched on sand mining in India by studying three villages in Maharashtra and realised that as global demand for sand is exploding and rising rapidly, the sources of sand and gravel such as riverbeds, beaches, creeks are being mined faster than nature can replenish. This creates a highly skewed supply-demand situation. Pereira noted that India has the third largest construction business in the world after USA and China, so sand and gravel are required in large quantities. Mining is done both legally and illegally. The country did not have a regulatory and monitoring framework for excavation of sand sustainably which increased the illegal mining rampantly. There had never been much control because people thought that the resources are low value minor minerals and inexhaustible. This has led the Mumbai High Court to issue a ban on sand mining in 2010 to all licensed and unlicensed miners who were damaging the riverbeds increasing threat of floods. Demand and prices of sand had increased from US$ 110 to 300 US$ per truck load (Pereira, 2012). Saviour (2012) discussed direct and indirect impacts of mining to the environment in Kerala region of India. The activity has increased since 1990s due to the boom of construction industry. River Bharathapuzha has become a victim of indiscriminate sand mining which has lowered the water table and reduced rice harvest. Illegal mining is high in Papagani catchment area in Karnataka. 17 According to Kuttipuran (2006), illegal mining is rampant in the Central Province of Madhya Pradesh with contractors emptying river beds of Narmada, Chambal and Wainganga. In the Southern Province of Kerala, miners loot soil from the second longest Bharathapuzha river and third river Pamba, which have become victims of indiscriminate sand mining. In India, soil mining is regulated by law but is still done illegally. Illegal sand mining is rampant on banks of Painganga river creating hundred by fifty feet tunnels across agricultural land. Bagchi (2010) further noted that the state government exempted mining of sand through Minor Minerals Rules of 1996 but this increased illegal extraction of sand. Many leases were issued by the Indian Mining Cooperation of Madhya Pradesh to excavate sand from state land, disregarding environmental regulations. Bagchi (2010) reported on how the communities view sand mining and gravel extraction. Generally communities in Palakkad and Goa expressed dissatisfaction with the uncontrolled illegal mining. The miners created one hundred feet long by fifty feet deep tunnels across their farmland as well as creating deep pits through crop fields. According to villagers’ reports, approximately eighty trucks were seen passing through villages on daily basis. Their reports to authorities seemed not to be heard.

2.3 SAND AND GRAVEL DREDGING IN AFRICA

There is a great concern on the way the environment is disturbed by excessive removal of soil for construction industry especially in urban development in Africa. Mwangi (2008) noted that for thousands of years, sand and gravel had been used to construct strong houses, roads and dams in Africa since they are cheap and readily accessible resources. Today demand has increased as socio-economic life of Africans has improved generally. Sand mining and gravel extraction are common in most African states but done both legally and illegally. 18 Lawal (2011) examined sand and gravel mining activities both on land and in rivers as a business venture in Minna Emirate Council of Niger State. Stakeholders from the mining activities were listed as landowners of quarry sites who sold the sand and gravel to private and government contractors. Local government authorities and Niger State where quarries are located, were also listed as beneficiaries. The activities also involve farmers whose cultivating and grazing lands are destroyed, wildlife community whose habitats are mined areas, aquatic community members as well as miners themselves. Aromolaran (2012) carried out a study to examine effects of sand mining activities on rural people living on agricultural land in Ogun State, Nigeria. Many people supported the good uses of sand but the negative impacts on their land were more than the benefits. Lawal (2011) highlighted that sand mining is rapidly becoming an ecological problem as demand increases in many states of Nigeria’s industry and construction sectors. The mining is done both legally and illegally leading to environmental devaluation. Mwangi (2007) discussed soil mining as a threat to the environment in Kenya though with both positive and negative impacts. The sand mining and gravel extraction are done legally and illegally on rivers, beaches and plain fields. Wachira (2009) supported Mwangi by reporting on a case study survey on sand mining in Machakos District of Kenya which is increasing due to the need for soil in construction industry. The survey showed that approximately two hundred thousand tonnes of soil are harvested and mined for construction every year. Streams around Machakos and Mwala Districts are seriously damaged as trucks transporting soil pass along Mombasa and Thika highways. The trucks pass at intervals of five every half an hour. The government had to establish Natural Environmental Watchdog of Kenya, with a list of guidelines to soil harvesters and traders in Eastern Province. Hill and Kleynhans (1999) carried out a research on authorisation and licensing of sand mining and realised that it is important in South African economy but the processes of prospecting, extracting, concentrating, refining and transporting the resources have great potential in disrupting the natural environment. The research concentrated on river sand mining which has adverse impacts on the biota and the habitats. Steps in mining sand and gravel in South Africa were given as firstly, finding a mining location and removal of 19 vegetation and topsoil using excavating equipment. Second step involves extraction using dredge machine to suck the resources. Thirdly, a separator is used to separate sand and gravel from large rock particles, while fine sand is removed from coarse sand. At the end, usually excess sand is returned to the pit using a discharge pipe. (Hill and Kleynhans, 1999). Methods of mining were noted as dry pit mining done when sand is extracted from dry streambed. Wet pit mining involves removing sand and gravel below water table using hydraulic machines while bar skimming is when top layer of soil is removed (Hill and Kleynhans, 1999). According to Lupande (2012), sand mining had not been a common business in Zimbabwe. There had been massive construction of new buildings, extensions and renovations in Harare and surrounding areas since 2009 when the US$ began to be used in the country. This had led to the formation of cooperatives by youth groups to mine sand from nearby farms like Stoneridge. Bedford trucks are used to transport sand into the city and residential areas. An Environmental Management Authority (EMA) sand abstraction licence is obtained first before mining. Steps followed in the mining process according to EMA are removal of topsoil, extraction of sand and gravel to a depth of one metre then land reclamation takes place. Chimbodza (2012) noted that river sand is abundant in Zimbabwe’s Zambezi Valley, particularly along the Ruckomechi and Chewore rivers such that a large mining company was awarded a licence to mine the resource to be used in infrastructural development. Mining methods used by the company include dredging or suction which works like a vacuum cleaner, sucking up sand from the river. Earthmoving is done to dig and remove sand then trucking it away for processing in nearby Chirundu. Botswana is not an exception in mining of resources. Mbaiwa(2008) noted that the country depends on mining of resources, including sand and gravel which contribute 34,2% of Gross Domestic Product (GDP). The Mines and Minerals Act of 1999 was introduced to control all mining activities in the country including sand mining and gravel extraction. National 20 Policy on Natural Resources Conservation and Development (1990) commonly referred to as the National Conservation Strategy (NCS) was instated for all members of society to develop but conserving the natural resources. According to Mbaiwa (2008), the country depend on extraction of mineral deposits such as diamond, gold, nickel but there is mining of soil done both legally and illegally. For thousands of years, pit sand, river sand and gravel had been mined from various areas for construction of roads and buildings as part of urban development with Gaborone inclusive and demand has increased today. Individual companies mine soil both legally and illegally causing land degradation and disturbance of ecosystems. Several communities had expressed their concern on excessive sand and gravel mining. A case was reported in an article in Mmegi Newspaper (2011) on sand mining in Moshupa, a village West of Gaborone. The article highlighted complaints on a lot of sand being mined and sold by individuals and companies. The Village Development Committee (VDC), a board responsible for running affairs of the community complained of lack of consultation by the Department of Mines, Land Board and miners who are the stakeholders in the activity. In a separate incident an article in the Daily News (2012) had a case in Mathangwane, a village near Francistown, a city in Northern part of the country, where a giant company was involved in harvesting sand from the village without licences and consultations with local authorities. Villagers were threatening to place stones across roads for company trucks not to pass. The Mines and Minerals Act (1999) of Botswana highlights requirements for application of a mining licence and minerals permit for any mining activity including sand and gravel. Anyone is eligible for a licence, citizen or non-citizen but the prospecting miner should obtain surface rights from responsible land board on land authority. The identified area should be surveyed first, then prospected to ensure no one else has exclusive rights over that area. If the area identified is a game reserve, or national park, then clearance has to be given first, by Department of Wildlife and Parks. A feasibility study of the proposed area is done and submitted with details of Environmental Impact Assessment study report and Environmental Management Programme and Mining methods to be used. According to the Act, lease charges are P100 per square kilometre or part thereof. There are royalties payments payable to Botswana government through Director of Mines paid monthly at 3% of gross market value, a fixed percentage for resources classified as other minerals for example sand and gravel mining.

2.4 POSITIVE IMPACT OF SAND AND GRAVEL DREDGING

Sand and gravel had been a useful natural resource for thousands of years worldwide and are fundamental to human existence. Today, demand for sand and gravel has increased. Mining operators in conjunction with resource agencies need to work hard and make sure the extraction is done responsibly. Schaetzl (1990) discussed sand and gravel as crucial resources to economic development activities when making aggregate in United States of America. Development is a process of adding improvements to a piece of land such as grading, drainage and access roads. Schaetzl defined aggregate as a substance made from several materials such as river sand and gravel. Pit sand is mixed with cement to form concrete, mortar and plaster for construction of strong structures. Aggregate is used to make road bases and coverings, concrete products and shoreline protection. Mining of sand and gravel had been done for road and cement aggregate for centuries worldwide. According to Draggan (2008), 50% of sand and gravel mined in USA is used in construction to make concrete for roads, durable bricks, blocks, pipes construction fill and sometimes mixed with asphalt. In industry, 39% sand is used to make glass, 22% as foundry sand, 5% as abrasive sand while 34% is for other uses. Kondolf (2008) supported the use of active channel deposits (gravel and sand) as desirable for construction aggregates because they are durable, well sorted and frequently located near market and transportation routes. Besides, sand and gravel being useful resources in construction industry, the resources are useful tools in flood control and river stabilization, in aggrading rivers since most reservoirs are not aggraded in developed countries. Sand mining helps to de-silt rivers which contain a lot of sand (Chimbodza, 2012). Puller (2009) discussed sand and gravel resources of Europe as large and their geographic distribution, requirements and environmental restrictions for some uses. The resources are mixed with bitumen to make roads, surfaces and gritting. Goddard (2007) viewed sand mining in Australia as important specifically in construction of buildings and economic development. Kuttipuran (2006) supported Goddard (2007) when he discussed the importance of sand and gravel in Indian economy as cheap and most accessible used in construction industry to build strong structures and road bases. Bagchi (2010) realised that sand and gravel are useful in landscaping projects which beautify gardens in India. Sand and gravel are important in construction and manufacturing industries when used in building, use glass foundry sand abbrassive sand other uses 23 making glass, electronic chips and ceramics. Sand mining underpins the development engine, so without sand the construction industry will come to a halt (Pereira, 2012). Most African states are still developing and benefit from use of natural resources such as sand and gravel for economic development. Lawal (2011) indicated that Nigerians also benefit a lot from sand and gravel mining which results in building of quality permanent structures from aggregates. The demand for the resources increased in most Nigerian States by 1990s when individuals were getting schemes for home ownership such as increase in salaries and house loans which were easily accessible. Every citizen could afford to build a better house. This led to better socio economic life for rural people. In Kenya, soil mining had led to development of better infrastructure (Mwangi, 2007). This was supported by Mbaiwa (2008) as a positive impact of sand mining in Botswana where more land had been used to develop infrastructure in form of shopping malls and residential areas. Zimbabwe is not an exception in benefiting from sand and gravel through infrastructural development (Lupande, 2012). There is creation of employment for families at mining sites in Indian regions (Saviour, 2012). Lawal (2011) noted that by year 2001 alone, a total of seven thousand, one hundred and thirty one sand and gravel miners had been employed in Nigeria’s Niger State alone, according to statistics provided by Mine Safety and Health Administration. Mwangi (2007) supported this positive impact of soil mining in Kenya when he highlighted that there is creation of employment to locals above eighteen years as manual loaders at mining sites. In Botswana, Mbaiwa (2008) realised the same impact of employment creation to youth, both citizens and non citizens seasonally at mining and construction sites to load tipper trucks. While in Zimbabwe, Lupande (2012) noted creation of employment for youth who are licensed to mine sand and some to load the trucks as a positive impact of mining. 24 Mining activities brought wealth to Indian communities (Saviour, 2012). Sand and gravel activities generate revenue and income to local governments and land owners in Africa’s developing nations which reduce poverty. This was noted by Lawal (2011) in Niger State of Nigeria where financial benefits from mining work shows that local government earn about eight percent of total profits from business while the miner gets about ninety two percent of accrued revenue. Kenyan local government also benefits from soil mining as highlighted by Mwangi (2007), when legal miners are to pay for the licenses’

2.5 NEGATIVE IMPACT OF SAND AND GRAVEL DREDGING

Sand and gravel are important natural resources in economic development worldwide but the continuous removal have adverse effects on the environment. Negative environmental impacts seem to outweigh positive effects in mining worldwide. Different negative impacts had been noted in United States of America due to in stream mining occurring in rivers and streams. Kondolf (2007) defined in stream mining as the mechanical removal of gravel and sand directly from an active channel. Forms of in stream mining such as pit excavation and bar skimming, causes bed degradation of rivers known as channel incision. The process occurs as head cutting or hungry water. When head cutting extraction is done on active channel, it lowers stream bed to create a nick point which steepens channel slope and increases flow energy.

Bagchi (2010) discussed environmental land and surface degradation as a serious impact of in stream mining on Indian rivers. There is damage to river banks and general ecosystems due to access ramps to riverbed. Soil erosion occurs as there is disturbance of groundwater and changes in river courses. Continuous removal of sand from river bed increases velocity of flowing water which erodes beds and banks. Kondolf (2007) noted that as the velocity increases, the river bed can propagate both upstream and downstream for many kilometres. This can lower alluvial water tables. Stebbins (2006) added that in stream sand mining causes destruction of aquatic and riparian habitat through large changes in channel morphology, lowered water table, instability and sedimentation at mining sites due to stock piling and dumping of excess mining materials. Pereira (2012) revealed that sand mining is a threat to water security resulting from loss of groundwater storage due to lowering of alluvial water table. For example major rivers in India’s Kerala district such as Pampa and Manimala have been lowered with four to six metres. If sand mining continues in India uncontrollably up to 2050, water table will drop to approximately 2537 square metres. A lowered water table due to mining leave drinking water wells dry, and people starving. Suspended solids affect domestic water users downstream which increase treatment costs. Saviour (2012) also noted the deterioration of water quality due to dissolved suspended materials and solids from mining activities. Water 27 quality can also be compromised by oil spills and leakages from excavation machinery and transportation vehicles which may poison aquatic life (Stebbins, 2006). Lawal (2011) supported Stebbins on that there are changes in channel morphology because of stream bank mining in Nigeria. Hill and Kleynhans (1999) discussed in stream mining as the main cause of destruction of riparian zone, changes in channel morphology and lowered flood plain. In their study, they revealed alterations of flow patterns, existence of suspended sediments reducing light penetration for photosynthesis by aquatic flora. Schaetzl (1990) explained some of the negative environmental impacts experienced by various states in America where sand and gravel mining are going on. He noted that depletion of sand in the streambed and along coastal areas causes deepening of rivers and estuaries as well as enlargement of river mouths and coastal inlets in Michigan and California. He further indicated that excessive mining leads to excavation as well as threatening bridges, bridge piers and buried pipelines. Goddard (2007) indicated that gravel extraction and processing have significant negative effects on scenic landscapes. Too much mining intensifies coastal and exposed hillside erosion, accumulation of seawater up rivers, leaving coasts more vulnerable to extreme weather conditions. Pereira (2012) noted that there is decreased protection from sea water and shoreline erosion rates increases especially during ocean disasters when mining continues uncontrollably and unscientifically. Lawal (2011) supported disturbance of landscape and distortion of topography as results of excessive soil mining in Nigeria. According to Bagchi (2010), there is contamination of sand aquifer water due to formation of ponds as harvesters tend to dig on areas with thick sand bed creating water ponds. Water accumulates in ponds combined with biodegradable materials from flora and fauna wastes causing contamination. Besides, stagnant water on gravel extraction ponds form an environment conducive to mosquito breeding. Lawal (2011) agreed with Bagchi on creation of pools as a result of mining which are breeding sites for pests in Nigeria. 28 Several negative impacts were noted on habitats. Stebbins (2006) realised that valuable timber resources and wildlife habitats are destroyed as all species require specific conditions to ensure long term survival. Native species in stream and rivers are uniquely adapted to conditions that existed before human began large scale alterations which favour some species over others. This leads to loss of fisheries productivity, biodiversity and recreational potential. As deep pools are filled with gravel and sediments, there is a reduction in habitat complexity and large predatory fish. Channel widening causes streambed to be shallow, producing braided flow or subsurface inter gravel flow in riffle areas hindering movement of fish between pools (Stebbins, 2006). Mining operations involve deforestation, habitat destruction and biodiversity erosion (Saviour, 2012). Schaetzl (1990) realised that sand and gravel mining generate extra heavy vehicles and traffic, impairing negatively on the environment. Heavy vehicles cause access roads on riparian zone and compact the ground. Kuttipuran (2006) supported Schaetzl (1990) on formation of access roads on river beds as heavy machinery and tipper trucks move to collection points. Some tracks are caused by pedestrians. There is general destruction to roads and bridges. This effect is felt more by villagers near mining sites as the continuous movement of heavy vehicles cause problems to cattle posts, agricultural land, borehole and well users. Besides compacting land, heavy vehicles are a source of pollution to the villages near mining sites. According to Lawal (2011), noise and air pollution occur as dust accumulates from gravel roads which are a reality to villages near mining areas. There is general degrading of ecosystem in Nigeria. Air pollution caused by dust particles can be a health hazard causing respiratory disorders such as asthma and irritation of lungs (Saviour, 2012). The sand is also extracted from rock blasting which generate noise pollution. The ground vibrations produced can cause ground tremors. Pereira (2012) realised that sand is dredged illegally twenty four hours a day, all year round even during monsoons using mechanical dredgers in India. These produce a lot of noise which hampers sleep and normal school operation hours. Vibration noise generated from overburden excavation and transport is severe at night and is an annoyance to people. 29 Stebbins (2006) noted that as mining occurs, there is loss of protection provided by soil as it filters out pollutants. Gravel pits are sometimes used as dumping sites with tipper trucks carrying waste to dump as they come to collect sand and gravel. Pollutants from waste filter and contaminate drinking water and affect people’s health in Maine State. Goddard (2007) added that there is formation of mine and waste dumps which pollute the environment as a result of soil mining in Australia. Mwangi noted the same impact of converting abandoned gravel pits into dumping sites as a serious effect of uncontrolled gravel mining in Kenya. Wokorach (2002) discussed air and water pollution in Botswana as negative impacts of mining on the environment. Tailing and waste dumps from mining processes pollute ground water resources near mining areas and contaminate soils. Saviour (2012) discussed pollution of water as a result of some physio-chemical and biological parameters which characterise degradation of water quality by colouration when it turns from brownish to reddish orange, lowering ph and increasing electrical conductivity. This is due to high concentration of ions of sulphate (SO), iron (Fe) and other heavy toxic metals such as Zinc, Nickel, Copper and low dissolved Oxygen (DO). When mined materials for example walls of open pits and waste rocks are exposed to oxygen and water, acid can be formed leading to an acid mine then acid mine drainage which run off into streams and rivers(Saviour, 2012). There is leaching of the acid into the ground causing water pollution. The ph increases to 4 affecting fish, aquatic plants and animals. Acid mine drainage may dissolve toxic metals like Copper (Cu), Aluminium (Al) and Iron (Fe). Iron may coat bottom of rivers and become toxic to humans and wildlife (Saviour, 2012). Stebbins (2006) highlighted destruction of soil structure and profile in American States due to mining. Continuous mining causes complete removal of vegetation and destruction of topsoil and subsoil resulting in a reduction in faunal population. Saviour (2012) discussed the destruction of existing vegetation and soil profile significantly in topsoil affecting flora and fauna in Indian regions as mining continues. Kuttipuran (2006) supported this impact by noting that loss of vegetation and ecosystems is common around and next to Indian rivers, an eyesore which gives an offensive look to the natural beauty of the environment. Still in India, Pereira (2012) recognised that there is destruction of mangrove forests due to illegal 30 construction of storage docks, roads, infrastructure for easy mining, storage and transportation of sand from the rivers. This has increased vulnerability of land to floods in Mumbai. Aromolaran (2012) noted land degradation in agrarian community by destroying the soil surface and structure as well as declining the nutrient status of agricultural land. Lawal (2011) discussed environmental devaluation as a result of man’s activities such as sand and gravel mining in Nigeria. There is loss of valuable fertile land and timber as well as habitat alterations which disrupt ecosystems and destroy native species. Increase in turbidity affect aquatic species, a major impact to fauna. Therefore, there is need for a preliminary investigation into the type of vegetation occurring there and possible impacts before mining. Gravel extraction and pit sand mining on open areas had left open pits around expanding urban areas in United States of America (Draggan, 2008). Scenes of accidents involving children and grazing animals are common due to the open pits left on bare ground in Nigeria (Lawal, 2011). Water accumulates in the open pits during the rainy season and domestic animals drown in the pits. Livelihoods of fishermen in India are threatened by sand barges which often destroy their nets (Pereira, 2012). Loss of lives had also been recorded in India which impacted tourism, agriculture and fishing potential. Bagchi (2010) reported on accidents as common in Palakkad District of India as children drown in water filled open pits when they try to swim, thus there is loss of recreational potential for the land. Massive construction has led to excess mining which create pits and holes in farms surrounding Harare (Lupande, 2012). Pits created by miners in Botswana pose a danger to wildlife and livestock. Disturbance of land surface areas leave huge open pits difficult physically and economically to rehabilitate after mining takes place (Wokorach, 2002). Bagchi (2010) gave other general impacts of general impacts of sand mining as a drop in water table in Godavari river in the west of India which is leading to dry wells perennially and drought. Villagers obtain the resource through tankers and pipes over long distances. There is environmental degradation on open land and rivers as well as high evaporation from exposed river beds leading to dry rivers and shortage of water for domestic purposes and animals. 31 Mining operations involve deforestation and biodiversity erosion. Ekosse (2004) conducted a research to find the environmental impacts of mining in general to soils around mining areas in Botswana. The research concentrated on areas around Kgwakgwe Manganese Mine. Chemical properties of soils and leaves of plants around mining areas were investigated to determine the effects of the mining activity. Demineralization and pollution of soils and the surroundings was noted which lead to formation of dead zones. The soils become contaminated and stunted growth in plants was noticed. Mining of sand near seas allow intrusion of sea water which is called salinisation (Pereira, 2012). The Mines and Minerals Act (1999) of Botswana listed some of the environmental impacts experienced due to legal and illegal sand mining and gravel extraction. These include accidents due to open pits left uncovered on bare ground. Sand act as a reservoir to charge ground water wells, so when removed, wells have to be dug deeper which increases water costs (Pereira, 2012). Generally, there is loss of employment to farm workers as agricultural land is destroyed to pave way for mining while there is human rights violation to farmers.

2.6 SOLUTION AND MITIGATION MEASURES TO SAND AND GRAVEL DREDGING OR MINNING

The United Nations Conference on Environment and Development Report (2002), Agenda 21 advocates sustainable use of natural resources. Sustainable means ability to continue and be used for a long time. Goddard (2007) highlighted that man benefit from sand and gravel, as cheap and readily accessible resources for development, so there should be conservation and rehabilitation of these resources for future use. All governments worldwide should advocate for environmentally sustainable development. Kondolf (2007) discussed the importance of an environmental assessment management and monitoring program as part of extraction licence in America. This is necessary to minimise negative impacts as mitigation and restoration strategy will be included. Monitoring regularly is important to ensure proper mining. Mitigation processes include minimising extent of mining, repairing and rehabilitation of mines as well as replacement of resources. There is need for restoration and compensation of biotic integrity of ecosystems. Most soil mining affect environment and India is inclusive as Saviour (2012) noted that the country is 32 working hard to tackle negative impacts. The miners are supposed to draft an Environmental Management Plan (EMP) which ensures that potential impacts of projects are assessed and incorporated into early stages of development planning. The preparation of EMP had become a statutory requirement for granting permits in India. Clearance should be obtained from Department of Environment (DOE) and Ministry of Environment and Forests before permits are issued (Saviour, 2012). Kuttipuran (2006) suggested watershed restoration through replanting of riparian vegetation to replace large woody debris while conserving spawning gravel. This will re-establish ecological carrying capacity of the habitats, ecosystems and increase fish production. Aromolaran (2012) recommended the planting of trees and shrubs that could help to regenerate degraded land and prevent erosion. People in rural areas must be educated on alternative resources to sand such as crushed stone as well as being involved in activities that are less degrading to agriculture land. Pereira (2012) also suggested use of crushed stone as alternative to conserve sand. The requirement of Environmental Management Authority (EMA) in Zimbabwe is to fill pits after mining, then plant trees and grass to minimise erosion. Land is levelled and growth of trees monitored until established as reclamation of land in Zimbabwe (Lupande, 2012). Stebbins (2006) noted that there is need to review potentially toxic sediment contaminants in or near streambed where gravel will be extracted while monitoring turbidity levels. There should be removal of in stream rough elements and sediments like debris, dumped far from rivers, streams and residential areas so that there is no filtration back into the water. Ekosse (2004) recommended reclamation of contaminated soils around all mining areas for resources to be used productively in future. Bagchi (2010) suggested management of sand and gravel extraction operations to minimise damage to streams, rivers and riparian zone. 33 Since Kondolf (2007) had realised that gravel bar skimming significantly impacts aquatic habitats, the method can only be allowed under restricted conditions like during low flows with construction of buffer strips to control the flow. Hill and Kleynhans (1999) highlighted that if bar skimming is used as a method of mining, then there is need for close monitoring and refilling of pits on the riparian zone. Allow bar skimming only under restricted conditions but if the river or stream has a history of eroding bars then avoid this method. Kondolf (2007) supported this by suggesting that monitoring of all activities should be done to ensure that there is no gravel recruitment downstream. If a river has a recent history of rapidly eroding bars, then skimming should be avoided. In bar skimming, there is need for strictly limiting gravel removal quantities so that recruitment and accumulation rates are sufficient to avoid extended impacts on channel morphology and fish habitats (Kondolf, 2007). According to Schaertzl (1990) there is generation of heavy vehicles on river banks and beds. He recommended that extraction should be done on one side of floodplain to eliminate crossing of active channels by heavy equipment. Generally, sand mining sites should be outside active floodplain. Hill and Kleynhans (1999) had also noted the need to apply dry pit mining method in sand mining project on one side of floodplain to avoid compacting active channels with heavy tipper trucks and front end loaders. Crossing active channels with trucks may lead to contamination of water with oil spills and leakages. Wachira (2009) recommended strict laws to be imposed on licence holders as a prerequisite to miners in Kenya. Mwangi (2007) recommended restriction of heavy front end loader equipment on mining areas and instead encouraged use of shovels which have less impact on the ground. Kuttipuran (2006) suggested that mining of river sand should strictly be done on larger rivers such as Bharathapuzha and Pamba in India containing a lot of sand avoiding smaller rivers and streams which may easily be destroyed. Braided river systems are recommended instead of straight, meandering and split rivers. Strictly, operators should never be allowed to divert streams and rivers creating inactive channels. Lawal (2011) recommended the use of abandoned stream channels on terraces, inactive floodplains and deltas as the best sources of gravel and sand. He noted that gravel pits on floodplain should not go deeper than water 34 table. He recommended that pit excavations on adjacent floodplain or terraces should be separated from active channel for two to three decades by constructing buffers or levees to reduce long term flooding. Stebbins (2006) researched on co-existence of gravel sand mines and water supply wells and revealed that continuous removal of the resources harm ground water quality. He suggested regulators to assess changes in ground water and develop a methodology on management of both resources effectively. Hill and Kleynhans (1999)’s research included recommendations to decision makers who are involved in reviewing sand mining and gravel extraction to make informed decisions when issuing licences. Lawal (2011) encouraged Nigerian authorities to discourage indiscriminate opening up of plots for sand and gravel mining. The government should evolve a policy compelling miners to reinvest and repair old disused mine sites so as to reduce occurrences of landslides or earth tremors in the locality. Government should consider changes in market prices of sand and gravel so as to charge according to economic value of environment. Ekosse (2004) recommended remedial measures for reclamation of the contaminated soil to appropriate land use. After reviewing the National Marine Fisheries Service (NMFS), Kondolf (2007) suggested that the government of USA should use modern technology and field sampling prior to extraction to establish and document baseline data and evaluate ways of minimising negative impacts. This can be done through calculating sediment and hydraulic flow budgets, then find possible changes in water quality and channel morphology. There is need to address cumulative impacts and propose possible mitigation and restoration strategies. Close monitoring permitted operations and verifying environmental safeguards by regulating extraction rates and volume is important. Channel cross sections should be benchmarked and documented using aerial photographs taken at regular intervals (Kondolf, 2007). The NMFS Policy highlights the need to give permits with five-year limits subjected to annual review and revision if fishery management objectives are met. This will ensure establishment and implementation of long term monitoring and restoration program in American States. 35 In Kenya, Mwangi (2007) discussed the establishment of the National Environmental Watchdog of Kenya with a list of guidelines to soil harvesters and traders in the Eastern Province. He gave mitigation measures to sand mining and gravel extraction as refilling and growing appropriate vegetation on eroded areas by licensed miners as a prerequisite. The National Environmental Management Authority (NEMA) was drafted by the Kenyan government to apply to all mining activities including soil. NEMA officials work with District Sand Harvesting Committees to ensure sustainable mining is done. Hill and Kleynrans (1999) gave fundamental considerations and recommendations on how to reduce negative impacts in all sand and gravel extraction operations. There is need for strict laws to govern sand mining and gravel extraction activities both in rivers and on land. Standard conditions should be part of mining operations. Mitigation and restoration must occur concurrently with extraction activities thus restoration becomes part of mitigation. This is done to restore biotic integrity of riverine ecosystems. Dry pit mining was recommended instead of bar skimming or wet pit mining in most activities because the depth of extraction can easily be controlled. The Mines and Minerals Act (1999) of Botswana gave guidelines on mitigation measures against negative impacts on mining. The distance of mining from banks of meandering rivers should be 2.5 to 5.0 metres but this depends on height of river bank and thickness of sand to be extracted. The Act prohibits digging of river banks within 500 metres for pit sand and gravel. At least 0.5 metres of sand bed should be left in situ while harvesting sand. No permits are issued to prospective miners who wish to mine near schools, villages, clinics or any other major human activities. The Department of Mine gave an example of intended reclamation/rehabilitation plan to be followed by the licensed miners soon after mining.

CHAPTER SUMMARY

In this review the researcher has sampled the opinions and views of several authors and scholars on sand, and grave dredging. The works of scholars who conducted empirical studies have been reviewed also. The chapter has made clear the relevant literature.