Trends and Sustainability of Groundwater in Highly Stressed Aquifers (Proc. of Symposium JS.2 at 193 the Joint IAHS & IAH Convention, Hyderabad, , September 2009). IAHS Publ. 329, 2009.

Integrated assessment of risk for contaminated sites due to on- site sanitation systems in mining area, , India

H. K. RAMARAJU University Visveswaraya College of Engineering (UVCE), Jnanabharathi Campus, University, Bangalore-560056, Karnataka, India [email protected]

Abstract The sanitation coverage in rural households of India is very low. A field study was carried out in the Gold Field mining residential area. The residents of the study area depend on bore wells and resort to septic tanks for disposal of domestic waste. The main objective of this study is to assess the impact of septic tanks/low cost sanitation systems on groundwater and soil environment in the unsaturated zones of the soil. The hydraulic conductivity of the soil in the study area varied from 0.13 to 0.31 m day-1. Higher concentration of nitrates and chlorides in well waters show that groundwater is getting contaminated with on-site sanitation effluents. Higher concentrations of major metals, salts and gases were also observed because the geology of the particular area has influence on the quality of water. Based on the investigations, appropriate technological options are proposed. Key words bacteriological; hydrogeological; infiltration; nitrification; onsite sanitation systems; unsaturated zones; weathered rock

INTRODUCTION Water for human consumption is perhaps becoming more vulnerable due to various strains on its qualitative and quantitative counts. Different types of pollution are making the issue more complicated and costly for mitigation. The sanitation aspect has to include a lot more issues, rather than only emphasising the construction of sanitary latrines. Even sanitary latrines require extensive post-surveillance on their proper upkeep and use. The issue of proper drainage systems for liquid waste conveyance (for processing) is another area which warrants improvement. There are also various other components of sanitation which are required to be dealt under one comprehensive management programme. The next hazard is the dust from the “Mill Tailing Dumps” all around Kolar Gold Field (KGF) called “Cyanide Dumps” because of their content of cyanide used to extract the gold from the ore. The continuous mining activity of the last 100 years in this area has resulted in the accumulation of huge dumps of mining waste (mill-tailings) occupying about 10% of the total land in the township; these tailing dumps rise to a height of about 30 m from the ground. Now the general public of all age groups have been affected by the cyanide dust which is spreading all over the KGF. The cyanide spill occurred in an area already stressed, deteriorated and contaminated with heavy metals from historic mining and mineral processing operations. Similar cyanide spills and tailings dam failures are likely to occur in the future (Lottermoser, 2007). The pressure of our growing population and the increasing affluence of our society have resulted in more and more people buying home sites in the relatively isolated areas. These home sites often require individual wells and sewage disposal systems. In many rural and suburban or old developed towns, especially in developing countries, like India, sewer-less sanitation would appear to be the only feasible and appropriate method of providing on-site sanitation. Septic tank systems/cesspools/pit latrines are low cost sanitation systems used for the disposal of domestic wastes in these undeveloped areas. Septic tanks are reported to be the major contribution to groundwater contamination. The existing septic tank system, developed nearly a century ago, has many functional inadequacies. Their performance depends on their design, construction, nature of wastes, climate, regional geology, topography, physical and chemical composition, nature of soil mantle, and care taken in periodic maintenance (Chen, 1988). According to the World Health Organisation (WHO) report “at least 2.5 billion people in developing countries lack an adequate system for disposing of their faeces”. The present study aims at checking environmental conditions to assess the extent of contamination from on-site sanitation systems.

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194 H. K. Ramaraju

A field study was carried out in the KGF mining residential area in the district of Kolar. The field investigation was limited to the 23 blocks/areas, where the sewerage system is non-existent. The migrants from the study areas depend on bore wells/tankers/piped water supply and resort to septic tanks/cesspools/pit latrines/open defaecation for disposal of domestic wastes. A majority of the disposal systems are faulty designs and their performance is far from satisfactory.

BACKGROUND has been famous for its ore exploitation since the end of the 19th century. However, in the late 1980s, the mine activity began to decrease due to a progressive increase of the production cost, connected to several factors (geological, managerial, socio-economic). Eventually, the mine exploitation was put to an end in 2001, leading thousands of former employees and their families to hardship. The women living in the KGF mining area are specifically concerned with access to water, community toilets, and with domestic waste management. Since the closure of the mine in 2001, the services under the responsibility of the mining authorities have been stopped. In the rural area of and Mulbalgal taluks, people affiliated to Kolar Gold Fields Women’s Association (KGFWA) are requesting improvement of access to water. It means that operation and maintenance systems have to be developed in order to allow the beneficiaries to take its responsibility (at some locations in partnership). In order to provide an adequate sustainable access to basic services to the requesting people, a technical feasibility study was carried out.

OBJECTIVE OF THE STUDY This study is the result of a request coming from ADER (an NGO-non-governmental organization), France. Indeed, since the closure of the mine in 2001, the provision of water and all the social services for the KGF town families, guaranteed before by the mining society, have been stopped, e.g. the operation and maintenance of the public toilets. Therefore, the toilet infra- structures have slowly deteriorated. Since 1999, ADER has been supporting access to basic services project requested by its partner KGFWA. Thus, experience has been achieved in toilet repair/renovation; 50 community toilets were renovated during 2003–2005. At the same time, a sanitation awareness programme has been implemented towards the families who took responsibility for the operation and maintenance of the community toilets. The main focus of the technical feasibility study is to assess, at each location, to what extent the toilet use is eco-friendly and assesses the impact to the groundwater and preservation of natural resources.

DESCRIPTION OF THE STUDY AREA is known worldwide for its rich gold deposits. It is bound by north latitude from 12°46′ to 13°56′ and east longitude from 77°21′ to 78°35′. KGF is situated at 12°57′ north and 78° east in the southeast corner of the Kolar District of Bangarpet Taluk in the State of Karnataka (Fig. 1), at the tri junction of Andhar Pradesh, and Karnataka. Mean annual temperature is around 23.8°C. KGF lies in the rain shadow area where average rainfall per annum is 820 mm, the population of KGF is 3 lakhs, as per 2001 census. The mining area has a population of 1.5 lakhs. The mining area, which is owned by Bharat Gold Mines Limited (BGML) a Government of India Enterprise, has 4900 ha (12 253 acres) of land, of which approx. 1600 ha (4000 acres) are in use. Karnataka Urban water Supply and Drainage Board has a reservoir at , 10 km away from Kolar Gold Fields. The plant capacity is 8494.34 million litres. Bharat Earth movers Limited (BEML), manufacturer of earth-moving equipment, is located at KGF and requires 10 lakh litres per day. A number of bore wells have been installed to augment the water supply. The KGF area is covered by red sandy soil, with light texture varying from sand or gravel to loamy, and is highly leached. Integrated assessment of risk for contaminated sites due to on-site sanitation systems in a mining area195

Fig. 1 Location map of Bangarpet Taluk, Kolar District.

KGF town consists of an immense expanse of gneisses classified as Peninsular gneisses, and granites of different phases with green stones, dolerite and amphibolite dykes. The quality of the groundwater is governed by the mineralogical composition of the rocks. In the absence of major sources of water like rivers, the KGF depends heavily on groundwater. But the groundwater table has receded beyond 200 m depth. Hence most people get their drinking water from outside town and only use local water for non-drinking purposes. Some make trips to nearby safe sources (1–4 km) to get a can of drinking water. The localities are using bore well water for non-domestic purposes. Few bore wells are supplying water for other nearby wards. The geology of the particular area has a tremendous influence on the occurrence and quality of water, and its movement in the zone of saturation below the surface. The chemical constituents present in groundwater are derived generally from the geo-environment in which they occur and the anthropogenic activities. The common constituents found in water are suspended impurities like bacteria, algae and silt/clay, dissolved impurities like salts (Ca, Mg, Na), metals (Fe, Mn, Pb), gas (O2, CO2, H2S and CI) and organic matter; few water samples from bore wells of various wards were collected to study the quality.

METHODOLOGY OF INVESTIGATION Physical site surveys were carried out during October 2006 to know the status of on-site sanitation systems and to select sampling points for water and soil collection. Sample survey of user’s opinion was also carried out to get to know the type of on-site practices (septic tanks/pit latrines/cesspools/open defaecation, etc. the depth of these on-site sanitation systems varies from 1.8 m to 2.5 m). Based on the discussions with the community and feedback from a questionnaire, 12 water samples (10 samples from bore wells, depth of the wells varies from 150 m to 210 m: located downgradient from the septic tank/soak pit and one sample each from cave-in point and Fatima tank water suppliers) and 6 soil samples (from 2 study points: located downstream, 3–5 m 196 H. K. Ramaraju

away from the septic tank and the soil is extracted from a depth of 0.3 m, 0.5 m, 0.8 m) were considered, depending on the topographical features. Observations of each septic tank by opening the cover of the slab to know the status (lining, material used, type of plastering, etc.) of septic tank was also done. Physical visits to each block of community toilets to check the status of pans, floorings, other toilet wares, etc. and condition of chambers, functioning status of chambers/drain pipe from chambers to septic tanks, were also noted. General observations in the blocks like drainage system, solid waste disposal and an interaction with the community by noting their grievances was also carried out.

PHYSICAL PROPERTIES OF SOILS The physical characteristics of soil depend chiefly on the texture or the size distribution of mineral particles, on the structure or the manner in which these particles are arranged, on the kind of clay mineral present and the kind and amount of exchangeable ions adsorb upon them, and on the amount of organic matter incorporated with the mineral matter. Textural classifications of soil are based on the relative amounts of sand and clay predominating in the solid fraction. Soils are classified as sand, loam, sit or clay, with various intermediate classes such as sandy loam, silt loam, or clay loam. Table 1 gives an example of soil classification according to particle size. The results of physical tests of soil samples are give in Table 2. The permeability of the soil in the study area varied from 0.13 to 0 .31 m day-1.

Table 1 Classification of soils according to system of international society of soil sciences. Fraction Diameter (mm) Sandy loam (%) Loam (%) Heavy clay (%) 0.1 Coarse sand 2.00–0.20 66.6 27.1 7.1 Fine sand 0.20–0.02 17.8 30.3 21.4 Slit 0.02–0.002 5.6 20.2 65.8 Clay Below 0.002 8.5 19.3

Table 2 Soil physical properties. Sl. Location Specific Permeability Bulk density Dry density Porosity no. gravity 1 J-block 2.31 0.13 m day-1 1.62 gm cm-3 1.36 gm cm-3 41.1 % 2 S.Palyam 2.2 0.31 m day-1 1.6 gm cm-3 1.45 gm cm-3 34 %

Table 3 Soil test analytical report, physico-chemical and biological parameters in relation to distance and depth of KGF Mining area. 2+ 2+ Location: Depth to pH EC OC P2 O5 K2 O Micronutrients (ppm) Ca Mg E. coli Distance sampling (dSm) (%) (Kgac-) (Kgac-1) (ppm) (ppm) (count between point(m) gm-1) the pit and 2+ 3+ 2+ 2+ sampling Zn Fe Cu Mn point (m)

J-Block: 0.3 5.1 0.45 0.60 32 220 0.65 0.7 1.0 1.4 58 23.7 ND 5.1 0.5 4.7 0.49 0.75 38 230 0.52 1.4 0.9 1.8 600 25.0 45 0.8 5.8 0.41 0.82 52 260 0.87 2.4 0.9 2.2 650 27.0 120 Susaipala- 0.5 4.3 0.58 0.52 34 200 0.76 0.6 1.4 1.0 500 18.0 ND yam:3.8 1.0 4.4 0.58 0.62 36 210 0.68 1.3 1.1 1.4 548 17.0 40 1.5 5.1 0.33 0.75 48 250 0.98 2.2 1.3 2.0 602 18.0 120 : pH (dimensionless); EC, Electrical Conductivity; OC, Organic Carbon; P2 O5, Available Phosphorus; K2O, Available Potassium; ND, Not Detectable.

Integrated assessment of risk for contaminated sites due to on-site sanitation systems in a mining area197

SOIL QUALITY The soil samples were considered as indicative elements for the pollutants. The observed results of analysis are compared with the rating chart for soil test values. Soil pH plays an important role in making nutrients available to plants. From the results of Table 3 it is clear that in the KGF area the pH of the soil is acidic. In all the study areas pH shows an increasing trend with depth. Since ions are the carriers of electricity, the electrical conductivity (EC) of the soil water system rises according to the content of soluble salts in the soil, giving rise to more ion pairs on dissociation as it happens, in the case of a dilute solution (Canter & Knox, 1984). Thus the measurement of EC (varied from 0.33 to 0.58 mmhos cm-1) can be directly related to the soluble salts concentration of the soil at any particular temperature, and EC is found to be in the normal range. The amount of mineralizable nitrogen in soil is closely related to soil organic carbon content. The relationship between OC and mineralizable nitrogen improves further if soils are texturally grouped. The general critical level below which a response to fertilizer N is expected, is around 0.5% OC. The immobilization of fertilizer N can occur in soils which have OC content (30:1 = C:N ratio) (Lawrence et al., 1997). The observed values of OC (as a measure of nitrogen) varied from low to high. Phosphorus is the second key plant nutrient and is required by all living organisms and every living cell. It plays a vital role in a large number of enzyme reactions that depend on phosphorylation. It is also important in the reproductive process of plants. The available phosphorus in the study area was observed to be in the medium range. Potassium is important in the photosynthetic process. Potassium deficiency in soils may be overcome by the application of potash fertilizers like potassium chloride or potassium sulphate. K2O ranged from 50 to 182 kg ac-1 in KGF. Available potassium is in the low to high category, which showed an increasing trend with depth and the value of available potassium in the study area was observed to be in the medium range. The potential for biological contamination of groundwater by percolation from wastewater, sludge, land spreading, septic tank systems and land fill leachate is high (Canter & Knox, 1984). E. coli count gm-1 of soil varied from 0 to 120. Table 3 shows that migration of bacteria, indicative of faecal contamination within the upper (0.3 to 0.8 m) zone, is widespread. This may possibly reflect the lithology of the area.

PHYSICO CHEMICAL QUALITY OF WATER The physicochemical characteristics of water mainly consider the concentration of organic and inorganic constituents and interpretations in relation to the sources, geology, pollution sources, 3- 2- - 3+ climate, etc. The range of values of pH, EC, TH, Cl, Na, K, PO4 , SO4 , NO3 , Fe , F, COD, BOD and coliforms for different samples of water collected from all the 12 locations of different blocks of study areas/mining area are presented in Table 4. The mine is located in a groundwater recharge area; the recharge characteristics may be affected by the backfill material, which may differ from the original characteristics of top soil and overburden in the leased area. The quality of groundwater can be affected, depending on the quality of leachates generated from the overburden material /mineral content. Natural water has pH 4–9 and in the study area, the majority of the water is slightly alkaline due to carbonates and bicarbonates of calcium and magnesium ions (total hardness). The pH of the water in the study area varied from acidic to alkaline. Electrical conductivity (EC) measurements estimate dissolved salts in water. Most of the in organic salts, acid and bases, when dissolved in water, make it a good conductor, but organics do not. Changes in conductivity of a sample may signal change in mineral composition of raw water, and intrusion of domestic wastewater. Raw and potable waters normally register specific conductance from 0.5 to 5 ms cm-1, with mineralized water having values over 5 ms cm-1. Electrical conductivity of the groundwater sample in the study sites possesses high EC values. Total hardness (TH) in water is objectionable for domestic purposes, particularly since it needs lot of soap to form a lather. The values vary from 592 to 2500 mg L-1, total hardness was very high in the NT block. It was also observed that nitrate- rich polluted groundwater possesses elevated concentrations of calcium and magnesium, i.e. 198 H. K. Ramaraju increase in hardness. This is due to the process of nitrification-producing hydrogen ions, which are able to dissolve more carbonate materials present in the soil. The origin of Chloride (Cl-) in groundwater is more complex due to leaching of evaporative deposits for washing of chloride from overlying rocks and soils. The chloride content in groundwater sources of KGF is in higher range (ranges from 78 to 861 mg L-1) as observed in bore well samples of different blocks of mining area indicating the point pollution. Leaching salts from septic tanks and chemicals used in the mining area may be the reason for higher values of sodium (Na). Although the abundance of potassium in the Earth’s crust (2.5%) is about the same as sodium, potassium is usually less than one tenth the concentration of sodium in natural water. Potassium (K) is released into the water consequent on weathering of rocks followed by leaching by rainwater. The range of potassium levels in the study areas is in the 3 normal range. Excessive amounts of Phosphate (PO4 ) actually constitute pollution, usually by infiltration of wastewaters from domestic sources, agricultural runoff, etc. Phosphate levels reported in the sampling areas are observed to be very low (0.01 to 0. 21 mg L-1). The phosphate concentrations are negligible in almost all the open well and borewell waters. Previous field studies have demonstrated that most soils, even medium sandy soils, exhibit a substantial ability to reduce PO4 concentration. The potential of soil to remove phosphate from septic tank wastewater disposal system effluent is controlled by the mineral content of the soils of the area rather than particle size. Clay minerals, iron and aluminium oxide have relatively high capability for phosphate sorption or immobilization (Ramaraju, 2000). Phosphorus is rapidly adsorbed by the soil and hence its mobility is slow. 2- Sulphate (SO4 ) occurs in most natural water in a wide range of concentrations. In well water samples of the study areas, the sulphate concentration is in the very high range. Groundwater contamination from septic tank sulphate was more pronounced and it may also derive from epsom salt of the mining area. This is importing a bitter taste to the water. Nitrate (NO3) is an end product of decay of nitrogenous materials such as human or animal excreta or nitrate fertilizers (Viraraghavan, 1976). In developing countries there is a risk of groundwater pollution by on-site sanitation. High nitrate levels in groundwater may serve as indicators of the type of pollution (UNDP, 1981). High nitrate concentrations in water have resulted in death of infants by Blue Baby diseases (metheamoglobanemia) and possible cancer-forming agents, though evidence is scanty and often confusing. Significant increase in chloride and electrical conductivity is noticed in areas such as mining area with high nitrate is reported. The presence of Iron (Fe3+) in drinking water is objectionable due to several reasons. Even though iron is an essential element in the human nutrition and is present in a number of biologically significant proteins, ingestion of these elements in large quantities results in haemochromatosis wherein tissue damage results. The desirable limit of Indian Standard is 0.3 mg L-1. Increase in iron in all the bore wells may be due to the effect of mining and may result in corrosion of pipes. The concentration of Fluoride (F) in drinking water is critical when considering health problems related to teeth and bones. The main purpose of bacteriological examination of groundwater samples of the study area was the detection of recent and potential danger of faecal pollution of drinking water by human or animal excrement. The examination of water pollution did not indicate any contamination, as many septic tanks have not been used from many years. But the results of water quality (chemical parameters) significantly indicate risk of contamination of groundwater from septic tank effluent. The depth of the septic tank varies from 1.8 m to 2.5 m. Improper design, construction, operation or maintenance of septic tank/onsite sanitation systems can lead to failure due to loss of infiltration capacity/inadequate effluent purification. The infiltration rate of the unsaturated zone is especially important for shallow aquifers beneath urban areas with onsite domestic wastewater disposal, because the infiltrating effluent contains a much higher organic load. Leaching from the septic tank does not go all the way down to 200 m. Seasonal rainfall, soil type, density of variation of septic tanks, etc. may contribute towards the same.

Integrated assessment of risk for contaminated sites due to on-site sanitation systems in a mining area199

Table 4 Variation of water quality parameters from 12 sampling stations in KGF mining area and town, October 2006. - + + 3- 2- - 3+ - Sl Location pH TH Cl EC Na K PO4 SO4 NO3 Fe F COD BOD MPN DC Cya Remarks no. Test nide 1 NT-block* 7.16 2500 861 5420 301 10 0.21 534 560 0.297 0.32 9 4 ND – ND Not potable 2 Cavin point ** 7.51 1610 245 3570 195 16 0.15 396 20 3.515 0.42 16 10 ND – ND Not potable

3 Henry’s 1st 7.15 1290 630 3670 265 05 0.16 294 174 0.177 0.48 6 2 ND – ND Not lane* potable

4 Masanary 6.95 1230 609 3480 229 06 0.12 243 500 0.338 0.35 8 3 ND – ND Not block * potable

5 Fatima tank 7.98 152 22 700 92 0.1 0.16 58 10 0.294 1.48 0 0 ND – ND Potable suppl* 6 D-Block* 7.07 1490 651 3840 190 05 0.18 290 404 0.14 0.35 6 4 ND – 0.001 Not potable

7 Hendriz 8.30 1124 328 4240 442 01 0.01 1152 23 0.086 0.4 NM NM NM NM NM Not drivers line* potable 8 Muss (North)* 8.32 592 182 1740 124 02 0.14 92 37 0.11 0.1 NM NM NM NM NM Potable 9 Dodda 8.24 568 132 2190 239 02 0.09 472 22 0.22 0.25 NM NM NM NM NM Not Valagmadi** potable

10 Champion 7.7 788 120 2190 369 03 0.12 1002 09 0.005 0.1 NM NM NM NM NM Not reef* potable

11 Plummers 8.42 448 78 1320 97 02 0.10 128 19 0.028 0.10 NM NM NM NM NM Potable shaft * 12 Nagavaram** 8.41 652 112 2300 227 02 0.11 594 09 0.005 0.10 NM NM NM NM NM Not potable

*, Borewell; **, Shaft water; All units are in mg L-1 , except pH (dimensionless) and EC (ms cm-1); MPN, Most Prabable Number per 100 ml of water; DC, Differential Coliform Test; +, presence of E. coli; –, absence of E. coli); ND, Not Detectable; NM, Not Measured (Slno. 7 to 12, results are cross verified with Mines and Geology, Government of Karnataka data).

CONCLUSIONS The study revealed that water quality of the nine wells is fast deteriorating, with high levels of Total Hardness, Chloride, Sulphate, Electrical Conductivity and Nitrate not fit for use. In some stray cases TH, Cl and sulphate reached 2500 mg L-1, 861 mg L-1, 1152 mg L-1, respectively, which are far higher than WHO stipulations. The quality of groundwater is governed by the minerological composition of the rocks. The ultramafic, metavolcanic and schistose rocks are seen as scattered masses. Soil samples collected near to septic tank systems indicated fairly high levels of OC, E. coli count in the subsurface soil profiles up to a depth of 0.8 m. As depth is increased, due to overloading from septic pits and dispersion of the pollutants higher contamination results. The permeability of the soil in the study area varied from 0.13 to 0.31 m day-1. Most of the latrines were constructed without a scientific basis and without considering the direction of groundwater flow and seasonal recharge trends. Improper construction of wells/septic tank systems/improper designs in some places/poor maintenance, is also noticed. It is observed that the supply and demand, which has to be met by the groundwater, is already over exploited. Another major grey area is poor maintenance and repairs of community toilets. Higher concentrations of major metals salts were also observed because the geology of the particular area has a tremendous influence on the quality of water. Nearly 20–30 million tonnes of mine tailings dumped for many years has created environmental and health problems to the people living in KGF mining area. Recent studies on water quality indicate that the area is highly contaminated with fluoride, cyanides, EC and nitrates. The sewage is disposed of without prior treatment into the nearby low 200 H. K. Ramaraju lying areas. The water is transported from peripheral areas at a cost of Rs.1 for an 8–10 L vessel. Community toilets are to be cleaned, pits de-sludged, and cleanliness in and around the toilets to be maintained. Awareness about domestic/municipal solid waste management is required. Most of the community toilets are unhygienic, with overflowing pits. Ecologically the surrounding areas of the toilets are to be cleaned as they affect the natural resources like water and soil. All community toilets need repair and periodical cleaning and maintenance. The groundwater is overexploited and the recently dug tube wells have reached a depth of 200 m to 270 m. The only source of supply is groundwater. Most of the toilet blocks except Coromandal ET Block, South Block, and NT and D Blocks lie in low lying areas and deny access to users during the period of water stagnation. Very old toilet blocks were built with size masonry stone and latest blocks are built with bricks; most of the toilet block structures are reasonably good. In a very few, e.g. Henry’s second line Gents toilet, ceiling plastering has completely come off. Brick masonry is exposed, showing poor quality of proportion in the construction, and cracks have developed all over the building. All the septic tanks are covered with stone slabs, in the majority of cases stone slabs are removed, kept aside and not covered properly; none of them have a ventilation shaft. The design aspect of the septic tank is technically correct, except for allowing effluent directly into the natural drain, which is not good practice from a hygienic point of view. None of them have either a soak pit or dispersion trenches for safe disposal of septic tank effluent. Careful consideration is to be given to all the technical factors (design as per the actual/- predicted population, construction, nature of wastes, climate, regional geology, topography, physical and chemical composition of the soil mantle, and care taken in periodic maintenance) to select an appropriate type of community toilet. Keeping the investment cost and O/M by the community septic tanks are found to be feasible, economical and sustainable (strictly constructed as per USEPA standards) for the KGF mining area. It is also likely that if deep rooted vegetation such as shrubs and trees (as in the case of improved septic tanks) could be introduced into the areas, the situation could be improved. We also have to bear in mind the long-term impacts of deteriorating groundwater and top soil zone, the effects of which may not be felt for several years or decades. In the short-term, however, we may need to accept that some contamination of groundwater is unavoidable if healthy gains from improved sanitation are to be realized (Franceys et al., 1992). This may also require a rethink on the technologies used. Changing practices of wastewater disposal from conventional septic tank to more environmentally friendly designs (improved septic tanks) or alternately increasing number of blocks/wards that are sewered together (under drainage system) for improving effluent quality.

Acknowledgements Sincere thanks to Dr B. R. Niranjan, Chairman, Department of Civil Engineering, UVCE. Dr G. Ranganna and Dr N. Munirudrappa, former Professors of Bangalore University for their constant encouragement and guidance. This study was supported by ADER (an NGO), France. Gratitude is also given to staff of CEADAT (an NGO), Bangalore for their assistance in the field and laboratory studies.

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