Rejuvenating Sirigaon: NEERI recommedations

National Environmental Engineering Research Institute based in Nagpur presented and invstigative report titled "Assessment of the depletion of ground water sources and land degradation in Sirgaon vilalge, Goa and mitigation measures" in March 2009 to the Goa bench of Bombai High Court, Panaji in respons to Sirgaon villagers Public Interest Litigation (PIL). Below are extacts from the report's page numbers 106-107 dealing with recommedations to rejuvenate Sirigaon.

Summary

i) The field visits were undertaken for assessing the water resources of Sirigaon village in the months of August’08, October 08’ and December 08’. Inspection was made for design and implementation of the recharge structures for augmentation of water resources in the month of January 2009. The field observation indicate that very less water (2-3 m water column) is present in the wells in the months of August and October. All the wells in Sirigaon village had gone dry in the month of December 2008.

ii) The mining activity has led to loss of capping material and at present the bottom of the mine pit has gone below (-20m) for all the three Minng companies.

iii) The ground water level (amsl) contours indicate that the groundwater flow direction is towards the mine pit. Seepage to the pit from the mine wall was also observed during the field visits which may lead to decline of water resources in the Sirigaon village.

iv) Water analysis from the dry wells and mine pits indicate that the quality is suitable for domestic water needs after conventional treatment as well for irrigation after proper sedimentation to avoid suspended matter.

v) It is essential to initiate groundwater recharge activity in a comprehensive and scientific way to recharge the aquifer as well arrest the flow to the mine pits from the aquifer. A comprehensive recharge scheme is accordingly recommended with a framework for implementation. Post-project monitoring needs are included in the overall recharge scheme. The post-project monitoring can be undertaken by NEERI in a project mode for three years.

vi) The findings indicate that silt accumulation has taken place in the neighboring agricultural land and soil fertility has been impaired. The restoration of the degraded land by Integrated Biotechnological Approach (IBA) has been suggested and the cost estimates are made in this regard. The silt accumulation in the agricultural field is caused by the run-off from the overburden dumped material during the monsoon season. Therefore, slope stabilization needs to be carried out to minimize the run off.

vii) The rooftop harvesting structures (60 Nos.) will cost an amount of Rs. 34 lakhs. Construction of recharge wells (60 Nos.) and water absorption trench is estimated at Rs. 73 lakhs. The third priority of construction of subsurface dyke and bentonite grouting will need Rs. 410 lakhs as capital cost. Other costs involved are preparation of Detailed Project Report (DPR), maintenance of the structures and monitoring of the environmental management plan

viii) The total cost of all the priorities for recharge scheme is estimated at Rs. 660 lakhs and the rejuvenation of silt affected soils needs Rs. 1.8 lakh/ha of the land. The cost estimates are based on the present (year 2008 SOR of Govt. of Goa) price level

What mining has done to Sirgao's Soil: NEERI conclusions

National Environmental Engineering Research Institute based in Nagpur presented and invstigative report titled "Assessment of the depletion of ground water sources and land degradation in Sirgaon vilalge, Goa and mitigation measures" in March 2009 to the Goa bench of Bombai High Court, Panaji in respons to Sirgaon villagers Public Interest Litigation (PIL). Below are extacts from the report's page numbers 77-78.

Conclusions

It is evident from the foregoing soil analysis that mining leads not only to pollution of surface and ground water but also accelerates by surface runoff which, in turn, results in deposition of mining waste in agricultural fields. Silt accumulation due to erosion by water on agricultural field result in significant changes in soil properties, which are linked with changes in crop growth properties, biomass production and seed yield. In present study, based on analysis of the different physico-chemical and microbiological properties of soil samples collected from specific sites of the study area and assessment of extent of agricultural land affected by open cast mining, following conclusions are drawn.

ü Erosion of mine overburden and mine land leads to its deposition down the slope in the command area. The silted soil belongs to the texture class “silty laom” whereas the control soil belongs to class “silty clay loam”. The low water retentivity, rapid permeability, low infiltrations (in soils with having clay pan) moisture stress conditions, etc, leads to decline in water use efficiency in irrigated areas in case of silty loam soil.

ü The water-logging problem in the silted soil was due to hard clay formed from deposition of silt which ultimately affects the growth of the plants. This has direct influence on the growth of the plants and also affects the availability of plant nutrients.

ü The information collected from farmers revealed that the acidity in the cultivated areas has been considerably increased (pH lowered) in the areas where deposition of sediments/ silt from mining took place with reduction in Paddy yield.

ü The water holding capacity, CEC, organic carbon and nutrients content of the silted soil were very low as compared to control soil. The microbial population, which is responsible for carrying out different bio-geo-chemical cycles and production of plant growth promoting hormones in the soil, which supports the plant growth, is highly affected in the silted soil as compared to good cultivated one. It is obvious that low organic matter content resulted in the reduction in CEC, nutrients and microbial activities of silted soil.

ü As silted soil developed from granite-gneiss parent rock formation of argillic horizon in the soil there is the soil there is the problem because of high free Fe2O3 and Mn contend. The overburden material rich in iron content and also contain lot of gravels and have deficiency of Ca, S and Zn.

ü Thus deposition of silt overburden from the mine waste resulted in changes in soil properties including soil texture, nutrient content and soil water status.

ü In view of the deterioration of soil quality due to silt deposition, it is essential that suitable mitigation measures are implemented for restoration of the degraded land. The mitigation measures are delineated in Chapter 4 of the report.

Sirigao: NEERI Report to High Court - Executive Summery

Nagpur based National Environmental Engineering Research Institute (NEERI) under Council of Scietific & Industrial Research of the Government of India submitted to the Goa Bench of Bombay High Court, Panaji, the Investigation report in March 2009 after being directed to do so by the Honourable High Court on the Public Interest Litigation of Sirgaon villagers (PIL No. 1/2008, dated 16th June 2008). The title of this 110 page report is "Assessment of the depletion of ground water sources and land degradation in sirigaon vilalge, Goa and mitigation measures". The executive summery is reporduced below in public interest

• The present study is an outcome of the directives of the Honourable Mumbai High Court at Goa (PIL No. 1/2008) to focus on the alleged depletion of water resources, degredation of agricultural fields’s vis-ả-vis the mining activity in Sirirgaon village (Bicholim Taluka) in the North Goa District.
• The study area (60 sq. km) has been delieanated on the basis of watershed and covers the working mining pits of the three mining companies namely M/s Dempo Mining Corporation Pvt Ltd., M/s. Rajaram Bandekar (Sirigaon) Mines Pvt. Ltd. And M/s Chowgule and Company Pvt. Ltd. It covers most of the dug wells in the Sirigaon village.
• The study area is covered by the Survey of India (SOI) toposheet No. 48E/14/SE (scale 1:25,000). The elevation in the village outside the mining pit varies from 0.095 m to 8.639 m.
• The topography in the nearby Sirigaon village has been altered significantly due to the open cast mining activity. The topographic highs which were present earlier have now been removed during the mining activity and large depressions have been created in the form of Mine pits. In view of the sustained mining activity, depressions have been created with the bottom level varying between -20 m (amsl) to 43 m (amsl).
• Goa receives rainfall from the Southwest monsoon and spans four months i.e. from June to September. The rainfall data for the last five years indicate that the average annual rainfall is approximately 2846 mm out of which 2785 mm is contributed by the south west monsoon.
• The Geology of the study area comprises of laterites followed by manganeferous clay. The manganeferous clay is underlain by iron ore formation. The thickness of laterites varies from 3 m to 15 m as evident in the lithologs provided M/s Chowgule & Company Private limited and M/s Rajaram Bandekar (Sirigaon) Mines Pvt. Ltd. The laterites are followed by manganeferous clay which is followed by limonitic clays.
• The iron ore formations underlie the clay formations. The iron ore formations vary from friable ore to powedery ore. At places, friable ore is followed by powdery ore though friable ore is absent at many places and only powdery ore is encountered. The available lithologs provided by M/s Chowgule and Company Pvt. Ltd. Indicates that the thickness of powdery ore zone varies from 10 m to 32 m in one of their drilling sites.
• The top lateritic formation constitutes the unconfined aquifer in the study area. The zone comprising the ore body serves as the confined aquifer. The unconfined aquifer is tapped for extraction of water. All the dug wells located in the Sirigaon village are tapping the unconfined aquifer only.
• Field visits were undertaken for assessing the water resources in the village in months of August, October and December 2008. Inspection was made for design and implementation of the recharge structures for augmentation of water resources in the month of January 2009. Observation well network was established for measurement of water levels and collection of samples for physicochemical and heavy metal analysis. It is observed that the water table in August’2008 varied from 0.50 m to 6.55 m. In October 2008 and December 2008, it varied from 0.90 m to 10.30 m and 2.70 m to 9.70 m respectively. The groundwater scenario was worse in December 08, when almost all the dug wells in Sirigaon village had dried up. However, the wells from nieghbouring villages had water column even in the month of December, 08.
• The mine pit water levels for all the three mines is below -20 m (amsl). The flow direction is indicative of water flow from the aquifer to the mine pit. Water seepage to the pit from the mine wall on the village side is also noticed during the field visits. Schematic diagram of ground water profile in the Sirigaon and mine area is presented in the Figure.
• The deepening of the mines has led to loss of recharge area for the dug wells seated at the foot hills of the plateau. Hence, the water scarcity in the viallge dug wells is attributed to the loss of recharge area as well as the deepening of the mine.
• Water samples were collected from the mining pit of the three companies and dug wells of the Sirigaon viallge. The water samples were analysed for physicochemical parameters and heavy metals levels. The analysis results indicate that the water quality is within permissible limits (BIS 10500:1991) for drinking water as well as for irrigation purpose as per the guidelines (BIS 11624:1986)
• Groundwater balance study was carried out for the Sirigaon village. It is established that the requirement of the village can be met by undertaking artificial recharge scheme in a holistic way. Roof top rain water harvesting, water absorption trench, sub-surface dykes and bentonite grout have been proposed for artificial recharge and control of water seepage to the mine pits.
• The State Government has provided organized piped water supply scheme to the Sirigaon village
• Artificial recharge schemes have been commissioned recently on a small scale by M/s Rajaram Bandekar Mines Pvt. Ltd. And M/s Chowgule and Company Pvt. Ltd. During the field visits it was observed that the recharge to the nearby dug wells was very insignificant.
• Roof top rainwater harvesting is proposed as Priority I to address the water scarcity problem in the village. Creation of recharge trench and control of mine water seepage are advocated as Priority II. Aquifer storage recovery (ASR) by construction of sub-surface dyke is proposed aas priority III. It is suggested that the artificial recharge of ground water is initiated stepwise. Roof top rainwater harvesting, if not adequate, is to be followed by the construction of recharge trench. Priority III is the last alternative.
• An estimated cost of Rs.660.25 lakhs will be incurred towards installation of the comprehensive recharge schemes to address the water scarcity in the village. The estimate includes the cost towards DPR preparation, maintenance charges and the post-project monitoring charges.
• Soil samples were collected from the silt affected area as well as the control sites. The collected soil samples were characterized for various physicochemical and microbiological parameters (such as bulk density, texture, pH, exchangeable calcium, magnesium, sodium, potassium, available N, P, K, heavy metals and enumeration of different soil microbes).
• The soil analysis results indicate that the silt deposition from the mining overburdens has degraded the soil fertility in the agricultural fields of Sirigaon village.
• Proper slope stabilization needs to be carried out in the mining areas to minimize runoff of the overburden dump material to the nearby agricultural fields.
• Integrated Biotechnological Approach (IBA) is suggested as mitigation measures for restoring the soil quality of the silt affected area. The cost estimated for remediation of silt affected soil by implementation of IBA technology has been worked out to be approximately 1.8 lakhs per hectares area which includes the material costs, land preparation cost and labour cost etc.