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August 25, 2009 - Goanet's 15th Anniversary
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http://mandgoa.blogspot.com/2009/08/sirigao-neeri-report-to-high-court.html
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.
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