Therefore, the main objective of the present
study is to assess the impact of sand mining
based on the hydrochemical characteristics of
groundwater emphasizing on the spatial extend
of salinity of groundwater, water-level fluctuation and tidal-level activities of shallow coastal
aquifer.
14.1.1 Study Area
14.1.1.1 Geographical Location
The present study area extends from south of
Vembar to the north of Kanyakumari, which lies
between latitude 8°08′ to 9°09′N and longitude
77°55′ to 78°35′E covering the districts of Tuticorin, Tirunelveli and Kanyakumari, Tamil
Nadu, India (Fig. 14.1). The study area has many
rivers such as Vembar, Vaippar, Tamiraparani,
Karamaniyar and Nambiyar, which drain into
Bay of Bengal.
14.1.1.2 Geomorphology
and Hydrogeological
Settings
The coastal area is mainly underlain by the
geological formations comprising crystalline
Archaean complex, tertiary and sub-recent to
recent groups (GSI 1995). The crystalline rocks
of late quaternary deposits and sandy materials
are present along the study area. The coastal
areas of Navaladi, Uvari and Periyathalai consist
of red color sand sheets and dunes which are
locally known as “Teri” that lies at some distance
away from the shore. The red “Teri” formation is
mainly composed of red-stained quartz with an
admixture of fine red clayey dust and fine grains
of iron ore. The coastal areas around Tuticorin
and Tiruchendur are mainly used by the salt
industry. The total coastal length of 223 km in
the area has been the most intensively mined
shoreline. The sandy shoreline is backed by
extensive dunes having the maximum height of
15 m. These sites are mined for placer minerals
such as garnet, ilmenite, zircon, sillimanite and
rutile which are of high commercial value. The
primary dunes and secondary dunes are exposed
to wave runup. The mining is mainly between the
primary dunes and mean water high level up to a
depth of maximum 6 to 10 m. High tide and
storm waves allow swash to undercut the dune
with sand sliding into the beach and causes the
seawater intrusion into the coastal aquifer.
The aquifer in the coast is shallow at −5 to
−8 m in MSL. The average thickness of nonconfining material is 3 to 12 m. Potentiometer
change across the coastal sand dunes −0.3 to
−0.6 m. The storage capacity of the coastal
aquifer generally increases with depth with the
increase in the grain size of aquifer material.
Vertical hydraulic gradient is −0.85 to +1 m. The
amount of seawater recharge in the mining area
and other area depends upon the non-confining
material is 0.02 to 0.08 m
2 /day. The susceptibility to intrusion in a particular location is
directly dependent on the vertical thickness of
the aquitard and permeability of the sand. In all
sites the wells are located between 10 and
5000 m from mining operations. Large and deep
pit as a result of deep excavation from the mean
high water level to the dunal area, the water
tables drops, quantity and quality of water are
affected especially during the dry season when
there is no rainfall. (Annual rainfall amount
ranges from 500 to 900 mm.) Due to lack of
rainfall in these regions, the water table is also
lowered in the mining site.
14.1.2 Materials and Methods
14.1.2.1 Sampling and Analysis
In order to evaluate the impact of sand mining,
open wells are fixed within a 5 km radius.
Groundwater samples in each of three sites at
various flow levels were collected for analysis.
The groundwater is mainly used for drinking,
domestic, irrigation or for blending with desalinated and recreational purposes. The groundwater samples were collected in a HDPE bottles
with a capacity of 500 ml, in minimally anthropogenically impacted. Before water sample collection, the bottles were thoroughly cleaned by
rinsing with HNO 3 and deionized water. At the
time of sampling, the bottles were rinsed three
times using the groundwater to be sampled. The
14 Impacts of Beach Placer Mineral Mining …
185
study is to assess the impact of sand mining
based on the hydrochemical characteristics of
groundwater emphasizing on the spatial extend
of salinity of groundwater, water-level fluctuation and tidal-level activities of shallow coastal
aquifer.
14.1.1 Study Area
14.1.1.1 Geographical Location
The present study area extends from south of
Vembar to the north of Kanyakumari, which lies
between latitude 8°08′ to 9°09′N and longitude
77°55′ to 78°35′E covering the districts of Tuticorin, Tirunelveli and Kanyakumari, Tamil
Nadu, India (Fig. 14.1). The study area has many
rivers such as Vembar, Vaippar, Tamiraparani,
Karamaniyar and Nambiyar, which drain into
Bay of Bengal.
14.1.1.2 Geomorphology
and Hydrogeological
Settings
The coastal area is mainly underlain by the
geological formations comprising crystalline
Archaean complex, tertiary and sub-recent to
recent groups (GSI 1995). The crystalline rocks
of late quaternary deposits and sandy materials
are present along the study area. The coastal
areas of Navaladi, Uvari and Periyathalai consist
of red color sand sheets and dunes which are
locally known as “Teri” that lies at some distance
away from the shore. The red “Teri” formation is
mainly composed of red-stained quartz with an
admixture of fine red clayey dust and fine grains
of iron ore. The coastal areas around Tuticorin
and Tiruchendur are mainly used by the salt
industry. The total coastal length of 223 km in
the area has been the most intensively mined
shoreline. The sandy shoreline is backed by
extensive dunes having the maximum height of
15 m. These sites are mined for placer minerals
such as garnet, ilmenite, zircon, sillimanite and
rutile which are of high commercial value. The
primary dunes and secondary dunes are exposed
to wave runup. The mining is mainly between the
primary dunes and mean water high level up to a
depth of maximum 6 to 10 m. High tide and
storm waves allow swash to undercut the dune
with sand sliding into the beach and causes the
seawater intrusion into the coastal aquifer.
The aquifer in the coast is shallow at −5 to
−8 m in MSL. The average thickness of nonconfining material is 3 to 12 m. Potentiometer
change across the coastal sand dunes −0.3 to
−0.6 m. The storage capacity of the coastal
aquifer generally increases with depth with the
increase in the grain size of aquifer material.
Vertical hydraulic gradient is −0.85 to +1 m. The
amount of seawater recharge in the mining area
and other area depends upon the non-confining
material is 0.02 to 0.08 m
2 /day. The susceptibility to intrusion in a particular location is
directly dependent on the vertical thickness of
the aquitard and permeability of the sand. In all
sites the wells are located between 10 and
5000 m from mining operations. Large and deep
pit as a result of deep excavation from the mean
high water level to the dunal area, the water
tables drops, quantity and quality of water are
affected especially during the dry season when
there is no rainfall. (Annual rainfall amount
ranges from 500 to 900 mm.) Due to lack of
rainfall in these regions, the water table is also
lowered in the mining site.
14.1.2 Materials and Methods
14.1.2.1 Sampling and Analysis
In order to evaluate the impact of sand mining,
open wells are fixed within a 5 km radius.
Groundwater samples in each of three sites at
various flow levels were collected for analysis.
The groundwater is mainly used for drinking,
domestic, irrigation or for blending with desalinated and recreational purposes. The groundwater samples were collected in a HDPE bottles
with a capacity of 500 ml, in minimally anthropogenically impacted. Before water sample collection, the bottles were thoroughly cleaned by
rinsing with HNO 3 and deionized water. At the
time of sampling, the bottles were rinsed three
times using the groundwater to be sampled. The
14 Impacts of Beach Placer Mineral Mining …
185