Cement Energy Environment

88 • Of the total water on earth, only 3% constitutes freshwater. Rest is saline water in the oceans. • 11% of the total freshwater on earth is groundwater available upto a depth of 800m which can be extracted for use. • Mindless extraction and over exploitation of very small quantity of this precious nature resource has caused a rapid depletion and deterioration in its quantity and quality both. • In alluvial areas where permeable rocks are exposed on the land surface or are located at very shallow depth, rain water harvesting can be done through recharge pits. • The technique is suitable for buildings having a roof area of 100 sq. m. These are constructed for recharging the shallow aquifers. • Recharge Pits may be of any shape and size. They are generally constructed 1 to 2m. wide and 2 to 3m deep. The pits are filled with boulders (5-20 cm), gravels (5-10mm) and coarse sand (1.5- 2mm) in graded form. Boulders at the bottom, gravels in between and coarse sand at the top so that the silt content that will come with runoff water will be deposited on the top of the coarse sand layer and can easily be removed. For smaller roof area, pit may be filled with broken bricks/ cobbles. • A mesh should be provided at the roof so that leaves or any other solid waste / debris is Rain Water Harvesting Pit prevented from entering the pit. A desilting / collection chamber may also be provided at the ground to arrest the flow of finer particles to the recharge pit. • This technique is ideally suited for area where permeable horizon is within 3m below ground level. • Recharge well of 100-300 diameter is constructed to a depth of at least 3 to 5m below the water level. Based on the lithology of the area, well assembly is designed with slotted pipe against the shallow and deeper aquifer. • A lateral trench of 1.5 to 3m width and 10 to 30m length, depending upon the availability of water is constructed with the recharge well in the centre. • The number of recharge wells in the trench can be decided on the basis of water availability and local vertical permeability of the rocks. • The trench is backfilled with boulders, gravels and coarse sand to act as a filter media for the recharge wells. • If the aquifer is available at greater depth say more than 20m, a shallow shaft of 2 to 5m diameter and 3-5metres deep may be constructed depending upon availability of runoff. Inside the shaft a recharge well of 100-300mm dia is constructed for recharging the available water to the deeper aquifers. At the bottom of the shaft a filter media is provided to avoid choking of recharge well. Figure 10: Rain water positive water harvesting pit J.K. White cement works, Gotan invited National Productivity Council (NPC) to this landmark for an audit under Bureau of Energy Efficiency – Star Labeling Program that resulted in the following Certification. Achieving of BEE Star Labelling Audit & Certification