CHENNAI: A report submitted to the Chennai Metropolitan Development Authority (CMDA) may recommend new building regulations in eight villages from Kottivakkam to Mahabalipuram on ECR as the South Coastal Chennai aquifer spread across these areas, which holds a substantial quantity of groundwater, is facing threat due to rapid urbanisation and its open space area has decreased by half, sources said.
The Centre for Urbanization, Buildings & Environment (CUBE), which is carrying out a study on the impact of urban development on coastal aquifer and measures to protect them in these villages between Bay of Bengal and Buckingham Canal, has submitted an inception report to the CMDA, sources said.
The study will have recommendations on development regulations for aquifer recharge areas, utilisation of open wells for groundwater recharge, and ban on borewells and commercial extraction of groundwater in these places.
The second master plan for the Chennai Metropolitan Area (CMA), to maintain aquifers and ensure full recharge of aquifers during precipitation, has declared an Aquifer Recharge Area (ARA), bounded by the coastline of Bay of Bengal on the eastern side, Buckingham Canal in the western side, city limits (Thiruvanmuyur) in the northern side, and CMA limits (Uthandi) in the southern side of the CMA.
Eight villages — Kottivakkam, Palavakkam, Neelankarai, Injambakkam, Okkiamthuraipakkam, Karapakkam, Sholinganallur and Uthandi — fall under the aquifer recharge area. Buildings constructed in the area are restricted to a maximum Floor Space Index (FSI) of 0.8 for all developments except for natham, earmarked for economically weaker sections, and EWS plots, where the maximum permissible FSI is 1.0, with maximum plot coverage of 40% and 50% respectively to reduce the runoff during precipitation. Rainwater harvesting structures are also mandatory in all buildings to improve groundwater recharge.
Sources said Geological Survey of India (GSI), United Nations Development Programme, and Metro Water Board conducted various hydrogeological investigations during 1975-1977 and reported that this aquifer is suitable for a well field with a potential yield of 20.5 million litres per day (MLD). Initially, well fields were constructed, and pumping began at the rate of 6.8 MLD to 9 MLD of groundwater.
With gradual increase in urbanisation groundwater usage increased, and from 1985 to 1997, seawater intrusion into the aquifer was noted. After government’s intervention and legal restrictions, pumping of groundwater was reduced to six MLD. However, due to urban density, people used tube wells to pump water for domestic purpose. In total, the pumping rate from the aquifer is beyond the limit of 9 MLD, reports said.
Former Anna University professor of urban engineering K P Subramanian said a total ban on construction of all types of buildings was initially in force in the area. The ban was lifted later. “That decision seriously impacted the environmental protection, ecological equilibrium, ground water augmentation, and micro climate of the area. It would be desirable if government reimposes the ban or at least allow only low impact developments,” he said.