Large volume of fly ash as obtained from coal based thermal power plants are deposited in specially designed ash ponds within 5-10 km of fly ash generation source. Several of these abandoned ash ponds are now quite close to residential locations and certainty requires serious efforts in marginalizing the environmental impact of fly ash ponding in the coming years.

Exhaustive investigations were undertaken at CBRI to explore the technical feasibility of habitable reclamation of abandoned fly ash ponds at ash pond of NFL captive thermal power plant Panipat and ash pond site of Badarpur Thermal Power Station, Badarpur (Delhi) (Table–1). Samples of ground water from the vicinity of ash ponds at Panipat and Badarpur sites were obtained and analysed for chemical properties and  the results are given in Table-2. These results show adequate compability with regard to limits prescribed in IS:10500:1983 for drinking water quality. Monitoring of indoor and outdoor air quality with respect to suspended particulate matter was also undertaken and the results of indoor and outdoor air quality as obtained at both the locations are given in Table 3.

These results show that the fly ash mass available at both the locations is of mildly alkaline nature (pH>7) with soluble salt content varying in the range of 0.1 to 0.8 percent (Table-1) which could be due inherent association of water solubles in the fly ash mass, due to coal quality, combustion conditions etc., besides soil and water mass overlying in the vicinity. The air quality data

obtained at both the locations indicates insignificant impact of fly ash ponding in the vicinity of experimental sites.

By and large, the inherently associated soluble salts with Indian fly ashes broadly fall in the category of gypsum i.e. the sulphates of calcium. The gypsum is a well known sparingly soluble material in water and therefore should not be considered as a major threat to the neighboring environment.

Water quality appraisal was carried out with respect to pH, turbidity, major and minor ionic species etc. and the results are given in Table 2. It is reported that the degree of solubility of toxic heavy metals and other associated oxides largely depend on the pH of the aqueous media. The mobility of metal ions as well as their oxides from solid phase is enhanced under acidic aqueous environment. The acidic environment (even with pH level marginally below 7) is expected under specific rain water leaching. Further, the release of toxic heavy metals from fly ash mass is a complex function of several factors including the composition etc. Further, the soil attenuation capacity largely govern the magnitude of migration of toxic heavy metal to the ground water level. In the present study, soil mass underneath the fly ash pond essentially belongs to alluvial type with high silt content, which generally show moderately low permeability. This is expected to cause substantial reduction in the downward movement of ionic species. However, maintaining the alkalinity level of fly ash mass and providing earth cover of 20-25cm thickness can further reduce environmental impact of fly ash ponding.