Chennai: Residents of Ernavoor are raising alarms over the pollution of a local pond once a vital groundwater source due to untreated sewage and rampant trash dumping. The Residents’ Welfare Association has complained that effluents from nearby commercial and residential buildings flow into the pond via underground pipes, compounded by residents now discarding rubbish directly into the water body.The Ernavoor pond, owned by the railways, has suffered from a lack of maintenance for a long period. It saw a brief respite after a restoration effort by an NGO through a Corporate Social Responsibility (CSR) initiative. However, those efforts have gone in vain.Residents say the escalating pollution has led to contamination of groundwater sources in the area. Despite repeated attempts to bring the issue to the attention of corporation authorities, no action was taken to address the issue, they said. “The pond bund was strengthened and desilted. This led to increased water capacity. But illegal sewage discharge from nearby residential and commercial complexes has persisted for a decade.If authorities fail to stop this, groundwater sources could be completely affected within a few years,” said Kamarajar Nagar Residents’ Welfare Association president B Niranjan Patnaik.Despite repeated warnings from the Greater Chennai Corporation, some residents continue to dump rubbish into and near the pond. The residents’ association urges the civic body to impose on-the-spot penalties on violators to deter such activities. “If the corporation stops the discharge of untreated sewage, water hyacinth will no longer grow in the pond, and groundwater contamination can be reduced,” said G Arun Kumar, project manager of Hand in Hand, a city-based NGO, which maintained the pond for the last three years.A senior official in Tiruvottiyur Zone (Zone 1) said, “Penalties will also be imposed on those dumping rubbish and construction or demolition waste near the water body,” the official said.