In May 2007, Billerica was the subject of legal action and forced to pay a $250,000 penalty for discharging pollutants into the Concord River. The action was brought by the U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (MassDEP) because the town of Billerica exceeded allowable effluent limits for phosphorus, fecal coliform bacteria, pH, and ammonia nitrogen. The town was also charged with failing to submit discharge monitoring reports, failing to comply with monitoring requirements, and failing to submit infiltration and inflow reporting. According to the EPA, Billerica's discharges of phosphorus created an overabundance of nutrients, which damaged the river by stimulating excessive aquatic plant growth.