In February 2011, water regulators cited the city for letting tens of thousands of gallons of sewage reach the ocean in six spills since 2005. A report in June 2011 by the Natural Resources Defense Council listed Avalon as having one of the 10 most chronically polluted beaches in the United States. The pollution was caused by the city's sewer system, made of century-old clay and metal pipes. By 2011, city had spent $3.5 million testing and rehabilitating sewer lines, but the water was no cleaner. In February 2012, a cease and desist order was issued against the city for illegally discharging polluted water into the bay. After the cease and desist order, the city invested an additional $5.7 million on sewer main improvements and inspection and tracking systems. As a result of these efforts, the 2014 report showed that water quality had improved, and Avalon Beach was removed from the list of the most polluted beaches.