Located within the Eco-City development area is an existing 3.0km2 wastewater impoundment lake that has been receiving domestic and industrial wastewater impoundment lake is surrounded by a 3m high perimeter earth dyke and has an impoundment capacity of 5.6 million m3. At the Southern end of this lake are two pipe sluice gates which enable lake discharge via the 1,000 year old Ji Canal directly to the Bohai Sea. During the rainy season when the Ji Canal is prone to overflowing, the sluice gates are closed to prevent river water backflow into the wastewater impoundment lake.
Central to the Eco-City development is the plan to remediate the wastewater impoundment lake that has become laden with contaminated sediments as a result of years of domestic and industrial waste runoff. The water and sediments within the impoundment are contaminated with high levels of heavy metals of mercury, arsenic, copper and cadmium, as well as hexachlorobenzene and DDT. According to the plan the wastewater impoundment was to be transformed into a wetland and recreational lake.