Kleinfelder completed a phosphorus evaluation study with two primary objectives: to determine whether designated uses were being impaired due to elevated levels of phosphorus in the Assunpink Creek in the vicinity of the ELSA Wastewater Treatment Plant (WWTP) discharge, and whether the plant was the source of impairment. The study was to become the basis for potential new effluent limits to be imposed upon the plant’s discharge.
Kleinfelder had to evaluate impairment using metrics including dissolved oxygen (DO), pH, phytoplankton biomass, and periphyton biomass. Each of the parameters was measured at multiple locations over variable durations and times of day. The sampling and analysis plan was designed to provide data that could support a regulatory determination and identify or exclude specific contributing nutrient sources.
The study determined that there is no evidence that phosphorus discharges from the ELSA WWTP were rendering the lower Assunpink Creek unsuitable for its designated uses. On the contrary, existing levels of plant productivity in the stream were below threshold levels for algae, and diurnal dissolved oxygen swings under critical conditions were below the productivity assessment threshold at all locations downstream of the ELSA WWTP discharge.
The data collected and the analysis performed demonstrated that there is no evidence of a eutrophication problem in the lower Assunpink Creek downstream of the ELSA WWTP. Based on this analysis, the New Jersey Department of Environmental Protection was able to determine that a phosphorus effluent limitation was not needed for the ELSA WWTP discharge.
Lawrenceville, New Jersey
Ewing Lawrence Sewerage Authority (ESLA)