Draft June 25, 2021


In September 2017 the Delaware River Basin Commission (DRBC) approved Resolution 2017-4 directing DRBC staff to perform fish and dissolved oxygen (DO) studies, modeling studies, and cost/feasibility studies to define the appropriate aquatic life use for the Delaware Estuary and its supporting DO criteria, and directed DRBC’s Executive Director to initiate DRBC rulemaking to revise the designated aquatic life uses consistent with those studies. The Academy of Natural Sciences (Stoklosa et al. 2018) completed a review of dissolved oxygen requirements for aquatic species in the Delaware Estuary. In May 2020 Kleinfelder submitted a report to DRBC that estimated the costs of nitrogen and ammonia reduction at the 12 largest wastewater treatment plants that discharge to the Delaware Estuary. The University of Delaware Water Resources Center (UDWRC) applied for and received (along with co-applicant DRBC) a grant under the Delaware Watershed Research Fund (DWRF) to estimate the Economic and Social Impacts of Improved Water Quality in the Delaware Estuary in accordance with the following approach.

The UDWRC estimated costs and benefits from increased levels of wastewater treatment (ammonia and nitrogen) to improve dissolved oxygen in the Delaware Estuary. The present DO water quality standard in zones 2, 3, 4, and 5 between Trenton, Philadelphia, and Wilmington is 3.5 mg/L as a 24-hour mean during summer and 6 mg/L seasonal mean criteria during spring and fall (Table 1.1 and Figure 1.1). Costs are derived from ammonia treatment levels of 10 mg/L, 5 mg/L, and 1.5 mg/L as per Kleinfelder (2020) report. Benefits are derived for population residing in the service areas of the 12 wastewater dischargers (low range) and population within Delaware Estuary watershed as a high range (Figure 1.2 and Table 1.2). The economic analysis is conducted at DO increasing from present standard of 3.5 mg/l to 5.0 mg/l (65% saturation of DO at 30 deg C).