Has EPA Shown its Hand on Steam Electric Effluent Guidelines?
By Larry Kane, Attorney, Bingham Greenebaum Doll LLP
A currently pending proposal for renewal of an NPDES permit for a New Hampshire power plant may provide some insight into U.S. EPA’s thinking for the next generation of effluent limitation guidelines (ELGs) for the steam electric generating point source category. The draft NPDES permit for the Merrimack Station of Public Service of New Hampshire (PSNH) was released for public comment by U.S. EPA, Region 1, on September 30, 2011. Merrimack Station has two coal-fired steam electric generating units, both built in the 1960s, totaling 470 MW in generation capacity, as well as two small oil-fired combustion turbines. Merrimack Station’s NPDES permit expired by its express terms in 1997 and has been administratively extended since that time.
Of particular interest is U.S. EPA’s approach to permitting of wastewater resulting from management of the flue gas desulfurization (FGD) system being installed at the station for control of SO2 emissions. Wastewater from FGD control systems is not specifically addressed in the existing ELGs that specify effluent limitations representing Best Practicable Control Technology Currently Available (BPT) and Best Available Technology Economically Achievable (BAT) for the steam electric generating category codified at 40 CFR Part 423. Instead, FGD wastewater is simply referenced in a catch-all category of “low volume” wastewaters from power plant operations.
In the Merrimack Station’s draft permit, U.S. EPA has developed technology-based BAT limits for several toxic and nonconventional pollutants projected to be present in the effluent from the proposed FGD wastewater treatment system. These BAT limits have been developed through the application of “best professional judgment” (BPJ), predicated on the authority of Section 402(a)(1)(B) of the Clean Water Act (CWA). U.S. EPA prepared a 52-page supplement (Attachment E) to the Fact Sheet for the draft permit to explain its methodology in using BPJ to develop BAT effluent limitations for the FGD wastewater. The BPJ/BAT limits were shaped in large part by PSNH’s selection (approved by U.S. EPA) of physical/chemical treatment for the FGD wastewater, following its evaluation of eleven candidate treatment technologies, including flue gas injection, fixation, deep well injection, effluent reuse/recycle, settling ponds, vapor-compression evaporation, physical/chemical treatment, and physical/chemical treatment with added biological stage. The selected physical/chemical treatment system includes two precipitation steps with chemical addition, followed by clarification and a final step for enhanced mercury removal involving filtration through proprietary adsorbent media. Proposed effluent limitations for BPJ/BAT were developed for eleven pollutants: arsenic, cadmium, chromium, copper, lead, manganese, mercury, selenium, zinc, chlorides and TDS. Proposed limits are relatively stringent, ranging between 10 and 50 ug/l (ppb) for six of the toxic metals. Notably, proposed BAT limits for five of these parameters were developed by the Engineering and Analysis Division of U.S. EPA’s Office of Water.
In addition to developing proposed BPJ/BAT for the FGD system at Merrimack Station, U.S. EPA also took into account an antidegradation review by the state water quality agency (New Hampshire Department of Environmental Services) triggered by the addition of a new wastewater stream from the proposed FGD system. Interestingly, under New Hampshire’s antidegradation program, the threshold for a significant lowering of water quality that triggers restrictions on the addition of new pollutant loadings is twenty percent (20%) of available assimilative capacity of the water body in question, as compared to 10% under Indiana’s antidegradation implementation rules for the Great Lakes Basin.
That U.S. EPA Headquarters staff assisted in development of the proposed BPJ/BAT effluent limitations for the Merrimack Station’s FGD wastewater may give rise to speculation that the result of this assistance offers a preview of BAT ELG values for the steam electric point source category to be unveiled when U.S. EPA publishes a proposed ELG regulation for comment sometime in mid-2012. The discussion of FGD wastewater dominated U.S. EPA’s final report on the Steam Electric Power Generating Point Source Category (EPA 821-R-09-008) issued in October 2009.