Implementing BMPs as Local Limits Implementing BMPs as Local Limits City of Boise, Boise, Idaho Pretreatment Section Public Works Dept/Environmental Div. Walt Baumgartner, Program Coordinator

40CFR403.8(f)(4) Local Limits The POTW shall develop local limits as required in 403.5(c)(1), or……… … demonstrate they are not necessary.

Local Limits in Boise ? The City of Boise has a rigorous, ongoing local limits data collection, evaluation, and implementation process. Our local limits evaluation efforts are conducted in accordance with EPA Local Limits Development Guidance (EPA, 2004) and continue to show that numeric local limits currently are not necessary for any metal pollutants. The City has a long history of assessing for, developing and implementing technically based local limits when necessary to protect worker safety, the collection and treatment system, water quality and bio-solids quality for a number of industrial users on a case-by-case basis. We continue to review all new potential discharges for the need for local limits.

Some background….. Two Wastewater Plants The Lander Street WWTF began operation in 1950, and discharges treated wastewater into the Boise River (River Mile 49.7) through a submerged diffuser. The Lander Street WWTF has a 15-million-gallon-per-day (mgd) peak-month capacity. Because of hydraulic limitations, all flows in excess of capacity are diverted to the West Boise WWTF. Lander Street WWTF provides secondary treatment of wastewater utilizing the following treatment processes: screening, grit removal, primary clarification, step-feed activated sludge, secondary clarification, and ultraviolet (UV) disinfection. Primary sludge along with thickened waste activated sludge are anaerobically digested and pumped to the West Boise WWTF

The West Boise WWTF began operation in 1976, discharging treated wastewater into the south channel of the Boise River through a bank-side outfall. The plant was expanded to 24 mgd in Spring This expansion resulted in a North Plant and South Plant at the West Boise WWTF. These plants have common headworks and UV disinfection processes, with separate primary and secondary treatment.. Digested sludge from West Boise WWTF is mixed with the digested sludge from Lander Street WWTF prior to the dewatering process. The resulting biosolids are trucked to a City-owned farm for land application.

2001 Local Limits Study The City of Boise currently operates its two NPDES-permitted Wastewater Treatment Facilities under administratively extended permits originally issued in January, Both of the original NPDES permits required the City to conduct a local limits study and evaluate the need for local limits. “Within one year of the effective date of this permit modification, the permittee shall submit to EPA for review and approval, the results of a local limits study. The permittee shall conduct a local limits study to determine whether local limits are necessary.” The study shall take into account water quality in the receiving stream, inhibition levels for biological processes in the treatment plants, and sludge quality goals.

2001 Local Limits Study The study shall address at least the following pollutants: arsenic, cadmium, chromium, copper, cyanide, lead, mercury, nickel, silver, and zinc. The study shall calculate the maximum allowable headworks loading for the metals set forth above, as well as any other pollutants that reasonably may interfere with or pass through the POTW. The study shall also determine what local limits are required to ensure that the maximum headworks loadings established by the City are not exceeded.

2001 Local Limits Study The local limits study shall include a “key manhole” sampling program to characterize potential sources of contaminants within the collection system. If the permittee encounters elevated levels of metals in any of its key manhole studies, the permittee shall undertake further investigation to ascertain the source of the metals. The Guidance Manual on the Development and Implementation of Local Discharge Limits Under the Pretreatment Program (EPA, December 1987), the Draft Local Limits Development Guidance (EPA, August 2001), and the Guidance to POTWs for Development of Local Limits in EPA Region 10: A Spreadsheet-Based Approach to Calculating Local Limits (EPA Region 10, May 20, 1997 and January 21, 1999) were consulted for evaluation of the need for local limits.

And away we go…..… To gather necessary data, the City conducted extensive monitoring including the following: 1) an accelerated sampling program of the river and effluents for copper and lead; 2) a Water Effect Ratio (WER) study for copper and lead; 3) key manhole monitoring for POCs; 4) commercial and industrial user monitoring for POCs; and 5) monitoring, including influent, primary effluent, final effluent, sludge/biosolids, and receiving stream background samples. A headworks loading approach was used to evaluate the need for local limits. This approach requires the calculation of the allowable headworks loadings for each of the following environmental criteria: protection of water quality, beneficial use of biosolids, and prevention of treatment process inhibition. For each pollutant, the most stringent of the three headworks loadings was used as the MAHL.

Conclusions A comparison of the MAHLs with the actual headworks loading to the treatment plant demonstrated that the Lander Street WWTF was below MAHLs for all pollutants and the West Boise WWTF was below MAHLs for all pollutants, except mercury. The average influent loads of POCs at the Lander Street WWTF were below 60 percent of the MAHL. The maximum influent loads were also below 80 percent of the MAHL for all pollutants of concern. Local limits were not necessary. The average influent loads of POC at the West Boise WWTF were below 60 percent of the MAHL. The maximum influent load was below 80 percent of the MAHL for all pollutants except mercury. With the exception of mercury, local limits were not necessary.

Hg ? A total of 12 influent samples were collected and analyzed for mercury. Two of the twelve samples exceeded the MAHL. All the other sample results were less than 50 percent of the MAHL. A review of the influent data for the West Boise plant indicated that the plant appeared to receive higher concentrations of mercury on occasion than the Lander Street WWTF. However, the industrial flow to the West Boise facility was only 2 percent of the overall flow and much of that was flow diverted from the Lander Street WWTF. In addition, low-level mercury analyses, using EPA Method 1631, were voluntarily conducted by Micron Technology, Inc., Boise’s largest significant industrial user. The results revealed that mercury loads in the discharges from this facility were essentially zero. We believed that our permitted users were not contributing mercury at levels that would account for the periodic spikes in influent mercury concentrations. We concluded the elevated influent mercury was coming from uncontrolled or other commercial sources.

BMP Approach for Hg Since mercury did not appear to be a POC with the City’s permitted industrial users, the traditional approach of developing and implementing a local limit would likely not result in reduced mercury loading to the WWTF. The City’s Haz Waste Program had already implemented a national award-winning mercury thermometer collection program. A local limit for mercury was not proposed. Our approach was to implement BMPs and P2 practices, such as those successfully implemented in Oregon and other states, in lieu of establishing a local limit for mercury.

Dental BMP The City met with the Idaho State Dental Association (ISDA) in August 2002 and initiated dialogue regarding the impacts of mercury discharges on water quality. As a result, ISDA developed and adopted BMP guidelines for dental care providers that included nine (9) mandatory and six (6) recommended BMPs. The BMPs were forwarded to the ISDA membership in August 2003 with the goal of full voluntary implementation state wide by October 1, Pretreatment staff developed and initiated a Dental Office inspection program in Boise during the 2005 reporting year and continued the effort through 2006/ facilities total were inspected during the outreach effort. All were found to be using amalgam traps. Over one-third have installed (non-mandatory) amalgam separators, and 60% of facilities were found to have implemented fluorescent tube recycling measures.

Streamlining and BMPs On December 1, 2006, the City of Boise notified the USEPA - Region 10 office of a non-substantial modification to its approved Pretreatment Program. The basis for the program modification was to revise the City’s Pretreatment Ordinance - Title 8, Chapter 14 so as to be consistent with changes to the General Pretreatment Regulations at 40 CFR 403, generally referred to as the Streamlining Rule. In the Streamlining Rule, EPA clarified that BMPs could be developed by a Publicly Owned Treatment Work (POTW) to enforce the general and specific discharge prohibitions in lieu of or in addition to specific numerical discharge limits. However, EPA made clear in 40CFR403 that “Such BMPs shall be considered local limits and Pretreatment Standards…”and as such must be fully enforceable. Language in City Code Title 8, Chapter 14 was revised accordingly.

The Legal Link Historically, Pretreatment staff has encouraged the voluntary use of BMPs by food service/restaurant facilities, photographic/printing facilities and dental offices in order to limit the discharge of specific pollutants to the sanitary sewer. The specific pollutants are, respectively: fat/oil/grease (FOG), silver (photo development) and mercury (dental amalgam). After EPA approved the program modification in January 2007, staff determined that the City should formally adopt the BMPs for dental offices, food service facilities and silver dischargers so as to provide a clear link to the City’s Pretreatment Regulations Title 8, Chapter 14 and the required enforcement authority it provides. The set of BMPs were formally adopted by the City Council on May 1st, 2007

The BMPs Adopted Fats, Oil and Grease (FOG) Best Management Practices (BMPs) for Food Service Facilities (2/2006) Best Management Practices for Dental Offices (9/2003) Code of Management Practice for Silver Discharges (11/1996)

City of Boise, Boise, Idaho Public Works Dept Pretreatment Section Walt Baumgartner, Program Coordinator Water Quality Laboratory Marcia Schmelzer, Lab Director