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EPA‑supported study recommends filtration for three McCall outfalls to address emerging contaminants
Summary
An EPA/DEQ technical‑assistance preliminary engineering report recommends a filtration‑based alternative to treat stormwater at three outfalls to Payette Lake, improving 6PPD‑Q removal and positioning the city for DEQ low‑interest loan funding.
City staff and consultants presented findings from an EPA/DEQ technical‑assistance preliminary engineering report on July 2, evaluating stormwater treatment options for three outfalls that discharge to Payette Lake.
Nathan Stewart, McCall’s public works director, introduced the project as a targeted study to identify treatment approaches that would make the city competitive for DEQ low‑interest loan funding to address "emerging contaminants." Chuck Kennedy, principal engineer with AECOM, described four alternatives the report evaluated: (1) maintain existing practices ("do nothing" baseline), (2) install an additional hydrodynamic separator, (3) add infiltration systems with sand prefilters, or (4) install filtration systems (biofiltration/EcoStream) with upstream hydrodynamic separators. Kennedy said the report selected alternative 4 because it best met the criteria for removing 6PPD‑Q (a tire‑related contaminant of concern for cold‑water fish), aligned with vendor testing, and would likely qualify for DEQ funding criteria.
Consultants noted tradeoffs: alternative 4 carries the highest initial construction cost but lower lifecycle maintenance and meets the 80% TSS removal standard and shows potential for 6PPD‑Q removal; infiltration alternatives could require periodic excavation and higher long‑term O&M. The report relied on EPA and other testing databases for expected pollutant removal; consultants clarified they did not sample Payette Lake directly for 6PPD‑Q within this scope.
Council asked about funding and monitoring. Staff and consultants said DEQ funding in this program is low‑interest loan (not grant), and that targeted monitoring—potentially including fish tissue sampling—would be necessary to assess whether the treatment materially improves lake conditions and to support funding applications. The council did not commit to construction but discussed using the report to pursue funding and refine designs.
Why it matters: The recommendation provides a technically justified pathway for McCall to address emerging contaminants while balancing lifecycle cost, constructability and funding eligibility. Next steps include additional monitoring, soil testing at candidate sites, design refinement, and pursuing DEQ funding when appropriate.
