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MS4 subcommittee hears DEC analysis on stream restoration as low-cost source of phosphorus-reduction credits
Summary
DEC staff presented analysis showing floodplain reconnection projects can generate phosphorus-reduction credits at roughly $321 per kg/year—far lower than many engineered stormwater or road erosion fixes—and the subcommittee asked DEC for more precise crediting methods before municipalities commit funds.
Emily Schelley of the Vermont Department of Environmental Conservation (DEC) presented to the Chittenden County Regional Planning Commission (CCRPC) MS4 Subcommittee on Feb. 4, 2020, describing how natural resource projects such as floodplain reconnection could generate quantifiable phosphorus-reduction credits.
Scheley told the subcommittee that TMDL (total maximum daily load) frameworks include both wasteload allocations (for wastewater, stormwater and treated CSOs) and load allocations (for forest and agricultural lands and stream-channel instability). She said reconnecting streams to their floodplains increases deposition and adsorption of phosphorus by boosting floodplain storage, and that calculating P-removal rates requires flow data, topographic data, surface-roughness estimates, land-cover information, export coefficients and floodplain efficiency factors.
Using test sites in the Lamoille River drainage, DEC staff presented an average Total P-removal cost for floodplain reconnection projects of about $321 per kilogram per year. By comparison, the presentation said typical stormwater treatment projects average $26,000–$85,000 per kg/year and road-erosion remediation projects average $14,000–$67,000 per kg/year. Scheley also noted co-benefits including improved habitat and greater flood resilience.
Staci Pomeroy (DEC) said she participates in a DEC "Functioning Floodplain Initiative" working group and offered to help identify candidate projects; she noted that older River Corridor Plans and Fluvial Erosion Hazard Assessments commonly recommended floodplain reconnection actions.
Members pressed on how much credit MS4 communities could expect to receive for such projects. CCRPC staff member Dan Albrecht said municipalities are still implementing projects identified in Flow Restoration Plans and completing their first Phosphorus Control Plans; he warned that without clearer, project-specific crediting, MS4s may be reluctant to invest staff time or funds. Members also emphasized the need to address significant upstream stormwater discharges—such as parking lots and roads—before undertaking reconnection projects.
Christy Witters (DEC) said the agency would continue refining its analysis to produce more specific credit estimates. The group also identified the Water Infrastructure Sponsorship Program (WISPr) grant as a potential funding source. The subcommittee concluded by agreeing that interested members and DEC staff should continue to explore whether and how stream restoration projects could generate reliable phosphorus-reduction credits.
The MS4 Subcommittee is expected to follow up with DEC staff as the agency refines its methods and as potential projects are identified; no formal crediting policy or binding decisions were adopted at the Feb. 4 meeting.
