Clark Fork Voluntary Nutrient Reduction Program (VNRP): Final Report, 1998-2008

VNRP basics: Montana’s first large-river TMDL Goal: “restore beneficial uses and eliminate nuisance algae growth in the Clark Fork from Warm Springs to the Flathead…” Negotiated by dischargers, DEQ, and environmental groups from 1994 to 1998. Agreement signed in 1998 for 10 years Ended October, 2008.

Long-term (1984-2004) Total Phosphorus Levels in the Clark Fork above the Flathead (mg/L) Total P > 0.045 mg/L Total P =0.035 -0.044 Total P < 0.035

VNRP Algae and Nutrient Targets VNRP Algae Targets: 100 milligrams/meter2 chlorophyll a (summertime mean), and 150 milligrams/m2 (peak), chlorophyll a VNRP Nutrient Targets: 20 micrograms/Liter of Total Phosphorus (upstream of Missoula) 39 micrograms/Liter of Total Phosphorus (downstream of Missoula) 300 micrograms/Liter of Total Nitrogen (anywhere in river)

Nutrient Dischargers: *Butte WWTP *Deer Lodge WWTP *Missoula WWTP *Missoula County (septics) *Smurfit-Stone *Non-point (all) *Minor point sources: Alberton, Superior, Drummond, Philipsburg, Rocker, Hamilton, Stevensville, other industries, etc.

Missoula City and County also reduced nutrient discharge to the aquifer and river by connected existing and new residences to sewer: Over 3,100 existing homes, apartments, mobile homes connected to sewer 1998-2007. This reduced nitrogen discharge to the aquifer by at least 260 lbs/day, much of which would have ended up in the river.

SUMMARY of POINT SOURCE Summer Nutrient Reduction: 1988-2008 Discharger: 1988-90 TN, TP Load: (lbs/day) 2006/08 TN, TP Load (lbs/day): Reduction N Load (%): Reduction P Load (%): Butte WWTP: 449 N 114 P 473 N 48 P - 5% 58% Deer Lodge WWTP: 78 N 19 P 69 N 9 P 11% 53% Missoula WWTP: 841 N 173 P 652 N 42 P 22% 76% Smurfit-Stone Mill: 309 N 116 P 182 N 45 P 41% 61% Total Point Source Load: 1677 N 422 P 1376 N 144 P 18% 66%

So how’s the river?

Compliance with algae targets, 1998-2008 Site: Percent samples in compliance with the target (100 mg/M2) : Percent samples exceeding the algae target: Algae density trend (PBSJ, 2007): Clark Fork above Little Blackfoot 29% 71% Increasing Clark Fork below Missoula 30% 70% Decreasing Clark Fork at Huson 74% 26% Static

Some conclusions: VNRP signatories decreased nutrient discharge in all areas of the river, including decreases of 30% in total nitrogen and 72% in total phosphorus from 1988 to 2008. River nutrient concentrations decreased significantly at all sites, and in both the 1990s and in this decade. Algae concentrations appear to be in a decreasing trend in the middle river (below Missoula), are static in the lower river (Huson) and may be increasing slightly in the upper river. Nutrient targets set in 1998 appear to correspond with actual levels of algae in the river, i.e. areas with nutrients above targets also tend to exceed algae targets, and vice versa. The type of algae (Cladophora) predominating in the upper river is notoriously hard to control. There is a need to better understand the river ecology in that complex situation.