Hangman Creek Water Quality Improvement

Planning Meeting

June 21, 2007

Chair:              Elaine Snouwaert, Department of Ecology

Present:          Ben Peterson, Spokane County Conservation District

Scott Fields, Coeur D’Alene Tribe

Reanette Boese, Spokane County

Gary Ostheller

Layne Merritt, Century West Engineering

Micki Harnois, Town of Rockford

Ben Brattebo, Spokane County

Joe Joy, Ecology

David Tysz

Richard Weatherly, Tekoa

Introductions

The meeting was called to order at 6:40 p.m.  The May 24th minutes were reviewed.  No corrections were noted.  It was motioned by Reanette Boese to approve the minutes, seconded by Gary Ostheller.  Motion passed.

Public Comment

Reanette announced that the county had a map of the septic system distribution in Hangman Creek. Joe Joy will be using this map to improve the septic system estimates used in the WARMF model. Reanette said she would send the map to anyone who would like it but it’s a very large file so she didn’t want to send to the entire email list.

Scott Fields noted that the Idaho DEQ TMDL is not yet approved. Elaine Snouwaert stated that she thought EPA may have some issues with the temperature portion of their TMDL.

Review of WARMF model inputs

Joe Joy (Department of Ecology) reviewed his progress calibrating and running the WARMF model.  The model calibration corrections included:

• Adjusting the current land use to reflect 10% of agriculture using a direct seed cropping system.
• Adjusted the cropping factor to suggested limits. The consultant had set the cropping factor (how erosive the land use is) an order of magnitude off of the recommended cropping factors of 0.1-0.9.  Joe will ask the consultants why they used numbers so far off of the recommendations.

Joe has also tried to determine why the model is predicting such low amounts of stream bank erosion on the Idaho side of the border. He tried to adjust snow melt and sediment particle size but was unable to find a workable adjustment. Several people suggested that maybe sinuosity inputs are affecting the models predictions.

Joe also used information provided by the CDA Tribe to verify septic system density on the CDA reservation.  Joe will use the septic tank information Reanette provided to adjust the density on the Washington side.

Joe presented comparisons of current conditions to reference conditions at:

• Hangman at mouth
• Hangman at state line
• Hangman at Bradshaw Rd
• Rock Creek
• Hangman at Duncan
• Marshall Creek

The reference condition (best future condition) was defined as

• No point sources
• Ten foot riparian buffers
• Increased forest cover above Rockford and Tensed
• Limited residential growth in lower watershed
• 60 percent of agriculture in direct seed

Joe explained how he combined the WARMF predictions with the monthly multiple regressions loads calculated at the mouth. The multiple regressions at the mouth have shown strong calibration with real data. Therefore Joe used the percent reductions the WARMF model predicted for the reference condition and applied those to the multiple regression loads.   Using the most recent WARMF configuration it was predicted that even under reference conditions (best possible future conditions) that the mouth of Hangman Creek would rarely meet the Spokane River DO TMDL allocations during April and May. 

The advisory group supported the direction and values Joe is using to model Hangman Creek despite some questions about the WARMF output. Comparing the relative values WARMF is predicting appears to be concurrent with the common sense test. 

The group asked Joe to compare current land use to current loading scenarios to make sure they are consistent.

NEXT MEETING

The next meeting is scheduled for September 20^th to allow Joe more time to complete modeling runs. 

ADJOURN

The meeting was adjourned at 8:30 p.m.