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Project 2: Coyote Gulch EutroSORB Pilot

There is an opportunity by the Association to conduct a pilot program on Coyote Gulch that could augment the wetland TP reduction. The Association has reviewed a pilot nutrient reduction system with the company EutroPHIXTM. They have developed a nutrient filtration technology called EutroSORBTM. The EutroSORBTM filtration bags contain a phosphorus absorption material that removes TP from the flow stream as the water flows through and over the bags. The pilot project would securely place specialized large bags of the EutroSORBTM below each of the seven rock drop structures in the plunge pools. The filtration system would remove the free reactive phosphorus from the water and rapidly form it into a highly stable insoluble mineral within the filtration bags. It is estimated that this pilot project would remove about 30 additional pounds of TP (about 1/2 of the current annual load) from reaching the reservoir. The pilot project will be operated for 1-year. The actual TP removal will be monitored using the existing Association monitoring plan and assessed seasonally.

The Bear Creek Watershed Association has monitored, since 2013, the Coyote Gulch erosion restoration and wetland enhancement project in the Bear Creek Park for nutrient load reductions. The monitoring is done at two sampling sites: above the restoration project (Upper Coyote), and at the discharge into the reservoir (Lower Coyote). The Association collects chemistry data for total phosphorus (TP) and total nitrogen (TN), measures bi- monthly flows, and collects data for temperature, pH, specific conductance and Dissolved Oxygen. Data results are incorporated into the Association annual data summaries. The Association has pre-construction and post-construction loading data. The post-construction monitoring project has established an annual total phosphorus trade credit for potential use of the Association membership. The effectiveness of the wetlands to reduce nutrient loads has diminished after the wetlands matured. As such, measurable increases in phosphorus loading into Bear Creek Reservoir has occurred in recent years. The Association phosphorus management program targets maximum TP reduction from tributary systems.

The estimated cost for this pilot project is $7,500 for the EutroSORBTM filtration system plus the labor for installation. The Association and City of Lakewood will provide labor and assistance for the project in cooperation with EutroPHIXTM. The Association will administer the monitoring program and cover the laboratory analysis cost. The Association may increase the field monitoring during the pilot project to monthly sampling, including more de-tailed flow assessments. The Bear Creek Watershed Foundation will seek grant funding for the pilot project, expected not to exceed $10,000. At the completion of the project, the filtration bags will be removed for disposal. There will be some labor and disposal fees.

The Association will need to coordinate this project with the Army Corps of Engineers. The pilot will determine the value of using a filtration reduction technology on small tributary waters. The cost effectiveness of TP reduction (total pounds/unit flow or load reduction) will be assessed and applied to the Association phosphorus trading program. This TP management technology can then be transferred to other tributaries in the watershed. The pilot program will monitor the TP/TN loading in Coyote Gulch. The Association will also need to monitor the soluble reactive phosphorus or ortho-phosphorus during the pilot project. The standard field parameters (temperature, pH, specific conductance and Dissolved Oxygen) will be measured. The pilot will estimate the additional benefit of filtration technology in conjunction with wetland nutrient removal and establish a trade credit value.

This project will align multiple partners which include but not limited to Bear Creek Watershed Association, Bear Creek Watershed Foundation, U.S. Army Corps of Engineers, City of Lakewood and EutroPHIXTM.

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