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Project 6: Coyote Crossing EutroSORB

The BCWA will conduct a pilot study on lower Coyote Crossing within Bear Creek Park to reduce phosphorus loading. The BCWA will use EutroSORB (a phosphorus filtration system) to reduce phosphorus loading. EutroSORB filters are a efficient and economical solution designed for intercepting free reactive phosphorus (SRP) from moving water. The EutroSORB reactive filter media is contained in mesh bags that is secured within the flow channel and left for a specified period of time. The filter media is safe to aquatic life, does not dissolve, and is removed from the environment when the filter has met capacity. The BCWA and BCWF will secure about 20 twenty –five pound mesh bags (total of about 500 pounds of EutroSORB filter media in the lower drainage channel above the bridge crossing culvert. The pilot project will run for about 8 months (May through December).

The Bear Creek Watershed Association (BCWA) has identified a nutrient load problem on Coyote Crossing. This tributary discharges directly into Bear Creek Reservoir along side the boat launch/fishing parking lot. This tributary was historically an intermittent flow system from Green Mountain. In the last 3-5 years, this drainage system has increased flows with flow year-round flow, although the winter flows are very low. The new and continued development on Green Mountain has definitely resulted in increased base flows and much larger stormwater flows. The new monitoring site 97a is located at the road crossing bridge near the parking lot. The site is monitored for background Total Nitrogen and Total Phosphorus. It appears some of the flow comes from a leak in the Ward Ditch near Morrison Road. This drainage has produced amphibian and bird kills in Bear Creek Reservoir in the past. The increased development on Green Mountain is likely to make this a year-year nutrient loading source to the reservoir. There are some opportunities for mitigation above the maximum pool level within the park. Based on 2020 monitoring data, this is a significant nutrient load tributary (June to December– 154 pounds of total phosphorus and 931 pounds total nitrogen). The BCWA and Lakewood staff will need to clean up excess vegetation in the channel and establish sites for securing the filter media mesh bags. The BCWA and BCWF will work with EutroPhix staff in site selection and installation. The BCWA will continue routine monthly monitoring for total phosphorus and total nitrogen at the current monitoring location. The BCWA will begin sampling for soluble reactive phosphorus (orthophosphorus) above and below the project and add a sample for Total phosphorus above the project. After installation of the EutroSORB filters, the BCWA will monitor above and below demonstration site. The project is projected to remove about 3 pounds of total phosphorus per month. The target for the demonstration project is to remove 30% of the phosphorus load. After the demonstration period, the filer mesh bags will be removed for disposal.

The cost of the EutroSORB media and mesh bags is about $1,300 plus shipping. The labor will be provided by the BCWF, BCWA and Lakewood staff. The additional monitoring cost for the BCWA for the demonstration period is $705 (orthophosphorus = $512; Total Phosphorus =$193). The total project cost is about $2,000.

The BCWA will monitor for field parameters including specific conductance, water and air temperature, dissolved oxygen, pH and water flow. Laboratory samples will be collected for total phosphorus, orthophosphorus and total nitrogen. The BCWA will be able to determine load reductions from the pilot project and project future load reductions using a EutroSORB filtration system. Additionally, the BCWA and BCWF will determine the cost effectiveness of this nutrient reduction system.

This project will align multiple partners which include but not limited to Bear Creek Watershed Association, Bear Creek Watershed Foundation, City of Lakewood, and EutroPHIX.

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