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Project 5: Rooney Gulch EutroSORB

The BCWA will conduct a pilot study on lower Rooney Gulch 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 effi-cient and economical solution designed for intercepting free re-active 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 will secure about 24 twenty –five pound mesh bags (total of about 600 pounds of EutroSORB filter media in the drainage channel below the culvert. The pilot project will run for about 6 months (May through October).

The Bear Creek Watershed Association (BCWA) has identified a nutrient load problem on Rooney Gulch. This tributary discharge is carried through a culvert under Morrison Road and discharges into Bear Creek near the park entrance. This historically was an intermit-tent drainage receiving flow from the large Rooney Valley area (2,740 acres). In the last 1-2 years, this discharge tended to flow more frequently, and within the last year there is flow most of the year, even in this drier year. There is a substantial new development and land clearing operation just north of Morrison Road in Rooney Valley. There is evidence of in-creased silty deposition within the stream channel in the park. There has also been increased large flow events. The new monitoring site 98a is located in the park below the culvert. The specific conductance is exceptionally high at this site (>4,500 uS). It is highly likely that this site will receive year-round flow in the coming years and will be a significant nutrient loading point to Bear Creek Reservoir. The site is monitored for background Total Nitrogen and Total Phosphorus. Based on 2020 monitoring data, this is a nutrient load tributary (August to December- 17 pounds of total phosphorus and 437 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 from 0.4 to 6.4 pounds of total phosphorus per month (averaging 3.2 pounds). The target for the demonstration project is to remove 30% of the phosphorus load. After the demonstration period, the filter mesh bags will be removed for disposal.

The cost of the EutroSORB media and mesh bags is about $1,500 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 $576 (orthophosphorus = $384; Total Phosphorus =$192). The total project cost is about $2,500.

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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