Big Four Hollow is located in Section 14 of Ward Township in Hocking County and lies within the 14-digit HUC unit #05030204060030. The project site covers 285 acres of a 410 acre sub-watershed (Big Four Hollow) draining to Monday Creek. Big Four Hollow is underlain by deep mines and has been surface mined around the hills where the coal crop was accessible causing many AMD seeps to discharge in the basin. The design was completed by USFS and TN & A for $19,000.
The treatment approach for this site was to install two limestone leach beds (3000 sq. ft) and approximately 1,400 linear feet of limestone channel (OLC). The goal of the project was to decrease acidity concentrations by 82% at station BF00400. However, only 27% of the acidity concentration has been decreased at site BF00400. Construction was complete September 17, 2001, by Pangea for a cost of $320,000. The funding sources for this project were USFS for the design and MCRP, ODNR-DMRM and USFS for construction. Approximately 121 lbs/day of acid and 0 lbs/day of metals were prevented from entering into Monday Creek as a result of this AMD reclamation project. This project was designed to reduce acidity, not metals.
Aluminum Retaining wetland was installed during the fall of 2015.
The Goal of the Big Four Hollow Wetland is to reduce the remaining metal (aluminum) loadings by 30% (1,145 pounds per year) and provide a location for aluminum ions to bond making them less toxic to fish in Monday Creek. Increased retention time in wetland cell 3 will allow for the settling of suspended aluminum resulting from the upstream LLB treatment. Aluminum that does not settle in cell 3 will move to cells 1 and 2 where these shallow plant filled wetland cells will allow the aluminum ions to come in contact with organic carbon and humic acids that are present in the wetland. Portions of aluminum become bound and less toxic when dissolved organic carbon is present (Evans, Brown and Hara). Although the reduction goal is relatively low (30%) the reduction in aluminum toxicity as a result of aluminum ions bonding with organic carbon in the wetland will significantly reduce the harmful effects on biology in Monday Creek. Aluminum can be very toxic to biological health in stream systems and is one of the limiting factors to a healthy biological population in Monday Creek.
By removing 30% of the aluminum load and allowing the aluminum ions to bond with organic carbon ions in a wetland environment (thus limiting their availability to fish) this project will help improve a reach of Monday Creek where water quality is relatively good (net alkaline and pH ¬> 6.5) and Qualitative Habitat Evaluation Index (QHEI) scores are very good (approximately 75), but biological populations are continuing to suffer due to excessive amounts of aluminum in the water resulting from AMD pollution. The additional removal of aluminum as a result of the Big Four Wetland project will help achieve the overall biological recovery goal in Monday Creek, which is to meet the aquatic life use designation of warm water habitat (WWH).