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Project Details

The Lark Monofill Project

CEL was contacted to conduct a field study on buried biosolids. CEL The Lark Monofill Site, which is approximately 190 acres in size, in Salt Lake, County. The site has been historically used by the South Valley Water Reclamation Facility (SVWRF) to surface dispose dewatered sewage sludge in narrow trenches. Historical data indicate that between the years 1983 and 1999, approximately 45,000 dry tons of sewage sludge were disposed in narrow trenches that varied from about ten to twelve feet in depth. With the high rate of building construction presently occurring in Salt Lake County, the Lark Monofill site property is now viewed as a valuable residential and commercial development location. However, recent studies have reported that the presence of buried sewage sludge severely reduces the bearing capacity of the soils as well as generates methane gas, which is a potential explosive/safety hazard for surrounding property. Owners and potential buyers of the site would like to determine the technical, regulatory and financial feasibility of removing the buried sewage sludge, treating it to at least a Class B quality and recycling the material as a low cost soil amendment and/or fertilizer. If results from the pilot treatment tests support the reclassification of the buried sludge to a Class B biosolids product, the treatment process shall be replicated at full scale to transform the entire 45,000 dry tons of buried sludge to a Class B biosolids product. The final biosolids product shall be land applied at agronomic rates on selected agricultural fields in Utah. The scope of work described in this workplan covers both an initial sewage sludge quality sampling activity as well as a three (3) month pilot test aimed at converting excavated municipal sewage sludge into a Class B biosolids product suitable for recycling. The initial sampling of excavated sewage sludge is to establish the background (or baseline) quality of the material prior to the three month pilot test. If it were determined that the baseline sludge quality meets the threshold for a Class B biosolids product, an appeal will be made to the State of Utah to have the Lark monofill sewage sludge reclassified a Class B biosolids without further treatment. However, if the State of Utah Division of Water Quality (DWQ) requires that the excavated sewage sludge be subjected to a legally recognized Class B treatment process, air-drying shall be the preferred treatment approach. A three month pilot study shall then be conducted to evaluate the effectiveness of air-drying to transform the excavated sewage sludge to a Class B biosolids.

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