Innovations in CSO and SSO Long Term Control Plans
Many cities in the United States are currently developing Long Term Control Plans (LTCP) to control Combined Sewer Overflows (CSO) and Sanitary Sewer Overflows (SSO). Most of these plans are mandated by Clean Water Act regulatory requirements such as consent orders from state environmental protection agencies and consent decrees from the federal Environmental Protection Agency (EPA). These plans are required to recommend a facility plan to meet an appropriate level of CSO and SSO control. Development of these plans requires innovative, efficient, and cost-effective surveying, mapping, monitoring, modeling, costing, and alternative ranking techniques. This paper will present some innovative techniques used in an LTCP project described below recently completed by Michael Baker Corporation of Pittsburgh, Pennsylvania.
Located in Southwestern Pennsylvania near Pittsburgh, the Rochester Area Joint Sewer Authority (RAJSA) owns and operates a wastewater treatment plant (WWTP) and interceptor system that treats and conveys wastewater flows from five municipalities. The service population is about 9,200 and service area is about 1420 acres. The secondary treatment WWTP was designed and permitted for an average monthly dry weather flow limit of 1.40 MGD, average monthly wet weather flow limit of 2.25 MGD, and a peak hourly flow limit of 4.70 MGD. There are six (6) active CSOs and two (2) active SSOs in the RAJSA sewer system. The RAJSA interceptor system, located along the Ohio and Beaver Rivers, consists of approximately 3.2 miles of sewers ranging in size from 10 inches to 24 inches. The Rochester Borough sewer system, which is partially combined, consists of approximately 14.5 miles of sewers ranging in size from 6 inches to 54 inches. The East Rochester Borough sewer system, which is largely separate, consists of approximately 3.47 miles of sewers ranging in size from 4 inches to 24 inches. The Freedom Borough sewer system, which is 100% separate, consists of approximately 8.31 miles of sewers ranging in size from 4 inches to 24 inches. The Rochester Township sewer system, which is 100% separate, consists of approximately 13 miles of sewers ranging in size from 8 inches to 10 inches.
The paper will focus on the following topics from the above case study:
1. GIS mapping
2. Hydrologic and hydraulic modeling using SWMM5 and PCSWMM
3. Model calibration
4. Alternative cost estimating tool
5. Alternative ranking tool
6. Recommended facility plan
7. Lessons learned
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