The Lost Assets:Protecting Sewer Creek Crossings and the Environment The Creek Protection Project, Sacramento Area Sewer District Sacramento, California
Abstract:Creek crossings are inherently the weak points of any wastewater system due to limited access and environmental issues which complicate maintenance and repairs, and large runoffflows that can damage pipelines and manholes. The Creek Protection Project (CPP) is the primary step to helping the Sacramen to Area Sewer District(SASD) increase the integrity of these criticalpoints. SASD owns and maintains approximately 3,000 miles of sanitary sewers. Of these sewers, there are 672 pipes that cross creeks, sloughs, and/or channels. Sanitary sewer overflows(SSOs) into open channels pose a risk to public health and safety and have significant environmental impacts. SASD has committed to the Central Valley Regional Water Quality Control Board to develop and implement a program to reduce therisk of, and improve the response to, SSOs that occur at crossings.
The primarygoal of the project is to protect public health and safety and to protect stream health by reducing the risk of SSOs at waterway crossings. The project objectives were separated into two parts: evaluateand prepare preliminary designs for crossings deemed “most at risk of loss of structural support ” by the District, and to prioritize the crossings for the development of protection plans. The work associated with these objectives was performed simultaneously.
As part of the preliminary design objective, a comprehensive field investigation program was conducted for 41 crossings previously found to have significant problems. This investigation was conducted by acivil engineer, a geomorphologist, an environmental scientist, and ageotechnical engineer and in some cases a structural engineer. Based on this investigation, the crossings were categorized as “Monitor ”, “Preliminary Design ”, or “Phase 2 ” based on the recommended action required for the individual crossing. Using the results and recommendations from the field investigation, the District now has detailed documentation and a better understanding of their highest priority crossings. Currently, the design documents are being developed for 14 sites.
The other component of the project was the prioritization of creeks for the development of creek protection plans. A model was developed using the concepts of risk analysis — consequence of failure and likelihood of failure. Due to the large quantity of creek crossings in the SASD system, the model was based on sectioning and analyzing the water ways with creek crossings instead of the individual creek crossing. Of the 100 waterway segments analyzed in the model, 17 waterways segments were found to be high priority. Creek Protection Plans were developed for these 17 waterways to assist the District during emergency situations by providing needed information in an easy to use format.
This paper discusses the project as awhole from inception to completion and provides an open discussion of the development of techniques used in the field investigations, categorization of individual sewer crossings, prioritization of waterways and creation of creek protection plans.
Document Type: Research Article
Publication date: 2010-01-01
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