The city of Martinsville, Virginia, has long been known for an economy built on tobacco, textiles, and furniture manufacturing. In recent years, with its legacy industries in decline, the city has strategically posi- tioned itself for next-generation technology and manufacturing sectors. Set along the state’s southern border with North Carolina, Martinsville is also known for its recreational areas, including the trout-filled Smith River, a state scenic river and popular local waterway for fishing and boating. The city’s 6.2-mile interceptor sewer, which runs adjacent to the Smith River, is the major collector for the city’s sanitary sewer system and also collects the majority of wastewater from the Henry County Public Service Authority. Constructed in 1963, the interceptor consists of 36- inch and 42-inch corrugated metal and reinforced concrete pipe. The line had been heavily used to serve the city’s industries for decades and, after more than 50 years of use, was showing signs of both severe corrosion and structural defects. Mitigating Risk: Protecting the Community The Martinsville Water Resources Department contracted with Dew- berry to perform a condition assessment using multisensory technol- ogy, including CCTV, laser, and ultrasonic profiling. The assessment revealed severe defects, including the heavy corrosion, excess pipe ovality, and numerous inflow and infiltration manhole and line defects. Dewberry’s team identified segments of pipe that were as much as 80 percent collapsed, a potential threat to the viability of local industries as well as the environmental integrity of the Smith River—not only a recreational destination but a source of drinking water for the region as well. Recognizing the high risks associated with the discovered collapse, Dewberry immediately provided assistance in mitigation planning. This effort led to the installation of an emergency pump bypass line, establishment of a pump staging area, and the execution of an agree- ment with an emergency pump provider. Additionally, a comprehen- sive Preliminary Engineering Report was prepared compliant with key funding agency requirements. The report included the results of the condition assessment, an evaluation of rehabilitation alternatives, work prioritization, and rehabilitation costs estimates. While the report was being finalized, Dewberry initiated design for the repair of the 80 percent collapse, which was located along an unstable, steep embankment at the edge of the Smith River. Before an excavation of the existing sewer could be made, a 35-foot soil nail wall had to be constructed. The retaining wall was also necessary to protect a major gas line and upgradient roadway and railroad. Rehabilitating the Martinsville Interceptor Creative Delivery Proves Cost-Efficient for Rural Community By Leslie Barksdale, PE
Bypass piping alongside the existing corrugated metal pipe was installed to prevent a major sewer release.
With full replacement of the interceptor estimated at an untenable $40 to $50 million, the City of Martinsville asked Dewberry to pursue fund- ing options as well as creative design and delivery methods to mitigate the costs and address the most critically needed repairs. The firm was able to secure a zero percent interest loan from the Virginia Depart- ment of Environmental Quality (DEQ) and grant funds, including a $1 million grant from the U.S. Department of Commerce Economic Dewberry devised an innovative, multiple-contract approach for the complex project that enabled contractors to select rehabilitation meth- ods for repair or lining of the corrugated metal pipe. The multi-phase delivery, separated into four construction contracts, proved effective, maintaining the sequencing of critical phases of work while allowing Development Administration (EDA). Creative Contract Sequencing A 35-foot-high retaining wall, extending more than 400 feet in length, was permanently installed along the site of the major collapse of the sewer line to enable safe excavation and protect a nearby gas line.
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may 2020
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