The City of Pineville is one of four (4) cities in the Commonwealth of Kentucky that has an existing combined sanitary/storm sewer system. In this collection system, sanitary sewage and storm water enter the same underground pipe network. During low flow, all this water and waste runs to the City’s wastewater treatment plant. However, during periods of high flow, a portion of the water bypasses the existing pumping stations, thereby dumping raw sewage into the Cumberland River.
In 2008, the City of Pineville entered into a consent judgment with the Environmental Protection Agency (EPA) and the Commonwealth of Kentucky. This consent judgment laid the groundwork for the separation of the sanitary and storm sewer within the City. The first step in this process was to separate the sewers along Kentucky Avenue and along the side streets one block to the west. Vaughn & Melton was awarded the project in early 2009. To qualify for certain stimulus funding, the project was required to be under a construction contract by February 2010. To allow time for the required Kentucky Division of Water review and to procure a construction contractor, the design had to be completed on an accelerated schedule.
The project design began with the surveying and mapping of Kentucky Avenue and associated side streets along with video inspection and survey of the existing combined sewer system piping. This initial phase of the design revealed the real challenge for this project: designing a system that would not interfere with the existing utilities, including the existing combined sewer. The existing combined system was required to remain in operation in order to carry the combined sanitary/storm sewer flow from the rest of the City to the existing pumping station and also to continue service of the project area until the project is complete and property owner laterals can be changed to the new sanitary line.
The most complicated design aspect of the project involved an existing 48” pipe that crossed Kentucky Avenue in an L-pattern. This pipe, which carries flow from other areas of the City, as well outside the City, could not be disturbed. To overcome this obstacle, the new sanitary sewer line was designed at an elevation below the existing 48” pipe and the storm sewer was designed above the pipe. The storm sewer design required the use of a 4’X2’ precast concrete box culvert due to the low clearance between the existing 48” pipe and the street pavement.