Dover Road Wastewater Pump Station Project
On August 3, 2009 the Durham NH Town Council held a public hearing on a bond referendum and approved applying for a low interest loan through the NH State Revolving Loan Fund for the rehabilitation of the Dover Road Wastewater Pump Station in the amount of $1,231,055. The Town received a Federal stimulus grant from the American Recovery and Reinvestment Act covering half the $1,231,055 project cost or approximately $615,000.
The existing Dover Road Pump Station is a small brick building that sits between Dover Road (Route 108) and the Oyster River near the outlet of Beards Creek. It was built in 1964 and operates 24 hours per day / 7 days per week continuously pumping virtually all of Durham's wastewater to the Wastewater Treatment Plant.
On average the pump station conveys 1.2 million gallons per day (MGD) of wastewater and up to 7 MGD during heavy rain storms. This pump station is one of the most critical pieces of infrastructure in the Town's wastewater system.
It still contains the three original 50 horse power pumps which all been rebuilt several times each. The building has a number of operational issues, including a leaky flat roof, outdated electrical controls, poor ventilation, and a wet well almost impossible to maintain. The pumps are located in dank basement area with restricted access.
The rehabilitation project includes the construction of a new submersible wastewater pump station with a self-cleaning trench-style wet well located underground and immediately next to the existing building.
In trench-type wet wells, the pump intakes are placed near the bottom of a deep, narrow trench sharing one axis with the inlet pipe but considerably below it. The closely confining walls of the trench prevent cross currents, which creates a good hydraulic environment for the pump intakes. The trench works very well for both water and wastewater.
The feature that makes the trench-type wet well so attractive to wastewater operators who have used one is its ability to self-clean by using only the main pumps. Other types of wet wells must be cleaned manually or by vacuum truck. During the cleaning cycle in a trench-type wet well, all scum, sludge, grit, gravel, rags and other trash are swept into the last pump by water accelerated to a high velocity by flowing down the curved ramp. Cleaning can be completed in one to four minutes with no manual labor beyond the touch of a button. The process can be automated to occur at any desired time intervals, such as once every three days or once per week. Because the trench can easily be kept clean and odor-free, this type of wet well can be placed anywhere (in residential, commercial or business districts) without adverse odor impact.
The existing building will house the new electrical controls and is slated to receive a more architecturally interesting (and functional) gabled roof. By locating the new pump station on the same site it will allow the existing pump station to continue to operate uninterrupted throughout the project.
Below are pictures of the project that is currently underway.