Four Mile Pump Station Upgrades

Location: 
Alexandria, VA
Client: 
Alexandria Renew Enterprises
Contract Value: 
$7,386,000
Year Completed: 
2016
Sector: 
Expertise: 
The Clark team performed a rehabilitation and upgrade of the existing pump station that services Alexandria Renew Enterprises’ wastewater treatment plant in Alexandria, VA. 
 
After demolishing the existing pump station, the team removed 2,500 cubic-yards of contaminated soil from the site before support of excavation (SOE) efforts began. Using deep wells, the area inside the SOE was dewatered in order to place forms, rebar, and concrete. The team installed 44 steel bearing piles to support four independent structures: the submersible pump station, valve vault, storm water management vault, and new electrical and odor control rooms. The team replaced the entire electrical system and installed all new pumping equipment. 
 
The new grinder structure was installed 26 feet below grade and consist of two 5 HP grinders with a 4,200 gallons-per-minute capacity. A 36-inch pipe and new pre-cast manhole was installed on the effluent side of the grinder structure.
 
The submersible pump station (SPS) houses two submersible raw-water sewage pumps that are used as the main pumping equipment for the Four Mile Run station. The SPS extends 30 feet below grade. The new submersible pumps are 60 HP and can handle 3,300 gallons-per-minute capacity. New valves also were installed in the existing effluent valve vault of the pump station. At the effluent force mains of the pump station, two new magnetic flow meters were installed to replace the existing meters. Next to the SPS, a new valve vault was constructed. The enclosure will house the control valves that will isolate the SPS piping and pumps from the existing pump station building.  
 
Additionally, the team constructed an electrical room and the odor control area. The entire electrical system and switch gear at the pump station was replaced to incorporated the new systems with AlexRenew SCADA system for easier remote monitoring. New odor control equipment also was incorporated into each step of the pump station process to better alleviate odorous air in the area. The project also includes a new HVAC system for the existing pump station building, with adjustable fans.
 
To complete the project, a new storm water management vault was constructed 15 feet below grade. It will house two new submersible chopper pumps, each with 7.5 HP and 245 gallons-per-minute flow capability. The structure will allow use of rainwater instead of potable water for the tank wash down.