SW3 – 91404 Bonn

STORMWATER TREATMENT

Bonneville Power House 1 on the Columbia River

Background

After the successful installation and operation of the stormwater system on the Dalles Lock and Dam, the US Army Corps of Engineers, Portland District, designed a stormwater treatment system to treat turbine oils and other oils and greases that accumulate in their collection system in the base of the dam and power house at the Bonneville Power House 1 on the Columbia River. The turbine oils come from leaks and maintenance activities on their equipment. The water comes from wash down activities and seepage from the dam. The water, oils and grease are collected in a central sump at the base of the dam.

The problem

The goal was to design a system that could handle up to 1000 gallons per minute, have the capacity to treat high concentrations of oils and grease and discharge less than 10 parts per million of oil and grease with no visible sheen. A further constraint was the system would use the existing underground API OWS to pre-treat the stormwater ahead of the MYCELX filtration system. The concern was that suspended solids would blind off the MYCELX filters, thus reducing their effectiveness.

The Solution

The Corps designed a vertical screen assembly for the OWS to hold oil absorbent mats. Specially designed MYCELX Versimats were selected for the vertical screen. The Versimats measured 14 ft x 5 ft, were sewn on all four sides and had 44 grommets with elastic loops installed around the perimeter of the Versimats. The Versimats were stretched over the screen and loops attached to hooks mounted on the screen. A steel frame and electrically operated hoist system raises and lowers the vertical screens. Two screens were installed in series. Two 52-round filter housings with 40-inch cartridges were installed in a parallel configuration after the OWS in a separate building. The parallel configuration allowed the power plant operators to handle higher flows when warranted or operate a single system with one system on stand-by. The flow through the OWS is constant, with intermittent high flows when the central sump is full. A float actuates the pump to send the water to the OWS. A monitoring system is installed to measure the quality of the discharge from the OWS and the 52-round housings at two different points. The 52-round housings only operate when the discharge from the OWS exceeds the discharge parameters. When a second alarm comes on after the 52-round housing, the operators inspect and change the MYCELX cartridges (if necessary).

The Results

All The project was designed in the Summer of 2003. The contract was awarded in May 2004 and installed in August and September 2004. The system is currently in undergoing final testing and acceptance by the Corps.