DA3 Stormwater System

Calbag SWPCP Map DA3_031522.pdf

Figure 1. The map above depicts the entire DA3 area in the facility, including the catch basins and OWS. For purposes of stormwater maintenance (i.e. backflushing and winterizing), it is most important to be familiar with the layout of the tanks, Aquip, purus, and Retenue system. 

CB 3-2

All of the stormwater runoff first enters the filtration system through the catch basin in the bottom left corner of the photo.

Oil-Water Separator

After traveling through the catch basin filtration system, water enters the oil water separator, shown in the picture on the left. Both the catch basin and the OWS are pretreatment units for stormwater before it enters the filtration system. The OWS works by removing POL (petroleum, oils, and lubricants), and other floating constituents and some settleable solids.

Detention Tank 18667

From the OWS, water is transferred to the detention (settling/holding) tank before making its way to the Retenue sand filtration system.

For winterizing purposes, the blue hose must be disconnected, drained, and the valve shut before disconnecting.

Detention Tank 18225

The image above shows the second detention tank. These black tanks were installed as of Fall 2019 to offer an additional 12,000 gallons of water storage.

For winterizing purposes, removal and drainage of the black hose is optional, but not mandatory.

Retenue Flow Meter

The top number above indicates the Retenue totalizer, while the number below is the flow rate of water going in. 

For backflushing purposes, always keep an eye on the flow rate, which should be in the 30-40 gal/min range. If below 30, like in the photo above, perform a backflush of the system.

Tank & Filters

In the picture above, the tank in the back contains water from the detention tanks that will be filtered through the three blue Retenue sand filters in the front.

For backflushing purposes, keep an eye on the pressure differential between the influent/outfluent pressure gauges. If greater than 15, the system is due for a backflush. The fluid window is located above the sand filters.

For winterizing purposes, disconnect the blue hose from the sand filters.

Retenue Tank & Inlet Sampling Point

For winterizing purposes, close the blue valve to the pump, drain the small blue valve under the pressure meter, disconnect the green hose from the gray PVC piping, and drain the second pump that feeds the sand filtration system.

Tank Valve & Hose

Located at the back of the sand filtration storage system, the valve must be closed and blue pipe disconnected for winterization.

Aquip

Pictured above: view from the side of the Aquip. Retenue sand filtration system and Purus Housing Vessels are located on its right.

Pictured above: view from the top of the Aquip. As of 05/10/23, the fine sand media was replaced for seasonal maintenance.

Pictured above: side view of the Aquip adjacent to the Purus Housing Vessels. 

For winterizing purposes, open the small blue valve, sending the water back into the OWS. Loosen the Fernco fitting to allow water to drain. 

For backflushing purposes, close the blue butterfly valve to prevent water from entering the sand filter during an asynchronous (non-rain event) backflush.

Purus Housing Vessels

Pictured above, the Purus Housing vessels act as the final filtration step before the stormwater is discharged into the Willamette River. Installed in 2016, the Purus Metals Polishing System adds an extra level of filtration, specifically for dissolved metals such as copper, zinc, lead, and aluminum.

For winterizing purposes, open the blue valve at the bottom of the polishing unit. Loosen the polishing unit drain plug, and when safe, remove and place it somewhere safe.

Purus Outlet Pressure Gauge & Sampling Point

Pictured above is the outlet pressure gauge and sampling point (F). The sampling point above should be used to collect stormwater samples for lab analysis as well as for monthly visual observations (note: DO NOT use the inlet sampling point by the Retenue system).

Purus Flow Meter

The meter above provides the most current discharge (gpm), the resettable totalizer, and the totalizer. The totalizer number we record for our monthly visual observations will be the value at the bottom.