Calbag Metals Co., a nonferrous scrap metal recycling facility
in Portland, Ore. had difficulty consistently meeting its Oregon
1200Z General Industrial Stormwater Discharge Permit
benchmarks for lead, copper and zinc. Over a two-year period,
particulate metal had been building up gradually on the 2.5
asphalt-paved acres surrounding the facility. After trying several
ineffective methods to address the problem, the company
turned to a best management practice (BMP) involving two,
above ground CatchBasin StormFilters filled with permeable
media to solve the problem.
The National Pollutant Discharge Elimination System permitting
program requires that industrial facilities monitor pollutants including total suspended solids, oil and grease,
particulate and dissolved metals (zinc, copper, and lead) and pH of stormwater leaving the site. Industrial
facilities are required to implement a program of stormwater BMPs that results in continued progress toward
designated benchmark water quality goals.
When Calbag first noted that it exceeded the benchmarks in 1998, the metals recycler tried various means to
reduce pollutants, including source controls, frequent sweeping, berming and catch basin inserts. All proved
to be ineffective. The company then turned to a stormwater treatment BMP offered by Contech Stormwater
Construction Products Inc.
Calbag Metals installed two CatchBasin StormFilter systems from Contech Stormwater Solutions to remove
solids and dissolved metals from runoff. Because the Calbag Metals facility was built on an old city landfill that
had been through Superfund remediation in the early 1990s, underground construction might compromise
the impermeable cap. Rather than using the standard procedure and installing the units flush with the
pavement, the two units had to be installed in series above ground. The company also installed a Contech
Stormwater Solutions Integrated Pumping System to direct runoff from the underground collection system to
the two CatchBasin StormFilter units.
The CatchBasin StormFilter is a multi-chamber, steel catch basin structure in which water enters an inlet chamber
that has a deep sump, an internal baffle to trap debris, floating oil and grease, and a high flow bypass baffle. The
heavier solids settle in the inlet chamber sump, but lighter solids and soluble pollutants flow under a baffle and
into the cartridge chamber, where polluted water percolates through the filter cartridge media. The cartridge’s
center tube collects the filtered water. Then it is directed by an under-drain manifold to the outlet pipe on
the downstream side of the overflow weir and discharged. When the incoming water flow exceeds the unit’s
capacity, excess water spills over the overflow weir bypassing the cartridge bay and out through the outlet pipe.
At the Calbag Metals facility, the first filter cartridge unit is configured with perlite media, a naturally-occurring
puffed volcanic ash material excellent for trapping sediments and adsorbing oil and grease. The cartridges also
include Sorbent Hood Covers for on-contact adsorption of free oil and grease. The second unit uses MetalRx™, a
fine-grained version of the patented CSF® leaf media that adsorbs and removes soluble heavy metals by means
of cation exchange and chelation. Particle filtration removes suspended solids.
After treatment by an oil/water separator, an Integrated Pumping System pumps site runoff to the perlite
CatchBasin StormFilter at surface level for sediment removal. Once filtered, the runoff goes into the second
CatchBasin StormFilter unit, configured with MetalRx media, for heavy metals removal before discharge to the
city’s storm sewer system.
Calbag Metals received a major contract in part because of its customer’s valuation of the environmental risk
reduction offered by the StormFilter system for preventing stormwater pollution from flowing off the site.
According to the site owners, since installing the CatchBasin StormFilter systems, the quality of stormwater
discharging from the site has improved consistent with its permit requirement to demonstrate progress towards
benchmark water quality goals.
Now, runoff flows into the existing catch basins and is conveyed to an oil/water separator, where more baffles
and coalescing plates have been installed to increase its effectiveness. Then the stormwater is pumped up to
the CatchBasin StormFilter units for further treatment, and the effluent flows by gravity back to the stormwater
conveyance line for eventual discharge at an outfall. Company staff also uses source-control BMPs to help