Jan 28, 2019

Under Pressure

Metal recycling company adapts to tightening storm water permit requirements

The facility reduced concentrations of copper, zinc and total suspended solids in its storm water.
The facility reduced concentrations of copper, zinc and total suspended solids in its storm water.

With growing water quality concerns over the past two decades, industrial storm water permit requirements have become ever more stringent. For more than 20 years, through its proactive environmental compliance program, a metal recycling company in the Pacific Northwest has adapted to these tightening storm water permit requirements and maintained compliance. Its program relies on a comprehensive strategy using combinations of storm water pollution control best management practices (BMPs), including source controls and structural and treatment BMPs. The combination of BMPs has resulted in consistent attainment and a monitoring waiver during each permit term. 

While the national trend has been that industrial general permits impose additional requirements with each five-year permit renewal period, this facility added incremental improvements to its BMPs and processes to remain compliant. Thanks to its management team’s aggressive implementation of BMPs during the last 20-plus years, the company successfully has reduced concentrations of copper, zinc and total suspended solids (TSS) by more than 90%. 

A vacuum sweeper is used daily in high-traffic areas.
A vacuum sweeper is used daily in high-traffic areas. 

Environmental Obstacles

While scrap metal recycling is an environmentally beneficial business, it also is one that poses environmental concerns with storm water runoff. Common storm water pollutants from metal recycling operations include oil and grease, TSS, and metals—copper, zinc, lead, nickel, cadmium, iron, aluminum and others. Permit compliance under modern-day industrial general permits requires a combination of effective source control, structural and treatment BMPs, and attention to the administrative elements of the permits. 

This recycling company operates two ferrous and non-ferrous scrap metal recycling locations that purchase scrap metals. Between its two facilities, the company recycles more than 100 million lb of scrap metal per year that otherwise would be produced from ore at a much higher energy consumption rate while more quickly depleting natural resources. Over the course of this metal recycler’s work to comply with evolving industrial general storm water permits for its Oregon facility, the permit benchmarks have decreased by 77% for TSS, 80% for zinc, 80% for copper and 90% for lead, requiring an aggressive approach to pollutant control.

The company’s Oregon facility is located on a 2.5-acre parcel in an industrialized section of the city. The facility includes administrative offices, as well as storage warehouses and processing operations. The lot behind the warehouse building is leased from the city and used for additional storage. The facility primarily takes in industrial scrap from other businesses—such as aerospace companies, electric utilities, automobile recyclers, metal products producers and electronics manufacturers—and primarily recycles non-ferrous metals, including aluminum, copper, titanium, lead, zinc, nickel and stainless steel, as well as alloys such as brass and bronze. The main pollutant load from this site is from outdoor processing and storage operations. Permitted under the Oregon DEQ 1200-Z Industrial Stormwater General Permit, storm water runoff discharges to the city’s municipal separate storm sewer system (MS4). In most cases, a facility’s industrial customers require their suppliers to have rigorous management standards that would protect those companies from liabilities associated with safety and environmental infractions by their suppliers.

The facility is located in a temperate region characterized by about 40 in. of relatively low-intensity rainfall per year. The minimum rainfall usually occurs in July and the maximum from November to December. Runoff from the site is vigorously managed to prevent industrial storm water pollutants from migrating off site. Both the U.S. EPA’s multi-sector general permit for industrial activities and state general industrial storm water permits must be renewed every five years. Each renewal period tends to bring more stringent water quality standards and, therefore, demands more corrective action. Other trends include electronic data and report submittals, watershed-specific pollutant parameters and standards—implemented through the total maximum daily load programs—and multiple agencies involved in permit enforcement.

The facility's filtration system includes catch basin inserts.
The facility's filtration system includes catch basin inserts. 

The Solution

The facility determined that the best strategy to achieve ongoing permit compliance is through rigorous implementation of evolving BMPs.

Environmental awareness and education. A strong environmental ethic and education program is among the most important and effective storm water pollution prevention strategies. The metal recycling facility informs customers and staff of its rigorous material acceptance and environmental policies with informational literature and signage throughout the facility.

Materials prohibitions. Control of accepted materials is of increasing importance in the scrap metal recycling business. Materials such as chlorofluorocarbon are prohibited. All incoming material shipments from unknown entities are documented in writing and/or on video, and reminders of the material acceptance policy are located on signage throughout the facilities.

Enclosed operations. The facility includes indoor and/or temporarily sheltered non-ferrous recycling operations. These operations would be primary sources of regulated storm water metals—including copper, lead and zinc—if they were located outdoors.

Yard organization. The facilities are well organized with established traffic routes that keep recycled metals and other industrial activities separated from traffic corridors that can track pollutants around the site. Materials of similar character are stored in block bunkers that allow for efficient materials management and help define traffic patterns.

Yard sweeping. The facility owns and operates a vacuum sweeper that is used daily in non-ferrous areas and weekly in ferrous areas. Forklift corridors and loading docks and bays where high material movement occurs are swept daily to prevent particle drag-out.

Paving and drainage. Yard paving and a well-maintained system of storm drains and storm water conveyance lines provide a water quality advantage in heavy industrial settings. A network of catch basins promotes storm water drainage from the paved surfaces, minimizing contact between runoff and industrial activities. Although paved sites shed more rainwater, erosion is minimized and allows heavy equipment and trucks to operate efficiently and safely. Drain inlets are retrofitted with devices that absorb oil and capture metal pieces, keeping them out of the conveyance pipes.

Updated BMPs

In addition to rigorous operational and structural BMPs, treatment BMPs and BMPs as physical plant structures are increasingly common and necessary to meet the benchmarks and narrative water quality criteria established by the NPDES permits. Existing industrial facility infrastructure typically predates EPA’s Clean Water Act, so facility infrastructure tends to lack the required amount of hydraulic head or elevation drop to filter storm water by gravity. 

The typical retrofit pump-and-treat storm water filtration system includes a simple bypass vault, installed downstream of a pollution source, and a pump with a float switch. The pump typically is sized to the jurisdictional storm water quality criteria, and the bypass vault allows greater-than-design storms to pass via gravity. The pump then is relied on to lift the water to the inlet of the treatment BMP and treated effluent will gravity-flow to the existing outfall. Physical aboveground treatment BMPs offer the advantage of quicker installation, lower installation cost, easy visual inspection, less costly maintenance and portability for industries that do not own the land on which they operate. Disadvantages of aboveground treatment BMPs include less available space for production purposes.

This metal recycling facility was an early adopter of storm water treatment BMPs. Leased in 1995 and starting operation in 1997, the initial site had a permanent cap and included a 6,000-gal buried coalescing plate oil and water separator vault. Storm water collected by the catch basins in the yard flowed by gravity through the oil and water separator to the city’s MS4. 

In 2004, the facility installed an aboveground two-stage canister filtration system and a pump at the outlet of the oil and water separator. In December 2008, the metal recycling facility replaced the canister filtration system with a 160-gpm Aquip enhanced storm water filtration system, utilizing patented passive-hydraulic controls and layers of inert and sorptive filtration media. The enhanced storm water filtration system offered additional capacity and higher performance in a passive, gravity-flow configuration. 

In 2009, the facility added a Clara gravity-plug flow-separation system that slows the water and allows sediment to drop out of the water column, extending the maintenance interval of the enhanced storm water filtration system.

Reacting to the 2012 permit requirements that reduced the copper benchmark from 100 ug/L to 20 ug/L, the company elected to install a storm water polishing system. The new advanced polishing system easily was adapted to the outlet from the filtration system and brought copper concentrations below the new benchmarks, once again earning a monitoring waiver.

Lessons Learned

Thanks to its BMPs, over the last 20 years, this metal recycling facility successfully has reduced copper concentrations in storm water by 92%, zinc by 93% and TSS by 93%. Historically, copper has been the primary pollutant of concern for storm water quality at this facility. Installation of the enhanced storm water filtration system in 2008 consistently brought concentrations below the benchmarks, but an increase in recycling activity around 2012—just as a new, more stringent permit requirement went into effect—once again pushed discharge concentrations higher, requiring polishing treatment technology be added to the system. 

In 2017, with the addition of the advanced polishing system, the copper concentrations were once again brought below the 20 ug/L copper benchmark. Zinc and TSS concentrations from the site consistently have been below the ever-lowering benchmarks since the enhanced storm water filtration system was installed in 2008. These results demonstrate that compliance with the multi-sector general permits and state-specific industrial general permits is achievable with a rigorous environmental program and the appropriate BMPs.

About the author

Calvin Noling, P.E., is engineer and CEO for StormwateRx LLC. Noling can be reached at 800.680.3543.

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