How the 75 GPM System Solved Stormwater Challenges at Two Industrial Facilities in Southern California

Industrial facilities operating under the California Industrial General Permit (IGP) often face challenges meeting Numeric Action Levels (NALs) and Total Maximum Daily Load (TMDL) requirements, especially when runoff contains elevated metals, sediment, nutrients, or oil and grease.

To address these challenges, Frog Environmental deployed its 75 GPM Stormwater Treatment System at two industrial facilities with documented stormwater exceedances. The results demonstrate how a compact, modular system can deliver measurable pollutant reductions and consistent regulatory compliance.

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The Challenge

Two industrial facilities, one specializing in steel manufacturing and another in structural steel fabrication, experienced elevated pollutant concentrations in stormwater discharges associated with outdoor operations and material handling.

Both sites required a treatment solution that could:

• Reduce metals, sediment, nutrients, and hydrocarbons
• Meet applicable CA IGP Numeric Action Levels (NALs) and TMDL Numeric Effluent Limits (NELs)
• Be deployed quickly without permanent infrastructure changes

To meet these needs, Frog Environmental installed 75 GPM modular stormwater treatment systems designed to treat runoff prior to discharge.

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Facility 1: Industrial Steel Manufacturing Facility

Site Conditions

This facility manufactures plastic-coated steel cables and bars. Stormwater runoff from outdoor operations contained elevated concentrations of:

• Total Suspended Solids (TSS)
• Oil & Grease (HEM)
• Aluminum (Al)
• Iron (Fe)
• Zinc (Zn)
• Nitrate + Nitrite (N+N)

Sampling data showed exceedances of CA IGP NALs and TMDL limits, placing the facility at risk of continued non-compliance.

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Treatment Solution

A 75 GPM stormwater treatment system was installed, consisting of:

• Stormwater storage to manage peak runoff volumes
• Media-based treatment modules engineered for metals, nutrients, sediment, and hydrocarbons

The system was designed to treat stormwater during qualifying rain events while maintaining operational flexibility.

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Performance Results

Post-treatment sampling confirmed significant reductions across all monitored constituents. Annual average results showed:

• 98.2% reduction in TSS
• 85.4% reduction in Oil & Grease
• 94–98% reduction in metals (Al, Fe, Zn)
• 94.9% reduction in Nitrate + Nitrite

All regulated parameters were reduced to below applicable CA IGP NALs and TMDL limits, allowing the facility to return to compliance.

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Facility 2: Structural Steel Fabrication Facility

Site Conditions

This facility performs outdoor steel fabrication and material storage. Stormwater runoff contained elevated concentrations of:

• Total Suspended Solids (TSS)
• Aluminum (Al)
• Iron (Fe)
• Zinc (Zn)

The facility required a compact, reliable treatment system capable of consistent performance during storm events.

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Treatment Solution

A 75 GPM modular stormwater treatment system was deployed, featuring:

• Temporary stormwater storage
• Media-filled treatment modules optimized for metals and sediment removal

The system footprint was minimized to fit site constraints while still achieving effective treatment.

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Performance Results

Stormwater sampling following installation demonstrated that:

• All monitored pollutants were reduced below CA IGP NAL thresholds
• Metals and sediment reductions exceeded 90%
• The system performed consistently across multiple storm events

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Influent vs. Effluent Performance Summary

Across both facilities, the 75 GPM system demonstrated documented, data-backed treatment performance, including:

• Up to 98% pollutant removal efficiency
• Reliable reduction of metals, nutrients, sediment, and oil & grease
• Compliance with CA IGP NALs and applicable TMDL requirements

These results confirm that the 75 GPM system delivers the same proven treatment strategy used at larger industrial sites, now optimized for lower flows and faster deployment.

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Key Takeaways

• The 75 GPM Stormwater Treatment System provides industrial-grade treatment in a compact, modular configuration
• Proven media technology delivers consistent reductions across a wide range of pollutants
• Ideal for facilities seeking fast, flexible compliance solutions without permanent infrastructure

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Proven Results. Scalable Performance.

The 75 GPM Stormwater Treatment System brings Frog Environmental’s field-tested treatment approach to sites with smaller flow requirements, without compromising performance or compliance confidence.

Looking for a right-sized stormwater solution?
Contact Frog Environmental to learn how the 75 GPM system can support your site’s compliance goals.