The Clean Water Act requires compliance with the National Pollutant Discharge Elimination System (NPDES) for point source discharges to the Waters of the United States. Today, construction areas over one acre of disturbed soil area are required to obtain NPDES coverage. In California, this coverage is achieve under the Construction General Permit (CGP, Order 2009-0009-DWQ, last amended 2012). The California State Water Resources Control Board is currently in the public comment phase on a proposed reissuance of the CGP.
Why does the CGP matter?
It is not a surprise to people that construction sites are typically erosive sites. As rain hits the bare, exposed soil, water brings along sediments and construction-related pollutants into our water bodies. Many of these discharges, whether due to storms or non-stormwater discharges, find their way into the [legally defined] Waters of the State and Waters of the United States. These major water bodies serve a variety of uses, from drinking water to recreation to natural resources. The Clean Water Act and the CGP helps make sure that our construction sites are good neighbors to our shared water resources.
As engineers, we most commonly cross paths with the CGP through the project Stormwater Pollution Prevention Plan (SWPPP). The SWPPP serves as a Clean Water Act compliance mechanism and as a guide on preventing construction pollutants in stormwater through best management practices (BMPs).
The bottom line?
The proposed CGP reissuance will help address construction impacts to pollutants in our watersheds, clarify permit requirements, create a culture of construction site improvement through action, standardize SWPPP requirements, and
Major Changes to the CGP
Total Maximum Daily Loads (TMDLs)
Total Maximum Daily Loads (TMDLs) are regulatory tools specifying the maximum amount of pollutant that a waterbody can receive while achieving water quality standards. The TMDL is the sum of allowable pollutant loads from point, non-point, and background sources. The proposed CGP reissuance will require point-source construction sites to identify, address, and take specified compliance actions for TMDLs within the project watershed.
Removal of Bioassessment Monitoring
Risk Level 3 and Linear Underground and Overhead (LUP) Type 3 projects disturbing 30 or more acres are currently required under the 2012 CGP to conduct or participate in benthic macroinvertebrate bioassessment of receiving waters prior to beginning construction. The proposed CGP reissuance would instead perform this monitoring through the State's Surface Water Ambient Monitoring Program via Risk Level 3 and LUP Type 3 fees. The State Water Board found inconsistent implementation across projects, and suggested that it may come back in future CGP's.
Passive Treatment Systems
The proposed CGP reissuance would specify requirements for passive treatments. Discharges can use passive treatment chemicals and products to reduce turbidity levels in stormwater runoff. Turbidity can be a Numeric Action Level (NAL) trigger during stormwater monitoring. The most common family of chemicals used for passive treatment are polyacrylamides (PAMs). Research has shown the cationic PAMs are toxic to aquatic wildlife such as fish. Anionic PAMs are instead to be used for passive treatment, but can be toxic to fish in large quantities.
The proposed CGP reissuance would require construction stormwater discharges to Areas of Special Biological Significance with an exception to the Ocean Plan to comply with new requirements.
Sufficiently Sensitive Test Methods
The US EPA is working to ensure uniformity in NPDES permittees that analytical test methods are used to detect pollutants at or below water quality criteria. Zero (0) values may be assigned as long as a laboratory uses sufficiently sensitive test method with a sufficient detection and reporting limit.
Under the proposed reissued CGP, the project Qualified SWPPP Developer (QSD) is now required to perform on-site visual observations prior to construction, upon replacing another QSD, twice annually during key times of year, and after Numeric Action Level (NAL) exceedances.
The project Qualified SWPPP Practitioner (QSP) will be required under the draft CGP to conduct additional inspections and actions in lieu of a REAP (discussed below).
Notice on Non-Applicability
Under demonstration that the project will not discharge (stormwater or non-stormwater) to Waters of the United States, a project owner can claim Notice of Non-Applicability under the CGP.
Removal of the Rain Event Action Plan (REAP)
Under the current CGP, QSPs for Risk Level/LUP Type 2 and 3 projects are required to develop a Rain Event Action Plan (REAP) 48 hours prior to any likely precipitation event. The proposed CGP would replace the REAP with increased QSD involvement, additional inspections and visual observations, and requirements to document and implement corrective actions onsite.
The new CGP now uses local MS4 permits as a benchmark. Projects located within an MS4 must now demonstrate that their MS4 post-construction requirements meet or exceed the CGP post-construction requirements.
Stormwater Pollution Prevention Plans (SWPPPs)
Emphasis on a site-specific document.
Provisions to keep SWPPP as a living document, up-to-date in SMARTS.
Increased narrative of site-specific applications of CGP compliance.
Additional drawings to show site characteristics and BMP implementation.
Incorporation of standard elements from current SWPPP templates into the CGP.
Simplified annual reporting requirements.
Sections to document applications of other changes in the reissuance.
The Water Board is also promoting the use of GIS tools in site risk determination.
Incorporation of Past Guidance
The reissued CGP incorporates concepts previously not in the permit, published by the State Water Board through CGP Reviews.
Ideas are better grouped together in the reissued CGP, and concepts are often in order of importance. Wording is also more consistent and discharger-centric (i.e. the project owner is responsible for Clean Water Act compliance, including responsibility for contractors and consultants).