What is a Construction General Permit?The California State Water Resources Control Board (SWRCB) regulates storm water runoff from construction sites through the Construction General Permit (CGP). All construction projects disturbing one or more acres of soil are subject to the Permit. The Permit influences project design, implementation, and reporting. The Permit prescribes quantitative methodologies to estimate the risk of a project to discharge sediment, classify project risk levels, and mandate monitoring activities. The State has adopted this approach to minimize the potential for construction site runoff to negatively affect downstream water quality. Permit requirements should be reflected in project compliance strategies. Significant fines may be levied for non-compliance. Key elements of the Permit requirements are summarized below.
Site Risk AssessmentProject monitoring and reporting requirements are based on the results of a two-part risk assessment calculation: project sediment risk and receiving water risk. A project’s sediment risk, meaning the relative amount of sediment that can be discharged from a construction site, is estimated using several factors, including, but not limited to, project size, construction schedule, rainfall data, soil erosion potential, and topographical data (i.e., slope length and gradient). Receiving water risk is based on the sensitivity of downstream waterbodies receiving runoff from the project site. A downstream waterbody is considered a sediment-sensitive waterbody if it is:
- maintained on the most recent “303d list” for waterbodies impaired for sediment;
- subject to a USEPA-approved Total Maximum Daily Load implementation plan for sediment; or
- provides beneficial uses to fish (“cold, spawn, and migratory” as defined by the Permit).
Project Design and ManagementThe risk assessment results are used to assign an overall Risk Level to a project. Risk Levels range from 1 (lowest) to 3 (highest). Compliance monitoring requirements, which varies by Risk Level, are shown in the following table.
Effluent LimitsTo protect downstream waters, the General Permit establishes numeric effluent limits for both turbidity and pH in construction site runoff. The permit describes two effluent limit thresholds: Numeric Action Levels (NALs) and Numeric Effluent Limits (NELs). Risk Level 1 projects are not subject to turbidity or pH effluent sampling. Risk Level 2 projects are subject to NALs, while Risk Level 3 projects are subject to NALs and NELs (NELs only apply when an Active Treatment System (ATS) is being utilized and discharging directly to a receiving water). Additionally, Risk Level 3 projects are subject to further monitoring requirements if they exceed the daily average receiving water monitoring trigger. See the Permit for more information regarding effluent limit thresholds.
ReportingRisk Level 2 dischargers must electronically report storm event sampling results when NALs are exceeded, while Risk Level 3 dischargers must electronically report all storm event sampling results. Exceedance alone does not constitute a violation of the General Permit conditions, but it does obligate the permit holder to undertake immediate corrective action. Additionally, an annual report must be submitted for sites with more than three months of continuous coverage under the Permit. Annual reports must include site inspection records, results of site sample analyses, corrective actions taken, and documentation of completed training.
Post Construction Storm Water RequirementsEffective September 2, 2012, discharges covered under the Permit are required to comply with the run-off reduction requirements described Section XIII(A) of the Permit. The objective of this requirement is to match post-construction runoff to pre-construction runoff for the 85th percentile storm event, which reduces the risk of impact to the receiving water’s channel morphology and provides some protection of water quality. As described in the State’s Construction General Permit – Post-Construction Notification (July 2012), compliance with this requirement depends on where your project is located and when the project received Permit coverage.
Waivers and Exceptions
- Construction sites between one and five acres in size are exempt from the Permit requirements if the rainfall erosivity factor (risk of erosion by rain) is less than 5 for the site’s location and construction period. Under this scenario, the site owner would apply for a rainfall erosivity waiver from the State.
- Construction sites smaller than one acre in size that are not part of a larger development plan are exempt from the Permit requirements.
Required Training and QualificationsTraining is mandatory for individuals preparing storm water plans, performing site inspections, and implementing Best Management Practices (BMPs). All individuals preparing and amending SWPPPs must have attended a Qualified SWPPP Developer (QSD) training course, have passed the QSD state exam, and have a recognized pre-requisite certification. Likewise, individuals conducting site inspections, collecting storm water samples, and implementing BMPs must have attended a Qualified SWPPP Practitioner (QSP) training course, have passed the QSP state exam, and have a recognized pre-requisite certification, or be working under the direct supervision of a certified QSP.
Permit DocumentsPermit Registration Documents (PRDs) must be filed electronically; however, the accompanying permit fee must be mailed. PRDs include:
- Notice of Intent
- Site Risk Assessment
- Site Map
- Storm Water Pollution Prevention Plan (SWPPP)
- Signed Certification Statement
If you have any questions regarding the Construction General Permit, please contact John Luper at 530.221.0440 ext. 7110 (Voice), 530-221-6963 (Fax), or e-mail at firstname.lastname@example.org. John Luper is a Qualified SWPPP Developer (QSD) and a Certified Professional in Erosion and Sediment Control (CPESC). Based in Redding, ENPLAN provides comprehensive environmental compliance services to the construction industry.
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