Construction Sites Stormwater Requirements

Construction projects are required to comply with two interrelated sets of municipal directives with respect to water quality management: (1) compliance with applicable discharge prohibition requirements set forth in the Water Quality Ordinance to prevent unauthorized non-stormwater discharges, and (2) implementation of Best Management Practices (BMPs) to the maximum extent practicable, in accordance with the County Drainage Area Management Plan (DAMP) and local agency requirements, to reduce contaminants in stormwater discharges.

In addition, construction projects that involve one acre or greater of soil disturbance must comply with the General Construction Permit. The discharge prohibitions and BMP requirements are consistent with and complementary to the requirements of the General Construction Permit. Therefore, compliance with the State’s General Construction permit will typically lead to compliance with the City’s BMP implementation requirements. However, the City requires Erosion and Sediment Control Plans (ESCPs) showing all BMPs for construction, even when a project disturbs less than 1 acre of soil and is not covered by the General Construction Permit (i.e., not a part of a larger common plan of development). 

For more information on the BMPs that may be used to meet the minimum requirements, view the County of Orange Stormwater Program “Construction Runoff Guidance Manual.” 

Project
General Requirements for Water Quality Management
Construction  Projects > 1 Acre Soil Disturbance •Apply for local grading or building permit
•Comply with grading or building permit and local ordinances
•Submit Notice of Intent for General Construction Permit Coverage to SWRCB
•Prepare and implement SWPPP
•Implement BMPs as required by the City and the General Construction Permit. Prepare and submit an Erosion and Sediment Control Plan for approval.
•Submit General Construction Permit Notice of Termination to the Regional Board at project conclusion.
Other Projects •Apply for local grading or building permit
•Comply with grading or building permit and local ordinances
•Implement BMPs as required by the City to meet Water Quality Ordinance and NPDES Permit.

Discharge Prohibitions on Construction Sites
Without exception, discharges of stormwater from a construction site to the municipal storm drain system or receiving waters are prohibited if the discharge contains pollutants that have not been reduced to the maximum extent practicable through the implementation of BMPs.  In general, construction activities require the implementation of a combination of BMPs to control erosion and sediment transport, and pollutants from materials and waste management storage and activities.  Non-stormwater discharges from a construction site to the municipal storm drain system or receiving waters are prohibited.  Exceptions to prohibitions of non-stormwater discharges include (a full list is available in the Water Quality Ordinance):

•Discharges composed entirely of stormwater, or;
•Discharges for which the discharger has reduced to the maximum extent practicable the amount of pollutants through implementation of BMPs, or;
•Discharges from certain activities that may be present on a construction site including landscape irrigation, diverted stream flows, rising groundwater and de minimis groundwater infiltration to the municipal storm drain system, passive foundation drains, and flows from riparian habitats and wetlands.
 
BMP Implementation
Construction project owners, developers, or contractors must implement the BMP requirements in the DAMP or equivalent measures, methods, or practices.  Proper selection of BMPs depends on numerous factors that are specific to individual sites and activities, and therefore the DAMP does not advocate or require the use of particular practices unless the City determines that BMPs implemented by the project proponent are not adequate to prevent discharges of pollutants.  In that case, implementation of specific BMPs, additional BMPs, and/or other controls may be required.

Minimum Requirements
All construction projects regardless of size are required, at a minimum, to implement an effective combination of erosion and sediment controls and waste and materials management BMPs.  These minimum requirements are summarized in Table 2 and must be conveyed to construction contractors as part of the plan notes or on a separate erosion control plan.

Category Minimum Requirements for all Construction Sites
Erosion and Sediment Control Sediments from areas disturbed by construction shall be retained on site using an effective combination of erosion and sediment controls to the maximum extent practicable and stockpiles of soil shall be properly contained to minimize sediment transport from the site to streets, drainage facilities or adjacent properties via runoff, vehicle tracking, or wind.

Waste and Materials Management Control Construction-related materials, wastes, spills or residues shall be retained on site to minimize transport from the site to streets, drainage facilities, or adjoining property by wind or runoff.