Project Risk Level Determination Guidance

SWRCB Risk Level Determination Guidance

The State Water Resources Control Board (SWRCB) provides a spreadsheet for assessing risk required by the Construction General Permit (CGP) (State Water Board Order 2009-0009-DWQ) that went into effect on July 1, 2010. The CGP is a risk-based permit that establishes three levels of environmental risk possible for a construction site.

The Risk Level (RL) is calculated in two parts: (1) Project Sediment Risk, and (2) Receiving Water Risk. The CGP Risk Level (RL) determination quantifies sediment and receiving water characteristics and uses these results to determine the project’s overall RL. Highly erodible soils, in higher rainfall areas, on steep slopes increase the ‘sediment risk’.

Monitoring and reporting requirements increase as the RL goes from 1 to 3.

Caltrans Stand-Alone Risk Level  Determination Guidance

Caltrans has stand-alone guidance for assessing risk required by the Construction General Permit (CGP) (State Water Board Order 2009-0009-DWQ). Caltrans Project Engineers and Consultants should use this guidance to determine if a project has a Risk Level 1, 2 or 3. Consult your local Design Stormwater Coordinator for more information about Risk Level Determination Guidance for Caltrans Projects. 

Water Quality Planning Tool

The Caltrans Water Quality Planning Tool can be used to assist with RL Determinations. K Factor, LS Factor and High Risk Receiving Watershed layers can be activated to view specific values for any sight within the State.

Note, the R Factor layer displays isoerodent contours for the state and provides a link to calculate the R Factor by hand using the isoerodent value obtained in the map. Alternatively, see below for EPA's R Factor Calculator.

EPA Rainfall Erosivity Factor Calculator for Small Construction Sites

This tool can be used to determine the R Factor, which is a component of the Project's Sediment Risk calculation. The anticipated construction start and end dates as well as the project location are required inputs for this tool. Refer to the Fact Sheet to calculate the R Factor for projects longer than 1 year in duration.  

  • EPA Rainfall Erosivity Factor Calculator
  • Construction Rainfall Erosivity Waiver Fact Sheet