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Last Updated: Wednesday, February 7, 2018 10:09 AM


The San Diego Water Quality Control Study is one component of the research and monitoring work for Caltrans Stormwater Management Program. With these studies, Caltrans is proactively gathering information that will provide crucial information for

Caltrans and other public agencies on how stormwater pollutants are affecting our waterways.

Caltrans has completed this two-year study to determine the most effective combination of Best Management Practices (BMPs)—both structural and non-structural—so that Caltrans and other permittees in the San Diego region can work together toward complying with their NPDES (National Pollutant Discharge Elimination System) stormwater permits. 

Study Objective

Caltrans will use the results of this study to determine what additional measures should be undertaken to control or treat discharges from its stormwater systems. The study will emphasize options where Caltrans works together with other San Diego municipal stormwater dischargers.

A few key study questions to be answered...
  1. What problems are caused by storm drain system discharges?
  2. What structural and non-structural BMPs should be implemented to eliminate either the discharges themselves or the problems?
  3. Where are the opportunities to construct structural BMPs, if required?
  4. What are costs to eliminate discharges or problems associated with them?
  5. What are the financial implications?
  6. Who would undertake this water quality management effort?
  7. What trade-offs might be involved?
  8. What results should be expected in the short-term and long-term?


  1. OUTFALL IVENTORY (COMPLETE) - GIS database of Caltrans storm drain systems has been developed with outfall locations and characteristics.
  2. OUTREACH & PARTERNING - Stakeholders & Oversight Team will assist with study design and developing scenarios
    • Meetings have begun with key stakeholders. Cooperative monitoring programs are being designed. Feedback on sample scenarios will be requested from stakeholders. Formal public participation program will be conducted.
  3. WATER QUALITY ASSESSMENT - elected receiving waters will be evaluated; report on runoff that is exceeding standards will be prepared; storm drain discharges and receiving water quality will be assessed ; assessment will be refined as more data becomes available.
    • Results will be used for calibrating a Load Prediction Model being developed for Caltrans
  4. TECHNOLOGY ASSESSMENT - Types of facilities and devices that could be used to treat storm drain discharges will be examined, including whether local (end pipe) or regional (watershed) treatment or combination is desirable. Will include data from literature review, in-field pilot projects, and ongoing research.
    • Twelve BMP types are already being designed, constructed, operated, and monitored at 33 sites in Southern California (12 in San Diego) for a separate Caltrans BMP retrofit pilot construction project.
  5. SCENARIO DEVELOPMENT & ASSESSMENT - Proposed scenarios will be developed jointly by Caltrans and stakeholders for water quality control, ranging from full compliance to more focused cost-constrained strategies. An assessment report will be prepared for each scenario.

Report of Findings November 2001

Report of Findings and Stakeholder recommendations to State Water Resources Control Board and Regional Water Quality control Board, San Diego Region - with request for modifications to NPDES permit, if applicable.

Multiple Scenarios

The San Diego Water Quality Control Study will produce multiple scenarios that are stakeholder driven to look at different levels of pollution prevention, source control, and stormwater treatment.

Regional Watershed Plan

This range of scenarios will allow regional decisionmakers to define a plan for the San Diego region to work toward compliance with the federal Clean Water Act and California Porter-Cologne Act. The plan will take the requirements of different watersheds into account while balancing a broad range of community needs.


California Department of Transportation
P.O. Box 942874, MS-27
Sacramento, CA 94274-0001