Site Mitigation Programs

As of July 1, 2019, Solano County will not be performing regulatory oversight for site mitigation cases. All LOP or site mitigation cases overseen by Solano County that did not receive Closure/ No Further Action (NFA) confirmation letter by June 30, 2019  have been transferred to either the California Regional Water Quality Control Board- Central Valley Region ( Sacramento Office) or the California Regional Water Quality Control Board - San Francisco Bay Region. The Central Valley Regional Water Quality Control Board has jurisdiction over the geographical areas in and surrounding  Rio Vista, Dixon, and Vacaville. The San Francisco Regional Water Quality Control Board has jurisdiction over the geographical areas in and surrounding Benicia, Fairfield, Suisun City, and Vallejo. The links to the appropriate Regional Boards are included in the Quick Links.

Monitoring Wells and Soil Borings:
Soil borings/monitoring well permits must be obtained prior to beginning exploratory borings and construction of environmental wells e.g. monitoring wells, soil vapor, vapor extraction wells, sparge wells, and ground water extraction wells. All borings and monitoring wells being installed and destroyed must be properly sealed according to Solano County Code Chapter 13.10 and California Well Standards. Wells must be secured to prevent unauthorized access. Drilling procedures, well design, and well construction must be accomplished in a manner that prevents the spread of contamination, and must be done under the direction of a California Licensed (C-57) Well Driller. As part of the application for borings/monitoring wells you must provide the following documents:

  • Site diagram showing proposed location of soil borings or wells including but not limited to the following; utilities, aboveground and underground storage of hazardous materials, property lines, buildings/ structures,  storm drains, and streets:
  • Encroachment permit for city streets, county roads, federal/state highways:
  • Authorization for encroachment on to utility easements:
  • Access agreement/authorization from property owner:
  • For site mitigation projects, written approval from the lead regulatory agency on proposed scope of work described in the application;

Underground Storage Tank System Closure/Removal:
California Law and regulations requires that if you own a property with underground storage tank (UST) system in the ground that has not been permitted for use for mote than one year you must permanently closure the UST by either legally removing the UST system or legally closing the tank in place by filling the tank with an inert solid such as concrete and typically, removing the piping see US EPA and SWRCB Tank Removal Requirements. You must obtain a permit from Solano County CUPA to either legally remove or legally close the UST system in place. Additionally, California Law and Regulations requires single wall UST systems to be permanently closed or upgraded by December 31, 2025.  For more information see Single Wall UST System NotificationSingle Wall Tank System Removal Requirement GuidanceUST Closure Application (Temporary, Closure In Place, & Removal). For specific requirements call (707) 784-6765 and ask for  the staff of the  Hazardous Materials Section.

Unauthorized Releases: 
An unauthorized release, as defined Health and Safety Code (H&SC) §25295, is a release which 1) escapes from a UST’s secondary containment, or from the primary containment, if no secondary containment exists, 2) increases the hazard of fire or explosion, or 3) causes any deterioration of the secondary containment of the underground tank system. An unauthorized release can happen at any moment—during tank fueling or by failure of tank, from the piping, at the dispensers, or from waste-oil tanks at service stations. Regardless of how or where the unauthorized release occurs, it is the responsibility of the owner or operator to respond and to report the release to Solano County CUPA and the applicable California Regional Water Quality Control Board.

Once an unauthorized release is detected, the first step is to take immediate action to stop the leak and prevent
further release. This may require removing the residual product from the equipment in question. It is critical to determine whether any fire, explosion, or vapor hazards are present and, if so, to mitigate them. Tank owners or operators shall provide an initial report to the local agency within 24-hours and then follow up with a full written report within five working days. Owners and operators shall transmit information regarding an unauthorized release to the local agency on a written form or using an electronic format developed by the State Water Resources Control Board (State Water Board) and approved by the Secretary for Environmental Protection see Unauthorized Release Reporting Form

Release Reporting:
An Unauthorized Release Report needs to include information regarding an unauthorized release to the local agency on a written form or using an electronic format developed by the State Water Board and approved by the Secretary for Environmental Protection. The report shall include, but is not limited to, the following:

Facility/site name, address, and telephone number;
Discharge date or discovered date, and report date;
Discharge cause and discharge source;

  • Any further corrective or remedial actions, including investigative actions, needed to clean up the release and abate the effects of the release;
  • A time schedule for implementing the actions specified above;
  • The UST system’s record of compliance with H&SC Chapter 6.7, including data on equipment failures;

    File Review, Solano County CUPA Records /Site Mitigation Records:
    You may contact this office at (707) 784-6765 for an appointment, email a file review request to [email protected] and fax a file review request to (707) 784-4805 on your letterhead listing addresses/locations for which you request. For these requests, please include a prospective date and time for the review. Appointments are necessary to allow staff time to pull retrieve active physical files, retrieve files for archives, obtain documents from the California Environmental Reporting System (CERS), and to review all file information for confidential information that can not be legally release to the public. Please be advised, if you request public records to be copied and shipped to you, the records clerk will respond to you within 10 days to let you know if the records are available, the cost of copying, and the cost for mailing/shipping.  Cal EPA has launched a web portal designed for environmental professionals and the public that contains information from multiple State of California databases -directories and this portal may be of use to  you, see Regulated Site Portal.

  • Quicklinks:

    Regulatory Links:


    Health and Safety Code Chapter 6.7 and 6.75

    California Code of Regulations, Title 23

    Cal EPA site cleanup

    California Regional Water Quality Control Board, San Francisco Region UST Program

    California Regional Water Quality Control Board, Central Valley Region

    Cal EPA Requesting Public Records

    Cal EPA databases and directories

    Databases Useful for Phase I Site Assessments:



    Regulated Site Portal

    Cleanup Criteria:

    Low Threat UST Case Closure

    Environmental Screening Levels (ESLs)



    Unauthorized Release Reporting Form

    Sealing Material Advisory

    Soil Borings Application

    Environmental Report for Monitoring Wells and Borings

    Well Construction Application 

    Well Destruction Application 

    Industrial Wastes into Septic systems

    Motor Vehicle Fluids into Septic Systems

    Small Business Guidance for Class V Injection Wells

    Storm water into Septic Systems and Dry Wells