Site Mitigation Programs

Effective on July 1, 2019, any LOP or site mitigation cases that have been overseen by Solano County that did not receive Closure/ No Further Action (NFA) confirmation letter by June 30, 2019  will be 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 Regional Boards are included as regulatory links in the Quick Links on this page.

Monitoring Wells and Soil Borings:
Soil borings/monitoring well permits must be must be obtained prior to beginning exploratory borings and construction of 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 should be secured to prevent unauthorized access. Drilling procedures and well design and 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 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. 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 GuidanceSolano County UST Removal - Closure In Place Application. For specific requirements call (707) 784-6765 and ask for a Hazardous Materials Staff.

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 a tank wall, 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 appropriate 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 attached 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 should 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, Hazardous Materials/Site Mitigation Records:
    You may contact this office at (707) 784-6765 for an appointment, email a file review request to 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 & Phase II Site Assessment:



    Regulated Site Portal

    Cleanup Criteria:

    Low Threat UST Case Closure

    Environmental Screening Levels (ESLs)

    California Human Health Screening Levels (CHHSLs)

    A Compilation of Water Quality Goals


    Unauthorized Release Reporting Form

    Sealing Material Advisory

    Soil Borings Application

    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