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California State Water Resources Control Board Leaking Underground Fuel Tank LUFT Guidance Manual

Conceptual Site Models. A living model of known or suspected sources of contamination at a LUFT site, how and where the contamination has/will migrate, and the human and environmental receptors that are likely impacted.. The California SWRCB has requested that lead regulatory agencies direct RPs to

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California State Water Resources Control Board Leaking Underground Fuel Tank LUFT Guidance Manual

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    1. Conceptual Site Models: The Key to Successful assessment and corrective action California State Water Resources Control Board Leaking Underground Fuel Tank (LUFT) Guidance Manual

    2. Conceptual Site Models A living model of known or suspected sources of contamination at a LUFT site, how and where the contamination has/will migrate, and the human and environmental receptors that are likely impacted. The California SWRCB has requested that lead regulatory agencies direct RPs to prepare a Conceptual Site Model (CSM) for LUFT sites Regulators, do you require a CSM? RPs, do you utilize a CSM as a tool even when not requested?

    3. Objectives of a CSM To convey an understanding of the origin, nature, and lateral and vertical extent of contamination To identify potential contaminant fate and transport processes and pathways To identify potential human and environmental receptors that may be impacted by the contamination Used by stakeholders to make decisions regarding investigation, remedial actions, data gaps, and risk management

    4. The Benefits of a CSM Provides a framework for the entire investigation, mitigation, closure process Serves as a communication tool for stakeholders Can help stakeholders reduce project costs and reduce the time to case closure Decreases the cost and time for individuals to get familiar with a project if changes in regulatory oversight, state funding, or environmental consulting personnel occur Help expedite the review of work plans, reports, reimbursement requests, NFA requests, and appeals Increases the ability to explain site data and predict future findings

    5. A CSM starts as a simple understanding of site historical information and previously-gathered data and builds details as investigation continues. Developing a CSM

    6. Background Information Site address, Parcel Number, Contact Info Current and future land use Summary of former land use and property ownership Brief description of former and existing contaminant storage and dispensing facilities Land use of adjacent properties and surrounding area Comprehensive plan and zoning designations for the site and adjacent properties Recent aerial photograph, and historical aerial photographs if relevant Future site use and development plans

    7. Geologic Setting Site topography and elevation Regional or local geologic conditions Site-specific soil texture/lithology, stratigraphy, and structures that may affect contaminant occurrence and extent A cross-section figure showing soil horizons and depth to groundwater

    8. Hydrology Nearby surface-water bodies and beneficial uses Groundwater basin beneath the site Designated beneficial uses of groundwater Groundwater occurrence Groundwater depth and its seasonal and known historical fluctuation Groundwater flow and the inter-connectedness of aquifers Summary of the results of any water-quality testing

    9. Historical Environmental Information Summarize contaminant release history and work performed to assess and mitigate the contamination The goal of this section is to provide a road map and dates of major actions, identify the major conclusions of each phase of work This section should not restate every detail of each past report or the laboratory results for each sample

    10. Release Identification and Description The source of the release Equipment details The location of historical and active USTs, dispensers, and product piping Details about the specific release location(s) The type of fuel released and the COCs The historical use of fuel additives (e.g., MTBE, other fuel oxygenates, lead, lead scavengers The media that are impacted (secondary ongoing sources of contamination)

    11. Nature and Extent of Contamination Lateral and vertical extent of: Non-aqueous-phase liquid (NAPL) COCs in unsaturated-zone soil COCs in saturated-zone and the smear zone COCs in groundwater COCs in subsurface vapor Their trend over time

    12. Source, Pathway, Receptor Examples of Receptors People living or working at the site or in the neighborhood People drinking from contaminated aquifer Children attending school near the site Potential Receptors

    13. Determining Receptors The current and future use of the site The current and likely future use of the surrounding area The location and depth of subsurface utilities in the area Zoning of the site and the surrounding area Conditional uses typically allowed in the site vicinity Other observations, land use data, and demographics

    14. Determining Receptor Radius If plume is stable and adequately assessed, radius can be justified by constructing a graph which plots the average COC concentration vs. distance along the direction of COC migration The area may be increased if assessment indicates the plume is unstable or that contamination has migrated beyond the limits of the previous survey. 400 Feet of the Site Land use Sensitive receptors Domestic wells Basements and sumps containing groundwater 2000 Feet of the Site Water-supply wells

    15. Pathways Three Components to a Complete Pathway An environmental media and transport mechanism A point of exposure A route of exposure

    16. Environmental Media and Transport Soil Groundwater Surface water Air

    17. Point of Exposure A utility corridor Drinking water well Recreational surface water body Basement

    18. Route of Exposure Ingestion (Eating or drinking) Direct contact Breathing

    19. Completing the Pathway A complete pathway includes a source of contamination, an environmental media and transport mechanism, a point of exposure, a route of exposure, and a receptor. In order to make decisions regarding investigation and remediation at the LUFT site, the RP must determine if complete pathway(s) exists. If they do: Immediate remedial action may be necessary Not enough information to determine: Additional assessment may be necessary If they don’t: Site may be ready for closure

    20. Your Input The LUFT Manual will be available at the SWRCB website for public comment Questions, comments, want to be altered when the Manual is public? Send your questions and comments to the LUFT Manual email address at luftmanual@onesullivan.com Or access http://caluftmanual.org/contact.php. and fill out the on-line form Contact Adrienne Barnes at abarnes@onesullivan.com or 720-413-9703

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