5-Years Later Low-Threat Petroleum UST Closure Policy Presented - - PowerPoint PPT Presentation

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5 years later low threat petroleum ust closure policy
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5-Years Later Low-Threat Petroleum UST Closure Policy Presented - - PowerPoint PPT Presentation

Jan 29, 2024 246 likes •357 views

5-Years Later Low-Threat Petroleum UST Closure Policy Presented by: Kevin Heaton Sean McClain Geologist, P.G., CHG Geologist, P.G. County of San Diego, Department San Diego Regional Water of Environmental Health, Site Quality Control

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5-Years Later Low-Threat Petroleum UST Closure Policy

Kevin Heaton Geologist, P.G., CHG County of San Diego, Department

  • f Environmental Health, Site

Assessment & Mitigation Sean McClain Geologist, P.G. San Diego Regional Water Quality Control Board, San Diego Region

Presented by:

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 Focus on high-priority cases (such as

impacted drinking water wells, human health, and sources of free product)

 Provide consistent regulation of the Policy

throughout the state

 Path to Case Closure Plans for each open

case, including specific milestones and timelines

SWRCB Low-Threat Petroleum UST Closure Policy

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SLIDE 3

LTC Policy Criteria Difficulties

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Site Conceptual Model

 Extent of release in both soil and

groundwater

 Definition of areas impacted by free

product

 Data analysis of dissolved plume stability  Quantify volume of residual impacted soil

remaining

 Maps of dissolved plumes (BTEX and

MTBE) and estimated time to reach MCLs

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Free Product Removed to the Maximum Extent Practicable

 Free Product Removal

 Bailers are not effective  Dedicated skimmers or hydrophobic bailers have

been effective in sandy soils not silty or clayey soils

 Vapor Extraction and Dual Phase Extraction

 Effective where free-product is present

 High Vacuum Dual Phase Extraction

 Effective in tight formations

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Free Product Removed to the Maximum Extent Practicable

 Free product removed to the maximum extent

practicable in a manner that minimizes the spread

  • f contamination into previously uncontaminated

zones

 Migration shall be the predominant objective in

the design of the free product removal system

 To make these evaluations the following methods

shall be considered

 Monitoring the extent of the LNAPL body (usually using

the apparent product thickness in monitoring wells) at a certain water level elevation over time

 Bail-down test  Pilot testing (vapor extraction or DPE)

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Free Product Removed to the Maximum Extent Practicable

 Additional removal or active remedial

actions shall not be required by regulatory agencies unless

 Necessary to abate a demonstrated threat  Dissolved phase plume is not stable  Free product is migrating

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UST Cases Closed with Free Product

 Non-beneficial use aquifers that posed no

threat to human health

 Free-product under roads or near

freeways that posed no threat to human health or the environment

 Free-product in beneficial use aquifers

greater than 30 feet bgs that posed no threat to water supply wells, future groundwater use, human health, or the environment

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SLIDE 9

Questions