Q1. Is contamination anything above the Tier 1 values?

A. No. Contamination as defined in Section 21302(c) "means the presence of a regulated substance in soil and groundwater." Presence means concentrations above the method detection limits (MDL).

Q2. Are the two bottom samples during removal of an underground storage tank (UST) for the site assessment sufficient to request closure of the site if the contamination is below Tier 1 values?

A. No. Site assessment sampling for a UST removal is to determine if a confirmed release has occurred. Verification soil samples for leaking underground storage tank (LUST) releases require additional sampling locations and additional analytical parameters beyond the locations and indicator parameters required for UST closure assessment sampling. If the analytical results for the UST closure assessment sample indicator parameters are above the MDL’s, then you must report a confirmed release to the Waste and Hazardous Materials Division (WHMD) within 24 hours of the discovery of the contamination and comply with the provisions of Part 213.

Q3. Following a confirmed release report, I believe the tank excavation can be closed under a Tier 1 evaluation. What additional sampling must I do?

A. Refer to the "Guidance for Parameters, Analytical Methods, Sample Handling, Quality Control, and Cleanup Limits for Petroleum Hydrocarbon Releases" and the "Verification of Soil Remediation Guidance Document." At a minimum, the number of floor excavation samples is two for a 500 sq. ft. floor area and a minimum of four (4) sidewall samples, where the total area of the sidewall is 500 sq. ft. Sampling should be biased, in an attempt to sample the locations which would reflect the maximum concentrations that would exist at the site. Recommended parameters for common petroleum products are found in Table 1 of the Guidance for Parameters, Analytical Methods, Sample Handling, Quality Control, and Cleanup Limits for Petroleum Hydrocarbon Releases.

Q4. Are the parameters listed in Table 1 of Guidance for Parameters, Analytical Methods, Sample Handling, Quality Control, and Cleanup Limits for Petroleum Hydrocarbon Releases the only parameters that have to be analyzed for after a release is discovered?

A. No. These are the recommended parameters for common petroleum products. If you are aware of other contaminants that may have been present in the UST, then you must also analyze the samples for those additional parameters. Keep in mind that Table 1 is a list of parameters commonly found in petroleum products. Regulated substances, as defined in Section 21303(d), includes (in addition to petroleum), substances defined in Section 101(14) of Title I of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, Public Law 96-510, 42 U.S.C. 9601 and substances listed in Section 112 of part A of Title I of the Clean Air Act, Chapter 360, 84 Stat. 1685, 42 U.S.C. 7412.

Q5. To what extent do I have to delineate the extent of contamination?

A. The horizontal and vertical extent of contamination must be adequately defined to below the Tier 1 unrestricted residential risk-based screening levels (RBSLs). Professional judgment plays a role when evaluating the contaminant mobility, site geology, and the age of the release to determine if additional samples are warranted to adequately define the extent of contamination. It is important to note that the highest contamination may not be at the source area depending on the soil type and/or the rate of groundwater and/or free product movement.

Q6. If a confirmed release occurs in sandy soils, and I collect the two bottom and four sidewall samples and they are all non-detect or below Tier 1 can I close the site?

A. If permeable (sands or gravels) soil conditions exist at the release location, contaminants may have migrated to the groundwater with little or no residual contamination remaining in the unsaturated soils. Therefore, at sites which have permeable soils, it is recommended that the groundwater be checked for the presence of contaminants below the point of the release in order to determine if groundwater contamination, in the source area, is significantly above the method detection limits, then the groundwater flow direction should be determined and groundwater samples collected from the source area and down gradient of the source area. If the groundwater contamination is present above the Tier 1 unrestricted residential land use RBSLs, then the horizontal and vertical extent of the groundwater contamination must be determined. It is recommended that the QC discuss the initial groundwater sampling results with the Remeditaion and Redevelopment Division district project manager before a determination to proceed with additional sampling or the submittal of a closure report based on the initial source area sampling.

 

 

Q7. Where can I find the calculations for soil saturation numbers?

A.The Soil Saturation Concentrations equation is found in Operational Memorandum number 4 in attachment 6.