Compliance Status Report Description of Delineation of Groundwater Contamination 391-3-19-.06(3)(b)3
Description
If a release to groundwater is known or suspected at the site, this portion of the CSR details site geology, site hydrology, and methods used to assess/sample the groundwater for contamination. Groundwater should be assessed using an appropriate number of data points (monitoring wells) at appropriate locations in and surrounding each of the source areas at the site. A complete definition of the horizontal and vertical extent of groundwater contamination should be completed. Satisfactory definition of the horizontal and vertical extent of groundwater contamination shall consist of an appropriate number of data points at sufficient locations with concentrations below those listed in Table 1 of Appendix III or, for those substances not listed, the highest concentration of any of the following: the detection limit, Secondary Maximum Contaminant levels for Drinking Water listed in Rule 391-3-5, or background. An acceptable determination of background concentrations shall be made from samples that are representative of groundwater conditions not affected by a release of a regulated substance.
Temporary wells and direct-push groundwater sampling can be used for screening, but should not be used to certify compliance or finalize delineation requirements for the site. Permanent monitoring wells including a casing, screen, filter pack, seal, and locking cap must be used certify compliance or delineate the site. In addition to addressing the delineation requirements listed above, the compliance status report shall, at a minimum, describe the following (Chapter 391-3-19-.06(3)(b)(3)):
- Analytical parameters selected and reason for selection.
- Regional, local, and site-specific geology and hydrology.
- Horizontal and vertical groundwater gradients, flow rates, and flow directions. (Complete calculations and references for input values must be provided.)
- Horizontal hydraulic gradient should be measured on a properly scaled potentiometric surface map. Horizontal gradient between monitoring wells should never be used to calculate site gradient since wells are rarely installed parallel to groundwater flow. ih = (upper head – lower head)/distance, where ih is the horizontal hydraulic gradient.
- Vertical hydraulic gradient is measured between adjacent wells set at different depths within the aquifer. iv = (head in well B – head in well A)/(depth well A – depth well B), where iv is the vertical hydraulic gradient.
- Velocity = Ki/ne , where K is hydraulic conductivity, i is hydraulic gradient, and ne is the effective porosity.
- Description and calculation for hydraulic conductivity. (Complete calculations and references for input values must be provided.) The Hvorslev (1951), Cooper et al. (1967), Papadopoulous et al. (1973), and Bouwer and Rice (1976) methods for calculating hydraulic conductivity are most commonly used.
- Groundwater monitoring wells locations and construction details. Installation should be in accordance with EPA Region 4 monitoring well installation guidance available at the Region 4 web site (http://www.epa.gov/region4/sesd/fbqstp/index.html). This should include the following:
- Site map showing locations of all wells.
*Map must be scaled 1” = 200’ or less.
- Table listing each monitoring well, top of casing elevation, total depth of the well, and depth/length of the screened interval.
- Well casing and screen materials, and slot size of screen.
- Description of filter pack, seal, and grout placement in well. Also include a monitoring well diagram (example).
- Description of well development procedures.
- Monitoring well sampling and analysis procedures:
The Hazardous Sites Response Program has adopted guidelines for acceptable groundwater sampling (HSRA sampling protocol memo).
Additionally, sampling should be in accordance with EPA Region 4 groundwater sampling guidance available at the Region 4 web site (http://www.epa.gov/region4/sesd/sesdpub_guidance.html). This should include the following descriptions:
- Procedures for collecting groundwater elevation data.
- Sample purging technique and procedures including list of equipment (type of pump, type of tubing, etc).
- Sample collection technique and procedures including list of equipment (example, “straw method” for VOCs from a peristaltic pump).
- Sample handling and preservation.
- Equipment decontamination procedures.
- Chain-of-Custody procedures
- Laboratory analytical techniques (methods & QAQC)
- Laboratory certification including the name of the laboratory, name of the accreditor, accreditation ID number, scope of accreditation, and effective/expiration dates of accreditation. See Chapter 391-3-26 for more information.
- Discussion of potential for non aqueous phase liquids (http://www.epa.gov/remedytech/site-characterization-technologies-dnapl-investigations).
- Background determination procedures: As groundwater is considered homogeneous, there is no need to do a statistical analysis to determine background. Instead, the highest value detected in the up gradient well(s) may be used as the background level.
*All samples representing background concentrations must have turbidity readings less than 10 NTUs.
- A summary of all pertinent field data and laboratory results to conclude horizontal and vertical delineation to background concentrations.
List of Figures to Include
- A potentiometric surface map showing all monitoring well locations and groundwater elevations. The map should have a scale of 1” = 200’ or less.
- A map for each regulated substance detected in groundwater denoting sample locations, date the sample was collected, and concentrations at each sample location. All detections below the detection limit or practical quantitation limit should list concentration values as “<(insert limit)” rather than “BB”, “<DL” or “<PQL”. Units of concentrations should also be noted on this figure.
- Monitoring well diagrams (example of monitoring well diagram)
List of Tables to Include
- A table of analytical data for all groundwater samples collected at the site. The table should list:
- Each sample number or other designator
- Concentrations of each regulated substances detected with units specified
- Units of concentration for each regulated substance
- Monitoring well data table listing each monitoring well name, total depth, top of casing elevation, depth of screened interval, and most recent water level.
Other Items to Include
- Copy of the Chain-of-Custody for all samples collected.
- Copy of the laboratory analytical report.
Common Mistakes
- Using temporary wells or direct-push groundwater sampling technology as compliance points certify compliance with risk reduction standards or delineate the site.
- Improper sampling technique:
- Using bailers for sampling when not warranted
- Not using proper sampling materials (stainless steel, glass, and/or Teflon)
- Not following proper low-flow micropurging procedures to ensure stability of the groundwater prior to sampling (HSRA sampling protocol memo)
- Failure to get turbidity below 10 NTUs
- Failure to provide a detailed description of groundwater sampling procedures including a description of sampling equipment, purging procedures, sample collection procedures, sample containers, sample handling and preservation, chain-of-custody.