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Alternate Concentration Limits

Learn about ACLs, concentration limits, compliance points, corrective actions, and more in this comprehensive guide by Katie Rader from May 2019 as per OAC regulations.

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Alternate Concentration Limits

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  1. Alternate Concentration Limits Katie Rader May 2019

  2. OAC 3745-54-91Required RCRA GW Programs Detection: No Contamination Detected Compliance: Detected at Compliance Point Corrective Action: Exceeds the GWPS Between unit and property boundary

  3. OAC Rule 3745-54-92 Ground Water Protection Standard • Four Components: • List of Hazardous Constituents • Concentration Limit for Each Constituent • Point of Compliance • Compliance Period

  4. OAC Rule 3745-54-94 Concentration Limits • Background Level • Table 1 = MCLs • Alternate Concentration Limit

  5. OAC 3745-54-94 • How does an O/O decide which to use? • Can the O/O use a combination?

  6. ACLs

  7. Question #1 ACLs – What are they?

  8. 1. ACLs – What are they? • “Trigger level” above which movement into ground water corrective action under OAC 3745-54-100 is required. • Standard often based on risk or MCL • An ACL may be approved by the Director for a hazardous constituent if the level will not pose a substantial present or potential hazard to human health and the environment • Set at POC – also must be met “between” POC & POE • Requires long-term monitoring

  9. Question # 2 How does an O/O apply for an ACL?

  10. 2.How does O/O apply for an ACL? Submit an ACL Demonstration as part of: Permit Application Permit Renewal Permit Modification Post-Closure Plan

  11. Question # 3 How is a RCRA ACL different from a risk-based or site-wide CC level or a CERCLA ACL?

  12. 3. How is a RCRA ACL different from a risk-based or site-wide CC level or a CERCLA ACL? • RCRA ACL does not have to be met under the unit • RCRA ACLs may be higher than risk-based clean closure levels – due to use of fate & transport between POC & POE • RCRA ACLs only pertain to constituents w/out MCLs or background as their concentration limit • RCRA ACLs require long-term monitoring

  13. Question # 4

  14. 4. How are ACLs derived? • Determine allowable human health and environmental exposure level at POE • If POE = POC, POE target level = ACL • If POE is downgradient of POC, run fate & transport model substituting levels at the POC iteratively until POE target levels are reached. • Input concentrations at POC = ACL. • ACL must not be exceeded “between” POC & downgradient property boundary.

  15. Question # 5 What are Ohio EPA’s assumptions regarding location of the POE?

  16. ACL Point of Exposure Case 1: POC = POE Case 2: Plume Boundary On-Property Case 3: Plume Boundary Off-Property Case 4: Plume intersects Surface Water Case 5: Non- Potable GW

  17. ACL Case 1: POC = POE All new units above usable GW No detected contamination POC = POE No fate and transport Must not reach a receptor at an unsafe level prior to the POE.

  18. ACL Case 1. POC = POE Uncontaminated GW or Unit Abuts Property Limit

  19. ACL Case 2: Plume On-Property Above potentially usable GW Contamination confined to property Evaluate all exposures w/in plume POE no further than edge of plume Fate and Transport may be used Verification Monitoring at POE

  20. Case 2. Units with Plumes Within Property Boundary

  21. ACL Case 3: Plume Off-Property Above potentially usable GW Edge of plume extends off-property Evaluate all on-property exposures POE no further than original property boundary Fate & Transport may be used Verification Monitoring at POE

  22. Case 3. Contaminant Plume has Moved Off-Property

  23. ACL Case 4: POE at SW Facility owns property to surface water Plume reaches surface water body No SW statistically significant increase No unsafe levels reach receptors prior to discharge to SW Verification monitoring at GW/SW boundary All gw discharge to river

  24. ACL Case 4: POE at SW cont’d. May be within 500 yds of PWS Intake but SW Standards in OAC 3745-01 must be met. No increase in size of plume or extent of land > conc limit. Use restriction on property Contaminant level in gw is decreasing

  25. Case 4. Plume Discharging into Surface Water Upgradient

  26. ACL Case 5: Non-Potable GW Not only present but potential use Non-potable must be isolated from potable GW No risk to HHE Case by case in Ohio: <0.1 gpm Site over a rubber company injection well brine-contaminated aquifer (Bridgestone-Firestone) USD (Textileather) Seasonally perched aquifer (DaLite Screen)

  27. Case 5. Plume in Non-Potable GW

  28. Exclusion of GW Pathway for Case 5 • Closure Plan Review Guidance - GW Scoring Matrix • Not to be used solely • GW not used or potentially used for potable purposes: • w/in 0.5 mi of facility • Saturated zone yields less than 0.1 gpm • Will not emanate beyond property or to another potable zone • All on-property risk-exposure limits are met

  29. Question # 6 Mixing & Matching – How do you determine the POE Target Levels?

  30. 6. How to determine POE (Not ACL) target levels? A. Options – MCLs, background, and risk (RSLs*) B. If POE=POC, then: • May use all MCLs w/out adjustment (VI) • Background (natural or upgradient source) (VI) • RSLs* for all non-MCL and/or background • RSL* Multi-chemical adjustment • No fate and transport may be used * Use RSL table with excess cancer risk of 1E-06 and HI=1 adjusted to 1E-5.

  31. If POE=POC cont’d. • If the GW concentrations meet the multi- chemically adjusted RSLs with 10-5 and HI 1.0, they may use the multi-chemical adjusted RSL as the ACL. • If the GW concentrations don’t meet the multi-chemically adjusted RSLs with 10-5 and HI 1.0; or if concentrations exceed the MCLs or background, then the facility moves into corrective action under OAC Rule 3745-54-100.

  32. C. Target levels if POE is downgradient of POC: May mix MCLs, Background and risk (RSLs*) May use Fate & Transport May use: • All MCLs w/out adjustment (VI) • Background at POE (natural or upgradient source) • ACLs: • RSLs* for all non-MCL and/or background • RSL* Multi-chemical adjustment at POE • Multi-chemically adjusted RSL* = Exposure Point Concentration. • Fate & transport back calculate higher ACL at POC. * Use RSL table with excess cancer risk of 1E-06 and HI=1 adjusted to 1E-5.

  33. C. Target levels if POE is downgradient of POC cont’d: • If the GW concentrations meet the multi- chemically adjusted RSLs with 10-5 and HI= 1.0, they may use the multi-chemical adjusted RSL as the Exposure Point Concentration and through fate and transport back calculate the concentration at the POC which will = ACL. • If the GW concentrations do not meet that ACL or exceed the MCLs or background, then the facility moves into corrective action under OAC Rule 3745-54-100.

  34. D. How to multi-chemical adjust at the POE? Two Steps: 1. List appropriate contaminants > DL • Exclude COCs with Concentration Limits based on MCLs or Background • Perform multichemical adjustment on remaining COC RSLs with cumulative risk meeting 10-5 & HI =1. • Compare Exposure Point Concentrations in plume to multi-chemical adjusted RSL (or higher fate & transport value if POC does not = POE). 2. Site-specific concentrations w/in plume • Exposure Point Concentration – 95% UCL

  35. 95% UCL Exposure Point Concentration • Data from 3 wells in the center of the plume • 12 data points over at least one year • If there are not 3 contaminated wells, or if good data does not exist, use the overall highest concentration • Calculate upper 95% confidence limit on the arithmetic mean • # = risk input value, NOT POE target level

  36. E. Target levels if UA is not a likely source of drinking water? • If it has ANY present or potential future use… • If it is truly non-potable, then POE based on: • Inhalation (VI) • Dermal contact • Safety of other non-drinking water receptors • Maintaining isolation from potable aquifers • No Surface Water Exposure

  37. F. POE target levels if POE at surface water? • Compare to Surface Water Standards in OAC 3745-01: • Determine if flow is to Lake Erie or Ohio River • If within 500 yds of PWS Intake: must meet Drink Std • If not within 500 yds of PWS Intake: meet Non-Drink & Biological Stds • Must not statistically exceed background in SW • Sampling based on up/downstream & point of discharge • Samples collected during seasonal near- average conditions • Include mid-depth and sediment samples • USEPA RCRA Directive: 9481.1987(04)

  38. F. SW POE cont’d. • No dilution factor allowed (USEPS RCRA #9523.00(14)) • Compare mid-depth surface water values to OMZA (Outside Mixing Zone Average) • If values exceed OMZA, perform biosurvey • Compare sediment samples to McDonald Sediment Screening Toxicity Values • Do not assume water will be treated prior to consumption • Do not assume that all GW is discharging into SW…demonstration is required

  39. Question # 7 What information must be submitted to Ohio EPA as part of an ACL Demonstration?

  40. 7. What information must be submitted to Ohio EPA for an ACL demo? • USEPA Guidance Part I: Appendix B thru E https://epa.ohio.gov/derr/gw_support#1842410468-acl-guidance • Easy if new unit, no gw contamination, POC=POE, or non-Table 1 MCLs • If POE not = POC: • Modeling documentation (TGM Chapter 14) • Natural Attenuation expanded parameter list • GW use restriction

  41. Question #8

  42. 8. How does Ohio EPA decide whether to grant an ACL? Rule lists 19 Criteria to be considered: • Potential HH&E adverse effects prevented…not delayed for: • ground water quality AND • hydraulically-connected surface-water quality • General Guidelines: • No increase >POE target in size horizontally/vertically/ or concentration • Buying more property will NOT extend POE • Off-property potable water should meet unrestricted use

  43. Issues for any ACL demo : • POE target levels are technically justifiable • All pertinent info included • Representative data used for POE targets • Metal data appropriate – filtered or not • No receptors between POC and POE • DL < ACLs • If new parameter detected – redo risk calc • Protects potentially usable water • No adverse impact on HHE ..any proximity • Source addressed

  44. Issues if POE not = POC • POE modeling adequate and documented • Model re-evaluated on periodic basis • Additional parameters for Natural Attenuation • Sufficient use/access restrictions • Review 19 factors • Not: 100 gpm, SWAP Area, Sole Source • Plume not increasing in size (see note) • Every effort to keep plume on-property • Point of Action…MCL/Risk lines

  45. For Further Information: • USEPA ACL Guidance Parts I & II https://epa.ohio.gov/derr/gw_support#1842410468-acl-guidance • DERR Regulatory FAQs on OAC Rule 3745-54-94(A) and (B) https://epa.ohio.gov/derr/gw_support#1842410465-regulatory-faqs

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