Code of Colorado Regulations
400 - Department of Natural Resources
404 - Oil and Gas Conservation Commission
2 CCR 404-1 - PRACTICE AND PROCEDURE
Section 915 - CONCENTRATIONS AND SAMPLING FOR SOIL AND GROUNDWATER

Universal Citation: 2 CO Code Regs 404-1 ยง 915

Current through Register Vol. 47, No. 17, September 10, 2024

a. Soil Concentrations. Operators will adhere to the concentrations for soil cleanup in Table 915-1. Operators will use Residential Soil Screening Level Concentrations as cleanup levels unless required otherwise by the Director. The Director will require adherence to the Protection of Groundwater Soil Screening Levels when a pathway to Groundwater exists. When the Director has reasonable cause to believe that oil and gas exploration-related compounds or parameters other than those listed in Table 915-1 may be present, the Director may require additional analyses of compounds included in the EPA RSLs, as incorporated by reference in Rule 901.b.

b. Soil Suitability for Reclamation. Operators will adhere to the concentrations for soil in Table 915-1 for restoring soil to the agronomic properties for electrical conductivity ("EC"), sodium adsorption ratio ("SAR"), pH, and boron for soils. Subject to prior approval by the Director, Operators may leave materials with elevated concentrations of EC, SAR, or pH in situ. In such cases, the Operator will provide a detailed Reclamation plan that includes, but is not limited to, soil analysis from adjacent undisturbed lands, revegetation techniques, site stabilization, and details of seeded species.

c. Groundwater Concentrations. Operators will adhere to the concentrations for Groundwater in Table 915-1. The Groundwater standards and analytical methods are derived from the Groundwater standards and classifications established by WQCC Regulation 41 numeric and narrative Groundwater quality standards and classifications, as incorporated by reference in Rule 901.b.

d. Additional Groundwater Analyses. When the Director has reasonable cause to believe that oil and gas exploration-related compounds or parameters other than those listed in Table 915-1 may be present, the Director may require additional analyses beyond the list of compounds included in Table 915-1 for Groundwater including but not limited to:

(1) Any element, compound or parameter listed in Table A and Tables 1, 2, 3, and 4 of WQCC Regulation 41, as incorporated by reference in Rule 901.b.

(2) In accordance with the Narrative Standards of WQCC Regulation 41.5.A, any element, compound, or parameter not listed in Table A or Tables 1, 2, 3, and 4 of WQCC Regulation 41, as incorporated by reference in Rule 901.b, which alone or in combination with other substances, are in concentrations shown to be:
A. Carcinogenic, mutagenic, teratogenic, or toxic to human beings; or,

B. A danger to public health, safety, and welfare.

e. Sampling and Analysis. Analysis will be conducted using EPA SW-846 analytical methods, as incorporated by reference in Rule 901.b, or, with the Director's approval, other analytical methods published by nationally-recognized organizations. Analyses of samples will be performed by laboratories that maintain state or national accreditation programs. Operators will adhere to the specialized agricultural analytical methods where required pursuant to footnote 2 to Table 915-1. A lab with experience with agricultural analysis will be used.

(1) Methods for Sampling and Analysis. Sampling and analysis for site investigation or confirmation of successful Remediation will be conducted to determine the nature and extent of impact and confirm compliance with appropriate concentration levels in Table 915-1 and WQCC Regulation 41 numeric and narrative Groundwater quality standards and classifications, as incorporated by reference in Rule 901.b.
A. Field Analysis. Field measurements and field tests will be conducted using appropriate equipment, calibrated and operated according to manufacturer specifications, by personnel trained and familiar with the equipment. Operators will provide all field measurements and tests to the Director upon request, including but not limited to field notes, field screening logs, soil boring logs, monitor well construction Logs, pump test reports, photographs, and soil vapor screening results.

B. Sample Collection. Samples will be collected, preserved, documented, and shipped or delivered to a laboratory under a chain-of-custody protocol using standard environmental sampling procedures in a manner to ensure accurate representation of site conditions.

C. Laboratory Analytical Methods. Laboratories will analyze samples using standard methods (including but not limited to EPA SW-846, as incorporated by reference in Rule 901.b) appropriate for detecting the target analyte. The method selected will have detection limits less than or equal to the cleanup concentrations in Table 915-1 and WQCC Regulation 41, as incorporated by reference in Rule 901.b.

D. Background Sampling. The Director may require the Operator to take site-specific samples, outside of the area disturbed by Oil and Gas Operations, of comparable, nearby, non-impacted, native soil, Groundwater or other media to establish background conditions.

(2) Soil Sampling and Analysis.
A. Applicability. If soil contamination is suspected or known to exist as a result of Spills or Releases or E&P Waste management, Operators will collect and analyze representative samples of soil pursuant to this Rule 915.e.(2).

B. Sample Collection. Samples will be collected from areas most likely to have been impacted, and the horizontal and vertical extent of contamination will be determined. The number and location of samples will be appropriate to determine the horizontal and vertical extent of the impact.

C. Sample Analysis. Operators will analyze soil samples for contaminants of concern listed in Table 915-1 as appropriate to assess the impact or confirm Remediation. If an Operator believes it is appropriate to modify the list of contaminants of concern, the Operator will submit, and obtain the Director's approval of, a modified list of contaminants of concern through a Form 19 or Form 27, as applicable. The list will be based on site specific E&P Waste profile and process knowledge. Operators will analyze samples for additional contaminants of concern upon the Director's request.

D. Soil Background Determination. For impacts to soil due to E&P Waste, samples from comparable, nearby non-impacted native soil will be collected and analyzed for purposes of establishing background soil conditions including pH, EC, SAR, and other constituents as identified in the E&P Waste profile.

(3) Groundwater Sampling and Analysis.
A. Applicability. Operators will collect and analyze representative samples of Groundwater if:
i. Groundwater contamination is suspected or is known to exceed the concentrations in cleanup Table 915-1 or WQCC Regulation 41 numeric and narrative Groundwater quality standards and classifications, as incorporated by reference in Rule 901.b;

ii. Impacted soils are in contact with Groundwater; or

iii. Impacts to soils extend down to the high water table.

B. Sample Collection. Operators will collect samples as soon as possible from areas most likely to have been impacted: immediately downgradient or in the middle of excavated areas in close proximity to the suspected source of the impact.
i. The number and location of samples will be appropriate to determine the horizontal and vertical extent of the impact.

ii. If the cleanup concentrations in Table 915-1 or WQCC Regulation 41 numeric and narrative Groundwater quality standards and classifications, as incorporated by reference in Rule 901.b, are exceeded, the direction of flow and a Groundwater gradient will be established.

iii. The Director may require the installation of temporary or permanent monitoring wells as necessary for sample collection. All monitoring wells will be constructed and permitted in accordance with the State Engineer's Water Well Construction and Permitting Rules, as incorporated by reference in Rule 901.b.

C. Sample Analysis. Operators will analyze Groundwater samples for constituents of concern listed in Table 915-1, or other parameters appropriate for evaluating the impact, to assess the impact or confirm Remediation. If an Operator believes it is appropriate to modify the list of constituents of concern, the Operator will submit, and obtain the Director's approval of, a modified list of constituents of concern through a Form 19 or Form 27, as applicable. The list will be based on site specific E&P Waste profile and process knowledge. Operators will analyze samples for additional constituents of concern upon the Director's request.

D. Impacted Groundwater. Pursuant to Rule 913.c.(6), if Groundwater contaminants exceed the concentrations listed in Table 915-1 or in WQCC Regulation 41 numeric and narrative Groundwater quality standards and classifications, as incorporated by reference in Rule 901.b, Operators will notify the Director and submit to the Director for prior approval a Form 27 for the investigation, Remediation, or monitoring of Groundwater to meet the required cleanup concentrations in Table 915-1 or in WQCC Regulation 41 numeric and narrative Groundwater quality standards and classifications, as incorporated by reference in Rule 901.b.

(4) Waste and Produced Fluids Sampling and Analysis. When required by the Director, Operators will collect samples necessary to adequately characterize the composition of produced oil, condensate, water, drilling Fluids, drill cuttings, production gases, Bradenhead gases, soil gas, and soil gas seeps. The Operator will submit, and obtain the Director's approval of the number of samples collected, the analyte lists, and analytical methods appropriate to the waste or production stream.

f. Remediations in Progress. For sites that are subject to an open Form 19 or Form 27 as of January 15, 2021, Operators may seek the Director's permission to comply with the version of Table 910-1 that was previously in effect, if Remediation is completed by January 15, 2022. If Remediation at a site subject to an open Form 19 or Form 27 is not completed by January 15, 2022, then the Operator will comply with the current version of Table 915-1.

Table 915-1

CLEANUP CONCENTRATIONS

Contaminant of Concern

Concentrations

Soil TPH (total volatile [C6-C10] and extractable [C10-C36] hydrocarbons)

500mg/kg

Soils and Groundwater - liquid hydrocarbons including condensate and oil

below visual detection limits

Soil Suitability for Reclamation

Electrical conductivity (EC) (by saturated paste method)1,2

<4mmhos/cm

Sodium adsorption ratio (SAR) (by saturated paste method)1,2,3

<6

pH (by saturated paste method)1,2

6-8.3

boron (hot water soluble soil extract)1,2,3

2mg/l

Organic Compounds in Groundwater4

Benzene

5µg/l

toluene5

560 to 1,000µg/l

Ethylbenzene

700µg/l

xylenes (sum of o-, m- and p- isomers = total xylenes)5

1,400 to 10,000µg/l

naphthalene

140µg/l

1,2,4-trimethylbenzene

67µg/l

1,3,5-trimethylbenzene

67µg/l

Groundwater Inorganic Parameters4

total dissolved solids (TDS)1

<1.25 X local background

chloride ion1

250mg/l or <1.25 X local background

sulfate ion1

250mg/l or <1.25 X local background

Residential Soil Screening Level Concentrations (mg/kg)7

Protection of Groundwater Soil Screening Level Concentrations (mg/kg) Risk Based (R) and MCL Based (M)7,8

Organic Compounds in Soils6, 9, 10

benzene

1.2

0.0026 (M)

toluene

490

0.69 (M)

ethylbenzene

5.8

0.78 (M)

xylenes (sum of o-, m- and p- isomers = total xylenes)

58

9.9 (M)

1,2,4-trimethylbenzene

30

0.0081 (R)

1,3,5-trimethylbenzene

27

0.0087 (R)

acenaphthene

360

0.55 (R)

anthracene

1800

5.8 (R)

benz(a)anthracene

1.1

0.011 (R)

benzo(b)fluoranthene

1.1

0.3 (R)

benzo(k)fluoranthene

11

2.9 (R)

benzo(a)pyrene

0.11

0.24 (M)

chrysene

110

9 (R)

dibenzo(a,h)anthracene

0.11

0.096 (R)

fluoranthene

240

8.9 (R)

fluorene

240

0.54 (R)

indeno(1,2,3-cd)pyrene

1.1

0.98 (R)

1-methylnaphthalene

18

0.006 (R)

2-methylnaphthalene

24

0.019 (R)

naphthalene

2

0.0038 (R)

pyrene

180

1.3 (R)

Metals in Soils1, 6, 9, 10, 11

arsenic

0.68

0.29 (M)

barium

15000

82 (M)

cadmium

71

0.38 (M)

chromium (VI)

0.3

0.00067 (R)

copper

3100

46 (M)

lead

400

14 (M)

nickel

1500

26 (R)

selenium

390

0.26 (M)

silver

390

0.8 (R)

zinc

23000

370 (R)

Table 915-1 (continued) footnotes

1 The Director will consider site-specific background concentrations or reference levels in native soils and Groundwater.

2 Soil suitability thresholds for electrical conductivity ("EC"), pH, and sodium adsorption ratio ("SAR") in soils are based on use of saturated paste preparation methods, followed by analysis. Soil suitability thresholds for available boron are based on hot water soluble (or DPTA/sorbitol) extraction followed by analysis. Methods for preparation and analysis of the soil suitability parameters can be found in Soil, Plant, and Water Reference Methods for the Western Region, as incorporated by reference in Rule 901.b.

3 With the Director's prior approval, SAR levels and the concentration for hot water soluble boron may be modified based on land use, depth, or characteristics of the vegetative community.

4 Concentrations for Groundwater are taken from WQCC Regulation 41, as incorporated by reference in Rule 901.b.

5 For toluene and xylenes (total), the first number in the range is a strictly health-based value based on the WQCC's established methodology for human health-based standards. The second number in the range is a maximum contaminant level ("MCL"), established under the federal Safe Drinking Water Act which has been determined to be an acceptable level of this Chemical in public water supplies, taking treatability and laboratory detection limits into account. The WQCC intends that control requirements for this Chemical be implemented to attain a level of ambient water quality that is at least equal to the first number in the range except as follows:

1) where Groundwater quality exceeds the first number in the range due to a Release of contaminants that occurred prior to September 14, 2004 (regardless of the date of discovery or subsequent migration of such contaminants), clean-up levels for the entire contaminant plume will be no more restrictive than the second number in the range or the Groundwater quality resulting from such Release, whichever is more protective; and

2) whenever the WQCC has adopted alternative, site-specific standards for the Chemical, the site-specific standards will apply instead of these statewide standards.

6 Concentrations for organic compounds and metals in soils are taken from the November 2020 EPA Regional Screening Levels ("EPA RSLs") for Chemical Contaminants at Superfund Sites, as incorporated by reference in Rule 901.b.

7 If there is no pathway for communication with Groundwater, then residential soil screening levels apply for organic compounds and metals. If the Director determines that a pathway to Groundwater exists, then the protection of Groundwater soil screening levels will apply, secondary to actual measured concentrations of the contaminants of concern in Groundwater.

8 The letter "(R)" following a protection of Groundwater soil screening level indicates the concentration is derived from a risk-based approach. The letter "(M)" following a protection of Groundwater soil screening level indicates the concentration is derived from the drinking water MCL.

9 If the method detection limit ("MDL") or practical quantitation limit ("PQL") for a pollutant is higher (less stringent) than a threshold concentration listed in Table 915-1, the Director may allow an Operator to substitute the MDL or PQL for the concentration listed in Table 915-1.

10 The risk based cleanup concentrations for organic compounds in soils shown in Table 915-1 are taken from the EPA RSLs, as incorporated by reference in Rule 901.b, tables for Target Risk ("TR") = 1x10-6 and Target Hazard Quotient ("THQ")=0.1. The risk-based cleanup concentrations for metals in soils shown in Table 915-1 are taken from the EPA RSLs, as incorporated by reference in Rule 901.b, tables for TR=1X10-6 and THQ=1. The EPA RSL Frequently Asked Questions pages suggest that the THQ=0.1 tables are appropriate when more than 1 compound of concern is to be considered as present or likely to be present as is typical in soils impacted with organic compounds in Spills or Releases of produced water or liquid hydrocarbons.

11 The Director will consider Residential Soil Screening Level Concentrations up to 1.25 times site specific background levels for metals in soil.

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