7 Colo. Code Regs. § 1101-14-5-2

Current through Register Vol. 47, No. 24, December 25, 2024

Section 7 CCR 1101-14-5-2 - Site Characterization

The purpose of site characterization is to define source area(s) of the release, determine the distribution of contamination in the subsurface, determine if POEs are impacted or potentially impacted, evaluate all exposure pathways and determine whether active remediation is necessary. Site characterization results must be submitted to OPS within 180 calendar days of the release discovery in the appropriate and current report format provided on the OPS website.

Upon confirmation of a release and completion of emergency response, the owner/operator shall complete the following tasks:

(a) Verify the source(s) and cause(s) of the release;

(b) Collect representative environmental samples for laboratory analyses in accordance with Section 5-3-1 to determine the vertical and horizontal distribution and extent of sorbed, dissolved, vapor, and free-phase contamination. Groundwater must be assessed when the potential for groundwater contamination has occurred;

(c) Identify potential receptors;

(d) Determine if POEs are potentially impacted or are impacted. If there are imminent threats to human health or the environment, mitigate completed exposure pathways to receptors (e.g., impacted water supply wells, surface water, or structures) in consultation with OPS;

(e) Evaluate all exposure pathways;

(f) Upon discovering the potential for contamination extending beyond the facility's property, or leased property boundary, the Responsible Party (RP) must notify OPS within 24 hours;

(g) If the extent of contamination extends beyond the facility boundary, request access to off-site properties, including rights-of-way. Send copies of requisition letter(s) to OPS and notify OPS within 30 days if access is not granted;

(h) Collect site-specific geologic and hydrogeologic data:

(1) Determine the predominant lithology in the unsaturated and saturated zones;

(2) Determine the depth to water, hydraulic gradient, and groundwater flow direction;

(3) Determine the site-specific hydraulic conductivity; and

(4) Evaluate other geologic conditions that influence (LNAPL), groundwater, and soil vapor movement;

(i) Develop a Conceptual Site Model (CSM);

(j) Calculate Tier II site-specific target levels (SSTLs) for on-site contamination;

(k) Evaluate the need for active remediation to meet Tier II closure criteria and identify feasible remedial technologies; and

(l) Determine whether active remediation is necessary. If pilot testing is necessary, provide the OPS technical reviewer with a detailed scope and cost for concurrence before execution.

5-2-1Laboratory Analysis of Samples

(a) Soil samples shall be analyzed for:

(1) Benzene, toluene, ethyl benzene, total xylenes, and naphthalene (BTEXN);

(2) The appropriate range(s) of total petroleum hydrocarbons (TPH) based upon the type of product released, as follows:

(i) Total volatile petroleum hydrocarbons (TVPH; gasoline range organics C6-C10);

(ii) Total extractable petroleum hydrocarbons (TEPH; diesel range organics 11-C28); and/or

(iii) Total recoverable petroleum hydrocarbons (TRPH; oil range organics C29-C35);

(3) Polynuclear aromatic hydrocarbons (PAHs) must be analyzed for the sample with the highest TEPH or TRPH concentration detected at the facility if the TEPH or TRPH exceeds the Tier I screening level of 500 mg/kg;

(4) The fuel additives tetraethyl lead (TEL; surface soil only), 1,2 dichloroethane (1,2 DCA), and ethylene dibromide (EDB) if any facility operated at the release location prior to January 1, 1996;

(5) Analysis of full volatile organic compounds (VOCs) when characterizing a release from a waste oil tank; and

(6) If stored at the facility, other regulated compounds, including ethanol, methanol, petroleum solvents, and glycols.

(b) Water samples shall be analyzed for:

(1) Benzene, toluene, ethyl benzene, total xylenes, and naphthalene (BTEXN);

(2) The appropriate range(s) of total petroleum hydrocarbons (TPH):

(i) Total volatile petroleum hydrocarbons (TVPH; gasoline range organics C6-C10);

(ii) Total extractable petroleum hydrocarbons (TEPH; diesel range organics C11-C28); and/or

(iii) Total recoverable petroleum hydrocarbons (TRPH; oil range organics C29-C35).

(3) Polynuclear aromatic hydrocarbons (PAHs), if any subsurface soil sample, contains PAHs above RBSLs. See the Petroleum Guidance for further information;

(4) The fuel additives 1,2 dichloroethane (1,2 DCA), and ethylene dibromide (EDB) if any facility operated at the release location before January 1, 1996;

(5) The fuel additive methyl tertiary butyl ether (MTBE) if any facility operated at the release location before May 1, 2002;

(6) Analysis of full volatile organic compounds (VOCs) when characterizing a release from a waste oil tank; and

(7) If stored at the facility, other regulated compounds, including ethanol, methanol, petroleum solvents, and glycols.

(c) Soil vapor samples shall be analyzed for:

(1) Benzene, toluene, ethyl benzene, total xylenes, and naphthalene (BTEXN);

(2) The fuel additives 1,2 dichloroethane (1,2 DCA) and/or ethylene dibromide (EDB) if these compounds are present in soil or groundwater; and

(3) Field measurements of oxygen, carbon dioxide, and methane.

5-2-2Tier I Risk-Based Screening Levels (RBSLs)

Identify all concentrations relative to the Tier I RBSLs in Table 5-1.

Table 5-1 Tier I Risk Based Screening Levels

Chemical of Concern	Surficial Soil RBSLs [mg/kg] (Ingestion, Dermal, Inhalation)	Subsurface Soil RBSLs [mg/kg] (Leachate to GW, Ingestion)	Reg. 41 Colorado Groundwater Standards [µg/L]	Soil Vapor [mg/m3]
Benzene	1.6	0.52	5	213
Toluene	4,889	91	560	44,200
Ethylbenzene	8	212	700	776
Xylenes	577	364	1,400	17,200
Naphthalene	3.8	143	140	227
TVPH¹	500	500	N/A	N/A
TEPH¹	500	500	N/A	N/A
TRPH¹	500	500	N/A	N/A
Polycyclic Aromatic Hydrocarbons (PAHs)
Acenaphthene	3,586	1,389	420	N/A
Anthracene	17,932	22,583	2,100	N/A
Benz(a) anthracene	1.3	18.6	0.16	N/A
Benzo(a) pyrene	0.1	6.2	0.016	N/A
Benzo(b) fluoranthene	1.3	63	0.16	N/A
Benzo(k) fluoranthene	13	617	1.6	N/A
Chrysene	131	1,898	16	N/A
Dibenz(a,h) anthracene	0.1	20	0.016	N/A
Fluoranthene	2,391	10,202	280	N/A
Fluorene	2,391	1,687	280	N/A
Indeno (1,2,3-cd) pyrene	1.3	205	0.16	N/A
Pyrene	1,793	7,498	210	N/A
Gasoline Additives³
Tetraethyl lead (TEL)²	0.01³	N/A	N/A	N/A
Ethylene dibromide (EDB)²	0.05	0.001	0.02 to 0.05⁴	0.0674
1,2-Dichloroethane (1,2-DCA)²	0.63	0.012	0.38 to 5⁴	0.204
Methyl tert-butyl ether (MTBE)	N/A	N/A	20⁵	N/A

[Notes:

¹ OPS has established a threshold value of 500 mg/kg for TPH in soil to define the extent of contamination and identify sites where PAHs may pose a risk to human health and the environment. See OPS guidance for further information.

² Analysis required at release locations where a facility operated on or before January 1, 1996 (TEL; EDB; 1,2 DCA) or May 1, 2002 (MTBE).

³ The laboratory reporting limit must be reported in all cases.

⁴ The first number in the range is a strictly health-based value. The second number in the range is a maximum contaminant level determined to be an acceptable level of this chemical in water supplies, taking treatability and laboratory detection limits into account. OPS will default to the second number in the range unless contamination is within the boundaries of an existing or reasonably anticipated water supply.

⁵ US EPA Drinking Water Advisory based on taste/odor threshold and adopted by OPS.

7 CCR 1101-14-5-2

37 CR 18, September 25, 2014, effective 10/15/2014

39 CR 18, September 25, 2016, effective 1/1/2017

40 CR 05, March 10, 2017, effective 5/1/2017

40 CR 07, April 10, 2017, effective 5/1/2017

41 CR 07, April 10, 2018, effective 5/1/2018

42 CR 04, February 25, 2019, effective 3/17/2019

47 CR 23, December 10, 2024, effective 1/1/2025