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

The purpose of site characterization is to define the extent of 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 days of the release discovery in the 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) Define the extent of the source area(s) and determine the distribution and extent of sorbed, dissolved, vapor and free-phase contamination. Access must be obtained to off-site properties, including rights-of-way, if the extent of contamination extends beyond the release property boundary.

(1) Collect environmental samples to define the extent of contamination in the subsurface. Groundwater must be assessed unless there is reason to believe that it is not impacted and with the concurrence of the Director.

(2) Laboratory analysis of samples shall be as follows.

(i) Soil samples:

(A) Benzene, toluene, ethyl benzene, xylenes (BTEX);

(B) The appropriate range(s) of total petroleum hydrocarbons (TPH);

(C) Priority poly-nuclear aromatic hydrocarbons (PAHs) must be analyzed for the sample with the highest TEPH or TRPH concentration if the TEPH or TRPH exceeds the Tier I screening level of 500 mg/kg; and

(D) Other petroleum fuel additives or petroleum compounds that are suspected to have been released.

(ii) Groundwater samples:

(A) BTEX, methyl tertiary-butyl ether (MTBE);

(B) The appropriate range(s) of TPH; and

(C) Other petroleum fuel additives or regulated compounds that are suspected to have been released.

(iii) Soil vapor samples:

(A) Benzene.

(3) Identify all concentrations relative to the Tier I risk-based screening levels (RBSLs) listed in Table 5-1.

Table 5-1. Tier I RBSLs.

Media	Complete Exposure Pathway	Benzene	Toluene	Ethyl-benzene	Xylenes	MTBE
Surficial Soil [mg/kg]	Ingestion/ Dermal/ Inhalation	2.8	4,000	2,100	10,000	N/A
Subsurface Soil [mg/kg]	Leachate to Groundwater Ingestion	0.26	140	190	>Sat* or 260**	N/A
Soil Vapor [µg/m3]	Indoor Air Inhalation	2,900	>VP	>VP	>VP	N/A
Groundwater [mg/l]	Indoor Air Inhalation	0.016	10	26	2.9	N/A
	Groundwater Ingestion	0.005	1.0	0.7	10* or 1.4**	0.020

> VP Denotes that even at a concentration equal to the vapor pressure of the chemical, a hazard quotient of 1 is not exceeded.

> Sat Denotes that even at a concentration equal to the saturation of the chemical, a hazard quotient of 1 is not exceeded. N/A Not applicable. No established RBSL.

* This RBSL will be in effect for releases that occurred prior to September 14, 2004.

** This RBSL will be in effect for releases that occurred on or after September 14, 2004

(b) Collect site-specific geologic and hydro-geologic 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 groundwater flow.

(c) Evaluate all exposure pathways and identify impacted or potentially impacted POEs.

(d) Calculate Tier II site-specific target levels (SSTLs) for on-site contamination.

(e) Develop a Conceptual Site Model (CSM).

(f) Evaluate the need for active remediation.

Notes

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