N.M. Admin. Code § 20.5.120.2008

Current through Register Vol. 35, No. 23, December 10, 2024

Section 20.5.120.2008 - MINIMUM SITE ASSESSMENT, PRELIMINARY INVESTIGATION - REQUIREMENTS

Owners and operators shall conduct a preliminary investigation in accordance with this Subsection and under a timeline approved by the department or the timeline set forth in Subsection E of 20.5.120.2000 NMAC. The preliminary investigation shall determine the following, unless otherwise approved by the department.

A. If not previously identified and reported under 20.5.120.2003 NMAC, the preliminary investigation shall determine the regulated substance released or suspected of being released at the site, the media of concern, current and potential receptors, current and anticipated use of property, complete and incomplete exposure pathways, and routes of exposure.

B. The preliminary investigation shall also determine the horizontal and vertical extent and magnitude of soil contamination.

(1) Owners and operators shall conduct a soil boring survey by advancing a continuously cored soil boring at each area of release where soil contamination is most likely to be encountered unless otherwise directed by the department. The initial incident report and a soil vapor survey may be used in locating these areas. Owners and operators shall advance at least one of the borings into the groundwater saturated zone or, with approval from the department, to a depth at which measured levels of contaminants in soil are no longer detectable by laboratory analysis, and vapor concentrations, as determined with a field instrument, are less than 100 whole instrument units.

(2) Owners and operators shall advance at least four additional soil borings to characterize the release within property boundaries. Borings shall be completed to the depth at which contaminants in soil are no longer detectable by laboratory analysis, and vapor concentrations, as determined with a field instrument, are less than 100 whole instruments units. If the soil borings indicate that contaminated soil extends beyond the boundary of the property on which the storage tank system is located, owners and operators shall advance soil borings sufficient to characterize the extent and magnitude of contamination within site boundaries.

(3) The preliminary investigation shall assess, at five-foot intervals, field estimates of concentrations of contaminants of concern in the soil borings and select and prepare samples for laboratory analysis.

(4) Owners and operators shall gather field data for soil classification, determining and recording color, grain size, texture, description of lithification, plasticity and clay content.

(5) The preliminary investigation shall include derived values for soil bulk density (g/cc), soil moisture content (percent by mass), and effective porosity, and fraction organic carbon content (percent by mass) using samples taken from an uncontaminated area of the vadose zone.

(6) The preliminary investigation shall delimit the horizontal and vertical extent of contaminant saturated soil as defined in 20.5.101.7 NMAC.

C. The preliminary investigation shall determine whether groundwater or surface water has been contaminated above applicable standards or whether a potential for groundwater or surface water contamination is present by performing the following:

(1) install at least three groundwater monitoring wells at locations where the results of the soil boring survey conducted pursuant to this section indicate that groundwater may be contaminated; owners and operators shall:

(a) locate monitoring wells so that groundwater gradient can be determined;

(b) install at least one monitoring well on site in the area of highest contamination as determined by the soil borings installed in conformance with the initial incident report and other relevant information;

(c) install one of the monitoring wells in the estimated down-gradient direction from the area of highest contamination;

(d) construct wells in accordance with all applicable federal, state and local laws and regulations; and

(e) survey the wells using a New Mexico licensed professional surveyor, in decimal degrees of latitude and longitude in accordance with NAD 83;

(2) calculate the direction and gradient of groundwater flow;

(3) inspect all monitoring wells for the presence of NAPL using a method approved by the department; if NAPL is present in any well, measure the apparent thickness, delimit its horizontal extent, and initiate recovery procedures in accordance with 20.5.120.2005 NMAC; and

(4) sample each monitoring well that does not contain NAPL and analyze the sample for contaminants of concern to determine whether:

(a) immediate mitigation procedures are warranted; and

(b) other hazardous conditions exist as a result of the release if not previously identified in accordance with 20.5.120.2002 NMAC by:

(i) identifying the location and depth of underground utilities and other subsurface structures on or adjacent to the site not identified earlier in accordance with Subsection E of 20.5.120.2002 NMAC;

(ii) checking for the presence of vapors in accordance with 20.5.120.2002 and 20.5.120.2008 NMAC; and

D. Owners and operators shall identify all other hazards and potential threats to public health, safety and welfare and the environment which may exist as a result of the release to determine if:

(1) immediate mitigation procedures are warranted; and

(2) other hazardous conditions exist as a result of the release if not previously identified in accordance with 20.5.120.2003 NMAC by;

(a) identifying the location and depth of underground utilities and other subsurface structures on or adjacent to the site not identified earlier in accordance with Subsection E of 20.5.120.2002 NMAC.

(b) checking for the presence of vapors in accordance with 20.5.120.2002 and 20.5.120.2008 NMAC.

N.M. Admin. Code § 20.5.120.2008

Adopted by New Mexico Register, Volume XXIX, Issue 14, July 24, 2018, eff. 7/24/2018