N.M. Admin. Code § 20.5.108.807

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

Section 20.5.108.807 - GROUNDWATER MONITORING REQUIREMENTS FOR USTS

Owners and operators of underground storage tanks may use groundwater monitoring as a method of release detection as long as the testing or monitoring for liquids on the groundwater meets all of the following requirements:

A. The regulated substance stored is immiscible in water and has a specific gravity of less than one.

B. Groundwater is never more than 20 feet from the ground surface and the hydraulic conductivity of the soil between the UST system and the monitoring wells or devices is not less than one one-hundredth centimeters per second (e.g., the soil should consist of gravels, coarse to medium sands, coarse silts or other permeable materials).

C. The slotted portion of the monitoring well casing shall be designed to prevent migration of natural soils or filter pack into the well and to allow entry of regulated substance on the water table into the well under both high and low groundwater conditions.

D. Monitoring wells shall be sealed from the ground surface to the top of the filter pack.

E. Monitoring wells or devices intercept the excavation zone or are as close to it as is technically feasible.

F. The continuous monitoring devices or manual methods used can detect the presence of at least one-eighth of an inch of non-aqueous phase liquid on top of the groundwater in the monitoring wells.

G. Within and immediately below the UST system excavation zone, the site is assessed to:

(1) ensure compliance with the requirements in Subsections A through E of this section; and

(2) establish the number and positioning of monitoring wells or devices that will detect releases from any portion of the tank that routinely contains product.

H. Site assessments conducted after the effective date of these regulations are signed by a qualified professional engineer or professional geologist, or equivalent licensed professional with experience in environmental engineering, hydrogeology, or other relevant technical discipline acceptable to the department and approved in advance by the department.

I. Monitoring wells are clearly marked and secured to avoid unauthorized access and tampering.

J. Owners and operators shall ensure that hand-held electronic and field equipment that is used for groundwater monitoring is:

(1) annually checked to ensure that the equipment is functioning properly; and

(2) calibrated prior to each sampling event in accordance with the manufacturer's instructions.

K. All records of the site assessment and groundwater monitoring system are maintained in accordance with 20.5.108.815 NMAC.

L. Monthly reports of groundwater monitoring and annual reports of functionality checks of electronic sampling equipment are maintained and provided to the department in accordance with 20.5.108.815 NMAC and 20.5.108.816 NMAC.

N.M. Admin. Code § 20.5.108.807

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