15A NCAC 02N .0504. METHODS OF RELEASE DETECTION FOR TANKS

(a)  The "Methods of release detection for tanks" contained in 40 CFR 280.43 (Subpart D) have been adopted by reference in accordance with G.S. 150B‑14(c) except that:

(1)           40 CFR 280.43 (d)(2) is amended to read:  "Inventory control, or another test of equivalent performance approved by the Department, conducted in accordance with the requirements of 40 CFR 280.43(a)";

(2)           40 CFR 280.43(f)(7) is amended to read:  "Within and immediately below the UST system excavation zone, the site is assessed to ensure compliance with the requirements of 40 CFR 280.43(f)(1) through (f)(5), as modified by this Rule, and to establish the number and positioning of monitoring wells or devices that will detect releases from any portion of the tank that routinely contains products"; and

(3)           40 CFR 280.43(f)(3), (f)(4), and (f)(5) are not adopted by reference.

(b)  Wells used for monitoring or testing for liquids on the groundwater shall be:

(1)           For new installations, located within and at the end of the excavation having the lowest elevation and along piping at intervals not exceeding 50 feet; or

(2)           For existing installations, located in the excavation zone or as near to it as technically feasible and installed in a borehole at least four inches larger than the diameter of the casing;

(3)           A minimum of two inches in diameter.  The number of wells installed must be sufficient to detect releases from the UST system;

(4)           Equipped with a screen that extends from two feet below land surface to a depth of 20 feet below land surface or two feet below the seasonal low water level, whichever is shallower.  The screen shall be designed and installed to prevent the migration of natural soils or filter pack into the well while allowing the entry of regulated substances into the well under both high and low groundwater level conditions;

(5)           Surrounded with a clean sand or gravel to the the top of the screen, plugged and grouted the remaining distance to finished grade with cement grout;

(6)           Constructed of a permanent casing and screen material that is inert to the stored substance and is corrosion resistant;

(7)           Developed upon completion of installation until the water is clear and relatively sediment free;

(8)           Protected with a water tight cover and lockable cap;

(9)           Labeled as a liquid monitor well; and

(10)         Equipped with a continuously operating liquid leak detection device; or

(A)          For tanks storing petroleum products, tested at least once every 14 days with a device or hydrocarbon‑sensitive paste capable of detecting the liquid stored; or

(B)          For tanks storing hazardous substances, sampled and tested at least once every 14 days for the presence of the stored substance.

(c)  Wells used for monitoring or testing for liquids on the groundwater at new installations, and constructed in accordance with Paragraph (b) of this Rule, shall be deemed to be permitted in accordance with the requirements of 15A NCAC 2C .0105.

(d)  Any person completing or abandoning any well, used for testing of vapors or monitoring for liquids on the groundwater, shall submit the record required by Rule .0114(b) of the Well Construction Standards (15A NCAC 2C .0100).

(e)  The site assessments required by 40 CFR 280.43(e)(6) and 40 CFR 280.43(f)(7) shall be conducted by or under the supervision of a person qualified to assess site conditions.

(f)  Wells used for monitoring for the presence of vapors in the soil gas of the excavation zone shall be equipped with a continuously operating vapor detection device or tested at least once every 14 days for the presence of the substance stored.

 

History Note:        Authority G.S. 143‑215.3(a)(15); 143B‑282(2)(h); 150B‑14(c);

Eff. January 1, 1991.