NAC445A.22745. Contamination of groundwater: Conditions for terminating remediation of release; monitoring.

     1. After any corrective action required by NAC 445A.22725 involving the treatment of groundwater is begun, the owner or operator may terminate remediation of the release after submitting written documentation and receiving written concurrence from the Division if:

     (a) An assessment of the contaminated groundwater is conducted and indicates that the level of contamination is consistently below the action level for that water established pursuant to NAC 445A.22735;

     (b) A test of asymptotic concentrations specified in paragraph (c) is not appropriate, as determined by the Division based on the nature of the treatment used or the conditions at the site which limit the effectiveness of any available treatment, and the owner or operator complies with the conditions for the termination of remediation set forth in an approved plan of corrective action or an approved amendment to such a plan; or

     (c) After the groundwater is treated for not less than 1 year, the concentration of dissolved constituents in the water, measured monthly, fits a curve that is substantially linear and approaches zero slope at the final portion of the curve. The curve must be established using the following equation:

C   =   Cf   +   Coe^-kt

Where:    “C”   means the concentration of the contaminant at “t” in micrograms per liter.

               “Cf” means the final concentration of the contaminant in micrograms per liter which the curve approaches asymptotically.

               “Co” means the difference between the final concentration of the contaminant and the concentration of the contaminant at time zero in micrograms per liter.

               “e”    means the base of the natural log or 2.718.

               “t”    means the time measured in days.

               “k”    means the decay constant.

     2. After any remediation is terminated pursuant to subsection 1, the owner or operator shall ensure that any contaminated groundwater is monitored for not less than 1 year to determine the level of contamination in the groundwater. The Division shall determine the frequency of any monitoring required pursuant to this subsection, except that the Division shall not require monitoring more frequently than once each month.

     (Added to NAC by Environmental Comm’n, eff. 10-3-96; A by R189-08, 8-25-2009)