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I ri Revii)nnl Recommendation. P;12e 30 of-?4 Appendix A vroundw,!ter to exceed water-qualify. Water clt!;ality objectives.' This may occur- at sites objectives. where hard to reach soil.contamination remains beneath building foundations. and the 4. ,-There are no existing water supply wells. contanainat'ion continues to leach to groundwater. surface +waters or other receptors threatened In these difficult cases. responsible parties may by the remaining contaminants in soil or arg tie that the incremental cost for funkier mass 'roundwater. removal exceeds the incremental benefit. 5. Pollutants remaining in Qrbundwaterdo not, Regional Board staff believe that in some cases it create or threaten to create risk to human' is reasonable to issue a NFA.R letterl'or sites that health and safely. or to facture beneficial do not meet \valer quality objectives but preserif:a use(s)of the 6roundwaler. Patterns of low risk and,are expecaed to meet water quality existing and fintrre demands for usable objectives in the near future. To receive such case water resources in the area must be closure; responsible parties need to demonstrate, considered in determining what period of that site contaminants are degradin2.. and that site time is reasonable to reach non-detectable contaminants will reduceao levels proieciive'of for backsroundl concentrates. beneficial uses in a reasonable period of time. - - 6. The plume size is stable-and.sufficiently Numerical water quality limits for petroleum fuel limited in lateral and.vertical extent and mixtures; constiruen►s and-additives; consistent contaminant concentratio'ns.delecled in with applicable water quality objectives, are groundwater show-a decreasing,trend +with available in the following staff document time.'One hydrologic cycle(four quarters) Beneficiol Use-AwJ/ee- ive Wan r Qualirn Limiis of riaonitoring after active remediation frn-C-•rnnl.2onenis ofPetrolc inn-Bo.+ed Fn ls. This measures have ceased is usually considered docuiiient is updated regularly and available on to he the minimum necessary to determine the Regional Board +wefsiteat: site ,ground+water and plume conditions. 1'1111:: w»�+.s�.+ cl?.ca.,�ov--rw(165 a ailtthic docu rrunrs ia!d 'x°:htrnl �\',',a1c rC)t!alityG?al�. . Issu•in6'NFAR letters for. low risk cases is consistent Nvith State regulations.and policies. Board siaff are currently requiring, the follovwing . The practice of closing low risk cases is also infbrrnation to support requests to issue a-NFAR . consistent widi the actions iakei-t by the State letter at UST sites with contaminant Water Resources Control Board and.Regional concentrations above ++rater quality objectives: Boards throu.�hout the State. 1. Demonstration that the plume is stable with 6_�; NFAR for Cases I_=xceedine \!1 ater_Quality either an overall annual decrease in size of- Objectives' rObjectives an annual decrease in contaminant concentration trend. . The ReL)ional Board .and LIA staff are receiving more requests each year from UST owners or ?. Calculations or modeling results. including Operators to 21-3111 closure of UST cases \\-here monitoring, verification-of model groundwater has not attained water quality conclusions. which show when water objectives. The responsible parties believe that quality objectives are predicted to be thew have implemented reasonable-cleanup and achieved. abatement at these sitesand that it is no longer technol021call+ a'econ.omicall-y feasible to� Verifledion that.there are no current or continue corrective actions and monitoring. anticipated uses of the impaired water within the timefranie projected to meet A common example is when remedial actions . ' water quality oli.jeciivzs. Institutional have reduced grounii+water contaminants by a controls may be needed to prevent such use large percentage. but constituents still exceed if this period is 11101 suflicienil\?shoat.