Agenda - 09-29-1999 - 5a - Laserfiche WebLink

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SEP-27-1999 •14 24 JOYCE ENGINEERING INC. 1 336 323 0093 P.02/04 StC~e of North Carolina • Department of Environment, Hevlth and Natural Resources ~ ` • ~ Division of Environmentol Monogement James 8. Hunt, Jr., GovgrnOr ~~'~ Jonathan B..Howes, Secretary Q ~ ~--~ A. Preston Howord, Jr., P.E., DlreCtor GROUNDWATER SECTION October 6, I995 Eavironmeatal Service Companies and Consuhagts ~ • Subject: Changes in Technical~Policy Concerning Slug Tests This is to notify you of specific corrections and revisions that -tiere made zo t~s slag t.~t policy statetnett! that oyes issued on Jute ~0, 1994. The June 3Q; 1994 statemer.L indicated that ~hz Division of Environmental Mariagemeat (DEM) would only reimburse for slug tests perrorrnea iii rt~Onitoring wills that were co~duettd with'the etrtire length of well screen aad sand pack within me saturated zone. Based on further evaluation. of the published scientific: literature, the DEM has arnendod-its policy to e1low for reunbursemcm of slug trsts~petformed in motitoring,wclls that ire screened across the water teh[e, provided that these tests are imQlemeated and analyzed in accuz'dauce with the peer-reviewed, published test. method utdized. Bauwer and Rice (1976 and 29893 aad Hvorsicv (1951}ere the most con~ori test ntetlict3s used for partially.penetrati:ig wells in uaconfiued aquifers .These aieciwds tray be used- Fur uotli "slug-in" tens .(falling head tests) and "slug-out" tests (rising head, recovery or bait tcstsj in monitoring weI1s where the weII screen .and sand pack are entirely below the water table . F~~r monitoring wdls screened acrws the water table, tueso methods may only be used for slug-out 'tests. Slug-in tests are Dot appropriate,.. since Bart of the water added, would Clow out o#' the ael1 ir~to the vadose zone resulting is ea ovErestimation of the hydraulic conductivity. Furthermore, it should be noted that only the length ofwcll screen located is the saturated zone should be used tar~ttrta:-tc hydraulic conductivity. Using the total screen-length would result in undares3mating this. pa:a.rctr "!'ht June 30, 1994 poli_ry statement alsoindicst~d that hydraulic conductivity values ~: btairc-d from sluff tests would not be allowable for use in groundwater. models. Hnwever, Sit~Cd Slug tests t~rc generally considered an appropriate means of estimating the order of tnagnitudr of hvdrauIi Conductivity, the.- DEM has revised its .policy to allow for the use of slug test data t~ .mode! groundwater flow ai locations-where there :are ao potentially impacted .receptors- that -pose. a . risk to human health and the ettvironmert and;wherc corrective actiau under NCAC 15.4 21_.DIOb(1:),(l)' o (m) is ,proposed. Pumping-tests will still be required for locations where it is uecessazy ~o ~btair, tl;r most accurate iydrogeologic data possible (e.g:, there. are potentially lmuacted receptors-that :raS- pose arisk to human health or the emrironment, or for designing groundwater remediation ~•ste~*.:s that involve the withdrawal of groundwater). P.O. Box 29535. RdeiAh. North Camino 276260836 TelepF+ot-e 919-J33-70 t 5 FAX 914-733-3=S9b ~, Eavai OoportunNV atArmath~- Amon ~o~re+ 6~ recycled t Oz ~-cansurat ~~~