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G Pitch Project Memorandum - September 13, 1984 2 site with similar hydrologic conditions. The use in this study of data from Saguaclie, Colorado, has probably resulted in a serious underesti- mation of potential annual infiltration. This study should address the necessity and adequacy of the clay- barrier containment system that is proposed for the stockpiles. The b- inch clay cap that is proposed would probably be susceptible to breaching because of settling in the stockpiles and underlying waste dumps and would be difficult to install without gaps. The study should investigate a range of conditions fvr each dispersion scenario which should include: 1) no breaching of the cap, 2> varying degrees of partial breaching, and ') total breaching of the cap (catastrophic failure or no-cap desigr.>. These different infiltration conditions should be studied because the rate of infiltration may greatly control the retention time of fluids in the piles. The"t'bnt`3ii`i'in'ent~asy"stem should•~6e-yam ly=ed°to"d`eterinine the 'static head•.necessary_to cause deakage_,at.-tk:e. base-.ard whether- retention..of fluid: in the piles will ~ause.wmecha'rn~3"`zrr t'a'tr'ility 'and 'possible .ca-tastre;,ha•c failure of the The limited data presented f:-vn the le.?ch tests indicate t~:at high concentratio.^.=_. a•f eleme.^.ts .may be teat:^.ed if leschates ha•re long retention times. The responses to the the adequacy review clarif~,• some of the q,_:es=ions that :-sere r=iced cant:=rning e::perimerta? condi±ions for the Ieach tests trot na additian.al resists were given. The responses -~al.r.e ±^.~ general ratirnale fcr the as~:r:pticns ~!.=_.ed to de±ermine the laa:=hate cencer.tratiors but n0 actual d3t; :s given to show the leach tit,;°s where ~.hese assumptions hold try:=. ~TJata is given fvr a i~~-day leach t_st b~ct ra indication is given ~.- the !:pper time limit t~:at th4 linear elation=.hip of ccnc.antr:=,tion =..^d 1e~ch time applies. Cancentratiars might ga to :r.•uch higher levels if rho relationship applies to ie.ach tim=s significantly longer t!-~an ten days. More detailed data should 5e available to c.•a:v leach a.tes and cancer.tra- ticns for periods cf time up to that required far eg~:ilibrium to be =~prvaci~ed b:_t;•+eer, the leaches*.s ar,d stc•~I:pile r,~.te-iais. ..- such data _~ not av-il.=.;^.ie from the repot±ed st!_oiies, s~ddi::e.^.al haci-: --_-s st:v~ad tre ~~.--•Jucted. Tha potential .or seepage of _~aci-:.=.te r. ~n _ .~ =s.se ~: tea piles ..and =_. ~__,--flan into the adjacent =_.I•~iis sho~;ld rcr_n=e=.+iaatFd .•• deiail. The Da;r,es and Moore st=:dy dues act .sde•~~cateiy addr:>ss this issue beca!:se a=_.sumptions used and =~..^.cius,ans dr=s^en :n other p=rts of the study indicate thsa the ~ffec± ware not sio .: _~_...^.t. T::^.a response G, ~ _. given to ±he .=r_ _~ evieaa ~a~_FS irdic.=,te that ., leachat.= toll°~ts i^ the piles that _eepage at ti!e base will occur .'end _hat the '_°n- tial for percolation _.•tv the _~.rrvundirg _vils e;ists. In-ormativn on tt.e pa_sibie consequences of sea?age of leachat= fr~:r. the base of the piles should be gi•:on. The ar:alysis of .~ ~tati:e up_ak:e of canstic~!ents from to piles d°~=,ls only :vit?i r.=.diar.!_:clides and i4nvres other eie;~:ents. The =_tudy also does mat deal with ±he potential f... ,egetativa uptaf::e of leached element=_. from the soli addjacent to the piles. The 'a*_*er potential was igrcred treca!_ise it was concluded in the study that infiltratior. of leachate into the soil ~;as not e, significant pc=__sibility.