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<br />\ 'F.N77<:.U I hVRA1UC Co.\DfCI7\ m, HE.HI1iJ:lff.Sn is THf DE\l ER HiS/.\'. COWR.-iiXJ
<br />
<br />r
<br />
<br />to the aquifers on I/w wholt' and It'.'s to th\" Individual
<br />la~.t;'rs (hat compri't:' them.
<br />:\. comprehensive unders!;.mdin~ of ~roundwater now in
<br />the Denn"r Basin will rl:':quire hydrogeolo)2:ic charal.tt.'riza.
<br />tion of individual Llyers within the aquifers De;:,ipherinlo:
<br />the characteristic" should nOI be limit,.J to tht" '-"atL'r-near-
<br />ing bYt.'rs, hut :-.hould abo h\" extl."nded to the lr:s:-.-permt'-
<br />able shale intt.'rvab. which rt'.'''lrict groundwater tlow
<br />throu~hout tht.' entire systt'm. The intemt;'tklt-d nJture;: of
<br />the st'dinwntary packa~e and .~;womt'uic sh;lpt' of the
<br />water-bearing inl'T.;ab imply mat tlw hydr"llllk char.1L"leri,-
<br />tics of tht.' shale interv:lls :Jre critical to the Oc.'h;l\'Jor of the
<br />entire sequence. Cllimatdy. long-If:rm yidds from wdb
<br />tappin~ the resmJrlt' will dt>pt'nJ to a ct'r1:lin ,.xtenl on
<br />how quickly watt;>r moves \'t.'rtically from one water-bt';H-
<br />ing sand inter\";ll to another Yet. t'mpirical d.JtJ from sam-
<br />ples of the sh:tle layers are availabk from only fin~
<br />kll.-"3tions ;lCross thl' Ibsin,
<br />
<br />TIlE OE!'iVER HASl~ AQUIFER SYSTEM
<br />
<br />Consisting of a thick sl'quenc\" of Pak"tlgt'ne ;lnJ lTprx'r
<br />Cretaceous (ahout -i9 [069 .\L1 [ttaynolds, 2(021) inlt'rht--o-
<br />ded sandston,', c{)n~l(}l1lL'r:HL', and .~halt', the Dt'lwer 13;lsin
<br />aquift'r :<Ylitt'm ha:< hL'en sulxlivi<kd into f(lUr principal
<br />aquifef!i n;lllled in ~ls"endin;.: order. tht' Llramie-Fux Ilills,
<br />Ar;lp;lhoe. Denn'f. and [);iwson aqllifers t i"'ig. 2A). Thi'
<br />nomencb[ure has h,~en fix,'d hy ,~tJtute for lilt' purpo:<t'" of
<br />a]kx:ating water within tIlt' Basin, ;md m;my lel-tal decrees
<br />granting watt'r ril-tht.~ tJ'in~ this nunlt'nd:llure h;l\'e J-x't'n
<br />grantt'd to d.lte.
<br />Shale. herein ll~L'J to indude :--halt', day",!One, rnud-
<br />",tont', :lnd ll1uddy"ihstonL' .1' v:lriou:--Iy desl.Tit'lt.'d in tht' li[-
<br />erature. L~ presenl [hroughoul [hI." entire :--equen<:e Srx~cilk
<br />shale intervals iJentifi~'d in geophp,iI,:al ]0;':' and correLtted
<br />hetwt'en horeholes han: tx'en u~ed [0 ,~t:parate till" pnnd-
<br />p;ll aquifers (VanSlyke, 2tXll I.
<br />The l.aramie-Fox Hills ,Iqllifer i... at the ba...e of thL'
<br />aquift'f .'ystem and con.~ish of lIlt' 15U- tn l(XJ-ft thick fine-
<br />grained Fox Hilb SanJ.'tnne, and ;1 )0- to ]OO-ft thk'k hnt.-
<br />to medium-~raineJ s:mdslolll:' in thL' (Werlyin~ L'Iramit' for-
<br />mation ntobson, 198-1. A thin ()"W fn shale separates the
<br />fox Hills :';llltbtone from s;lnJstones m [he Lar;unie F<lr-
<br />mation. TIll" llJ1pt:,r ,..00 [0 son tt of tht' LU;lllllt' FormatIon
<br />eon...ist.~ of shale wllil coal "'t'am' and minor ;tll1ount.~ of
<br />siltstone and 'i:Il1U.,lOne, TIlt' ,edilllentary rlll.-'k, forming
<br />tht' Fox Hilh Sambton,' and Ll.rantit' Forma[ion ""'t're
<br />deposiled hy the regrt.s.....ion of tht, CrL'laLeOlI' \'(i:'sh:rn
<br />Inl\"rior Seaway prior to, or at tht' Illception of, SuhSltknn'
<br />of me DCll\'er Basin (R;t'ynold,~. 20(2). The Larami,' FOfllM-
<br />tion forms a confining Iap,'r hetween the;: br.Jrnie-Fox llill,
<br />J.qllifcr and tilL: ()\'erlrjn~ Arapaho!:' aquih:,r.
<br />
<br />:\ext is thc Arap:lhoe aquifer, which i."- perhaps the most
<br />imponant aquifer in use JUt' to il, ~reater ',aturated thick-
<br />nes,' OVCT J.n extended area comhinL'u with gt;,ner<llly
<br />hi""ht'r hydr.lUlic conductivily v;llue.'. and, hence, hi~her
<br />over.11l translllissi\"iry, This aquifer COll-'!.'l" of a -tOO-- t':l
<br />-ao-ft thick ~eqUt:nct' of l'pper Creta,'eous intt'rlx'dded
<br />con,!..:lomer:ue, sandstone, .~ilt-"tone, and shale (Rohson,
<br />198"'"). Individual sJ.nustonc hodies within the Arap;lhoe
<br />aqmfl'r ;ue heliewd (0 he lelb-,hapt'u :llld r.Jnge in thick-
<br />ness from Ie.....' Ih;lll ;1 toot to ...0 ft or more. The;: sanustonl'
<br />Ien....e" can he dosely ,{xll"L-"t.1 and hvdr.wIiL-ally cOlllWnt-"t.1.
<br />forming. a relati\"t:,ly uniform hydraulic unit. nH' nd lhkk-
<br />ne',~ of thl." watl:r-he;lfin."lsanJstonc and ('on~lonlt"r;ltC'
<br />gener.JlIy ranges from 200-500 ft. ;llthollgh thL' net sand
<br />thkknes.... can \"xcet'd -100 ft, TI1CSL' Sl.:'uinlL'llury rocks were
<br />dep(~itt'J in a "'~TIorogt.'nic t1ll\'ial envirnnm\"nt wherein
<br />Sl.:'dimenl..; wt're Ik"in,s;: sht'd from ttl\" t.'ml'rging Llramlde
<br />Front tbnge uplift to Ihe w\"st :llld depositeu hy rivers ;llld
<br />s!rt'am... in till:' subsiding rknn'r stmetural ha,sin tR;lyno]d"
<br />20(2). :\ !ayt'r of shale up to SO ft thick j.;t'ller,i1ly st'p;tr.Jtt:'s
<br />thl." Ar.1pahoe aquif,~r from thl:' o\'crlyin).t Denw'r aquif\"r
<br />tYanSlyke. 21)0]),
<br />Tbl." Denver :ICjuift'r occurs in Upper Crel;ln;,olls and
<br />f>ak"og\:'ne U1t\"r1)('ddeu slule, daYS1(lJ)t', sil[.~lOne, lig.nllic
<br />co;II, ;lllJ ,~:ll1lblOnt' (Rohson. 19l'i7) with ;1 [otallhickness
<br />apprna\'hin,l..: WOO h. As with the Ar:lp:l!loe aquifer, tht'""-e
<br />rocks were depo....itt.d in a synoro).(e;:niL' lluvial environment
<br />a.... the [.ar;lmidt' Fronl Ran~e eomimll."d to rise and thl:'
<br />f),'nw'r structural ha,in ...ubskkd Individual samblOne
<br />bodies :If'" abn kns,shapt'd. hOwt'\'l'r, "bale is mort' pre\':!-
<br />lent ;\lld [he :--andstonl' hodies art. les.... Iikdy to hl' imer.
<br />connectl'd. Tht: to[al [hicknL"'" of IhL' :--:lluratt:d .;,;lnd....tonL'
<br />within thili inlerv;ll genn:llly rang\".' from 1CO lD j)O ft. A
<br />shdl~ layer :l\l'raging 2'; to 'iO ft [hick .RCn~r.ll1y ,,\:'pMale;:s
<br />tht' Ikn\'er aquift'r frum thl." on'rlyill5! J);lwson aquifer
<br />(V:lnSlyke, 2001 l.
<br />At [he top of the Denn'r Basin aquifer .~r~tcm is the
<br />I)"\',,'.'on aquifer, "on~islin~ uf Pal\"oj,(L'ne conglomeratk to
<br />nXIf:<e-,!..:r:iinL'd arkosic santbtone intt:rhedtletl \vjth clav-
<br />SlOne ;lntl shale (Rohson, 19frn. TIll""l' ~t'dimen[s \vere
<br />depositt'd III fluvial ,'nvironmenh in [ht' sub.~iding Dem'n
<br />Baslll with ..and comlllg frolll [he risinl-\ Front Ran~c 10 Ihe
<br />"~L'St. TIleY rt'ach a tot:il !hkknl;''''~ of oVer loon ft in the
<br />center of thL' Ha,in The w:uer,lx-arin,lo: sand.,tonl;' and con-
<br />~lonlt'r:Jtt: of [ht, Daw,~(m is up to .100 It thkk.
<br />The "'ulxll\.j~ion of [he sl:'dilllcntarv 'l:'4u\"nu~ h(lldin~
<br />[he D,'nn'r Basin aquifer sy...!t:lll i' simplistic in it!i Iayer-
<br />cake ("flOet'pt, blll it allows an orderly allocation of the
<br />w;lter rt',ourCt-. Ilowever. it hdk.... the complexity of the
<br />,Io:t'ology. much of whidl has come to light with [he ~row-
<br />inl-\ I)(xly 01 suh...urface Jat.J made;: ;l\'ailahle "... [ht' resource
<br />j.., I:>t:in~ developed ';inn' the ...ynorogenk ha'in was heing
<br />filled with da...tic ...edimenb derivl:'tI from [h~ flsinl-\ From
<br />!bnge to [he;: we:--!. tht:rt' i., considt:rable horizontal variability
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<br />n,... R....h \touma;n A'''''lal,on oI(;eol"~,,I.'
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