GENERAL34772

• Permit No: M1988112
• IBM Index Class Name: General Documents
• Doc Date: 5/5/2000
• From: US ENVIRONMENTAL PROTECTION AGENCY
• To: WQCD
• Media Type: D
• Archive: No

RMC I: ~'J35o~o9`.9 ~A° _~ ;.',~ 1 ~ ~':: >+o .C!: P.03
. M3-'tor?or,_r
May T. 2!X10
Page 2
Tt•.e perrnR raconaie ~ndicatas n the segna lull para;raph on page ~: tat
~, It 9~
•Tl'e ne!erogentyty of ;he siluvlum and !':e +ariabrlity ~t tna grounawal8r fbw ~n G"a
ailWi,srt and the R+tn Seca are cuch that mere are r>o diseete ~dcauons at ~urnc^ a
numeric eftlueet limimtian can ba meas.rsd. In addition, the system k orsrecierizad
Cy a diffuse and dispersed seepage hoot. Thus, It is terrhn:!:ariy Inteasiae ;o estadisn
numeric etAuen! 1lmiiatlona for die seepage front.'
V>rhlle Tye agree that the ailuvlum Is hererogerwoui, we diayrse VNth fie con~u6~on ;ttet the 6aapeQe
Trent is so diffuse and aisprxsed that the CaPhE cannel Identify ~sczte Itlcations for ac.~npiiar.;x.
The applicant in both TR•?O and In the Augus13G.1999 Technical Support Comment, carefully
points out that the rontaminslion from the West ?it is tlowlnQ thro::gh a'reatnc!ed zone' where fhe
badtBl contacts the ailuvi;~m ;eee state from page 3 of the'echnrcai Support GocumeM aoove).
The lateral extent of this ~esvicte0 zone or yrindcN' le carefully mapped in i•`gure °rb of iR-26. The
hetarogerr_~ty of thn aquifer dldafes that a single monllor wail is insufficient !o rharacterixe flow
tllrougl^. the window, as is vrpposed in TR•028, Hov+ever, the wlndo+v Is narrpw ena:gh that a series
ct wa1!s in the window should be ebb to cnaractsrize the Aow. This m41t(ple watt mentioning epprpaCfi
is r;onsistent wtth the monitoring program proposed .n Sedidn 6.4.2. t of TR•29. We recanmend that
the Weat Pit discharge through tt•~e window be rtqu~amd ur'der the pehnlt, and ba aeslgnared as
Diaeharge Petrt 002. Threshold level {complianx level) for spsa5c parameters in tl1e groundwater
shouin be ecWblished, and ntpnitAred in the exisUn9 TR.: 6 weds In and adptoent tC ttw `rnndoul'.
Paragraph 26 Of the August z0, 1999 NOV/CGO maKes roferentx to '...toe aeeas tote the Rite Seco,
as described M paragraphs f3 end !t above...'. Paragraph 13 at iha NOVICAO refers tr w+e
spr:citlc seep, white paragraph 14 pt the NOWCDO natant to throe cthH seeps 'JVe recomrnand that
these c~acific seapc be designated in the parrn:t as Discharge Points 003 ttuough QOB. Mdnliorlrg of
these aespa w~outtft~via~f[If'!i~nc'-OrilrtNSUmp~yrtoro~n3lar y t~~test Year.
4. tdQa•Term Water Qraurtrrhwater Draefrerne rseues
It !s our opinion that the TR•26 monfterlrg system ('urcludirlg the adjuctrnenx'a that system made by
l]MG subaequeM to iesuanca of TR-2$) should be maintained ttroughout the long ternL SpeclAcal!y,
wells vadYn Ufa flow 'wlraow' chpul0 t1a idenllAed as points of campoance, sod discharge ttxough the
wlndtnv ptld tram the slaps must ba quxniAed. M1Mnp has p~tanen~ altered the groundwater flow
regime In the vlCln4)r of the ~xat pit (sex TF26, at pages e.tt)), Consequenly, we believe'long tens'
here should mean urdh the applicant stn demomtrale 9rat fire West Pit is indapable of ganwaHng
poor quality eon an extended period of limo once fns active rvmedution programs are eurtarted and
the hydrologic oenneegon from the West Pit andthe Rito Sew hoe been re.eetabiished,
We do not AeWV1 Ufa 9cng term monitoring' ere dascritxd In TR•28 It suffldant given the appllcant'i
characterisation of the hydrologtc system to 7R•25 unp In the august 30 Technicad Support Doetrment
RCdutlng the long term monilonng regturemert to the walls IderttlCed In Section a.1 of TA-ZB Is
u+sulsetent to mtow rocogrJtlon or quenifieation of robsws to groundwatw betoro they signiAcanty
impact surtace water. Of the 4 alluvial wdhs identded, wells AA•t{1 end M-34 ors romote from fhe
window. OnIY wed M•t 9 !s in the vicniry of the window as mapped In 'R-2fi. As the appllgM pplMSr
out, the alluvial aquifer !e heter7gerwoui. A Single mpnltor wall In tt!e vic;nily of the window ii