•c   «. -  *)        UNsrr.f.'STATSSiCKVinONMr-HrALPROTECr'OhAOFNCY
i          I                      WASHINGTON, D.C.  ?0480
"i         ,*•
                                                                             WSG 180
                                         FEB  - 4 2010   Date Signed: February 4, 2010
 Sl'BJECT:   OGWDW Review of Small System Monitoring Requirements Under the Long
              Term 2 Enhanced Surface Water rreatment Rule
         .     ,  ,  _..•  ?  /f-,,,
           /  Cynthia C. Dougherty, Director
          / f '  Office of Ground Water and Drinking Water
          (/'
 TO:          Water Division Directors

       in the preamble to the final Long Term 2 Enhanced Surface Water Treutmeitt Rule (LT2).
 the Agency stated that it would issue guidance lo States on alternate indicators and E.culi trigger
 levels used to determine Cnpfw/wnc/tais (Cr)
 choose to not allow these alternative levels to be used or may propose other alternative levels as
          in LT2,

       If you have any questions, you may contact me at (202) 564-3750, or have your staff
 contact Michael Finn at (202) 5
 Attachment
 Cc:    Regional Branch Chiefs
        Jim Taft, Association of State Drinking Water Administrators

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                                                                               WSG M
                                                         Date Sisned: February 4. 2010
       OGWDW Review of Small System                          Under the Long Term
                       2 Enhanced Surface Water Treatment Rule
       Under the Fmaf Long Term 2 Enhanced Surface Water Treatment Rule (LT2), the Stale
may approve an alternative to the      water svsiem E. coll trigger levels of LT2 (source water
mean £ coli levels less than 10 £, co/i/IOOral for hike/reservoir sources or less than 50 £
c«///100ml for flowing stream sources) if the alternative nigger levels prov ide a more accurate
identification of whether the s> stern will exceed (1.075 t 'rypto*poridiut» n}rypto) oocysts per
liter. OGWDW  analyzed the impacts of using alternative £ coli trigger levels and determined
tl.al alternative levels would more accurately identify systems required to meet the treatment
technique requirements of L'1'2 and prevent a large number of smalt systems from incurring
Crypto monitoring costs. OGWDW has reviewed the £  cause nearly half of small systems (about 2,700 of 5,600)
to monitor for Crypiot which we estimate would ultimately result in about 218 systems being
required to meet the treatment technique requirements of LT2.

       We estimate that 24 systems thai would have been required to monitor for Crypto and
then required to meet the treatment requirement of L'1'2 under the current LT2 triggers will not
be required to meet the treatment technique requirements using the alternative levels. We
estimate the alternative levels could exclude 1,300 systems from monitoring for Crypio, which
translates to approximately SI? million in monitoring cost savings While there is uncertainty
with the estimates, we also compared the accuracy al different levels of alternative trigger and
determined that the accuracy would diminish for trigger levels above 100 F.. call per ! 00m!.

        If the State chooses to allow the alternate trigger levels suggested in this guidance^
documentation  of that decision should be maintained by the Region. If the State proposes to
approve other alternate trigger levels,  that proposal must be described in the State's primacy
application under 40  CFR 142,16 (n) (I}.  For States that choose to allow an alternative trigger
level, the LT2 rule requires that the State notify' the systems in writing and include the basis for

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                                                                          WSG M
                                                   Date Stoned: February 4,2010

the State's dctet initiation. In calculating the annual mean E.calt level for comparison wilh the
trigger levels, individual E.coli results (every two weeks) should not be rounded and significant
figures should be maintained In calculating the annual mean.

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