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<br />. <br />. <br />I <br />. <br />I <br />I <br /> <br />t <br /> <br />I <br />f <br />t <br />i <br />( <br />I <br /> <br />i <br />i <br />i <br />f <br />I <br />f <br />. <br />. <br />~ <br />. <br />a <br />4 <br />~ <br /> <br />" <br />" <br />~! <br /> <br />. <br /> <br />. <br /> <br />June 10, 1992 <br />Mr. John Pri.rchard, Town M"n"&er <br />Town of Granby <br />Page 3 <br /> <br />Beca:use of the highly-tumid waters that enter the intake .rete:Ilioo. polld from the <br />backwash ponds, the quality of water in the IaW water' pond is degr..ded.. FurtI-.e:r, there <br />is no bypass around the intlkl: retention pond which wocld allow delivery of Fraser :River <br />W""..rerdirectly into the treatment plant. <br /> <br />The thirdiDter-IC1ated problem stems from the raw water in!2kcoff the FrASer River. .. <br />The elevation of the intake is too high onn"g the low flew, winter time perlods. This.. <br />:requiIes tha1 the To~ build up a downstream. divCISion dam to mse, or back up v,,'ater, <br />to the intake. The Town accomplishes this by instllIing ~I3p and rocks in voids in the <br />dive."'SiO'll dam. When Ilows increase to s,prlng IImofIlcvels, the divemon dam backs up <br />water upstream to dangCItlusly highlcvels.. Tn some cases, the wat.er, level is close to .. <br />over-topping adjac=t banks wbich could eauseproperty n"m"~e downstream. 'Ibis <br />problem. is ftuther rn"~;ned by increases in the Fnser RIvet levels from mid-Apm to <br />July by relea..~ from the Denver Water Board. As a IeSll1t of the increased sea.."Onal. <br />flow and rele:;..<:es from the Denver Water Beard, the- Too;;u must semi-amlU2lly modiff <br />the size of the div~~oll. dam. <br /> <br />2. <br /> <br />Rec.omme::ded Soh..'tions <br /> <br />In order to improve the q""H-ry of raw v.c.ter:in the intake rer1>!1t1O!l. pond and prev-e:lt the <br />llIlIl.ual v.";"t..,.,"n~ re:::uire:::l of the dive:-slon .-;".., J th..-ee SPecific solutions a..-e ide:t1iE.ed <br />- - <br />as follows: <br /> <br />A] Backwash Poods <br /> <br />We ==e:ld installing th...-ee new backwasJl ponds. The bcclo.-..sil. ponds <br />would be COI'.s::ructed of concre:.e. Tne elevations of the ponds would be b--...sed <br />upon fur.her- su:"vey work. Tne ponds would be constructed to illow direct access <br />00"'11 inro the ponds for re:nov--d of de"""'.~"e:: alum sludges. Tue piping would <br />be an-...nged sucll that t."le ponds could be o~ted in par-~el or series. In. or~ <br />to ;:::;5-. me elevation of the ponds, the piping from the fJ:er bo('i.~........sb. and <br />c:o"';;:;er dr.J!l should be hard-piped. At the preset time, the d...,,;,.,~ ror the <br />back-;;.-ash ware: and cla..-:ner a..-e direc::ed to a. floor-level su...p. <br /> <br />orne ponds ~'ld associ:s.te:C piping "W.ould be designed such. U:2.t cr,,~ pond could be <br />take:l off lir.e for aoorcxima:elv six ::non!hs to allow. the alum s:udze to de,,;;~:.. <br />\Ve have ide:ltified 'prellmir:e,;J lcc:;.:ior..s for t..'le t!lIe: po..ts 00.- ':.he e:lC~Osed <br />Gn.'i4'ing. <br /> <br />SC:"i:,~-':~s~~ OC~::CN ...~E":.E..':'_ J:-~':. <br />