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<br />\-"11. ALTER.'l/ATlVE DE\'ELOPMElIoT ANIl SELI':CTION
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<br />DESIGN STORM
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<br />Througlldi<cussionw;ththeCily. ilwasdclcnninedmalalthoughlhcCritcriadcfi""sooththl:2.year
<br />and the 5-ycar 'IOrms a,[heb.i,js [n' design of minor stc>rm systcms, the 2 -year event would be the
<br />ha,;s ror cvaloa,;on of exiHing ""d proposed minor runoff system, within Ihe MSA The Criteria
<br />requires Iheuseofthe2-yearevel1la.\lhcbasis for dcsign ol minor drainage ways in urban residential
<br />arc",. and the S-yearcvenl incoffimercialtinduslrinl, iiChool and Of"'n spacc area,. It was perceived
<br />Ihalmanycxi,ringsY5lcms3rc inadequate forel'en the 2-year runoff, and thecos{ofirnplcmellling
<br />tetro-fit improvements for 2-year runoff nows will likely exceed (he available res()urc~ of the City.
<br />As co,( of implementing 3 S-y.at ferro-fil improvements program would be evcn greater, it was
<br />determined to be mo,! feasible to p]on for 2.year runoff manage"'ent. The 2-year event was th~s u~ed
<br />for all areas to provide a eomistombasi, for analysis, ]n accordaneewith the Criteria. lOO-year
<br />rainfall has been Wled as theba,i, for determining majQl storm runotf,
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<br />ALTERNATIVES DEVELOPMENT
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<br />Thc 'copc of the City". Master Plan wos 10 evaluate thecxisting and required C apaeitie,ofslOrm
<br />,,"wer trunk systems throughout the City. and to identify and evaluate potential alternative systems
<br />locorm;tsy'teminadcquaciC$,
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<br />For the Master Plan. -loca]SY"em,. ....cdcfined "drainage,y,temsthatcolleclrunofffrc>ma'ea,
<br />,,,,aller ,han sub-basin si'e and outfall to larger trunk 'yslem~. Oiocharges from local sy<lems are
<br />e'limated through overall suh-basin di"harges and arc u'Cd to eSlimarc requirement' for the main
<br />'y.'tems analpe<! in this 'lUdy Thedesignofloc.11sYSlem' Wa.' not included in the <e<'JlCl'fthe
<br />MasterPlan,
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<br />TI>e ,ysrems pre'Cn<ed ;n the Alten'ative, E.'aluation Report w.:re devdoped to oddre," both 2-yea,
<br />and I(XJ.-)'c", runoff management. In the report [he fea,ibility of alternative. wa, evalnaled based on
<br />co.t. availahility or potential availahilily of rights-of-way and easements, phasability and
<br />tonstroctabHity. The report generally recommended a Ipedfic SYltem for each of Ihe are..
<br />in,e"ig,ued.
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<br />The reader is referred to ,he AhernmivesEv"luationRepoMforadditiooalinformationconccrningthe
<br />devdopmemof altematives,
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<br />ALTERNATIVES SELECTION
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<br />Upon eomplnion of the Alternalives Evaluation Report, the report wa, submitted to the City for
<br />rcv,ew, Sub"'quem to the review the Cily agreed. with a few exccplions. with WRC's
<br />recommendation, with re'pect to the system impwvemenls presentcd in the rl1,ort
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<br />In generaL improvements wi,hin the MSA are limited 10 2-yeat sySlem'. The extreme cost of 100-
<br />year imp,",'ements for Spring G~lch and Oligarchy Ditch made infeasible their inclU.sion into ,he
<br />Master Plan. It wa, e!limaled t!tallor}..)'ear impw,emems for the Spring Gulch channel wouid alone
<br />cost appwximatdy $5-6 mil]ion Irnpw'Cmenl. 10 Ihe Oligarchy Dileh within the MSA [0 provide
<br />lOO-year cap.city would cost it! eXCeSS of S7 million. Given the limiled City capital improvement
<br />bndget. itwa, anticipated tha.< ,hc..e loo-year improvements will ''''1 beeonstructed in U\e no" 20
<br />years or more. Therefore. in view of the,e economic eon,traints, pr"l'O.led MasterPlan facilities
<br />within the MSA are typically limited to 2-)'ear systems, A description of the selected alternatives is
<br />included as raM of [he following ehapter.
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