FLOOD07908 - Laserfiche WebLink

Home Browse Search

spillway is designated which discharg~s directly into the Channel adjacent to Jewell. The entire berm is to be faced with broken concrete riprap covered with earth and grass to protect against overtopping by greater floods. During ~xtreme flood occurrences, water would overflow the entire berm. Drawing No. N$-l A reco~~ended plan for separating the Agricultural Ditch from the flows in Main Sanderson Gulch is indicatcd. on the m",ster plan!1.ing sheet. This improvement is considered the responsibility of the Agricultural Ditch Co. based upon the recommendations of the legal counsel. The proposed improvements consist of placing the ditch in a conduit across the lake at the present ditch alignment. The conduit would act as an overflow weir during major storm occurrences. A low flow conduit is indicated beneath the ditch to allow normal flow to continue through the Jewell Park Pond. The lower portion of North Sanderson Gulch is designated to be flood plain zoned with no improvements planned. The KLIR Rcser- voir will be breached by any major storm, but its effect on the overall drainage system is considered minor ",nd improvc~ents are not justified. A portion of grass lined channel must be constructed immedi<ltely east of Pierce St. to allow the installation of new conduit beneath Pierce St. Right-of-way must be acquired with this improvement. The conduit indicated beneath Garrison St. has undergone final design by the City of Lakcwood and will be constructed within the near future. The Pierce St. conduit is designed to accommodate a 10 year storm runoff with runoff greater than this flowing across the street surface. Very little property damage should occur from greater storm occurrences up to the 100 year. West of Garrison St. the existing channel is reldtively deep and very unstable due to ground water accumulation in the channel in- vcrt. The reco~~nded improvements consist of laying an under- drain along the existing channel bottom and connecting the under- drain to the toe drain system of Kendrick Reservoir. The channel should then be filled to the design invert level and a very wide shallow grass lined Channel formed. Fill to be utili~ed in this area may be obtained fro~ channel construction adjacent to Jewell Ave. Drawing No. NS-2 Between Pierce St. and Quay Drive, the gulch is contained in a man- made channel in a 22 foot easement. The existing easement is not wide enough to allow construction of a grasslinecl Channel with adequate capacity. Therefore, the recommended improvements con- sist of a gabion lined channel with l:l side slopes utilizing the entire easement area. The Channel will be adequate to carry only the lO year storm runoff. Dr3winq No. S-12 The existing Quay Drive culvBrt shall be replaced with new cul- verts capable of passing the 10 year storm discharge. Approximately 150 cfs will leave the Channel at this point during a 100 year storm and flow northerly to Kalahan Ave. Between Quay Drive and Upham St., the channcl again flows through an cxisting 22 foot drainage easement and a lined channel cross section is recommended. The existing spillway on Kendrick Reservoir does not meet State ~ngineer requircments and should be reconstructed to such stand- ards by the Foothills Metropolitan Recrcation and Park District. From Kendrick Reservoir to the Smith Reservoir embankment the recommended improvcments consist of forminq a small grasslined channel in a dedicated utility easemcnt. An underdrain is recommended beneath this channel to intercept the ground water from the Smith Reservoir berm toe drain. Construction of the channel and crossings indicated in this area should be consid~red thc responsibility of the developer of the area. The existing culverts beneath Upham St. should be replaced with new culverts capable of passing the 10 ycar storm runoff. During a 100 year storm, approximately 150 cfs would leave the ch,mnel (tad flow northerly to Kalahan Ave. The channel should be constructed within the existing ownership of Agricultural Ditch and Reservoir Co. parallel to the Smith Reservoir embankment. The present junction box of the spillway chute and the East Reservoir diversion should be reconstructed to allow spillway discharges to remain in Sanderson Gulch. A suggested "lethod of revising thc junction box is i:ldicated on drdwcng No. S-l2. Between Upham st. and Kalahan Ave., the channel is in a 36 foot easement. This easement is not largc enough to allow construction of ",n adequate grass lined channel and the recommended improvements indicate installation of a gabion mat lined channel with 2:l side slopes. The existing culverts beneath Kalahan Ave. may be left in place as they are adequate to pass the 10 year storm runoff. All alternative design to th€ channel from Pi..,n;(, St. Lo i<dlahan ,;ve. would be installation of a concrete lining in place of the -10':;- -lOl-