FLOOD03286

• County: Adams
• Community: Wheat Ridge, Arvada
• Stream Name: Lower Clear Creek
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 10/1/1981
• Prepared For: Adams County
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

Channel-Crossing Costs

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COMMENTARY

COST ESTIMATE

Station 300+00 to Station 360+00
1000-feet upstream of Lowell Blvd. to
1500-feet upstreiJ11 of Sheridan Blvd.
Portion of Reach II B

Station 300+00 to Station 360+00

CONSTRUCTION

The proposed Colorado State Division of Highways (CSDH) channel and hiker/
biker/maintenance trail continues through the m~jor portion of this segment
to upstream of Tennyson. As a part of the Interstate-76 construction pro-
ject, CSDH al so proposes a Nature Preserve and Wi Idl ife Area, downstream of
Tennyson, from the highway embankment south to Clear Creek. Therefore, the
floodplain management strategy, downstream of Tennyson Street is Floodplain
P reserv at ion.

Channel Improvement Costs

$ 228,200

Ut il ity Relocation Costs

$ 27,200

The most recently proposed CSDH channel improvements upstream of Tennyson,
which are still subject to change, increase the 100-year flood dischargp. at
the Tennyson Stref>t bridgp. structure. Unless improvements are made at
Tennyson St. the increase in flood discharge will raise the 100-year water
surface elevations above the existing 100-year flood level by approximately
I-foot immediately upstream of the bridge. The increased flood discharge in
the main Clear Creek channel may alter the limits of the existing 100-year
floodplain between Tennyson St. and Lowell Blvd. The 100-year floodplain
for the cond itions after 1-76 improvements shaul d be determined and
considered by the CSDH.

TOTAL CONSTRUCTION COSTS

$ 255,400

ENGINEERING AND CONTINGENCIES (30% of Construction Costs)

$ 76,600

FISCAL, LEGAL AND ADMINISTRATIVE (10% of Above Total)

$ 33,200

PROPERTY ACQUISITION COSTS

$ 2,200

Limitf>d construction at Tennyson is recommended as Major Drainagp.way
Improvements. The improvemp.nts incl ude a rock-l ined transition channel from
the proposed CSDH channel to a concrete-l ined channel through the Tennyson
Street bridge, the addition of dp.bris wall s and wing wall s to improve the
entrance conditions to the existing bridge structure and the .relocation of
the Kershaw Ditch, 350-feet upstrp.am.

TOTAL IMPROVEMENT COSTS
(1981 Do II ars)

$ 367,400

MAINTENANCE

A grass-lined drainage collection channel has bp.en designed for 5,500 cfs,
to capture the shallow overland floodwaters north of the 1-76 embankment,
from Shf>ridan to Clear Cref>k upstream of the Denver and Rio Grande western
Railroad (see shep.ts 13 and 14). It is recowmended that future developnf'nt
in this area bear the expense of thesf' improv811f>nts needed for flood mitiga-
tion, since f'xisting flood diJ11ages in this arp.a do not warrant the f>xpendi-
ture of publ ic funds.

Annual Operation/Maintenance Cost

$ 15,600*

* Incl udes $3,000 for reach of Clear Crp.ek within Jefferson County