FLOOD05088

• County: Adams
• Community: Arvada
• Stream Name: Hidden Lake, Bates Lake
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 11/1/1975
• Prepared For: Urban Drainage and Flood Control District, Arvada and Adams County
• Prepared By: Hydro-Triad, LTD.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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for existing channel conditions. A detailed cost estimate was pre-

pared and the benefit/cost comparison was made. A final report was
then prepared, consisting of two volumes; one containing the narrative
description and the other consisting of plan and profile drawings

reduced to 11" x 18".

The alternative plan chosen for preliminary design (Modified Plan

E) specifies no improvements above Hidden Lake, improvements to the

Hidden Lake dam and spillway, extensive channelization, storm sewer

and utilization of existing lakes for the area below Hidden Lake.

The recommended plan for the Bates Lake Basin (Plan B) consists of on-

site detention per current Arvada regulations, and the channelization and

detention ponding for the lower reaches of the Bates Lake Planning

Basin. A summary of the Benefit/Cost Analysis for the Modified Plan

E and Plan B is presented below.

BENEFIT/COST ANALYSIS SUMMARY
(6% Interest Rate)

COST PWF PRESENT WORTH REMARKS
ITEM Adams Arvada 6% Adams Arvada
Construction1 'f59,300 102,900 .9434 433,300 97,100 Table IV-2,3
Site Acqui-
sition 28,100 59,200 .9434 26,500 55,800 Table IV-2,3
Fiscal & ~
Administration' 4,874 1,621 15.762 76,800 25,600
Operations &
Maintenance 13 ,300 5,300 14.819 197,100 78,500 Table IV-2,3
TOTAL: ------ ------ ----- 733,700 257,000
DAMAGES ------ ------ ----- 762,900 449,200 Phase A Analysis
BENEFITS3 ------ ------ ----- 804,400 404,000 Phase A Analysis
NET BENEFITS ------ ------ ----- 70,700 147,000

NOTES: 1. Includes 15% contingency
2. 1% of total of construction and site acquisition
3. Includes intangible benefits