FLOOD07758

• County: Denver
• County: Jefferson
• Community: Lakewood, Denver, Jefferson County
• Stream Name: Lakewood Gulch
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 12/1/1979
• Prepared For: Denver / Lakewood / Jefferson County
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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VI BENEFIT-COST ANALYSIS

20

An analysis was made of the benefits and costs associated with

different alternatives evaluated in the Phase A report, prepared

by McCall-Ellingson & Morrill, Inc; and in the Addendum to the

Phase A report, prepared by Sellards & Grigg, Inc. The values

determined in those reports were pre&iminary and presumed to be

accurate enough to allow comparisons between alternatives. The

values, benefits and costs of the present Phase B report have

been greatly refined and updated to July, 1979. The estimated

costs of and benefits to be derived from the construction of the

master plan are presented in this report. While the details of

the original Phase A Benefit-Cost analysis are not repeated here,

a brief discussion of the elements of the analysis is presented.

reduced. The proposed Master Plan for Lakewood Gulch incor-

porates predominantly construction of facilities capable of

conveying a 100-year flood without damage to property. In

order to evaluate the full. spectrum of damages before and

after construction of the Master Plan, the anticipated

financial losses are converted to average annual damages.

Column 2 of Table VI-l illustrates these averoge annual

damages. Column 2 of Table VI-1 illustrates these average

annual damages in each Reach. The average annual benefit to

be derived from the facilities is the difference between the

average annual flood damages without improvements and the

average annual damages with improvements. Table VI-l illus-

trates (Columns 2 and 3) that the entire basin is subject to

average annual damages without improvements of $248,684. These

damages could be reduced to $63,360 by implementation of the

first construction phase of the Master Plan. Benefits derived

from prevention of flooding of major arterials, like Sheridan

Boulevard and Wadsworth Boulevard and from a properly maintained

drainageway were not quantified for this report.

Detemination of Flood Damages
An estimate was made of the dollar value of the damages which
would be caused by each of the 5-year, 10-year and lOO-year
floods, under fully developed watershed conditions and without
channel improvement. This was achieved by evaluating the
anticipated flooding depths which would occur at each building
site.

Evaluation of Costs

The costs of the Master Plan include land acquisition, facilities

construction, operation and maintenance, and engineering and

legal fees. A contingency allowance of 20% is also applied to

construction and land costs. Columns 5 and 6 in Table VI-1

Determination of Benefits
The construction of drainage facilities results in benefits to
the public to the extent that damages caused by flooding are