FLOOD09312

• Designation Number: 370
• County: Crowley
• Community: Ordway
• Stream Name: Local Drainage
• Basin: Arkansas
• Title: Floodplain Study and Master Drainage Plan - Ordway, Colorado
• Date: 6/1/1987
• Designation Date: 7/1/1994
• Floodplain - Doc Type: Floodplain Report/Masterplan

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45

Within the Eastern and Central Basins, pipes have been sized to convey
the runoff along Railroad Avenue and Ninth Street. An alternative to the pipe
system is a concrete channel. A channel system provides an easier means of
conveyance in situations where mild grades exist. Additionally a channel will
generally operate more efficiently and would be easier to maintain. The cost
of a typical concrete channel for these areas is estimated at $65 per lineal
foot. The total length of the pipe which can be replaced with a concrete
lined channel is estimated at 5,700 lineal feet. Compared to the pipe cost
along these streets, approximately a $20 lineal foot savings can be affected,
which when considered with the 20 percent engineering contingency, a $140,000
savings could be realized over the improvements shown on Figure 10,
The combination of these savings is estimated at $300,000 and wou1 d
decrease the total drainage cost to $2,288,900 for the Planning Area,
Several stormwater facil i ti es have been sized adjacent to developments
proposed within the Planning Area. It is recommended that the system shown on
the Selected Plan be used as a starting point for the design of the future
stormwater management system whenever a new subdivision is proposed. However,
the Town shou1 d be flexible in the review process, and make allowances for
other systems whi ch can provi de an equal conveyance at a lower cos t. The Town
should pay only for the cost of conveying the existing condition flow, with
the developer paying for the cost of the facility devoted to carrying the dif-
ference between the existing and future condition flow rate. The breakdown of
these costs should be determined during the Preliminary Plat phase of a given
development.
The annual cost of the improverrents itemized in Table 13 are far above
the annual damage cost estimates. This is not an unexpected result, because
of the inherent high cost of large diameter storm sewer systems. The use of
PVC in pl ace of RCP, and the use of an open concrete channel in the Central
Basin can bring the annual cost of the system(s) closer to the damage losses,
but still a benefit-cost ratio of greater than one cannot be achieved.
Intangi~le. benefits such as increased property values and lower annual main-
tenance costs which result from in a municipality served by a stormwater mana-
gement system must be examined closely to more accurately justify the
development of the drainage system(s) proposed herein.

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