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<br />City 0/ Littleton
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<br />~...1a5.sey Draw and SJCD (Scum) M~Jor DrM1agevvay Planning UpOOle
<br />ConceptlJili Design Report
<br />February 2006
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<br />elevation for all human occupied structures build adjacent to, or within, the l00.year
<br />floodplains.
<br />7. Continue to participate in FEMA's flood insurance Community Rating System and public
<br />education programs.
<br />
<br />Table 8 - Cost Summary by Jurisdiction
<br />
<br />. Priority 1 improvements include channel and culvert improvements that are intended to reduce
<br />or eliminate structure flooding.
<br />. Priority 2 improvements include culvert improvements that reduce or eliminate street
<br />overtopping_
<br />. Priority 3 improvements include low flow check structures, drop structures and bank
<br />stabilization intended to reduce stream erosion.
<br />
<br /> Jefferson City of Littleton Arapahoe Total
<br /> Countv County
<br />Construction S13,806,OOO SO S34.400 S13,840,400
<br />Easement Acquisition S5,893,OOO SO SO S5,893,OOO
<br />ContinQencies (25%\ S3.451 ,500 SO SB.600 $3.460,100
<br />EnQineerinQ Services 115%1 S2,070,900 $0 $5,200 $2,076,100
<br />Construction Inspection
<br />I nO%) $1,380,600 SO S3.400 $1,384,000
<br />leoall Administration 15%\ S690,300 SO $1,700 S692,OOO
<br />Total S27,292,300 SO S53,300 S27,345,600
<br />
<br />6.4 Prioritizing and Phasing Plan
<br />
<br />The master plan improvements were prioritized according to the following criteria.
<br />
<br />6,6
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<br />Water Quality Impacts
<br />
<br />In general, implementation of the improvements should begin at the downstream end of the
<br />drainageway. Although the modeling does not account for inadvertent detention and channel storage,
<br />some storage may be occurring due to inadequate culvert and channel capacities. The master plan
<br />improvements will tend to reduce the storage, resulting in an increase in flows over what is currently
<br />observed.
<br />
<br />The master plan improvements will help to reduce the erosion in the drainageways, thereby improving
<br />stormwater quality. The recommended regional detention basin on the North Tributary of Massey
<br />Draw will attenuate the peak flow rate, which should also help control erosion.
<br />
<br />Contingencies
<br />Engineering design services
<br />Legal and administrative services
<br />Construction observation and material testing
<br />
<br />25%
<br />15%
<br />5%
<br />10%
<br />55%
<br />
<br />6.7 Operations and Maintenance
<br />
<br />Projects recommended in the Master Plan are intended to stabilize channels, reduce headcutting,
<br />reduce or eliminate culvert overtopping for up to a 1 OO-year flood flow, and remove structures from the
<br />100-year floodplain. Impacts of the improvements during both low and high flows were considered.
<br />The amount of maintenance required should be reduced due to the stabilizing nature of the
<br />improvements. During extreme flood events, such as the 1 DO-year flood, it is anticipated that cleanup
<br />of debris will be required. Culverts and the outlet structure at the recommended detention basin at
<br />Carr Street on the North Tributary of Massey draw should be periodically inspected for debris blockage
<br />and cleaned out as necessary. Grade control structures should be inspected after major flood events
<br />to determine whether damage has occurred and to monitor their effectiveness.
<br />
<br />6.5 Cost Estimate
<br />
<br />Conceptual level cost estimates were prepared using unit costs obtained from the 2003 COOT Cost
<br />Data (Reference 15), UDFCD construction bid tabulations and in-house cost data. Costs for
<br />contingencies, engineering, legal and administration were included as a percentage of construction as
<br />follows.
<br />
<br />Easement acquisition costs were estimated using $1.50 per square foot, based on information
<br />provided by Jefferson County. The cost of property acquisition was based on a review of the Jefferson
<br />County Tax Assessor's records.
<br />
<br />The recommended levee at the Deer Creek Golf Club would be subject to FEMA requirements such as
<br />development of a specific operations and maintenance plan for the levee. The plan should include
<br />items such as identification of responsibility for the levee and regular inspection and maintenance
<br />schedules. All items necessary for a levee to be recognized as providing protection from the 100-year
<br />flood must be certified by a registered professional engineer
<br />
<br />During final design of the improvements, maintenance access and measures to minimize maintenance
<br />needs should be considered and incorporated.
<br />
<br />The unit costs used to prepare the cost eSllmates are presented in Table B-3 in Appendix B
<br />
<br />Table 8 presents a summary of the costs of by jurisdiction.
<br />
<br />6.8 Master Plan Drawings
<br />
<br />Preliminary design drawings and details are contained in Appendix G. The drawings show the
<br />preliminary sizes for culvert improvements, the locations of proposed drop structures and low flow
<br />check structures, channel improvements, bank stabilization and regional detention.
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<br />6-7
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