FLOOD01374

• Designation Number: 521
• County: Weld
• Community: Erie, Firestone, Dacono
• Stream Name: Tri-town drainageway, Godding Hollow Basin
• Title: South Weld I-25 Corridor Master Drainage Plan
• Date: 9/8/1999
• Prepared For: Weld County
• Prepared By: Anderson Consulting Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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photography was utilized from a 1998 aerial flight, Survey requirements included
the collection of data necessary to defme existing structures (bridges, channels,
culverts, outlet structures, etc.) with respect to geometric configuration, invert and
overtopping elevations, etc,

4. Inventory of Existing Facilities, All information related to the major storm
drainage facilities within the major drainageway of each basin was compiled.
Existing detention facilities, culverts, bridges, road crossings, drainage channels, '
irrigation ditches, and major storm sewers were inventoried and evaluated. The
capacity of each structure was determined and the feasibility of integrating existing
facilities into the master drainage plan investigated.

5. Hydrologic Analysis and Modeling. A detailed hydrologic model was developed
and utilized to simulate the stormwater runoff for three scenarios: (a) existing or
"as is" condition; (b) future development conditions with existing facilities; and (c)
future developrrient conditions with on-site detention and proposed improvements,

6, Hydraulic Analysis and Modeling. A detailed hydraulic analysis was completed
to evaluate the structures identified during the inventory of existing facilities. All
proposed improvements were also evaluated during the hydraulic analysis and
modeling efforts.

7, Drainageway Planning and Alternative Development Storm drainage
improvements were identified to mitigate the existing and potential future flood
hazard problems. Alternative stormwater management plans were conceptually
developed and internally reviewed and refined with input from the staff of the Weld
County Public Works Department and the 1-25 MDP Task Force.

8, Basin Drainage Criteria, Criteria for the planning and design of drainage facilities
were developed in conjunction with the 1-25 MDP Task Force. The criteria
specifically focused on the planning and design of major drainageway facilities/road
crossings and on-site detention requirements,

9. Funding/Financing Alternatives. An investigation of various funding and financing'
alternatives was completed. The results of the investigation along with a
recommendation were presented to the governing bodies and interested parties,

10, R~orting and Technical Documentation The results of the master planning effort
are summarized in this report. All recommended improvements are identified
along with preliminary design drawings and detailed cost estimates. An
implementation plan for the construction of the proposed improvements is
presented, Documentation in the form of technical appendices and a project
notebook is provided to allow replication of the steps taken to: (a) generate the
design flows , (b) estimate the capacity of the existing and future facilities, (c)
develop and evaluate the alternative plans, and (d) generate the cost estimates.

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Sepu.mbe.r 8, 1999