Vote — approved

Steve Gallardo	yes
Jack Sellers	yes
Bill Gates	yes
Clint Hickman	yes
Steve Chucri	yes

84.ON-CALL CONTRACT WITH WEST CONSULTANTS, INC FOR DEPTH AREA REDUCTION FACTOR STUDY Award Contract FCD 2020C014 On-Call Services for the Depth Area Reduction Factor (DARF) Study to WEST Consultants, Inc. (WEST) to provide professional engineering services. The contract will be effective for 730 calendar days from the date of execution or the expenditure of $500,000, whichever comes first. The Flood Control District of Maricopa Country (District) and WEST will mutually agree to a detailed scope 

Item Text

84. ON-CALL CONTRACT WITH WEST CONSULTANTS, INC FOR DEPTH AREA REDUCTION FACTOR STUDY Award Contract FCD 2020C014 On-Call Services for the Depth Area Reduction Factor (DARF) Study to WEST Consultants, Inc. (WEST) to provide professional engineering services. The contract will be effective for 730 calendar days from the date of execution or the expenditure of $500,000, whichever comes first. The Flood Control District of Maricopa Country (District) and WEST will mutually agree to a detailed scope of work for each work assignment. This is a qualifications-based selecti on in accordance with the Maricopa County Procurement Code, Article 5, Paragraph 504 and Article 5 Procurement Procedures Manual, Chapter II – Section 2. Engineers use rainfall depths developed by NOAA to complete studies that identify and evaluate flood hazards. These values are also used to design drainage facilities (culverts, basins, bridges, etc.). The rainfall depth is the depth that is expected to occur at a point or points in a study area, typically a watershed. However, this depth should not be used over the entire watershed because the rainfall will be overestimated. A depth-area reduction factor (DARF) is used to convert the point rainfall to an equivalent uniform depth over the study area. This factor is used to account for the observation th at average precipitation intensity decreases as the area of the storm increases. The current Drainage Design Manual, Hydrology Volume includes reduction factors developed in 1974 for the 6-hr storm event and 1984 for the 24-hr storm event. Recent studies have been compared to gage data and other storm evidence, and have shown that updates are needed. In many cases the DARF should be increased, which would decrease the rainfall values used for a watershed. For instance, if a project includes a des ign of a culvert, this update could potentially decrease the required size of the culvert. This Agenda Item impacts all Supervisor Districts. (C-69-21-079-X-00)

Attachments (2)