Granite Reef Watershed Drainage and Flood Control Improvement



The primary objective of the Granite Reef Watershed Improvement Project is to eliminate the risk of structural flooding, eliminate the Federal Emergency Management Agency (FEMA) floodplain along Granite Reef Wash, and reduce street and yard flooding. The project will also include a new storm drain in Pima Road that will help reduce floodwater flows in Granite Reef Wash and provide street drainage for the future Pima Road widening project. The existing FEMA floodplain is approximately 2 miles long and encompasses over 600 homes; extending from Thomas Road downstream to the City’s southern boundary at McKellips Road, generally between Granite Reef Road and Pima Road.


The project area is bounded by the Arizona Canal on the north, Loop 101 on the east, the Salt River on the south and the drainage divide that runs between Hayden Road and Granite Reef Road on the east. The project will be designed and constructed in two segments - NORTH, the area north of Indian School Rd., and SOUTH, the area south of Indian School Rd.


Drainage improvements are being planned for the project area to control the runoff from the 100-year storm in order to eliminate the FEMA-designated floodplain on Granite Reef Wash. The improvements will be implemented in two phases. 

NORTH Improvements - Currently Under Construction

Construction work began on June 29 and will include new storm drain laterals that will connect to the existing storm sewers on Heatherbrae Ave. and Granite Reef Rd., in addition utility relocations, re-grading and paving will occur in selected areas.  Construction of this segment is anticipated to be complete in October 2020.

Most construction work will take place between 5 a.m. and 4 p.m. Monday – Friday and traffic restrictions will be in place.  Night and weekend work is anticipated to be minimal, however, it will be required.  To maximize efficiency, complete road closures may be needed within the residential areas during active work hours, and local residents will be required to seek alternate routes to reach their home. Any work zone closure will be limited to 250 feet and emergency access will be provided as needed. 

Additionally, the water delivery main that brings water into your neighborhood will be impacted by this project.  As a result, intermittent water shutdowns will be necessary and advance notice will be provided in the affected areas prior to any anticipated shutdowns.  

Work will begin on the intersection of Heatherbrae Dr. and Granite Reef Rd. and move east and south.  Construction will take place concurrently on Heatherbrae Dr. between Granite Reef Rd. and 86th St. and on Granite Reef Rd. and move south to Indian School Rd.  Traffic on Heatherbrae Dr. will be limited to local access only.  Traffic on Granite Reef Rd. will be limited to one way.  Please use caution and pay attention to all traffic control signs in the area.

Trash and recycling collection will be affected by construction work. Trash will be picked up in the alleys every Wednesday between 5 a.m. and 6 a.m.  with the exception of the Mackenzie Dr. cul-de-sac on the west side of Granite Reef Rd. where trash is collected curb side.  The contractor will ensure the cul-de-sac is accessible for trash pickup.  Recycling will be picked up curb side on Monday between 5 a.m. and 6 a.m.  If your house is in the immediate work zone, the contractor will make sure the recycle containers are accessible by moving containers to an area where they can be picked up and then return them to your home.  Remember to place your containers curb side before 5 a.m.

Construction is complete on new storm drain laterals that connect to the existing storm sewers on Jackrabbit Road, Chaparral Road and Camelback Road. The next phase of the project will take place on Heatherbrae from 86th Street to Granite Reef Road and on Granite Reef Road from Heatherbrae to Indian School Road.  The new laterals will discharge more flow to the existing storm drains allowing more runoff to be diverted to Indian Bend Wash, so it doesn’t flow south, resulting in flooding problems downstream. The proposed storm drain laterals will control all the 100-year runoff north of Indian School Road.   


NORTH Area Exhibits


SOUTH Improvements

The SOUTH area implementation plan includes new drainage improvements south of Indian School Road that, together with the North area improvements, will hopefully eliminate the FEMA floodplain on Granite Reef Wash.  Construction of this segment will begin during the fall of 2020.

These improvements include:

  • A storm drain in Thomas Road between 82nd Street and Pima Road
  • A stormwater detention basin in Pima Park
  • A storm drain in Pima Road from Thomas Road to McKellips Road
  • Granite Reef Channel improvements both upstream and downstream of McDowell Road
  • A storm drain in McKellips Road between 82nd Street and Pima Road, and
  • A storm drain in the Granite Reef Wash alignment from McKellips Road to the Salt River.


The project includes the development of a two-dimensional hydrologic and hydraulic computer model, utilizing new technology, to analyze storm water runoff in the project area. Now that the analysis is complete the City can submit an application to FEMA to reduce the size of the current, effective floodplain, as well as the 100-year flood elevations.  The application is called a request for Letter of Map Revision (LOMR). The city plans to submit the LOMR application to FEMA in mid-2018. Assuming FEMA is in agreement with the new hydrologic and hydraulic modeling results, it usually takes about 12 to 18 months to obtain the official map revision.

Project Information

Budget: $12,178,770

Sponsoring Division: Stormwater & Floodplain Management

Funding Source: Bond 2000, General Fund, in cooperation with Flood Control District and Salt River-Pima Indian Community

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