White Tanks Flood Retarding Structure No. 4 Rehabilitation
Ninyo & Moore, a SOCOTEC Company, contributed to the rehabilitation of a deficient Flood Retarding Structure, by providing 100-year flood protection to safeguard 50,000 potential residents.
Key Information
Project Name: White Tanks Flood Retarding Structure No.4 Rehabilitation
Provided by: Ninyo & Moore, A SOCOTEC Company
Client: Flood Control District of Maricopa County
Location: Buckeye, Arizona
Services Provided: Geotechnical Services, Environmental Site Assessment, Construction Materials Testing, Engineer of Record Services
Awards: AGC Marvin M. Black Excellence in Partnering and Collaboration Award, ACEC Engineering Excellence Honor Award (2018), and the APWA Arizona Chapter - Project of the Year for Structures $5-$25M
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The Challenge
Addressing Urgent Structural Deficiencies and Safety Concerns
Originally built in 1954, the White Tanks Flood Retarding Structure No. 4 dam was designed to protect downstream communities from storm water runoff from the White Tanks Mountains. After more than 60 years of service, this 6,800-foot-long dry earth dam had surpassed its expected lifespan and began showing critical safety deficiencies including:
- Transverse and horizontal cracking of the earthen embankment
- Inadequate spillways that no longer met design standards
- Aging corrugated metal pipe outlets vulnerable to failure
- Inadequate flood pool storage
The Arizona Department of Water Resources classified the structure as deficient, requiring urgent rehabilitation and repairs to comply with modern dam safety standards. With nearly 1,600 buildings and an estimated 50,000 people projected to live in the downstream area by 2040, the importance of ensuring reliable storm water protection could not be overstated.
Originally built in 1954, the White Tanks Flood Retarding Structure No. 4 dam was designed to protect downstream communities from storm water runoff from the White Tanks Mountains. After more than 60 years of service, this 6,800-foot-long dry earth dam had surpassed its expected lifespan and began showing critical safety deficiencies including:
- Transverse and horizontal cracking of the earthen embankment
- Inadequate spillways that no longer met design standards
- Aging corrugated metal pipe outlets vulnerable to failure
- Inadequate flood pool storage
The Arizona Department of Water Resources classified the structure as deficient, requiring urgent rehabilitation and repairs to comply with modern dam safety standards. With nearly 1,600 buildings and an estimated 50,000 people projected to live in the downstream area by 2040, the importance of ensuring reliable storm water protection could not be overstated.
The Solution
Reinforcing Infrastructure with Geotechnical and Engineering Solutions
The flood retarding structure rehabilitation involved significant upgrades to the dam’s structure:
- Raising and widening the earthen embankment to increase flood storage capacity
- Re-grading the flood pool to eliminate dead-storage areas and improve drainage efficiency
- Building a new 570-foot-long concrete auxiliary spillway
- Constructing a new principal outlet spillway meeting modern safety criteria
- Abandoning outdated inlets and upgrading structural components for long-term resilience
Ninyo & Moore, a SOCOTEC Company, partnered with the Flood Control District of Maricopa County to deliver a full suite of services. Our work spanned both the design and construction phases, ensuring every aspect of the rehabilitation met the highest standards of quality, safety, and performance.
Our services included:
- Geotechnical investigations to assess soil conditions, embankment seepage, embankment stability, and structural integrity issues
- Phase I Environmental Site Assessment to evaluate potential environmental risks and ensure compliance with local regulations
- Construction materials testing for embankment fills, concrete, and structural elements to ensure structural integrity and durability
- Post-design engineering support during rehabilitation
- Construction quality assurance oversight throughout the construction process to verify compliance with specifications and safety standards
- Engineer of Record services during construction and development of a construction completion report.
The Results
Delivering 100-Year Flood Protection for Buckeye and Beyond
The rehabilitated White Tanks FRS No. 4 now meets modern safety standards for dam infrastructure and provides 100-year flood protection for the community of Buckeye and surrounding areas. The improved structure safeguards:
- Nearly 4,000 current residents and up to 50,000 residents by 2040
- More than 1,000 residential and commercial properties
- Agricultural lands, infrastructure, and future development within the protected area
Beyond flood protection, the project also supports community growth. The City of Buckeye in Arizona plans to develop recreational fields and public facilities within a portion of the flood pool area, adding long-term social and economic value.
This project has been widely recognized for its engineering excellence, earning prestigious awards such as:
- AGC - Marvin M. Black Excellence in Partnering and Collaboration Award (2018)
- American Council of Engineering Companies (ACEC) of Arizona - Engineering Excellence Honor Award – Water Resources (2018)
- American Public Works Association (APWA) Arizona Chapter - Project of the Year for Structures $5–$25M
The rehabilitated White Tanks FRS No. 4 now meets modern safety standards for dam infrastructure and provides 100-year flood protection for the community of Buckeye and surrounding areas. The improved structure safeguards:
- Nearly 4,000 current residents and up to 50,000 residents by 2040
- More than 1,000 residential and commercial properties
- Agricultural lands, infrastructure, and future development within the protected area
Beyond flood protection, the project also supports community growth. The City of Buckeye in Arizona plans to develop recreational fields and public facilities within a portion of the flood pool area, adding long-term social and economic value.
This project has been widely recognized for its engineering excellence, earning prestigious awards such as:
- AGC - Marvin M. Black Excellence in Partnering and Collaboration Award (2018)
- American Council of Engineering Companies (ACEC) of Arizona - Engineering Excellence Honor Award – Water Resources (2018)
- American Public Works Association (APWA) Arizona Chapter - Project of the Year for Structures $5–$25M
Geotechnical Expertise for Dams and Reservoirs
This award-winning project highlights SOCOTEC's advanced capabilities in geotechnical and environmental services. We are a trusted partner for complex infrastructure and civil engineering challenges. Through our technical and people-centered approach, we successfully address complex safety deficiencies and transformed an aging dam into a modern flood protection asset that will serve the growing communities around White Tanks Mountains for generations to come.
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