By Ms. Sandra Arnold (USACE)September 6, 2012
Q. What are the Addicks and Barker Dams and Reservoirs?
A. In response to devastating floods that occurred in Houston in 1929 and 1935, the U.S. Army Corps of Engineers Galveston District began construction of Addicks and Barker Dams in what was then undeveloped areas in far west Harris and east Fort Bend counties to prevent the loss of life and property and provide flood damage reduction along Buffalo Bayou downstream of the reservoirs and through the center of the City of Houston. Construction of the Addicks and Barker structures were completed in 1948 and 1945 respectively.
Q. Where are the dams located?
A. The Addicks and Barker Dams and Reservoirs are located in southeast Texas in the San Jacinto River basin approximately 17 miles west of downtown Houston. The reservoirs are strategically located above the confluence of Buffalo Bayou and South Mayde Creek. The majority of both Addicks and Barker structures fall within Harris County, however, a small portion of the Barker Reservoir crosses into Fort Bend County. The structures are located near the intersection of Interstate Highway 10 and State Highway 6, with the Addicks Reservoir located north of I-10 and the Barker facility located south of I-10.
Q. How does the Corps operate the dams?
Both reservoirs are normally operated with the gates open to allow free flow of water through the outlet works structures, which keeps the reservoirs dry and preserves their overall capacity to impound storm water and reduce flood levels in Buffalo Bayou. When a rain event occurs, the gates are closed on the Addicks and Barker dams to reduce flooding below the reservoirs. When the downstream runoff has receded to non-damaging stages, reservoir operations resume, the gates are opened and water is released.
Q. How much water is released from the dams and reservoirs?
A. Under normal operating conditions, the combined outflows from the structures plus downstream inflows are limited to 2,000 cubic feet per second at the Piney Point regulating gage. As part the Addicks and Barker Reservoirs' Interim Risk Reduction Measures Plan, district staff worked with partners (the Harris County Flood Control District and local emergency management offices) to submit a request to USACE Southwestern Division for an operational deviation to make releases (combined outflows from the reservoirs plus downstream inflows) up to 4,000 cfs at the Piney Point regulating gage to maintain reservoir pools below a target elevation. The district's request was approved by Southwestern Division in July 2010. The incremental release capability has not been used since it was granted. Harris County underwent a significant rainfall event in 2012 in which the dams continued to perform as intended. Staff continues to closely monitor the dams for any changes in conditions.
Q. How often are the dams inspected?
A. The Corps continually inspects all of its dams nationwide under its Dam Safety Program, a program that is designed to ensure that all federal dams are designed, constructed, operated and maintained as safely and effectively as possible. The Corps of Engineers Dam Safety Program provides a framework to ensure that both short and long term solutions are studied and applied as well as ensures the protection of life and property. The last periodic inspection of both dams was completed in May 2012.
Q. Why were Addicks and Barker Dams and Reservoirs labeled "extremely high risk?"
A. The Corps operates 692 dams throughout America. As part of the responsibility for managing these dams, USACE has a comprehensive Dam Safety Program that features public safety as its primary objective. In the past, staff looked primarily at the structural integrity of the dams to assess its risks to the public. Today, staff uses a formula that combines dam safety risk and potential consequences when making the risk status assessment. For example, if a dam protects a large metropolitan area with a significant population, such as Houston, the consequences of any failure are much greater than that of a dam protecting farm or ranch land. The potential consequences of a dam failure affecting the Houston metropolitan area are very great, however, the likelihood of failure is minimal.
As part of the Corps' transition to approaching dam safety risk differently, the Corps began a risk assessment on all Corps-owned dams nationwide in 2005. The structures' potential failure mode analysis completed in 2009 identified unacceptable risks associated with the outlet work structures that allow outflows to Buffalo Bayou and the uncontrolled auxiliary spillways at the ends of the dam. The risks associated with these concerns combined with the potential consequences to the Houston metropolitan area (should there be a failure), elevated Addicks and Barker's classification to "extremely high risk."
Q. Is there a threat to Houstonians?
A. All dams present risk potential; however, it is important to know that Addicks and Barker dams are not in imminent danger of failing. These two dams form reservoirs that are dry much of the time. They are continuously monitored by a full-time staff to ensure structural integrity. However, the fact that the Houston metropolitan area is the nation's fourth largest population center is a primary concern. Any dam safety issues at Addicks and Barker could have a far greater impact due to the magnitude of people and property downstream, as opposed to other dams around the country located in rural or low-population density areas.
Q. What is being completed to address the issues with the dams?
A. The Corps has implemented interim measures to reduce the risks associated with the existing structures until permanent solutions are implemented. The interim risk reduction measures include filling voids around the conduits that drain water from the reservoirs, installing additional monitoring points around the water control outlet structures, constructing a filter around the outlet works conduits to prevent voids from forming in the future, installing additional lighting to aid in increased inspection and monitoring, and the addition of generators to ensure uninterrupted power to the water control structures.
After the permanent solutions are implemented, the Corps will continue to monitor the dams through our comprehensive Dam Safety Program. The USACE Dam Safety Program is critical to addressing the nation's aging infrastructure, reducing the risks of flood and storm damage and ensuring federally-owned and -operated dams are adequately safe and present minimal risk to the public.
Q. What improvements will be made to the reservoirs?
A. The Addicks and Barker Dam Safety Modification Report is currently under review and is scheduled for approval in the spring of 2013. The recommended plan (as contained in the DSMR) supports the expeditious and cost effective reduction of risk within the overall U.S. Army Corps of Engineers portfolio of dams. The recommended plan is designed to minimize the risk of significant failure modes (cause of failure) that drove the "extremely high risk" classification so that the project meets the USACE' tolerable risk guidelines.
Q. When are the improvements expected to be completed?
A. Contingent upon funding, staff anticipates construction to begin in the summer of 2014 and for the project to be completed in the fall of 2017.
Q. Do you have a ballpark estimate of a repair cost?
A. Upon completion, review and acceptance of the study, the district will be able to determine the appropriate course of action and associated costs.
Q. What is targeted lifespan of the long-term solutions for the dams?
A. The Addicks and Barker dams and reservoirs have served the Houston metropolitan area for more than 60 years, saving taxpayers an estimated $6.4 billion (2012) in potential flood prevention. With interim risk reduction measures implemented and proposed long-term measures planned for the future, it is expected that the dams and reservoirs will continue to serve the City of Houston for another 50 years.
Q. What are the phases of the Dam Safety Modification Study?
The Dam Safety Modification Study is being conducted in two phases. Phase I of the Dam Safety Modification Study will address the issues at the outlet works structures, which were the major contributors of risk and resulted in the Addicks and Barker dams being classified as "extremely high risk." Having Addicks and Barker dams designated as "extremely high risk" is a significant step toward increasing their safety because it receives priority for funding and actions. Phase II of the study will address the non-breach risk, risk exposure (both downstream and upstream), potential operational changes and potential failure modes associated with the uncontrolled auxiliary spillways at the ends of the dams. This phase will require a non-federal cost sharing sponsor to conduct the study and implement the recommended plan identified by the Phase II Study.
Q. Is recreation offered within the reservoirs?
A. The Addicks and Barker dams were authorized as flood risk management structures however, they serve a dual purpose. The Corps has made land available through lease agreements with local municipalities including the City of Houston, Fort Bend County, and Harris County Precinct 3 to provide an added recreational benefit for the Greater Houston Community. Bear Creek Park, George Bush Park, Millie Bush Bark Park, Cullen Park and Cinco Ranch Park are available for the public's enjoyment.
With the continued development of lands outside the reservoirs, the value of undeveloped land within the reservoirs continues to grow. The USACE Galveston District staff realizes the importance of these natural resources to the local community and works diligently to balance the development of recreational facilities within the reservoir for the protection of the natural resources.
Q. Where can I learn more about the Corps' Addicks and Barker Dam Safety Program?
A. To learn more about the Addicks and Barker Dam Safety Program, please visit www.addicksandbarker.info. For more news and information, visit the USACE Galveston District website at www.swg.usace.army.mil. Find us on Facebook, www.facebook.com/GalvestonDistrict, or follow us on Twitter, www.twitter.com/USACEgalveston.