Construction began on the modernization of the Great Northern Detention Pond in February 2009. It is expected to take about nine months to complete. During construction, access to the site will be limited. However, there will always be a way to go between the neighborhood and the pedestrian bridge across MoPac Expressway.

Please contact Project Manager, Darryl Haba, at (512) 974-7205, with any concerns during construction.

History
The Great Northern Detention Pond is at 6900 Great Northern Boulevard, near the intersection of Far West Boulevard and MoPac Expressway. This is a small, high hazard dam with an embankment that is 20 feet high. It was built in 1978 and was modified in 1983 in response to the Memorial Day flood. It helps reduce the risk of flooding for many homes along Shoal Creek in the Allandale Neighborhood. A water quality pond was added in 1993. The dam was last inspected by the City in March 2006 and by the state on February 13, 2007 (TCEQ Inspection Report, 344 KB pdf).

Project Summary
There are two main components to this modernization project:

• The safety of the structure will be enhanced in the event the dam is overtopped during an especially severe storm. A short wall will partially encircle the pond. It will direct any overflow over a concrete-lined spillway, so that the overflow will not weaken the structure of the dam. The wall will not restrict access to the site.
• Unfortunately, many trees need to be removed, including all the trees and brush on the embankment itself. We have limited the tree removal as much as possible, but it is necessary to ensure the dam remains in good condition. The root systems of trees and brush tend to weaken dams and decrease their ability to resist the force of flood waters.

Emergency Action Plan
The state requires all high hazard dams to have an emergency action plan. An emergency action plan is a carefully conceived plan to reduce the risk to lives and property from consequences of dam failure. A Flood Early Warning gauge will be installed at this site to allow the City to monitor the site during storms. In the event of an emergency, the City will notify impacted residents using a reverse-911-type system; they will receive a phone call with a recorded message.

Download a copy of the presentation (3 MB pdf) from the February 4, 2008, public meeting.

Return to the Stormwater Pond Safety Program page.