Recovering from Hurricane Rita at Lake Livingston Dam

WEFTEC®.06

RECOVERING FROM HURRICANE RITA AT LAKE LIVINGSTON DAM

Thomas Sanders Trinity River Authority of Texas P.O. Box 60 Arlington, Texas 76004

ABSTRACT

On September 24, 2005, incredibly powerful winds on the dry side of Hurricane Rita caused a combination of surge and waves that damaged approximately 11,000 feet of the rip rap that provides upstream slope protection on the 13,480 foot long Lake Livingston Dam, north of Houston, owned and operated by the Trinity River Authority of Texas (TRA). Lake Livingston Project staff, responding immediately to the crisis, worked night and day during and after the storm to minimize further damage and initiate repairs. Quick funding, 75% by the Federal Emergency Management Agency (FEMA) and 25% by the City of Houston, combined with efficient work by TRA management, land surveyors, engineers, and the contractor, resulted in remarkably fast repair of the dam. This presentation documents the steps taken to move from the hurricane damaged dam back to full service within 7 months of the hurricane’s landfall.

KEYWORDS

Trinity River, Trinity River Authority, hurricane damage, hurricane recovery, dam repair, Emergency Action Plan

INTRODUCTION

The damage done to Lake Livingston Dam by Hurricane Rita is severe, but the structure is stable. So started the announcement made by Danny Vance, the General Manager for the Trinity River Authority of Texas (TRA), immediately after Hurricane Rita hit Lake Livingston north of Houston, Texas. Figure 1 shows the dam after Rita removed the rip rap.

On September 24, incredibly powerful winds on the Figure 1 – Rip Rap Gone dry side of the Hurricane Rita caused a combination After Rita

of surge and waves that damaged approximately 11,000 feet of the rip rap that provides upstream slope protection on the 13,480 foot long structure. See Figure 2 for a photo of storm conditions. Some of the upstream clay fill was also eroded. TRA project staff recorded winds of 70 mph sustained, and 117 mph gusts. Upon

Figure 2 – Rita Attacks the Dam

the discovery of the on-going damage, staff followed the downstream notification procedures in the project’s Emergency Action Plan and began to make releases to lower the lake elevation to prevent further damage to the exposed earthen dam. Lake levels were lowered from the normal pool elevation of 131 feet above mean seal level (MSL) to 127 feet MSL.

All Lake Livingston personnel pitched in and reported immediately for extended duty, even though their own homes needed attention due to power outages and damage from the storm. The entire Lake Livingston staff worked with little rest for days after the damage occurred.

LAKE LIVINGSTON

Built, owned and operated by the Trinity River Authority of Texas (TRA), Lake Livingston (Figure 3) is the largest lake constructed solely for water supply purposes located totally within the State of Texas. The lake covers approximately 83,000 surface acres, with a normal pool elevation of 131 feet MSL. The Livingston Dam, constructed across the Trinity River approximately seven miles southwest of the city of Livingston, is 2½ miles in length and has an average height of 55 feet. The lake represents approximately 70% of the City of Houston’s water supply.

Figure 3. Lake Livingston Dam

Figure 4. Lake Livingston Outlet REMARKABLE REPAIR OF THE DAM

Within days of the damage, land surveyors completed an assessment of the damage and declared the dam stable. The survey documented the damage to the dam and allowed engineers to determine how much material would be required to repair the severely damaged, protective rock covered face (rip rap) of the structured. Plans and specifications for the repair were available by October 14, 2005, less than a month after the damage occurred, and contractors’ proposals were presented to TRA by October 21, 2005. Figure 5 provides a schematic of the scope of the project.

Figure 5. Lake Livingston Dam Repair Project

The estimated cost of repairs was $9.6 million. By December 20, 2005, full funding of the project was in place. The Federal Emergency Management Agency (FEMA) provided 75% of the funds. The City of Houston provided the remaining 25% of the funds.

The contractor selected to make the repairs was authorized to start work in January 2006. It was estimated that the work would require 6 months to complete. To repair the dam, 15,808 tons of eight-inch crushed rock bedding material and 72,215 tons of 32-inch limestone rip rap were required to replace the 11,000 linear feet of upstream slope protection that was stripped away by hurricane generated wave action. Truckloads of rock began arriving during the week of January 8, 2006 at the rate of about 1000 tons, or 50 truckloads, per day. Figure 6 shows ongoing work on the dam. By mid-February, 28% of the 11,000 foot damaged portion of the embankment had been repaired.

Figure 6. Work on the Repairs

RETURN TO SERVICE

On April 26, 2006, the repair to the dam was declared substantially complete – 52 days ahead of schedule. The rapid repair of the dam is a function of efficient management on the part of TRA, quick turnarounds on surveying and engineering plans and specifications preparation, effective logistics on the part of the contractor, and good weather in which to work. Pictures of Lake Livingston Dam, before and after repairs were completed, are shown in Figure 7. Now, rain is needed to fill the lake back up!

Figure 7. Lake Livingston Dam – Before and After Repairs