The panel’s final report reiterated its initial findings when looking at Lake Gonzales and an area stretching from Hwy. 80 to Gonzales County Road 143.
The second report designates areas at least 550 feet upstream of the H-4 Dam, 2.4 miles downstream of the H-4 Dam and 700 feet upstream of M.A. Wade Dam as “prohibited unsafe zones,” while the area between the downstream H-4 prohibited zone and the upstream Wade prohibited zone is designated as a “restricted unsafe zone.”
“The completed independent expert panel reports reinforce the safety concerns surrounding the aging dams by reaffirming and extending previously outlined restricted areas on the Guadalupe Valley Lakes,” the Guadalupe-Blanco River Authority said in a public statement. “We appreciate the members of the independent expert panel for their thorough effort to understand and define areas of each lake that can pose a hazard to those on and around the lakes in the event of a spillgate failure."
The independent expert panel has since prescribed safety measures at all Guadalupe Valley Lakes, including signage and buoys. Additionally, all activities on or in the water, including boating and canoeing, are prohibited within designated prohibited unsafe zones, and water activities such as swimming, wading and tubing are prohibited in restricted unsafe zones.
In its initial report the panel concluded that a single gate failure resulting in a maximum flow of between 11,000 cubic feet per second and 13,000 cubic feet per second was the most likely scenario at each dam on Lakes Dunlap, McQueeny, Placid and Meadow Lake and that “cascading failures” of gates located at dams downstream are unlikely.
“It is the opinion of the independent expert panel that a ‘sunny day’ gate failure, i.e. a gate failure occurring during non-high-flow periods, is the critical scenario due to gates being in full upright position, elevated population at risk, and no advanced warning of the failure,” the panel said in the first report. “This is deemed the most likely failure scenario ... not multiple gates at one dam. The independent expert panel’s understanding ... further suggests that cascading failures of gates at downstream dams would not be expected in the event of single gate failure at an upstream dam.”
Looking at lakes and river segments between Dunlap Dam and FM 1117, the panel determined in its first report that an area 900 feet upstream of the TP-3 Dam at Lake McQueeney and an area 250 feet downstream should be declared a prohibited unsafe zone.
An area 800 feet upstream of the TP-4 dam near Lake Placid is considered a prohibited unsafe zone, and an area 300 feet upstream of Son’s Island and 300 feet downstream of Hwy. 78 is now considered a restricted unsafe zone.
Downstream of the TP-4 dam, a 1,050-foot area of the Guadalupe River and Meadow Lake and a 1,200-foot area upstream of Nolte Dam are now considered prohibited unsafe zones. A segment of the Guadalupe River downstream of Nolte Dam up to the FM 466 crossing is a prohibited unsafe zone, and a section of river from FM 466 to FM 1117 is a restricted unsafe zone.