General

Live Oak and Post Oak trees are generally found near the rivers while Mesquite, Huisache, Blackbrush, and grasses cover most of the rest of the area. The area has long and hot summers, mild winters, and erratic precipitation. Occasional hurricanes produce major storms and flooding. The Nueces River Project is located on the coastal plain of South Texas midway between the cities of San Antonio and Corpus Christi. Choke Canyon Dam is on the Frio River about 4 miles west of the town of Three Rivers, named for the confluence of the Frio, Nueces, and Atascosa Rivers. Low-lying hills force the three rivers into a constricted channel, thus the name Choke Canyon.

History

Rattlers, gators, armadillos, and javelina were companions of early survey crews as they worked in the area of the Nueces River Project near Three Rivers, Texas. One contract worker in 1976 referred to them as 'critters.' He said the real 'Legend of Choke Canyon' was a 9-foot alligator that made his home in ranch ponds. The aggressive alligator frequently left the tank to greet visitors and eventually had to be relocated. Other alligators also had to be moved from one location to another during construction activities.

For many years Mexico claimed the Nueces River as the boundary between Mexico and Texas. The Nueces River is in the area south Texas known as Brush Country where Texas cattle industry had its beginning as settlers built herds from wild cattle in the area. The settlers lived in towns for the most part because isolation threatened their survival. The frontier towns were located along banks of rivers, with Tilden and Oakville being the first towns in McMullen and Live Oak Counties.

In the late 19th century, that pattern began to change as the cattle industry expanded and the sheep and wool industries evolved. The isolation of ranch life became a standard. Agriculture is very limited in the area. Around the turn of the century, oil an gas exploration exploded.

One of the first oil wells was on the Calliham ranch. The owner immediately built a store, and the town of Calliham was born. Calliham was quickly a 'boom town,' but declined just as quickly some 30 years later. Since the town of Calliham was to be inundated by the construction of Choke Canyon Dam, Reclamation relocated the Town and its residents about 2 miles to the south adjacent to relocated State Highway 72.

Uranium and lilgnite mines now add to the area's economy along with oil and gas, but ranching is still predominate.

Construction

The project organization commenced with the opening of an office in Three Rivers, Texas, on May 16, 1976. Bids for construction were opened at the Three Rivers City Hall on May 11, 1978. The construction contract was awarded to the Holloway Companies August 8, 1978 with a notice to proceed August 10, 1978 and scheduled completion date of February 10, 1982.

The contractor began earthwork operations at Choke Canyon Dam on October 2, 1978. By July 1980, the geological mapping of the foundation for the dam cutoff trench was complete as well as the foundation for the outlet works. Excavation revealed that the preliminary interpretations related to the geologic conditions were remarkably accurate.

Twenty-four modifications were necessary during the construction of the dam. Earth materials and aggregate for construction of the dam embankment were obtained from the reservoir area. Riprap for the outlet works and downstream from the spillway was obtained from commerical limestone quarries about 135 miles from the damsite.

Hurricane Allen made landfall on August 11, 1980 causing 11.13 inches of rain over the project area within a three day period. As a result of the excessive rains, the contractor was unable to resume work until August 18, 1980.

By May 18, 1982, Choke Canyon Dam was considered substantially complete. The only work remaining at that time was placing of soil cement at the closure section and final testing of the radial hoist and gate position indicators. The official dedication ceremony was held at the spillway structure on June 8, 1982. There were approximately 1,300 persons in attendance for the ceremony.

The Final Construction report for Choke Canyon Dam was completed January 12, 1984. The Nueces River Project was selected to be the first major construction project to use SI metric units of measurement in lieu of English units except where SI metric units were not practical.

Plan

Choke Canyon dam is a rolled earthfill structure about 115 feet high and approximately 3 miles long. Almost 6 million cubic yards of earthfill were used in construction of the dam. The dam has a cutoff trench along its entire length excavated to sound rock and backfilled with select impervious material and was completed in 1982.

A concrete spillway, located on the left abutment of the dam, consists of an inlet structure, a chute, a stilling basin, and a gate structure with seven radial gates designed to pass the probable maximum flood without endangering the safety of the structure. The radial gates are 50 by 24 feet with a a release capacity of about 250,000 cubic feet per second. The river outlet works include a multi level intake structure which allows water of different temperatures, nutrient values, and dissolved oxygen contents to be released as necessary for fish and wildlife benefits downstream. A 99-inch diameter steel-lined upstream conduit, a gate chamber structure, a horseshoe downstream conduit, a control structure, a covered chute, and a stilling basin complete the system.

When filled to the top of the conservation pool at an elevation of 220.5 feet, Choke Canyon Reservoir covers 26,000 acres along 34 river miles in Live Oak and McMullen Counties. The reservior would cover 35,000 acres at the maximum water surface elevation of 233.0 feet. The reservior capacity for conservation storage is over 700,000 acre-feet with room for an additional 380,000 acre-feet of surcharge capacity.

Some timber was left standing in the reservoir area to improve fishery resources. Selective clearing was done for boating access and multiple-use purposes. Choke Canyon reservoir is operated in conjunction with Lake Corpus Christi to provide 252,000 acre- feet of water per year for municipal and industrial use. Choke Canyon Reservoir yields about 139,000 acre-feet annually of that amount.

Water released from Choke Canyon Reservoir flows through the Frio River about 10 miles to the Nueces River and then down the Nueces River about 30 miles to Lake Corpus Christi where it is re-regulated. The Frio River drainage area above Choke Canyon Dam is over 5,000 square miles within the Nueces River basin.

Overview

No text for this section

Other

No text for this section