Bridgeport Dam piezometer drilling and installation

Solicitation #24-117. Issued by Infrastructure Engineering. Lake Bridgeport Dam is owned and operated by the Tarrant Regional Water District (TRWD) and is located on the West Fork of the Trinity River in Wise County, approximately four miles west of Bridgeport, Texas. The dam was constructed in 1930s as a municipal water supply and flood control dam. The reservoir has a normal pool elevation of 836 feet. The dam consists of a main embankment section, the Saddle Gap Levee, the Berkshire Levee, a gated service spillway, an outlet works, and an emergency spillway. See Figure 1.

Figure 1: Location Map of Lake Bridgeport Dam The main embankment section consists of a rolled earthfill with a total length of about 2,000 feet, a maximum height of 130 feet above the natural streambed, and a top of dam elevation of 874 feet. FM Road 1658 was originally located on the crest of the dam and was reconstructed just upstream of the embankment crest when the dam was raised in 1971. The road is approximately 40 feet wide. The actual embankment crest has a width of approximately 16 feet. The upstream slope of the main embankment is 3 horizontal to 1 vertical (3H:1V) up to elevation 826 feet, and 2H:1V up to the original crest elevation of 863 feet. The original portion of the upstream slope is protected with hand-placed rock riprap, and the raised portion is protected by dumped rock riprap and gravel bedding. The downstream slope of the main embankment was constructed on top of the original downstream slope, is 3H:1V, and is protected with grass cover. See Figure 2 for a cross section of the main dam. The proposed project will consist of the drilling and sampling of borings, installation of new piezometers, and the retrofit and/or abandonment of two exiting piezometers in and near the main embankment section.

Figure 2: Main Dam Typical Section