COMPREHENSIVE REHABILITATION IMPROVEMENTS AT CEDAR CREEK RESERVOIR DAM AND SPILLWAY

摘要

Tarrant Regional Water District (TRWD) owns and operates Cedar Creek Reservoir in Henderson and Kaufman Counties, Texas. The reservoir is retained by Joe B. Hogsett Dam, with pool levels controlled by radial and bascule spillway gates. This dam is a zoned earthen embankment. During first filling in the 1960s seepage and boils were noted downstream of the embankment. A relief well network was installed to manage the seepage. This relief well network served the project well, but degraded over time and the efficiency of the system diminished to the point that seepage-related issues reappeared. TRWD contracted with Freese and Nichols, Inc. to study the dam and spillway, and to develop and design improvements. A variety of solutions were developed, and several design packages were approved and constructed at the dam and spillway over the course of several years. The primary improvement was the installation of a new relief well network to and restore dam safety. The network include 76 new relief wells and collecting piping with stainless steel well screens and risers, a two-stage seepage collection toe drain that parallels the well collection piping, two pump stations, new instrumentation, grouting of upstream rip rap, a shallow slide repair, a 1,400-linear-foot grout curtain to close cutoff windows, and a left abutment seepage collection trench. The design allows for the reclamation of the collected water and provides innovative solutions for access and maintenance of the network. This new network increases dam safety by being more robust than the older network, and easier to access and maintain. It also has the benefit of improving access to downstream areas for both inspection and emergency operations. Since completion, the project has seen a significant improvement in piezometric levels across the site and access conditions in the downstream field are markedly improved.