Project Overview
The 80-year-old dam at Lake Gregory Regional Park will undergo rehabilitation proposed and managed by the County of San Bernardino Special Districts department. After being deemed a “high hazard dam” by the California Division of Safety of Dams (DSOD), the Lake Gregory Dam must be retrofitted to meet seismic safety requirements. To reinforce the structure, an earthen stabilization buttress will be built on the downstream side of the dam.
Lake Gregory Dam History
Lake Gregory is a man-made lake in the heart of Crestline that was created by Arthur Gregory. Fueled by the water from Houston Creek, this recreational facility offers fishing, swimming, waterslides, boating, and a walking trail along the lake’s perimeter.
The Lake Gregory Dam was completed in 1938. The dam is 97 feet high and has a 2.5:1 upstream slope and 2:1 downstream slope.
Project Outline
The Lake Gregory Dam Rehabilitation project is being overseen by the County of San Bernardino Special Districts department and the project management is through Griffin Structures to retrofit the existing dam to meet state earthquake safety standards. A specific contractor will be selected in late 2017. The dam rehabilitation process has already begun and is expected to be completed in 2019. Dam rehabilitation will include adding a 40-foot earthen buttress to the downstream side of the dam that will extend 62 feet beyond the toe of the embankment. The buttress will be made of 70,000 cubic yards of earthen material. In order to add the buttress, the overgrown vegetation and sediment currently filling the dam will be removed. To date $17 million has been funded by the County of San Bernardino for the rehabilitation project.
In conjunction with dam improvement efforts, supporting efforts such as lake dredging, the installation of an outlet valve, and work on the basin on the west mouth of the lake are separate projects overseen by the County of San Bernardino through the summer of 2017. The dredging will increase the depth of the lake and improve water clarity; material dredged from the lake bed will be used in the buttressing of the dam.
To avoid structural damage to the dam, the DSOD has initially required a lowering of the lake of 5 feet, which was discharged through the new outlet valve in Houston Creek. The lake is expected to remain open for recreational purposes, and habitat will not be harmed in the lowering of the lake’s water level.
The County of San Bernardino will enforce a stormwater and erosion control plan to ensure that there will not be a project-related impact on California water quality.
Potential Impacts to the Crestline Community
Lake Gregory Dam improvement work will occur from Monday through Friday from 7 a.m. to 4 p.m. Lane restrictions and road detours may periodically occur during construction with alternate routes available to motorists. Flaggers, traffic lights, and signs will visible around detour roads for driver safety throughout the project.
See the Project FAQs for more details on specific aspects of the rehabilitation project.
