Griffin Structures provided program and construction management services for the seismic retrofit of the 80-year-old dam at Lake Gregory Regional Park in the San Bernardino National Forest. The dam was deemed hazardous by the California Division of Safety of Dams, and the County of San Bernardino Special Districts department initiated plans to retrofit the aging dam to protect the community and preserve Lake Gregory as a popular recreational destination. The local Lake Gregory Improvement Committee was also instrumental is supporting the project.
The multi-faced, $24.6 million project began with the installation of an outlet value allowing water to be released from the lake to Houston Creek. The lake was dredged to remove sediment and vegetation, deepening the lake and clearing the water. A total of 30,000 cubic yards of material was removed. A 40-foot buttress—comprised of 70,000 cubic yards of earthen material–was installed on the downstream side of the dam, extending 62 feet beyond the toe of the embankment.
Lake Gregory was able to remain open to recreational enthusiasts during the construction; and despite one of the snowiest/wettest seasons on record, the project was completed on schedule. In order to mitigate the temporary closure of Lake Drive, nearby San Moritz Drive was widened to provide residents and visitors with an alternate route during construction. The project also provided for the ultimate widening of Lake Drive.