Lake Gregory Dam Rehabilitation Project

In late 2008, Regional Parks began working with Special Districts to provide rehabilitation of the Lake Gregory Dam infrastructure to comply with the seismic standards outlined by the California Department of Water Resources, Division of Safety of Dams. Over the course of the last few years, a series of sediment removal projects have been completed, in addition to the current work being done to repair the outlet valve and buttress for the dam. This page will serve to provide the latest updates on the project.

Outlet Valve Replacement Project

August 25, 2016
Pro-Craft has completed all work inside the outlet tunnel. A slurry back fill of the tunnel with “Cell-Crete” has been completed. This back fill has encased the new outlet pipe and has filled the tunnel. The new concrete vault, located outside the old tunnel entry, has been formed and concrete installation is currently underway. The vault, when complete, will house the new outlet valves.

November 4, 2015
The construction contract for the Outlet Valve Replacement Project was awarded to Pro-Craft Construction on July 28, 2015. Pro-Craft mobilized to the Tunnel site in early October, 2015. Current challenges to overcome include the alignment of the tunnel, which was found to be less than straight; and the fit of the pipe plugs to be used on the lake side or wet side of the inlet pipes through the bulkhead within the tunnel to prevent water release during construction. 

The size of replacement pipe to be plumbed the length of the tunnel is 32-inches, more than double the size of the existing 12-inch outlet pipe. The new pipe was sized to meet State discharge requirements which calls for the capability to lower the lake by one half of its volume in 7 days. Due to the gradual undulation of the tunnel walls and the size of the new pipe, it prevents a “straight shot” of pipe from the concrete plugs to the existing mouth of the tunnel. Design consultant Tetra-Tech is working with Pro-Craft to remedy and insure a constructible solution within the tunnel’s constraints.

A positive seal of the pipe plugs to the existing inlet pipes on the lake side or wet side of the tunnel is important; proper fit will prevent the unintentional release of lake water and provide for worker safety throughout construction of the new outlet valve assembly. Inlet pipes, located roughly 330 feet under the dam can only be reached by divers. Recently, divers discovered an inconsistency inside the inlet pipes preventing the pipe plugs from fitting securely and properly. New plugs are being manufactured according to tolerances discovered during an attempt to fit previously manufactured plugs. The gathering of information to design and fit plugs is difficult given the dive conditions and limited amount of time divers can spend under water due to lake depth and other factors.

Dam Design & Environmental Impact Report

August 25, 2016
The 90% complete Construction Documents and the final Geotechnical Engineering Study were returned to the County from DSOD after their comprehensive review. Comments made by DSOD are currently being addressed by engineering consultant Tetra Tech. A response to DSOD on the numerous comment will ready by the end of August. Plan approval by DOSD is not expected before late fall 2016.

The final EIR documents were adopted by the San Bernardino County Board of Supervisors on April 5, 2016 and the Notice of Determination has been filed.  

April 5, 2016
Final EIR approved by the San Bernardino County Board of Supervisors

November 4, 2015
Progress continues with the design plans to strengthen and buttress the Lake Gregory Dam. Design consultant Tetra Tech is working with representative of the Department of Water Resources, Division of Safety of Dams (DSOD) to address specific items in detail to ensure a successful project.

Environmental consultant Aspen in the process of completing draft EIR documents and should be released for public review the week of November 9th, 2015.

Draft EIR Now Available! Comment period open until January 5, 2016.

Sediment Management & Bio-Retention

August 25, 2016
The final plans and bid package prepared by engineering consultant CWE were released for competitive bid on May 3, 2016. The competitive bid process involved five (5) addendums issued for bidder clarity; finally closing the bid on June 28, 2016. The result of the bid process culminated in the award of the project to Earth Construction and Mining of Garden Grove, on August 23, 2016. Earth Construction and Mining was determined to be the lowest responsible bidder in the amount of $1,887,517.

Construction the for capture and retention of sediment within the Houston Creek channel, along the ball fields at San Moritz and the established basin at the County Library, Houston Creek West, are illustrated on the accompanying plan sheets. The San Moritz Ball Field area has been identified and will be utilized as a sediment stockpile area as illustrated on the included graphic. The temporary use of this area is necessary to accomplish dewatering for transport and/or reuse of the material for the dam project.
Permit applications have been completed and submitted to the Regulatory Agencies; California Fish and Wildlife, Lahontan Water Board and US Army Corps of Engineers. Permits are pending.

West Basin

South Basin

Ball Field Stockpile
Click on the Images Above to Zoom

May 6, 2016

Final design and construction drawings for the Lake Gregory Sediment Management and Bio-Retention Project have been completed. The project was released for competitive bidding by Board action on May 3, 2016. The project will address sediment inflows at Houston Creek West, the Library Basin; and Houston Creek South, near the San Mortiz Lodge.

Work at the West Basin includes vegetation clearing, excavation and removal of sediment from the existing basin, and construction of a concrete weir box with a low flow outlet system. A concrete retaining wall and landing with removable handrails are to be install to provide ease of access for ongoing sediment removal.
The South Basin work includes realignment of the existing ball field fence line, vegetation clearing and selective tree removal, excavation and removal of sediments in and along the existing creek bed, and installation of natural, step-down rock levees comprised of light weight rip-rap rock. Additional creek bank reinforcement and a low flow outlet system will also be addressed.
Concurrently, Construction Permit applications have been prepared and submitted to the Regulatory Agencies; California Fish and Wildlife, Lahontan Water Board and US Army Corps of Engineers. An additional set of permits for long term maintenance are currently being prepared.

The Initial Study for the Sediment Management and Bio-Retention Project

Click on the Image Above to Zoom

November 4, 2015
Design and construction drawings for the for capture and retention of sediment within the channel along the ballfields at San Moritz and the established basin at the County Library is being undertaken by engineering consultant CWE. The improvements planned for these locations will allow for the fallout of sediment before it has an opportunity to enter the lake. Along with the design changes to current structures; a sediment management plan is in development to detail maintenance practices for permissibility through applications that will be made to the Regulatory Agencies: California Fish and Wildlife, Lahontan Water Board and US Army Corps of Engineers.
The preliminary timeline for channel and basin improvements is: February – March of 2016 for the Library basin, and May – June for the San Moritz Lodge channel along Houston Creek South.