Water Resources Program  |  Holymead Dam Improvement

Hollymead Dam Improvement Project

Construction period: December 2018 – July 2017
Construction cost: Approximately $2.3M

Construction Progress Updates

 December 20, 2018 survey stakeout, silt fence and other erosion control measures, construction entrances, detour signage
 January 7, 2019 start of partial road closure and detours 

The dam at Lake Hollymead is being improved by “hardening” the downstream slope (first image below) through the installation of articulated concrete blocks (ACBs) (second image below). In the event of an extreme storm event, this project will prevent scouring of the downstream slope and possible failure of the dam.
Downstream slope of Hollymead Dam

The Lake Hollymead Dam is a 43-ft high, 300-ft long earth embankment that was originally constructed in 1974. The dam impounds a 20-acre lake lying between the Hollymead and Forest Lakes subdivisions. Water is conveyed through the dam via two pipes: a principal spillway consisting of a 36-inch diameter riser connected to a 24-inch diameter reinforced concrete pipe (RCP) and an emergency spillway consisting of a 48-inch diameter RCP. Timberwood Parkway crosses the dam and serves as its crest.

Example of ACB InstallationThe dam is regulated by the Virginia Department of Conservation and Recreation (DCR) – Dam Safety program. Regulations require that the dam be able to withstand the flood resulting from the Probable Maximum Precipitation (PMP) event – an extreme storm used for design purposes. The PMP for the Hollymead Dam is 32.2 inches of rainfall in a 24-hour period. A dam break analysis and inundation zone mapping exercise conducted in 2013 indicated that this PMP would result in water flowing over the crest of the dam at a depth of nearly 5 feet.

The primary feature of the improvement project is the hardening of the downstream slope with ACB – concrete blocks held together with cables (see image). In addition, the project will include replacement of the riser spillway and installation of a low-level outlet, improvements to the pipe system and the point where the pipes discharge into the stream below, the construction of a small parapet (wall) along the top of the dam, and various features to manage seepage through the dam.
Following the construction of the improvements, the dam will look much like it does currently. The contractor will restore topsoil over the ACBs and establish grass. The guardrail and sidewalk will be reinstalled.

What You Can Expect During Construction

• The northbound lane of Timberwood Parkway (the side farthest from the lake) and the adjacent walking path will be closed for the duration of the project. The closure will be along the entire length of the dam. The southbound lane and walking path will remain open. Recommended detour routes are indicated in the image below.

• The construction contractor will use the northbound lane to operate equipment and store materials. In addition, equipment and materials will be stored in two staging areas on the north end of the dam.

• Early in the construction process, the contractor will partially lower the lake to facilitate the installation of a new riser – the structure through which water primarily flows.

• Contractor personnel will be wearing clothing that will identify them and make them more noticeable to drivers. The contractor personnel should not be on your personal property. The contractor supervisor’s name and phone number will be posted on the job board at the start of the project.

• Construction activities will generally occur between the hours of 7:00 AM and 5:00 PM.

• As with any construction site, please be safe by observing all signage and fencing. Be observant when traveling south Do not go onto any area that has been deliberately restricted by the contractor.

Please contact Walter Harris – the County’s project manager for this project – if you have any questions or concerns [wharris@albemarle.org or 434/872-4501 ext. 3421]. Thank you for your patience while the County makes these necessary improvements to our infrastructure.

Recommended detour routes for Hollymead Dam northbound lane closure