Hall Dam Repair Alternatives Study

In September 2012, the Division of Water Resources State Engineer Office, Dam Safety Branch notified Jefferson County Open Space (JCOS) that maintenance was required for Hall Dam. The dam is located on a tributary of Clear Creek, named Magpie Gulch. JCOS selected Muller to evaluate three alternatives to address the maintenance requests of the State Engineer Office (SEO):

1. Remove or breach Hall Dam, meeting SEO criteria for dam removal

2. Modify Hall Dam to remain jurisdictional and meet SEO requirements

3. Modify Hall Dam so that it will be considered non-jurisdictional (lower the dam height)

Muller recommended a thorough investigation of the underlying bedrock surface in hopes that excavation of material down to this surface might serve to stabilize the creek grade and not require construction of costly drop structures. We arranaged for a geotechnical assessment and hazard assessment as part of our study. The team created profiles of existing channel conditions with profiles of the three alternatives superimposed for comparative purposes. Conceptual plans for the three alternatives were developed along with hydrologic and hydraulic studies, project cost estimates, dam break analysis, and anticipated requirements for required permits. We documented the study with report to JCOS.