WSP10308

• File Number: 8449
• Description: Platte River Studies
• State: CO
• Basin: South Platte
• Date: 3/23/1993
• Author: Smith Geotechnical
• Title: Design Report Peterson Lake Dam
• Water Supply Pro - Doc Type: Publication

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slon and Perkins published probabilistic maps of expected rock accelerations for
the next 50 years and assign a value of O,07g for Colorado.

Based on this Information, a O.lg acceleration level was used In the design of
the dam, The design method using these values makes no attempt to account for
attenuation and damping and the etabll1ty was determined using the O.lg level as
a static force in both the vertical and horizontal directions,

f. Drains. Dralnllge at the dllm site was limited to toe drlllns beneath the
plunge pool basin and along the right side of the downstream face of the dam.
The drains below the plunge pool were considered to Improve the plunge pool
stability. The toe drains along the downstream face of the dam were considered
due to the thickness of the overburden In this area and to Improve the stability
of the steep slopes on the right side downstream of the dam,

Drains were considered In the dam foundation and In the dam Itself but were
dismissed due to the cost and due to the size of the dam. The dam Is stable
without Installing Internal drainage and It was determined the added stability
was not necessary for the cost Incurred. Also, the history of drains in the RCC
dams Indicates they are a high maintenance Item and require redrllllng frequently
to keep them In operation.

I!. Foundation Grouting. Grouting of the foundation was considered during
the design but was dismissed at this time until further Investigation of the
foundation rock Is conducted. Due to the type of rock expected and due to the
relatively low head on the dam. we would not expect to have to grout the
foundation rock. This wlll be reviewed again after conducting the drllllng
program at the proposed site.

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Peterson Lake Dam Design Report