2006-06-12_REVISION - M1982015 (23)

Home Browse Search

Weld County Public Works Attn: David Bauer, PE • January 30, 2006 JN: 3075 Page 3 be incorporated into the design of the lake reclamation. We have also recently met with the State Engineer's office regarding the existing embankment. Based on this meeting, we have designed a widened embankment to provide a minimum top width to height ratio of 10:1. Although our HEC-RAS model includes a lateral weir with split flow analysis in the north overbank (existing lakes) area, we are projecting the floodplain elevations associated with the main river channel for this area. This conservative assumption eliminates a levee effect for the existing embankment. 6. The report does not address the length of time that the peak flow occurs. The 12/12/05 CLOMR report assumption, that the ponds located at the St. Vrain Lakes site have capacity to receive the proposed overflows, needs to be evaluated. It may be that the ponds' storage capacity is soon exhausted and that the remaining peak flows pass downstream unattenuated in the main river channel causing higher water levels than projected. Response: The portion of the flow that overtops the berm and flows into . the proposed lake area is directly connected to the St. Vrain River at a junction at cross-section 64715, which is modeled as an in-line weir. This flow is therefore effectively conveyed through the lakes and back to the river with no attenuation. 7. The CLOMR report cannot be accepted until it has been stamped, signed and dated by a professional engineer licensed in the State of Colorado. Response: The CLOMR report has been stamped, signed, and dated by a professional engineer licensed in the State of Colorado. If you have any further questions or comments, please do not hesitate to contact us, Sincerely, CARROLL & LANCE, INC. Kevin Jennings, EI Engineer II • cl Attachments cc: E / R