HomeMy WebLinkAboutCT 02-16; ROBERTSON RANCH EAST VILLAGE; HYDROLOGIC AND HYDRAULIC ANALYSIS; 2005-03-19•
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March 19, 2005
Don Mitchell
McMillin Land Development
2727 Hoover Avenue
National City, CA 91950
Subject: Robertson's Ranch -East Village
Dear Don:
•
P.O. Box 9496
Rancho Sanla Fe, CA 92067-4496
T: 858.692.0760
F: 858.832.1402
wayne@changconsullanls.com
My September 2, 2004 report, Hydrologic and Hydraulic Analyses for Robertson's Ranch East
Village, contains a proposed condition 100wyear HECwRAS hydraulic analysis of Calavera Creek
north of the Rancho Carlsbad Mobile Home Park wall and south of Cannon Road (planniIlg Area
22). The analysis is based on a 100wyear flow rate of 472 cubic feet per second and models a
proposed 4.4 acre pad designed by O'Day Consultants. The pad elevations range from
approximately 50 feet on the west to 55 feet on the east. The attached exhibit shows the pad
grading and adjacent HEC-RAS crosswsections. The pad and 100-year water surface elevations at
each cross-section are as follows.
Proposed Condition
HEC-RAS 100-Year Water Proposed Pad
Cross-Section -Surface Elevation, ft. Elev~tion, ft.
60 45.5 ---
90 45.7 50.0
100 47.9 52.2
110 49.6 53.5
115 50.1 54.4
120 50.5 55.0
140 50.5 ---
Typically, one foot of freeboard is required above the 1 OO-year water surface elevation. The table
indicates that this criteria will be exceeded within the entire pad. Therefore, the pad will be
appropriately elevated above the 100-year floodplain.
Sincerely,
Wayne W. Chang, M.S., P.E.
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