_PERMIT FILE - C1981008A ‎(13)‎

• Permit No: C1981008A
• IBM Index Class Name: PERMIT FILE
• Doc Name: Sedimentation Pond 004
• Section_Exhibit Name: Tab 13 Attachment D
• Media Type: D
• Archive: Yes

TABLE 4
Weighted Curve Number (CN)
Vegetation Hydrologic Area
Cover Soil Group CN (Acres)
Reclaimed C 81 6.3
Use CN = 81
TABLE 5
Area
Soil Type "k" Factor (Acres)
Reclaimed 0.25 6.3
Use "k" = 0.25
Precipitation and Storm Type
Precipitation depths for the 10-year, and 25-year storms were developed
using procedures and data published in the Soil Conservation Service
publication "Procedures for Determining Peak Flows in Colorado". A
standard SCS Type II storm was utilized for each analysis.
Unit Hydrograph and Surface Condition
The SEDIMOT II computer program provides three unit hydrograph shapes to
choose from in determining the runoff characteristics of a watershed.
The disturbed hydrograph (No. 1) was used for disturbed and reclaimed
areas.
Time of Concentration
The time of concentration, tc, is defined as the time required for water
to flow from the hydraulically most remote point in the watershed to the
watershed outlet. The runoff time of concentration was calculated using
the following equation (USBR, 1977) :
6