2008-03-13_PERMIT FILE - C1992081A ‎(10)‎

• Permit No: C1992081A
• IBM Index Class Name: Permit File
• Doc Date: 3/13/2008
• Section_Exhibit Name: Tab 12 Facilities
• Media Type: D
• Archive: Yes

The following briefly describes the input and output from the small area exemption SEDCAD+
analyses.
Input Summary
10-yr. 24-hr Precipitation 1.6 in.
CN Factor 48
K Factor 0.25
CP Factor 0.075
Output Summary
Runoff Volumes and Sediment
Topsoil Pile 1 0.0
Topsoil Pile 2 0.0
Topsoil Pile 3 0.0
Substation: There is an electrical substation located in the northwest corner of the
facilities area as shown in Exhibit 12-2, Surface Water Control Plan Map (Revision 11, dated
03/07). The substation is enclosed within a 30 by 40 foot area which is graveled and
fenced. Also associated with the substation is a small disturbance area outside the chain-
link fence. Runoff from the substation area does not drain to the Truck Loop Pond and is
controlled using a sediment fence. The location of the sediment fence is shown on Exhibit
12-2 (Revision 11, dated 03/07). The sediment fence is designed to safely pass the peak
discharge from a 10-year, 29-hour event. The design demonstration is presented in Appendix
12-2, Small Area Exemption Demonstrations. Given the limited size of the disturbance area
and the demonstration that a sediment fence provides adequate control, HGTI requested, and
received CDMG approval to permit this area as a small area exemption.
Office/Parking Lot/Leach Field: An office/change building, parking lot and leach field were
constructed on the west side of the facilities area circa 1979 as shown on Exhibit 12-2,
(Revision 11, dated 03/07). In 2007, as part of MR-15, HGTI placed a temporary office
trailer adjacent to the existing office/change building. The trailer will be placed over a
portion of the existing parking lot area, which is already permitted as a disturbed area.
Consequently, there will be no new disturbance associated with the temporary office trailer.
The-total disturbance associated with the office/change building, temporary office trailer
and parking area is approximately 0.3 acres. The disturbance associated with the existing
leach field (0.45 acres) has been successfully revegetated. Runoff from these areas does
not drain to the Truck Loop Pond and is controlled with a sediment fence. The location of
the sediment fence is shown on Exhibit 12-2 (Revision il, dated 03/07). The sediment fence
is designed to safely pass the peak discharge from a 10-year, 24-hour event. The design
demonstration is presented in Appendix 12-2, Small Area Exemption Demonstrations. Given the
limited size of the disturbance area and the demonstration that a sediment fence provides
adequate control, HGTI requested, and received CDRMS approval to permit this area as a small
MR-15 4 Revised 03/07