2008-04-15_REVISION - M1980244 ‎(332)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL V APP 8 Appendix C.9 Underdrain Calculations
• From: CC & V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

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•
•
PROJECT: JOB NO: SHEET,Z_OF~}
Arequa Phase 5 VLF 1125
FEATURE: BY: DATE:
Underdrains DTW 2/8/08
DETAILS: CHKD BY: DATE:
Underdrnin Capacities ALD 2/19/08
Primary, Secondary and Tertiary Underdrains
• Criteria: 1) Underdrnin to be sized for o max flow of 25 gpm based on reported measurements of other
springs within the general vicinity
• Primary Underdrnin Ar~lysis:
Primary Underdrnin extends beneath the PSSA and will discharge into an underdrain pond near
the downstream toe of the PSSA, o
The minimum grade of the PSSA is 0.5%. A 6" CPE pipe at a 0.5% grade has n capacity of 155 gpm.
Therefore, under gravity flow, the primary underdrain capacity is sufficient
DEPTH OF STRUCTURAL flLt REQUIRED
TO ACHIEVE SOIL LINER FILL SUBGRADE.
ELEVATION VARIES
l2 oz/yd° NONWOVEN
GEOTEXTILE 6" MINIMUM SELECT
(2' MINIMUM OVERLAP) STRUCTURAL FILL
"
4
OIA. CPe PIPE ~ 3' MNIMUM
~\
~
UNDERDRAW FILL ^--~ ~ (T
_ GRADE VARIES
Fes- 5~ MINIMUM -~\` COMPETENT SUBGRADE AS
APPROVED B'I ENGINEER
• Secondary Underdroin Analysis:
Secondary underdrains to be routed into upper reaches above the PSSA
Use Leps (1973) and Wilkins (1956) equations for turbulent flow through rockfill to size capcity
of secondary underdrain. Rockfill has a D50=6" and fins content of 0-5%. A factor of safety
of 5 will be applied to design. Asuume rockfill porosity of 33%nnd o minimum grndinet of 5%
(grading plan indicates grading will be much greater than 5%).
DEPTH OF STRUCTURAL fILL REQUIRED
TO ACHfEVE SOIL LINER FILL SUBGRADE.
ELEVATION VARIES
12 oz/yd2 NONWOVEN
GEOTEX7ILE
{2~ MINIMUM OVERLAP) (" MINIMUM SELECT
STRUCTURAL FILL

2' MINIMUM

UNDERDRAIN FILL -~ ~ GRADE VARIES
F-~~-- 4' M{NIMUM --~
COMPETENT SUBGRADE AS
APPROVED BY ENGINEER