Raleigh Mine Mod EC Calcs 1-15-21

110-
WithersRavenet
NoOur People. Your Success.
EROSION CONTROL CALCULATIONS
HANSON RALEIGH QUARRY
Raleigh, NC
Prepared For:
Hanson Aggregates Southeast, LLC
3825 Barrett Dr.
Suite 300
Raleigh, NC 27609
[phone]
ATTN: Jack Garvey
Prepared By:
WithersRavenel
137 S.Wilmington St., Suite 200
Raleigh, NC 27601
[phone]
License No. C-0832
January2021
WR No.09200040.00
CA
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Ryan Fisher, PE

SEDIMENT TRAP CALCULATIONS
Hanson Raleigh Quarry WR No. 09200040.00
Erosion Control Calculations January 2021

Q25 yr SEDIMENT TRAP DESIGN -HANSON AGGREGATES-RALEIGH QUARRY
If Rock Baffles Used:
Drainage Denuded Volume of Remaining
Area(ac) Area(ac) Storage Volume Req'd(cf) Surface Area Req'd(sf) Length Width Depth Storage Volume Provided Surface Area Weir Length Weir Length Rock Baffle Storage
Basin# (Da) (Du) (3600 cf/ac Denuded Acre) (Q25)(435 sf/cfs) (ft) (ft) (ft) (cf) Provided(sf) Req'd(ft) Provided(ft) (cf) Volume(cf)
A-11 2.26 2.26 8136 2342 70 35 4 9800 2450 6.00 10 525 9275
A-7 3.00 3.00 10800 3109 80 40 4 12800 3200 7.00 10 600 12200
Note:1'of freeboard is provided for each Basin(4.0'Total max depth).Cleanout Basin when 1/2 full. 125= 7.94 in/hr
Surface Area Required based on Q25 flows(C=0.30;Tc=5min; 125=7.94 in/hr);Rainfall Data based on Neuse 2 NE(31-6091)location data.
Weir length based on Q25 flows(C=0.30;Tc=5min;125=7.94 in/hr)