SW6230401_Response To Comments_20230612

PO Box 249, Sanford, NC 27331
[phone]
TRANSMITTAL
To:
Division of Energy, Mineral & Land Resources
Stormwater Program
Att: Brianna Holland
1612 Mail Service Center
512 N. Salisbury Street
Raleigh, NC 27699-1612
Date:05/19/23
Project:Phalanx Crossfit
HE#:HC2217
Please find enclosed the following:
One (1)Original hard copy of all revisions
Two (2)CopiesSigned and Sealed Affected Plan Sheets due to revisions
The enclosed are submitted for approval per comment letter received via email May 19, 2023
Responses to comments are below:
1a. The word 'infiltration basin' has been revised to 'wet pond' on the Culvert Drainage Area Map
2a. The plan shows a 36" culvert
2bi. The calculations use figure 8.06b from the design manual and that discharge amount and pipe size is not on the chart because it is so small.
The calcs have been revised to use the smallest pipe on the chart and the plans show an apron larger than required by the calcs.
2.c.i. See attached calcs showing min. apron width of 10.5' and revised plan sheet showing 10.5' rather than 10.0'
2.d.i See attached calcs showing a min. length of 9'.
2.d.ii See attached calcs and plan showing min. width of 10.5'. Due to minimal discharge, this is also off the chart. Min. size has been used.
3.a The plans have been revised to 36". The calculations are correct. The 0.66% is the MINIMUM slope required. We show a slope of 1.1% in the plans.
3.b. The capacity calcs are used to determine the MINIMUM slope required to pass the runoff through the pipe. The on-site pipes meet the minimum.
The 0.69% slope is rounded to the 0.7% minimum slope and the 8% is greater than the minumum slope required.
3.c. All permanenet swales are called for to be stabilized with sod. NAG S150 is called for to be used on 2:1 slopes. This is more than required by the
calculations and this information is shown in the call-outs pointing to the swales in the erosion control plans.
4.a The main pool surface area and volume has been sized using The SA/DA method. Calculations showing storage and area beneath the normal
surface, and average depth calculations are included. The wet pond contours were revised to reflect the calculations and the supplement revised.
The landscaping required on the vegetative shelf has been revised to reflect the number of plants needed for the shelf.
4.b Calculations showing the forebay volume have been enclosed and the supplement sheet updated to reflect the calculations.
5.a Cover sheet of supplement has been updated to show the 30' vegetated setback.
5.bi The supplement was updated to show the 3/4" orifice.
5.b.ii The depth of the forebay at entrance and exit has been revised to match the plans
5.b.iii. The turf has been listed in the supplement
6. The maintenance easement has been adjusted to include the rip rap outlet apron.
Please let me know if you have any questions or need any additional information.
Jarrod E. Hilliard, PE, CFM
Hilliard Engineering, PLLC