HomeMy WebLinkAboutSW3221005_Response To Comments_20230216"0
Dewberry
February 7, 2023
Mr. Jim Farkas
State Stormwater Engineer
DEMLR Post -Construction Stormwater Program
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
Re: Request for Additional Information
Stormwater Permit No. SW3221005
Boulder Run — Cabarrus County
Dear Mr. Farkas,
The above referenced application has been revised per your comments dated January 11, 2023.
1. The plan has been adjusted to remove all proposed pipe networks except for those required to
convey stormwater runoff across roadways or future driveways.
2. All level-spreader/filter-strips (LS/FS) have been removed from the plan.
a. All LS/FS have been removed from the plan.
b. All submission items have been revised to remove the references to the LS/FS.
3. On -site surface waters and their associated vegetated setbacks have been added to the plan.
Surface water area has been excluded from the project area and project density calculation in the
updated Application and Supplement-EZ Form included with this submission.
4. Scales shown on the specified sheets have been corrected as requested.
5. Roadways proposed with this plan are designed using NCDOT typical sections which include
roadside ditches with slopes steeper than 3:1. All ditches/vegetated conveyances outside of the
roadway are designed using side slopes less than (shallower than) or equal to 3:1. Engineering
calculations for all ditches are provided in the Stormwater Report included with this submission.
6. A drainage area map has been added to the plan showing drainage areas and runoff coefficient
values for all drainage areas to storm inlets and vegetated conveyances. An assumed time of
concentration of 5 minutes was used for all drainage areas. Pipe and ditch computations are
included in the Stormwater Report.
7. The Stormwater Report includes all ditch computations. North American Green ditch lining
computations are included for all ditch sections that are close to or above the maximum non -
erosive velocities, as shown in Part C-11 of the Manual.
8. A table listing the per lot BUA allocation has been appended to the Deed Restriction document
and has been included with this submission.
9. The Application has been corrected as stated below:
a. Section IV, 6-8 has been corrected to remove surface water area from the total project
area calculation.
b. Section IV, 10 table has been corrected to only have 1 column due to the removal of all
LS/FS. This table and the Supplement-EZ form have been updated to match each other.
10. The Supplement-EZ Form has been corrected as stated below:
a. Cover -Page:
i. Line 2 and Line 4 have been corrected to consider on -site surface water area.
Pagel of 2
Boulder Run — DEMLR Application
Stormwater Permit No. SW3221005
February 7, 2023
ii. Line 9 has been corrected and surface waters and vegetated setbacks are now
shown on the plan.
b. Drainage Areas Page:
i. The entire site column has been corrected to include the entire project area.
ii. No SCMs are proposed, therefore a single low -density drainage area is provided
that is identical to the entire site column.
c. Low -Density Page:
i. Line 4 has been updated to show the different ditch side slopes proposed in this
plan.
ii. Line 5 has been updated and ditch lining computations are provided in the
Stormwater Report.
iii. Line 14 has been answered.
iv. The swale table has been completed for all ditches proposed in the plan set (see
drainage area map for ditch callouts)
d. LSIFS Page:
i. All LSIFS have been removed therefore this section has been removed from the
form.
Any questions or comments pertaining to the responses shown above, please reach out to me at any time. I
can be reached at 704.631.5206 or blafranchia.Dewberry.com.
Thank you,
G..
Brian LaFranchi, P.E.
Senior Project Manager
Dewberry® Page 2 of 2