SW5190201_2019-06-19 Response to 1st NCDELR Stormwater Review_6/20/2019

DEVELOPMENT -ENU NEE N NGfl O NC.
Pro f e s s i o n a l E n g i n e e r i n g C o n s u/ t o n t s
June 19, 2019
Corey Anen - Raleigh Office
Division of Energy, Mineral and Land Resources (DEMLR)
512 North Salisbury Street
Raleigh , NC 27699
RE: Cambridge Southeast Estates — SW5190201
Response to 1s` Plan Review
Mr. Anen,
We offer the following responses to your plan review comments dated May 14, 2019.
1. In Section 10 of the application, the proposed impervious area in the two table don't match. The first
table states the proposed impervious area is 71,560 sf and the second states that it is 76,830
(excluding existing). If the actual impervious surface is 76,830 sf, the total BUA will be over 7% and
will trigger local peak flow requirements according to the stormwater narrative.
RESPONSE: Section 10 of the application has been revised. The second table indicates the same
amount of proposed impervious area as indicated in the first table. The proposed BUA is less than
7%. The proposed BUA for the Cambridge Southeast Estates property is 71,560 SF.
2. The narrative states that no local peak flow requirements apply. State regulations do not require
mitigation of peak flows and the low density regulations promote diffuse flow and vegetated
conveyances. Therefore, the dry ponds are not necessary, unless the actual proposed BUA exceeds
7% as result of the previous comment.
RESPONSE: The narrative has been revised to indicate that the proposed BUA for the Cambridge
Southeast Estates property and the Country Living Estates property are both less than 7%. The
stormwater dry ponds from the previous plan have been removed.
3. If the dry ponds are to remain on the plan, the maintenance agreement must be signed and
notarized.
RESPONSE: The stormwater dry ponds have been removed from the plan, therefore the maintenance
agreement is not required.
4. Please complete all applicable sections of the low density supplement and provide calculations for
the swale showing that they will not erode during the 10-year storm.
RESPONSE: See enclosed low density supplement form as requested.
5. Please provide calculations for any outlet showing that the rip rap apron is designed to prevent
erosion during the 10-year storm.
RESPONSE: See enclosed calculations for each rip rap outlet as requested.
6. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other documents.
PDFs must be uploaded using the form at:
https://edocs.deg.nc.gov/Forms/SW Project Submittal
RESPONSE: The revised plans and documents will be provided as requested.
Let us know if you have any questions.
Sincerely,
Tom Harrell
Development Engineering, Inc.
244 W, Millbrook Rood, Roleigh, NC 27609 Phone: [phone]
P. 0. Box 17705, Ro/eigh, NC 27619 FAX [phone]