20180847 Ver 1 _Request for Additional Info _20180725

Moore, Andrew W
From: Moore, Andrew W
Sent: Tuesday, July 24, 2018 4:20 PM
To: 'Alea Tuttle'
Cc: '[e-mail]'; Leslie, Andrea J
Subject: Request for Additional Information, White Oak Phase 5, Henderson County (DWR
Project #20180847)
Alea,
On June 18, 2018, the Division of Water Resources (Division) received your application dated June 8, 2018, requesting a
401 Water Quality Certification from the Division for the subject project. The Division has determined that your
application is incomplete and cannot be processed. The application is on hold until the following items are addressed:
Please demonstrate that alternative lot layouts and configurations have been evaluated in an effort to avoid
stream and wetland impacts and that the project purpose cannot be practically accomplished using an
alternative lot layout or configuration. [15A NCAC 02H .0506(f) and (g)]
2. Please provide building envelopes for all lots with wetlands and streams on the site plans to demonstrate these
lots are buildable without additional jurisdictional impacts. [15A NCAC 02H .0502(g)]
3. In order to comply with the stormwater conditions of the General Certification, the project is required to
provide either:
a. A completed Stormwater Management Plan, or
b. The following items to document that the project will not cause degradation of downstream surface waters:
A discussion on how the project will not cause degradation of downstream surface waters when
considering the volume and velocity of the increased flows and the current size/condition of the
receiving stream. It appears the site is currently open space including a wooded buffer around the
streams and wetlands. The proposed percent impervious will increase from 0% to 28%. The site
drains to the southwest corner of the property. The calculated flow rate used for the pre -
development velocity calculation is 115 cfs, while the flow rate used to calculate the post -
development velocity is only 68.6 cfs. It is unclear how the post -development flow rate would be
lower than the pre -development flow rate. Please provide revised post -development calculations
that take into account the entire drainage area for the receiving stream and the resulting cumulative
discharge rate.
Delineation of each drainage area and accompanying calculations to show that flows from every
discharge point will be non-erosive to both the land surface and the receiving surface water during
the peak flow from the 10 -year storm event. Please also show that the cumulative flows to the
receiving stream in the southwest corner of the property will be non-erosive. You may refer to the
guidelines from DEMLR - Sedimentation and Erosion Control to determine an appropriate non-
erosive velocity. The permissible velocities for erosion protection are under Appendix 8.05 (i.e.
Chapter 8).
III. Calculations to demonstrate that for any discharge points proposed to increase flow rate and
volume, the structural stability of the receiving surface water will not be compromised. Please note
that there will be a monitoring requirement to demonstrate that the project will not cause
degradation of the receiving stream. Monitoring will not be required if the project follows an
approved Stormwater Management Plan.

IV. Designed drawings (both aerial and profile views showing the actual designed dimensions) and
calculations of any proposed diffuse flow or detention systems and any vegetated conveyances (if
provided). [15A NCAC 02H .0506(b)(3)]
4. The storm pipe cross section detail appears to depict a rip rap pad at the stormwater pipe outlet. Is a rip rap pad
proposed at the stormwater pipe outlet? If so, will the rip rap pad be placed within the stream channel, and if
so, are those impacts included as part of the 149.5 feet of proposed stream impacts? [15A NCAC 02H .0502(a)]
Will additional stream or wetland impacts be required to connect each proposed residence to the sewer line?
[15A NCAC 02H .0502(a)]
6. Please provide a sequence of construction for the proposed wetland impact W1 that details how the proposed
0.09 acres of wetland will be filled without causing a violation of wetland standards in the remaining portion of
the wetland, including any un -permitted fill, or a violation of any stream standards. Please include details
regarding sediment and erosion control measures and construction access. [15A NCAC 02B .0211, 0231 and 15A
NCAC 02H .0502(c)]
Pursuant to Title 15A NCAC 02H .0502(c), the applicant shall furnish all of the above requested information for the
proper consideration of the application. If all of the requested information is not received within 30 days, the Division
will be unable to approve the application and it will be returned.
Feel free to contact me if you have any questions or would like to discuss further.
Andrew W. Moore, P.G.
Environmental Specialist — Asheville Regional Office
Water Quality Regional Operations Section
NCDEQ — Division of Water Resources
828 296 4684 office
email: [e-mail]
2090 U.S. Hwy. 70
Swannanoa, N.C. 28778
Email correspondence to and from this address is subject to the
North Carolina Public Records Law and may be disclosed to third parties.