20131070 Ver 1_More Info Letter_20140731

North Carolina Department of Environment and Natural Resources
Pat McCrory
Governor
July 31, 2014
CERTIFIED MAIL
Mr. Angelo Accettum, Manager
Elk Creek Development Company of Banner Elk, LLC
PO Box 725
Banner Elk, NC 28604
Subject: Elk Creek at Banner Elk Project — Request for Additional Information
Response Deadline: 60 calendar days of receipt of this letter
Dear Mr. Accetturo:
John E. Skvarla, III
Secretary
DWR # 13 -1070
Avery County
7012 1010 0002 1967 8852
The Division of Water Resources staff has been working to complete the review of the stormwater management
plan for the Elk Creek project at Banner Elk. Unfortunately, the review was delayed for several months as the
project was put on hold for a Notice of Violation at the site and we are now trying to facilitate the process to
meet your needs. However, the design and engineering information received thus far has not been sufficient to
enable us to perform a final review. We believe that most of the difficult design work has been done but some
of the information is either not in a format that we can effectively review or it is not provided with the
submitted plans. Accordingly, we are placing the review of the project on hold until all of the following issues
are addressed and all of the requested information is received.
1. One of the most difficult issues slowing our review has been trying to interpret the plan drawings.
Several of the sheets are extremely crowded and therein, difficult to evaluate. Some contain essential
text and numbers that are printed over other information which makes reviewing and understanding the
plans difficult. Please review the drawings that we received on 6/30/14 and revise them such that all
text and numbers can be readily seen. Some of the other difficulties in reviewing the drawings are:
a. There is very limited legend information or identification of symbols in most of the drawings.
b. Combining erosion control and drainage on one drawing (sheet 4 or 9) unnecessarily complicates
the critical drainage plan analysis. At this point, we do not need to see the erosion and sediment
plan material.
c. All drawings should be reviewed to determine what elements do not contribute to the
understanding of the stormwater plan and those elements removed.
Water Quality Regional Operations— Asheville Regional Chloe
2090 U.S. Highway 70, Swannanoa, Nonh Carolina 28778
Phone: [phone] FAX: [phone]
Internet htlp:llpomemcdenrogIvn vq
An Equal Opportunity I Affirmative Action Employer

Mc Aug [. Ac turn
DWR 913 -1070
July 31, 2014
2. The most significant issue in reviewing the plans is the lack of clarity on the flow and destination of the
stormwater runoff. Our staff disagrees with you engineer's assertion that the existing drawings provide
adequate information to enable a determination of drainage areas and stormwater volumes. From the
available information, we cannot determine what area of the total site is to be treated by the wet
detention pond. Your plans or engineering calculations and explanations should address the following
issues:
a. Will any of the stormwater from the upstream 7.1 acre single family area be treated in the basin?
From the contour lines, it appears that some flow will enter the basin from this or other offsite
areas. However, the 132,717 sf impervious area total presented in the drawings and the
Supplement for the multifamily areas seems to be all that will be treated. The stormwater
application form indicates 0 sf of offsite drainage area entering the site. Is this correct?
b. The Wet Detention Supplement sheet shows a total drainage area of 327,757 sf but page 1 of 9 of
the latest set of drawings shows a total project area of 479,159 sf. The Supplement shows
40.49% impervious and the drawing on page 1 of 9 shows 27.7 %. Since several calculations use
the total site impervious percentage, this figure must be accurate. Because of these and other
inconsistencies, our review cannot proceed without revised drawings and supporting
calculations. Please review you documents to assure consistency of the numbers.
c. The "Site plan Drainage Calculation Check" on page 5 of 9 shows the peak flow calculations for
a 7.54 acre site. Page 1 of 9 shows the multifamily area as having 11.0 acres. Why was the peak
flow calculation only done for a portion of the site? Is this because some of the site is not
draining to the stormwater treatment device? Although there may be an explanation, the
information provided is unclear. We did not receive any additional documentation other than the
plan sheets and the PCN. Some written explanation is needed. Also, you are to demonstrate
how the runoff coefficient and intensity numbers were derived in calculating the "Historic Peak
Discharge."
Similar to the issues cited in #2 above, the drawings submitted do not enable our staff reviewers to
verify how much flow goes to each stormwater inlet and to the wet pond. This deficiency has been
discussed with the project engineer and stated in our 6/12/14 note to John Vilas. However, we have not
received any additional or revised information that enables us to review the stormwater flow aspects of
the plan. Please provide a full -sized plan sheet(s) showing the entire site with all drainage areas, all
impervious areas (with calculations), and all topography around the site perimeter along with areas
contributing to flows entering the site. All stormwater drainage system devices, including every inlet,
outlet and conveyance should also be shown.
4. There appears to be a ditch or open channel (with a wetland symbol ?) that drains the southern part of the
site yet the contour lines do not accurately reflect the presence of the channel. The plan should provide
calculations for the open channel "ditch" indicating volumes and velocities with recommendations for
any liners, matting and etc. to minimize erosion on the site. This information is also needed for the
northern channel.
S. Based on the various plans received, the design engineer has chosen to provide design elements that are
different from those specified in the Division of Water Resources' rules and design Manual. The
Stormwater Best Management Practices Manual provides designs which have been approved in advance
and, if followed, will expedite our review. There are also many "supplemental forms" linked on our web
site that provide further guidance and specifics to assist the design professional in meeting the State's
requirements. For design elements different than those in the Manual, you are required to demonstrate

Mr. Angelo Accenuro
DWR #13 -1070
July 31, 2014
their effectiveness through calculations and other documentation to show that they provide "equal or
better treatment "
6. The "Required Item Checklist" found via the supplement forms link shows the type of submittals that
are needed for a wet detention pond BMP. http: / /portat.ncdenr.org /web /lr/bmn- manual See the Wet
Detention link under the `BMP Supplement Forms" and see the five attachments for a copy of the
"Required Item Checklist." The most significant deficiency is the information listed as #5 "A table of
elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay, to
verify volume provided." We could not find any stage- storage information. Also, your plan must show
how pond surface area and average depth were determined. See Chapters 3 and 10 of the Stormwater
BMP Manual for examples.
7. The requirement that the discharge from the wet detention basin flow over a vegetated filter strip has
been discussed with the engineer. This must be included in the final drawings and engineering
calculations provided showing that there will be non - erosive flow through the 30' filter stip. The
engineer's statement that because existing development has not caused erosion, no erosion should be
expected must be supported with calculations documenting that position. It appears that some type of
energy dissipating and flow spreading devices are needed.
8. Page 5 of 9 of the most recent drawings that we received (6/30/14) contains significant changes to the
wet detention pond design from the previous drawing we had received (From J. Vilas 2/10/14). The
staff communications with the engineer did not indicate that the forebay design was to be modified.
Both submittals of the "Sediment Basin Plan" are shown as being sealed by the engineer on the same
date (02/06/14). Please clarify that the wet pond design of the 02 -06 -14 drawing that was received on
6/30/14 is the intended design. That version of the "Sediment Basin Plan" drawing is at a 1 " =30' scale
while the previous one was at a 1 " =20' scale. The littoral shelf is 6' wide and flat as compared to the
earlier drawing which included a 10' sloped littoral shelf consistent with the BMP Manual's
specifications. The differences in the drawings were noted to the engineer on 6/27/14 and we were
surprised that the revised submittal did not address the date issue and the desired changes. The later
(black and white) version contains an unusual forebay discharge design which seems to include contour
lines that cross over each other. Is the stormwater detention capacity of the second design the same as
the first? Also, because the newer design of the forebay is different from that in the BMP Manual, please
explain how this design will provide "equal or better" treatment than that specified in the Manual.
Please note that the area and "Q" flow information is also illegible due to double print.
9. The line indicating the Section A -A of drawing 5 or 9 is in the wrong location.
10. The Stormwater BMP Manual, the Supplement Sheet and EMC Wile 2H. 1008 require that the BMP
should be located in a recorded drainage easement with a recorded access easement to a public ROW.
The Supplement Sheet asked about this and your submittal recorded a "No." The need for an easement
was mentioned in an earlier note to your engineer but we have received no correspondence addressing
the issue.
11. The "Water Quality Notes and Calculations" on page 5 of 9 of the latest version (received 6/30/14)
needs to be reviewed as there appear to be labelling mistakes. The drawing still refers to a "filter area"
which was noted to the engineer earlier. The "V= ".....132,717.17 is not a volume but actually the
square feet of impervious area and the "Volume provided in the filter area is 11,059.76 CF" is not the
volume provided in the wet pond (or not in the "filter area") but the calculated volume necessary to treat
the l" storm. Similarly, 42 is not "The storage volume of the proposed pond" but is the "Total

Mr. Augelo Accettum
DW 413 -1070
July 31, 2014
Page 4 of 5
Required Storage ". As has been mentioned, 41 indicates that there is a "volume of discharge from the
parking area." Is the volume of discharge only from the "parking area" or is that statement in error?
12. We strongly suggest that the detention pond riser structure be reconsidered and revised to be consistent
with Section 10.3.9 of the Stormwater BMP Manual. We believe that the recommended design will
provide for simpler maintenance and reduce the potential for obstruction compared to your proposed
perforated riser design. Our manual requires that floatation calculations be provided. Also, please note
that on the riser portion of the "Water Quality Notes and Calculations" section of drawing 5 of 9, it
appears that the area of .0417 is stated in cubic feet not square feet.
13. The "Site plan Drainage Calculation Check" on page 5 of 9 refers to the "Total Drainage Area" of
327,756.69 sf or 7.54 acres. The "SITE DATA" on page lof 9 of the latest version (received 6/30/14)
indicates that there are 132,727 sf of total impervious and 346,432 sf of "Open Space" for a total of
479,159 sf Please explain the inconsistency in these values.
14. On the Erosion Control and Drainage Plan the statement regarding the retaining wall "design is to be
determined during construction" is of concern. At a minimum, we need to know the specific elevations
of the wall and the adjacent impervious areas in order to determine the fate of the stormwater runoff in
that area..
15. As mentioned in an earlier note, the pond must be designed to prevent short- circuiting. The location of
the outlet is close to one of the southern -most forebay and is likely to result in short- circuiting. Please
reconfigure the pond or add a berm or baffle to increase the flow path for the storrwater that passes
through this forebay.
16. Please revise and resubmit the Wet Detention Pond Supplement Form. Any indications of deficiencies
must be addressed.
17. We are concerned over the stormwater runoff expected from the single family dwelling portion of the
property. We are seeking to determine if there was an approved stormwater plan for these lots? Was the
existing stormwater pond a part of that plan? We are looking into this and any information you can
provide will help expedite our review.
18. Due to the confusion with several plan changes, please submit all components that you wish us to
consider in one complete package.
Please understand that this does not represent our final review of the stormwater plan submittal. There
are significant areas where the absence of information or confusion regarding information submitted
does not enable the technical review that is necessary. We recommend that your engineer review
Chapter 10 of the Stormwater BMP Manual and related supplement fors and guidance provided on the
Department's web site at: http: / /portal.nedenr.orgYweb /]r /bmp- manual to assure that the next submittal
will comply with those specifications. Any deficiencies will result in future requests for additional
information which will delay the approval of the stormwater plan.
It is requested that all information discussed above be received in writing within 60 calendar days of receipt of
this letter. If the information is not provided, the Division will be unable to approve the application and it will
be returned. The return of this project will necessitate reapplication to the Division for approval, including a
complete application package and the appropriate fee. Please send the requested information to the 401 and
Buffer Permitting Unit, 1617 Mail Service Center, Raleigh, NC 27699 -1617 and one copy to the Asheville
Regional Office.

Mr. Angelo Ac tturo
DWR #13 -1070
July 31, 2014
Pup 5 of 5
Thank you for your attention to this matter. If you have any questions, please contact either Mr. Boyd DeV ane
at 919 - 807 -6373 for stormwater related questions or Mr. Tim Fox at 828 - 296 -4664 for any other 401 related
questions.
Sincerely,
G. Landon Davidson, P.G., Regional Supervisor
Water Quality Regional Operations
Asheville Regional Office
cc: Tasha Alexander - USACE Asheville Regulatory Field Office —email copy
David Ramsey, PE —email copy
John Vilas — McGill Associates, P.A. - email copy
Cheryl Buchanan — Town of Banner Elk — email copy
DWR ARO 401 files
DWR 401 & Buffer Permitting Unit — file copy
G:\WR\WQ\Avery\40ls\Non-D0T\Elk Creek ® Banner Elk\ ADDINF0. 401EIkCreek@BannerElld- 31- 14.doc