20131070 Ver 2_More Info Received_20150713

DavidFRamsey,PE - PSM
R &S Engineering and Construction Corporation
434 Skinner Boulevard 61 The Glens Boulevard
Dunedin, F134698 Banner Elk, NC 28604
webpage: www.ramseveniiineerinti.com
727 409 -4639 e-mail davidf.ramsevna,verizon.net 828 963 -5875
Professional Engineer Ohio - Florida -N Carolina -S Carolina- Georgia- Louisiana - Mississippi
Professional Surveyor Ohio - Florida -N Carolina
General Contractor Class A Florida CGC 010310 North Carolina 44555
Please reply to North Carolina Address
June 10, 2015
Ms. Karen Higgins
401 and Buffer Permitting Unit
1617 Mail Service Center
Raleigh, NC 27699 -1617
RE: Elk Creek of Banner Elk
DWR# 12 -1070
Dear Ms. Higgins:
Enclosed herewith you will find the additional information as requested in an email to Angelo Accetturo dated
May 19, 2015. regarding the aforementioned project and application. Following you will find the response to
your request in the order as presented in your letter with my response in Bold.
The size of the wet detention pond orifice was not calculated according to our Manual as we specified
and a considerably over -sized orifice was specified. Your plan indicated that a 4" orifice would drain
the pond over a 48 hour period. That is not correct. Our quick calculation showed that a 4" orifice
would drain the pond in approximately 8 hours. Some of the reasons for the error were that the .0085
SF orifice calculated by your engineer converts to approximately 1.25" diameter orifice, not 4 inches as
was stated. Although 1.25" diameter seems to be a reasonably close to our estimated number, had we
not caught the error, the stormwater would have never been treated during the life of the project. This is
of concern. Furthermore, being one of the most critical calculations relative to the stormwater treatment
device, we would have expected it to be checked before submittal. As we said in our December 30,
2014 letter, please have your engineer refer to Section 3.5.2 "Orifice Equation" in calculating the
estimated drawdown time. In that letter, we specified that the H value should be divided by three to
get an accurate assessment of the average head. His drawing needs correction to show the "driving
head" at 2' not 3' and the average head less than that. His "Calculations" on Sheet 9 of 9 show an
incorrect "Orifice Equation" formula. His "Average Head" formula shows a division by 2 although he
did not use an average head but rather the maximum "driving head" in his actual calculation.
The size of the orifice is 1.5" as shown on the Sheet 8 and 9. The barrel is 4" and the orifice is
1.5" and will provide the draw down over a three day period.
2. We were surprised that the specific requests in our July 31, 2014 letter, December 30, 2014 letter and
at our February 3, 2015 meeting regarding the "Water Quality Notes and Calculations" (sheet 9 of 9)
have not been addressed. Again, these are:
a. There is no "filter area" in this plan.
The reference to a filter area is no longer on the plans.

Page 2:Elk Creek/June 12, 2015
b. The unidentified number (147,580) after the "V" is not the volume. It is the area in SF.
The number 147,580 is not involved in this permit application. The correct number is 134,950.90 SF
which is the square footage of the Impervious Area. The V =A *1" is volume and the results of that is
11,245.91 CF. Section 15A NCAC 02.11.1017 (B) indicates 1" of runoff over the impervious area. That
calculation is shown on the spreadsheet attachment in the drawing on Sheet 9. The area of the impervious
is 134,950 square feet which is shown on the drawings for each breakdown of the drainage areas and also
shown on the application. The equation in the manual for the volume of runoff to be treated does not
agree with the NCAC referenced code. The equation in the manual for the volume of runoff to be treated
is 341.05 cubic feet greater, however the volume provided by the pond is 16,806 cubic feet.
c. The "volume provided for retention pond is 12,298.33 CF" is an incorrect statement. The
supplement Sheet indicates that the "Volume, temporary pool" is 16,806 CF. The 12,298.33 CF
number is probably the required treatment volume.
The volume required for treatment is 12,298.33 CF but the volume provided is 16,806 cubic feet.
Language on the spreadsheet has been modified. See Sheet 9.
3. Although there were some changes made to figures on the "Supporting Calculations" sheet, it still
contains inaccuracies and is still presented in a manner that makes its review difficult. This issue was
discussed at our February meeting but was not addressed. Some of the issues on this page that were
discussed but not modified are:
a. Under "Peak Flow Calculations ", there is still the "DA -1 ..... 11 developed area" statement.
What does that statement reference?
The total project area is 11 acres but only 8.0 acres drain into the retention area. The project is in a
mountainous area and 3 acres of the property drains into a drainage stream that will not be affected by
the development. The 3 acre area that drains into the drainage stream is not included in the calculations
for the area that drains into the retention basin.
b. Also under "Peak Flow ", there is a reference to the "A" being 8.5 acres. We noted that the
previous submittal's 11 acre reference was changed in this submittal to the 8.5 acre number.
However, the calculations below that indicate an 8.0 acre drainage area. Since other
calculations in the submittal were based on 8.0 acres draining to the pond, we assume that
these other numbers were an oversight in the engineers review. Although the inconsistencies
in the project's drainage area may seem minor, it has been such a significant area of our concern
in our correspondence and discussions that we expected this to be correct in this final
submittal.
The "Peak Flow" is A being 8.0 acres. As stated previous the 11 acres is the project area but only 8.0
acres drain into the retention area and only 3.098 acres of the project is impervious.
c. We mentioned in our February meeting that the "Pollutant Removal Calcs: Bioretention" is an
inaccurate heading and should be changed. This was not done.
The words have been removed.

Page 3:Elk Creek/June 12, 2015
d. As was in the previous submittal, the misalignment of almost every column with the column
headings makes reviewing the calculations difficult. Please correct.
The Quality Notes and Calculations is preformed on a spreadsheet and inserted into the drawing.
The calculations and in the cells of the spreadsheet and the column appear to line up. The results is a
1.5 inch orifice to drain down over a three day period. The barrel is 4 inches with an orifice of 1.5
inches. The previous submitted shown the 4" barrel with an orifice in the bottom of the barrel but
the orifice was not label and the spread sheet calculation indicated a 4' barrel with a orifice but part
of the spreadsheet did not print and was on a block cell. That has been corrected.
Please review the enclosed and if you have any questions please do not hesitate to call or email.
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David F Ramsey, PE, PSM
General Contractor