SW1240604_Response To Comments_20241024

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CDesiivil
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Concepts,PA
October 24, 2024
Brianna Holland
Stormwater Engineer
DEMLR Post-Construction Stormwater Program
North Carolina Department of Environmental Quality
Address
City, State Zip
Re: Workforce Outdoor Training Site
NCDEQ Project No.: SW 1240604
CDC Project No.: 22414
Dear Ms. Holland,
On behalf of the Haywood Community College TRS, we are pleased to submit the requested
additional information for your review and approval. The comments identified in the letter from
your office dated September 24, 2024 and the associated responses (in blue) are listed below.
General
1. As designed, the proposed project will not meet all of the requirements for a high-density
project upon completion: 15A NCAC 02H .1003(3)(a)—The proposed SCM design does not
meet Runoff Treatment. In order for a project to meet Runoff Treatment, the net increase in
BUA must be captured and treated in one or more primary SCMs. Currently, there is BUA
associated with this project that is not directed to a primary SCM.
Please confirm the existing BUA. "Existing BUA"refers to BUA that was located within the
project area prior to the rules going into effect in this area(July 1, 2007), not just what
happens to be currently located within the project area. The northern driveway appears to be
dirt(which would not meet the definition of BUA) and added after 2007 according to
historical aerial photographs. Verify which BUA meets the definition of existing, and then
revise the package as needed.
The sand filter is now designed to treat 2.84 acres of BUA, which is 100% of the final built
upon area for this site. While 4,308 sf of impervious surface associated with the driveway
Mailing Address: P.O.Box 5432,Asheville,NC 28813
168 Patton Avenue,Asheville,NC 28801 52 Walnut Street—Suite 9,Waynesville,NC 28786
Phone [phone] Fax [phone] Phone: [phone] Fax: [phone]

will bypass the sand filter, this area is smaller than the 5,243 sf of BUA that existed circa
2006, thus treating the net increase in BUA and satisfying this requirement. Aerial imagery
with delineated BUA c. 2006 is provided in"Appendix B" of the hydrology report, while
areas for BUA have been provided in the "Impervious Calculations" section of the report.
Delineated drainage areas can be found in the "SCM Drainage Area Map" section of the
hydrology report.
Sand Filter MDC
2. SAND FILTER MDC 1 a:
The minimum separation between the lowest point of the sand filter system and the SHWT shall
be two feet for open-bottom designs.
15A NCAC 02H .1002 (45) "Seasonal High Water Table" or"SHWT" means the highest level of
the saturated zone in the soil during a year with normal rainfall. SHWT may be determined in the
field through identification of redoximorphic features in the soil profile, monitoring of the water
table elevation, or modeling of predicted groundwater elevations. The provided geotechnical
report does not appear to identify the SHWT.
Additional field work was performed by a soil scientist, Wilcox &Mabe, identifying the
seasonally high water table. A copy of this report is included with the resubmittal.
Additionally, the seasonal high water table information has been amended on C942.
3. SAND FILTER MDC 9. CLEAN-OUT PIPES.
At least one clean-out pipe shall be provided at the low point of each underdrain line. Clean
out pipes shall be capped.
Please show the cleanout pipe on the low point of the underdrain in the plan view of the
detail sheet, and specify that the cleanout pipe must be capped.
The cleanout pipe has been indicated on detail sheet C942. Callout specifies that cleanout
pipe is to be capped.
Application
4. The sum of the impervious areas listed in Section IV.10 of the application do not match the
total impervious area listed. Please confirm the final site layout and associated impervious
areas is presented consistently throughout the application documents. 15A NCAC
02.1042(2)(a)(iv), .1003, and 1050(1).
This issue has been corrected.
Supplement-EZ Form
Cover Page:
Mailing Address: P.O.Box 5432,Asheville,NC 28813
168 Patton Avenue,Asheville,NC 28801 52 Walnut Street—Suite 9,Waynesville,NC 28786
Phone [phone] Fax [phone] Phone: [phone] Fax: [phone]

5. Line 7-8—Per 15A NCAC 02H .1017(10), the vegetated setback width from surface waters
is 30 ft. Please revise.
This value has been adjusted accordingly.
Sand Filter Page:
6. Line 12—The drainage easement must comply with General MDC 9.
Acknowledged. The easements have been drawn to comply with General MDC 9 as if this is
a privately owned property, however as this is publicly owned land the easements are not
actually required.
7. Line 27—The physical depth of the sediment chamber is the depth from the lowest bypass
invert(Line 35) to the excavated bottom of the sediment chamber(Line 25).
This value has been adjusted.
8. Line 28—The ponding depth of the sediment chamber is the depth from the lowest bypass
invert to the top of the permanent pool in the sediment chamber(or to the excavated bottom
of the sediment chamber if there is no permanent pool in the sediment chamber). For sand
filters without a permanent pool, this value is the same as Line 27.
This value has been adjusted.
9. Line 33 —The physical depth of the sand chamber is the depth from the lowest bypass invert
(Line 35)to the lowest excavated point of the sand chamber(below the underdrains).
This value has been adjusted.
Line 34—The ponding depth of the sand chamber is the depth from the lowest bypass invert
(Line 35)to the top of the sand layer(Line 31).
This value has been adjusted.
Calculations
10. The "Discrete"NRCS Curve Number Method used in the calculations is incorrect since it
utilizes a composite curve number for the drainage area to the SCM. The "discrete"part of
the Discrete NRCS Curve Number Method means that the runoff volume is calculated for the
impervious portion of the drainage area and for the pervious portion of the drainage area and
then added together to get the total runoff volume from the drainage area. Please revise the
package as necessary to account for the change in minimum required treatment volume.
The calculations have been revised and are now using the simple method rather than the
discrete method.
Plans
Mailing Address: P.O.Box 5432,Asheville,NC 28813
168 Patton Avenue,Asheville,NC 28801 52 Walnut Street—Suite 9,Waynesville,NC 28786
Phone [phone] Fax [phone] Phone: [phone] Fax: [phone]

11. 15A NCAC 02H.1042(2)(g)(ii): Please provide dimensioned project boundary with bearings
and distances. The extent is not clearly delineated and may result in additional surface water
being considered part of the project area.
A signed and sealed survey has been included in the drawing set.
12. 15A NCAC 02H .1042 (2)(h): Ensure all elevations are labeled on the SCM details so that
the calculations can be confirmed. For example, per the calculations, the bottom of the
sediment chamber is 2,624.25' and should be labeled on the plans.
All elevations have been added to the section view of the SCM detail. Please see sheet C942.
O&M Agreement
13. Please ensure an electronic copy of the signed&notarized O&M Agreement is provided per
15A NCAC 02H .1042(2)(j) and per Sections V &VI, 3 of the Application.
Acknowledged. We have included the signed and notarized O&M Agreement with this
submittal.
If you should have any questions or comments regarding this submittal,please do not hesitate to
contact our office.
Sincerely,
0/0r
D. Harry Luzius, Jr. P. .
Civil Design Concepts, P.A.
[e-mail]
Mailing Address: P.O.Box 5432,Asheville,NC 28813
168 Patton Avenue,Asheville,NC 28801 52 Walnut Street—Suite 9,Waynesville,NC 28786
Phone [phone] Fax [phone] Phone: [phone] Fax: [phone]