HomeMy WebLinkAbout20010550 Ver 1_NCDOT Division request to delete stormwater device constructed on NC 98 Bypass (R-2809B) in Wake Forest_20170814Carpenter,Kristi
From: Murray, Christopher A
Sent: Thursday, August 10, 2017 9:52 AM
To: Ridings, Rob
Cc: Wheeler, Millard S; Hancock, Richard W
Subject: NCDOT Division request to delete stormwater device constructed on
NC 98 Bypass (R-2809B) in Wake Forest
Attachments: 981 crossing proposed design with labeled information.pdf; OM
Agreement 981 Crossing Wake Forest (003).pdf; 14-107-SWM-
REPORT-2017-06-Ol.pdf
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NCDOT Division 5 has been approached by a developer concerning disposal of NCDOT
right-of-way located at the northeast intersection of NC 98 Bypass (Dr. Calvin Jones
Highway) and Retail Drive in Wake Forest. Note that this portion of the NC 98 Bypass
was constructed around 2005-20007. A review of the roadway construction plan sheets
and permit drawings reveals the following information concerning this general area:
-Stormwater runoff from a portion of Retail Drive is picked up by two 15 inch corrugated
metal pipes.
-These two pipes discharge the runoff into to two special lateral v ditches that are
located within NCDOT right-of-way. These lateral v ditches are classified as grass swales
that are perpetually maintained by the NCDOT.
-Runoff from the grass swales is then conveyed by a 24 inch corrugated metal pipe
(located under Retail Drive) into a pre-formed scour hole that is perpetually maintained
by the NCDOT. This pre-formed scour hole is located within 30 feet of a NCDOT stream
mitigation site.
See the following:
R-2809B aerial photo depicting existing features
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R-28096 plan sheets 4 and 14
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A review of the riparian buffer permit drawings 4 and 15 indicate that the that the
special lateral v ditches are considered grass swales.
See the following:
R-2809B buffer permit drawing 4 of 20 at Retail Drive
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As noted above, the special lateral v ditches classified as grass swales are located within
the area of NCDOT right-of-way. A private engineering firm working for the real estate
advisor has developed a final site plan for an adjacent parcel that would require the
abandonment of NCDOT right-of-way that contains the special lateral v ditches/grass
swales. The plan would eliminate the special lateral v ditches/grass swales by conveying
4
stormwater runoff from the NCDOT-maintained roadway and private development
footprint into a combination sand filter/detention chamber. This device was chosen due
to several factors, including Town of Wake Forest's stormwater management
ordinance. The system is designed to manage the 10-yr, 24-hr storm Peak Runoff Flow
to pre-developed levels and actually shows decreases in the 2, 5, 10, 25 and 100 year
event. The designers do not anticipate runoff from the combination sand
filter/detention chamber to be a burden to the stream mitigation site and pre-formed
scour hole on the other side of Retail Drive than what would exist today using the
special lateral v ditches/existing grass swales. Note that NCDOT Hydraulics Unit has
reviewed the stormwater calculations and findin�s and a�rees with the assessments
made by the private en�ineerin� firm.
See a screen shot of the proposed design with labeled information (NOTE THAT THIS IS
ALSO PRESENTED IN THE FIRST ATTACHMENT TO THIS EMAIL):
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This issue was discussed with you on December 2 or 3, 2015. At that time, you had
indicated that the Department must provide the following information to your agency
tor review deletion of the lateral v ditches/grass swales (my responses are in RED):
-Request for this revision must come under NCDOT letterhead from the Division.
The Department formally requests your approval to delete the special lateral v
ditches/grass swales at this location and replacement with a combination sand
filter/detention chamber. The design captures and treats stormwater from the NCDOT
6
ROW to Town of Wake Forest Standards which is a Phase II Stormwater Community by
NCDEQ.
-Approved letter from the Town of Wake Forest approving the site design/stormwater
plan.
The Town of Wake Forest has approved the design/stormwater plan. See the attached
Stormwater Facility/BMP Operation and Maintenance Agreement (June 30, 2017).
-Information on who will provide permanent maintenance of the combination sand
filter/detention chamber .
The Stormwater Facility/BMP Operation and Maintenance Agreement (June 30, 2017)
indicates that MREA Wake Forest, LLC has agreed to operate and maintain the system to
provide storage and/or stormwater runoff as part of development of the
property. They (or subsequent owners) are required to permanently maintain the
system.
Verification that the combination sand filter/detention chamber is sized and designed
appropriately to handle both the private development at the site and also to take on the
runoff from Retail Drive.
The system is designed to capture runoff from the NCDOT roadway and the private
development. The system manages the 10-yr, 24-hr storm Peak Runoff Flow to pre-
developed levels and actually shows decreases in the 2, 5, 10, 25 and 100 year
event. See the attached Stormwater Management Calculations (June 1, 2017). Note
that NCDOT Hydraulics Unit has reviewed the stormwater calculations and findin�s and
a�rees with the assessments made by the private en�ineerin� firm.
Verification that the runoff will not result in destabilization of the pre-formed scour hole
on the other side of Retail Drive.
The designers do not anticipate runoff from the combination sand filter/detention
chamber to be a burden to the stream mitigation site and pre-formed scour hole on the
other side of Retail Drive than what would exist today using the special lateral v
ditches/existing grass swales. The designed system shows decreases in the 2, 5, 10, 25
and 100 year event. See the attached Stormwater Mana�ement Calculations (June 1,
2017 . Note that NCDOT Hvdraulics Unit has reviewed the stormwater calculations
and findings and agrees with the assessments made bv the private engineerin� firm.
I have discussed the project with the Wake County District Engineer and there are no
records of additional development in the foreseeable future at the tract and in this
specific area of the intersection.
Please review this information and advise if you need further clarification.
Thanks,
Chris Murray
Christopher A. Murray, PWS
Division Environmental Supervisor
Division 5
(919) 220-4633 office
cmurravC�ncdot.gov
NCDOT-Division 5
2612 N. Duke Street
Courier: 17-27-03
Durham, NC 27704
Email correspondence to and from this sender is subject to the N.C. Public Records Law and may be disclosed to third
parties.
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