NCS000405_30_2016-12-20 Gibsonville Self-Storage Response to Comments_20211119

Stoltzfus Engineering, Inc.
MEMORANDUM
Date: 12/20/2016
To: Josh Johnson, P.E. and Troy King, P.E.
Town of Gibsonville
Re: Response to comments, 10 Federal Storage - Gibsonville
We have reviewed the plan comments and offer the attached revised plans for review and approval.
The comments listed below offer further clarification or explanation to the revised plans.
Construction Plan Review Comments
1. Is water and sewer required for the building? No domestic water service is currently shown on plan,
only irrigation. No sewer service is currently shown on plan.
No domestic water or sanitary sewer service are required for the self -storage buildings per North
Carolina Building Code.
2. Chart on Page C2 shows Pipe-5 as 18", detail on C3 shows (2)12" pipes. Please verify which is correct.
Detail C3 was correct. However, we have revised the Sand Filter design to address additional comments,
which changes our storm sewer design.
3. Please provide documentation of Seasonal High Water Table (SHWT) to verify sufficient separation is
provided from bottom of sand filter.
Based on boring reports from ECS dated May 2nd, 2016, the water table ranges from 6' to 24' below
existing ground. Based on this range, the Sand Filter does not appear to be within 2' of the SHWT but we
have asked ECS to conduct a SHWT test and we will forward the results upon completion.
4. Show 20' wide access easement through the site from Huffine Street to (and including) the sand filter.
BMP Access and Maintenance Easement has been shown.
5. Revise the elevations shown on the Emergency Spillway Detail (Sheet C3).
Emergency Spillway detail has been revised and updated based on Sand Filter design changes.
6. Please clarify where the woven filter fabric begins/ends on C3.
Woven fabric has been more clearly defined and labeled in the Sand Filtration System Detail on Sheet
C3.
747 Park Lawn Court ♦ Kernersville, NC 27284 ♦ [phone]

7. It appears that an average head of 1.5ft is being used in the calculations. Based on the elevation of
the emergency spillway (494) and of the top of the sand chamber (492) that the average head should
only be 1. Please clarify.
Sand Filter design has been revised to account for V of average head.
8. According to page 11-10 of the BMP manual, Step 3 — It appears the combined 1,250 sf of surface area
is not sufficient to contain the adjusted water quality volume, based on the previous comment.
Surface Area has been increased to provide enough surface area to contain the adjusted water quality
volume.
9. Please show washed #57 stone on the surface of the sand filter to avoid sand blowing or washing
away.
#57 washed stone has been shown in the plan view and in the Sand Filtration System detail on Sheet C3.
10. Justify how you obtained a pumping rate of 58 GPM to the sand filter.
Pumping rate has been revised per the new Sand Filter Design. The pumping rate is now 15 GPM based
on the Q outflow of the Sand Filter of 0.033cfs.
11. How are you ensuring that you are capturing the entire first 1" of runoff? It appears if you were to
have rainfall in excess of 0.15 in/hr, portions of the first flush could bypass.
We have revised the Sand Filter system to route all water to the Sand Filter in order to capture the
entire 1" of runoff to prevent any by-pass.
12. Are you proposing a single pump system or a duplex pump system?
Single Pump System
13. If you are proposing a single pump system, how is the first flush being treated if the pump fails?
The first flush is now being treated since it is routed to the Sand Filter prior to being pumped or by-
passed. In case of pump failure or malfunction on the single pump, we have provided an overflow outlet
from STMH-1. This overflow outlet will drain based head pressure if water was to build up in the
manhole. This overflow pipe invert is below the Sand Filter weir elevation to ensure water does not
back-up above the top of the Sand Filter system.
14. What type of retaining wall is being proposed? If segmental block, verify that tie -backs would not be
impacted by storm drainage installation or maintenance.
Segmental block retaining wall has been proposed. We have attached email correspondence from ECS,
who will be conducting the retaining wall design, stating there are no issues with the proposed storm
sewer location.
747 Park Lawn Court ♦ Kernersville, NC 27284 ♦ [phone]

15. Confirm the inverts on the existing 36" CMP crossing the railroad. The invert information on the
plans appear to indicate that runoff in conveyed to the north, while GIS topo information appears to
indicate that drainage is conveyed to the south.
The inverts had been relayed incorrectly and therefore shown incorrectly on the plans. Invert elevations
of the existing 36" CMP crossing have been revised and show proper drainage from the site.
747 Park Lawn Court ♦ Kernersville, NC 27284 ♦ [phone]

From:
SGeiaer
To:
Aden Stoltzfus; Clifton Minsley
Cc:
JCallaham; Josh Robbins
Subject:
RE: Gibsonville Retaining Walls & Update
Date:
Thursday, December 1, 2016 8:43:55 AM
Attachments: image001.pn
Aden
The 18" RCP can be dealt with as drawn using special details and backfill requirements. No issues
with where you show it. They will have to install the RCP and drop structures concurrent with the
wall construction to avoid damage to one or the other.
Thanks
STEPHEN J. GEIGER, P.E.
Chief Engineer / Senior Vice President
ECS Carolinas, LLP - Special Projects Group, 4328 Wade Hampton Blvd. Suite E, Taylors, SC 29687
D: 864-987-1813 C: 864-325-2190 F: 864-271-0265 www.ecslimited.com
Confidential/proprietary message/attachments. Delete message/attachments if not intended recipient.
From: Aden Stoltzfus [mailto:[e-mail]]
Sent: Wednesday, November 30, 2016 6:15 PM
To: Clifton Minsley
Cc: SGeiger; JCallaham; Josh Robbins
Subject: RE: Gibsonville Retaining Walls & Update
Steve,
Please see attached for the proposed retaining wall on the Gibsonville site. Please check to ensure
you can live the with the storm sewer separation from the proposed retaining wall. We cannot shift
the wall further away from the storm due to the railroad right of way. Call with any questions.
Thanks,
Aden R. Stoltzfus, PE
oil
Stoltzfus Engineering, Inc.
Civil Engineering Consultants
747 Park Lawn Ct.
Kernersville, NC 27284
Office: [phone]
Cell [phone]
aden @seien ineeringcorn