SW3180304_Ltr Sand Filter Response_20180523

SHABELDEEN ENGINEERING, PA
3145 TATE BLVD ● BOX A ● HICKORY, NC ● 28602 PHONE: [phone]
CIVIL/WATER/SEWER/ENVIRONMENTAL FAX [phone]
CONSTRUCTION ADMINISTRATION [e-mail]

Ltr Sand Filter Response

May 23, 2018
Mr. Cory Anen, PE
NC Dept. of Environmental Quality
DEMLR Stormwater Program
512 N. Salisbury St.
1612 Mail Service Center
Raleigh, NC 27699-1612

SUBJECT: Kontane Warehouse Additions – Request for Additional Information
Stormwater Permit No. SW3180304
Sand Filter System
Mr. Anen:
On behalf of May Rivers Properties, LLC (Owner), Shabeldeen Engineering, PA (SE) is submitting two (2)
hardcopies of the revised plan sheets and one (1) copy of calculations for the referenced project information.
It should be noted that the stormwater control measure (SCM) has been changed from a Wet Pond to a Sand
Filter, therefore some of the comments are no longer valid.
1. The scale block on Sheet C2 is not to scale. Is the scale on the design plans 1”=40’?
Response: The scale block on Sheet C2 has been corrected. The scale is 1” = 40’.

2. The contour lines for the sediment chamber overlap each other.
Response: The contour lines for the sediment chamber have been corrected.

3. A new operation and maintenance plan and agreement is required for the sand filter.
Response: Attached is the operation and maintenance plan and agreement for the sand filter.

4. Please complete and submit a Supplement EZ form for the sand filter.
Response: Attached is a copy of the Supplement EZ form for the sand filter.

5. Sand Filter MDC 1 requires that all open bottom sand filters require two feet of separation
between the lowest point of the sand filter and the seasonal high water table. The submitted
geotechnical report does not include any tests in the location of the SCM or specify the
elevations that the tests took place or the elevations at which the borings were terminated.
Response: No borings were performed within the sand filter area; however, based on the
geotechnical report, we believe seasonal high water table is greater than 2 ft. below the
proposed sand filter.
Mr. Cory Anen, PE Page 2 of 2
Kontane Warehouse Additions – Response to Comments 5/23/2018

Ltr Sand Filter Response

Three (3) borings B-1, B-2, and B-3 were performed at the north end of the proposed building,
approximately 110 feet south of the sand filter system. Based on the existing survey the ground
elevations of these borings are 914, 896, 897, respectively. The borings were 20 ft., 20 ft, and
24 ft. deep. As stated in the geotechnical report:

“Water Levels: Groundwater level measurements were attempted in the borings at the completion of
drilling operations and again in the deeper borings before leaving the site. Groundwater was not
encountered in any of the boreholes at the termination of drilling. Groundwater was measured at depth of
31 feet and 23.3 feet in Borings B-4 and B-10, respectively, after a waiting period of one day.”

6. Does grate S-20 include a diversion structure to allow runoff to flow into the sand filter or
does it entirely bypass the SCM? If it bypasses the SCM it appears that a significant amount of
new BUA will not be treated.
Response: Flows through structure S-20 entirely bypass the SCM. The system has been
designed to route runoff from the existing parking lot to the SCM. Structures S-41 through S-
44 were intended to collect roof drainage from the existing building. To prevent parking lot
runoff from bypassing the SCM, drop inlet structures S-41 through S-44 have been eliminated .
The roof drains will be manifolded and piped directly into structure S-20.

7. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other
documents. Pdfs must be uploaded using the form at:
https://edocs.deq.nc.gov/Forms/SW_Project_Submittal
Response: The files have been uploaded as requested.
I appreciate your assistance on this project. If you have any questions, please do not hesitate to contact me.

Sincerely,

Dan Shabeldeen, P.E.