WQ0037781_Narrative_20240805 (2)

CSD
ENGINEERING
Sewer Permit Modification Narrative
August 2024
PERMIT NUMBERS: WQ0029938, WQ0037781 & WQ0037696
PERMIT NAME: The Preserve at Tidewater
DESCRIPTION OF PROPOSED MODIFICATIONS:
The purpose of these modifications is to permit the final 18 lots to be added to the overall development. In the process
of compiling and completing the necessary documents several items came to light that we wish to address with these
permit modifications. Those items are:
1- The pump station permit has not been updated with the two low-pressure sewer (LPSS) permits as new
sections have been added to the development.
2- The flow allocation was duplicated in two permits.
3- There is a new flow reduction for this service area.
The sewer permitting for this project is complex in that it involves three permits: a private LPSS permit held by the
developer (WQ0029938) that covers the grinder stations on the lots, a public LPSS permit formerly in the name of
PLURIS but now held by ONWASA (WQ0037781) for the low-pressure sewer collection system, and another public sewer
permit formerly in the name of PLURIS but now held by ONWASA (WQ0037696) for the duplex pump station and high-
pressure force main. With the recently proposed addition of eighteen (18) lots to the development, it will be necessary
to modify all three sewer permits associated with the project. While preparing for these modifications we discovered
two notable items; 1- the pump station permit was not modified along with the other two LPSS permits as new sections
were constructed, and 2- that the flow for the subdivision has somehow ended up allocated in both public permits. We
are requesting that NCDEQ remove the flow allocation from the public pump station permit and have all flow associated
with the development allocated on the public LPSS collection system permit. Based on our experience in working with
NCDEQ on other pump station projects, we feel that the flow should be placed on the collection system rather than the
pump station which allows for future flow to be directed to the pump station.
Therefore, the modification to the pump station permit (WQ0037696) will be not only to update the flow from the final
18 lots being added, but also several prior sections. To further complicate matters, the previous permits all used a flow
reduction of 80 GPD/bedroom. We were informed by PLURIS (before they were absorbed by ONWASA) that a flow
reduction to 65 GPD/bedroom had been granted for this service area. We are providing updated pump station
calculations that use this GPD value to demonstrate that the pump station can handle the required flow for the full
build -out of the subdivision at 349 lots. The 76,800 GPD in the current permit(s) was based on 320 lots, each with 3-
bedroom homes at 80 GPD. While PLURIS was still in existence, they informed us that, based on the CO's, many of the
homes were actually 4 and 5-bedrooms. As you will see from the revised calculations, we have adjusted the flow for the
existing 278 lots to reflect this based on information provided to us by PLURIS. We also have calculated the remaining
3805 Cherry Avenue - Wilmington, NC 28403 - 910 7914441- www.csd-engineering.com — License # C-2710 I CSD
ENGINEERING

Sewer Permit Modification Narrative — The Preserve at Tidewater 12
71 lots as all 5-bedroom homes. This brings us to the current final lot count of 349. This also means that the 76,800
GPD value is no longer valid in any way since it was based on a different flow reduction value.
The modification to the private grinder station permit (WQ0029938) will simply be to update the total number of
simplex grinder pump stations to 350. This value is based on the 349 lots plus one (1) for the amenity center.
The modification to the public collection system permit (WQ0037781) will be to add the new flow for the 18 additional
lots, as well as applying the 65 GPD flow reduction to all previously permitted lots. While the ASEA application and USE
only list the new additional flow of 5,850 GPD, we are providing the below table to describe how the updated numbers
should be reflected in the modified permit.
*Here is a breakdown of the proposed flow allocations for permit WQ0037781:
Existing 278 lots (mix of 3, 4 & 5-BR, 1140 bedrooms total @ 65 GPD) = 74,100 GPD
**Recent/Pending 71 lots (all 5-BR, 355 bedrooms total @ 65 GPD) = 23,075 GPD
Amenity Building (1 building @ 1,000 GPD) = 1,000 GPD
Future {50 bedrooms @ 65 GPD) = 3,250 GPD
Total Flow Tributary to Pump Station = 101,425 GPD
* Please see the enclosed Pump Station and Force Main calculations for reference.
** These 71 lots include the final 18 lots being added at this time.
We do not anticipate any more lots being added to this development, so these numbers should be valid for the final,
built -out condition of the Preserve at Tidewater
3805 Cherry Avenue - Wilmington, NC 28403 - 910 7914441- www.csd-engineering.com — License # C-2710 D