WQ0004059_Correspondence_20230602

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Nathaniel Thornburg
North Carolina Department of Environmental Quality
Division of Water Resources
Water Quality Permitting Section
Non -Discharge Permitting Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
Via email: nathaniel.thornburgAdey.nc.gov
6/2/2023
Subject: Guidance on discharge to wetlands from high rate systems
Dear Nathaniel;
This letter requests your guidance on the permitting requirements for re -permitting the Sugarloaf High -
Rate System in Atlantic Beach NC. This system is currently permitted under Permit WQ0004059 for
100,000 gallons/day (gpd) with the treated effluent disposed of using two rotary distributors as shown on
the attached map. We are currently performing a preliminary analysis on behalf of a group considering
purchase of the subject system and associated property.
We have completed a detailed hydrogeologic investigation that built upon a similar assessment made by
Ed Andrews and Associates (EAA) in 2020. The site soils evaluation and a preliminary wetlands
assessment for the property have been completed by Soil and Environmental Consultants (S&EC)
Our hydrogeologic assessment has used a calibrated groundwater flow model to evaluate options for
disposing of both a minimum of 250,000 gpd and as much as 350,000 gpd. All the options were configured
to not require the use of any groundwater lowering drains because of the potential permitting and cost
considerations of getting a discharge location approved. The following three high rate options were
evaluated:
1) Retrofitting the plumbing and surface conditions of the existing two rotary distributors and
applying treated effluent to them;
2) Using the two existing distributors and adding an additional one between them and another next
to them (4 distributors); and
3) Constructing a high rate basin with a berm elevation of 15 ft, maximum water level of 13 feet and
a bottom elevation of 10 feet.
As you are aware the rotary distributors were approved as part of the original permit which was issued
before the non -discharge rule was updated to include setbacks from residences. We understand from you
that DEQ has previously considered rotary distributors as the same as spray systems which require a 400-
foot setback, which would now be required for option 1 or 2. If this is now a requirement then the site
could not be re -permitted for any additional capacity or condition because these setbacks cover essentially
all of the non -wetland areas of the property.
Eagle Resources, P.A.
215 West Moore Street Southport, NC 28461
919-345-1013 www.eagleresources.com

As we have discussed with you in emails and discussions with David Honeycutt of McGill Associates, it
is our collective professional opinion that rotary distributors are not equivalent to spray systems for the
following reasons:
• It is our understanding that the setbacks for spray systems to residences is primarily driven by the
concerns from exposure at the residences to airborne constituents contained in the sprayed water.
• Rotary distributors apply water by direct gravity discharge from the rotor arm which is suspended
less than two feet from the ground surface below it. This minimizes the opportunity for airborne
transport away from the footprint of the distributor.
Therefore, we request approval to use rotary distributors on the site and that the residential setbacks for
them to be set at 100 feet or the same as for drip or high rate basins.
Additionally, we need your concurrence on the impact of water from the rotors in either option 1 or 2,
Although setbacks are maintained, the modeling indicates that the application of the treated effluent will
cause water levels to rise within the wetland areas shown on the attached map and increase discharge to
the surface. I cannot find any such a prohibition in the non -discharge rule. The following table shows the
percentage of water that is so discharged to the wetlands as a function of the water applied to the two
existing distributors. The numbers are essentially the same for four distributors. All of the wetlands
shown on the attached map are isolated and therefore not connected to waters of the U.S.
Drip or Distributor on Existing 2 Rotors
Q
Steady-state Seepage to wetlands
total gpd
gpm
cfd ea
cfd
gpm
% of Q
100000
69
6684
0
0
0.00%
250000
174
16711
456
2.37
1.37%
300000
208
20053
2633
13.69
6.57%
350000
243
23396
6397
33.27
13.69%
Note that our analyses that produced the numbers in the above table were independent of how the water
was applied to the distributor areas (drip or rotor). Consequently, we need your assessment of this issue
independent of your input on drip vs spray as discussed above.
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We know that you are very busy and understaffed, but we would appreciate your input so that our client
can make the decision as to purchase the site and system and proceed with re -permitting it. We also can
provide you with the complete hydrogeologic study we have completed if that would help your decision
making, but I need to get permission from the client to do so.
Sincerely yours,
1---o401
Eric G. Lappala, P.E., P.H.
Attachments:
Site Maps for Discharge to 2 Existing Distributors of 250,000 and 350,000 gpd.
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EXPLANATION
— Steady State Watertable Q= 250,000 GPD
Areas with Surface Leakage
Section line for mounding charts
Potentially-lurisdictionalWetlands
Model Boundary
Property Line
,"PU
Figure 1. -- Modeled watertable elevation and areas of surface discharge from applying water to the two existing rotors at 250, 000 gpd.
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. •WICIOP�..1. r —;.
t^� EXPLANATION
— Steady State Watertable Q= 350,000 GPD
Areas with Surface Leakage
P otentia IIyJ u risd ictiona I W etlands
Model Boundary
Property Line
F Wes` i A f 1-apt=. 3
200 0 200 400 600ft
Figure 2. -- Modeled watertable elevation and areas of surface discharge from applying water to the two existing rotors at 350, 000 gpd.
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