20240035 Ver 1_Setzer Fish Hatchery Heavy Sediment Removal System Memo (06-16-2023)_20231221

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MEMORANDUM
TO: G. Landon Davidson, P.G, CPM — NCDEQ Regional Supervisor
FROM: Kyle Seaman, P.E. — Project Manager
DATE: June 16, 2023
i
RE: Proposed Setzer Fish Hatchery Heavy Sediment Removal System Sand
Disposal Alternatives
The Bobby N. Setzer (Setzer) Fish Hatchery is located in Pisgah National Forest about 12 miles
from Brevard and 37 miles from Asheville, North Carolina. Setzer is a cold -water rearing facility
which produces rainbow, brook and brown trout. The facility is supplied with water from the
Davidson River, and Grogan Creek.
The facility has several water supply issues that impact production. Sediment accumulation
following storm events is one of them. This naturally occurring material is mostly inorganic
sedimentary bed load from the influent streams that become suspended in the water column
during storm events. This sediment load, which is comprised mostly of sand and silt, passes into
the hatchery system since it is not removed by the coarse screens at the intake. As the flow
velocities decrease in the various rearing tanks in the hatchery this sand/silt settles out of
suspension and then must be manually removed by Hatchery staff to prevent flow restrictions
and or stoppages. The potential for loss of flow, even for a short period of time, can cause
massive fish loss and requires several hours of hatchery staff time to correct.
The proposed Setzer Improvements project intends to remove this sand/silt well before it enters
the hatchery process. This will help prevent the sand/silt from causing flow stoppages and will
also prevent it from settling in the rearing units where it has the potential to mix with uneaten
fish food and fish waste. As seen in the attached drawings, a vortex separation system which
uses centrifugal force to separate the sand/slit from suspension in the water will be utilized for
this purpose and will be located adjacent to the two intakes. It is assumed that a majority of the
material that will be removed by the proposed system will be sand as silt is much finer and is
carried through the system to be discharged back to the river through the facilities outfall without
settling out of suspension. Once captured the sand is fluidized using the clean water at the
discharge and pumped out of the unit utilizing a submersible wastewater pump capable of
pumping sand and solids.
There are several alternatives for dealing with this sand once pumped out of the unit. Land
application, hauling the material off -site for disposal or return the sand and river/creek water
back to the bodies of water they came from.
As seen in the attached drawing a majority of the site is used for the hatchery process. In the
portions of the site not used for the hatchery process a large amount of the area is in 100-year
floodplain and trout buffer which would not be suitable for loose fill material. Additionally,
stabilizing the loose material to prevent erosion and potential release to surface waters would
create an ongoing maintenance issue.

G. Landon Davidson
June 16, 2023
Page 2 of 2
These restrictions severely limit the areas for land application, especially in the volumes
anticipated. Accordingly, land application is deemed unfeasible due to site limitations.
Hauling material off -site would require further dewatering to make this alternative feasible. This
would increase the capital cost of the project marginally but more significantly would increase
O&M costs for Setzer due to hauling and proper disposal fees. Due to the increased O&M costs
this alternative was deemed unfeasible.
The pumping of naturally occurring sand back to the bodies of water they came from is a
common practice at Water Treatment Plants as a way to deal with sand and silt that
accumulates at their screened raw water intakes. The site has enough space for these
technologies to be located near the intakes. The O&M and capital costs are the least of the
three alternatives evaluated. Further by returning the sand and silt back to the river prior to the
rearing tanks, the impact of the hatchery process on the natural sediment transport of the
Davidson River and Grogan Creek is minimized while also removing the potential of introducing
accumulated solids produced by the facility to the surface waters. For these reasons returning
the sand and silt removed by the vortex separation system was deemed the most feasible
alternative for this project.
MCGILL ASSOCIATES 55 BROAD STREET, ASHEVILLE, NC 28801 / 828.252.0575 / MCGILLASSOCIATES.COM

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