HomeMy WebLinkAbout[External] Re Request for Additional Information, Mirror Lake Sediment Removal, Macon County (DWR #20230930)1
Winston, Joey
From:John Bryant <john@riversandinc.com>
Sent:Wednesday, September 20, 2023 12:25 PM
To:Winston, Joey
Cc:Healy, Shannon CIV USARMY CESAW (USA); Leslie, Andrea J
Subject:[External] Re: Request for Additional Information, Mirror Lake Sediment Removal, Macon County
(DWR #20230930)
Attachments:image001.png; Mirror Lake Map.jpg; Label.jpeg; FLOPAM C 12267_US_EN_SDS.pdf
CAUTION: External email. Do not click links or open attachments unless verified. Report suspicious emails with the Report Message
button located on your Outlook menu bar on the Home tab.
Joey,
1) Please see the attached map. The area outlined in white is the same as previously submitted and is the initial area to
be dredged. With additional funding, dredging may extend into open water areas of the lake but not those areas for
example as outlined in green or the fringe wetlands we discussed in the cove to NW of the bridge. The area in red is to
be dredged and is approximately 560 square feet (approximately 0.01 acres).
2) We have the capability to dredge with many methods, but believe this process removes the sediment (which is a
detriment to the lake and creating eutrophic conditions) with the least impact possible. The process involves the dredge
collecting (really vacuuming) the sediment from the bottom of the lake and pumping it via pipeline to the dewatering
area. The slurry averages about 10% solids and 90% water. Mechanical separation techniques works on a certain
percentage of the particle sizes (not the smallest particles at the rate the dredge operates normally) and it does not
require flocculant/coagulants (i.e. polymers) to separate the sediment from the water. The sediment dewatering bag
works best with a polymer injected prior to the slurry entering the bag. The actual holes in the bag (even though they
look solid) are larger than many of the particle sizes. The bag works by creating a thin layer of sediment on the inside of
the fabric to filter the remaining sediment and allow water to pass through. Without the use of polymer, the particles
don't settle fast enough and may not settle at all which either allows for the particles to pass through the fabric or
remain in the bag with the water and the dredging process cannot continue once the bag reaches its capacity (as
designated by the height). So using polymers allows the bag to act as both the sediment basin and the filter in a manner
that can both separate the sediment from the slurry quickly and effectively including small particles that are joined by
the polymer to make a larger floc particle and settle out. The result is clear effluent from the bag to return to the
lake. The turbidity curtain can retain any small percentage of particles that escape during the first "sealing" of the bag
(when you are pumping a small amount of sediment to create the filtering layer inside the bag) at the point of entry for
the return water in the lake. The area within the turbidity curtain can be re‐dredged at the end of the project if any
sediment accumulates. However, this is often less than an amount that can be measured to change any bottom
contours in that small area in our experience. The solution of the polymer (emulsion) is injected between the dredge
and sediment bag to allow for adequate mixing within the pipeline. It is either pre‐mixed to a solution of 0.5 to 1% or is
combined within the flow of the pipeline to achieve this solution based on the slurry GPM (which averages 1,000‐1,500
GPM from the dredge but has 3,000 GPM capability). The dredge contains production meters that the operator relays
back to the operator for the polymer injection and dewatering station. The dosage is set based on the sediment type
and production of the dredge. It can be adjusted by the operator based on this information and samples taken at a
sample port before it enters the bag, and samples from the return water. The sediment bag actually helps to create
enough retention for the average production and dosage to correlate and eliminate the small changes based on the
dredge operator (working around obstacles, re‐positioning, etc.). Our typical dosage ranges between 1 and 8 lbs/ton
(max), but averages at 3 (this will be based on both laboratory analysis and an on‐site field testing as necessary). The
dosage changes with the production. This is based on the type of sediment (within the lake there is high sand content to
high silt/organic content in different areas). I have attached the SDS for cationic polymer intended for use on this
2
project. I have reviewed the list of approved flocculants and almost all of these are sourced from the same supplier that
we use with different brand names. I think the majority of these are used more for the application of a BMP for
preventing soil erosion. However, they effectively work the same way by attaching to the soil particle. Our method
injects it into the slurry so that the polymer contacts sediment within the system and remains within it. No direct
treatment of the lake water is done with this project. The dosage protocol and adjustments gives us the ability to
capture the sediment effectively without overdosing (which also creates unwanted excessive production cost). We have
experience in similar lakes/ponds/streams with excellent results and positive impacts for many projects. Attached is the
requested data related to the product.
Can you give me an update of the timeline for a response?
Thanks,
John Bryant
VP of Business Development
(706)348-7327
www.riversandinc.com
To help protect your priv acy, Microsoft Office prevented automatic download of this picture from the Internet.
On Mon, Aug 28, 2023 at 11:08 AM Winston, Joey <joey.winston@deq.nc.gov> wrote:
Mr. Bryant,
On June 30, 2023, the Division of Water Resources (Division) received your application requesting a 401 Water Quality
Certification from the Division for the subject project. The Division has determined that your application is incomplete
and cannot be processed. The application is on‐hold until all of the following information is received:
1. A site visit on August 8, 2023, showed wetlands present within the proposed dredge area. Please include a map
showing the location of wetlands, the extent of the proposed dredge area, and a measurement of the area of
wetlands that will be converted to open waters. Discussions during the site visit indicated that only wetlands
within the lake will be dredged and that fringe wetlands will remain to provide shoreline stability. [15A NCAC
02H .0502(a)(4); 15A NCAC 02H .0502(a)(9); 15A NCAC 02H .0506(b)(1)]
2. The PCN indicates that a polymer injection system may be used in addition to other dewatering techniques to
prevent turbidity and sedimentation within the receiving waters. Because of the potential for adverse effects to
aquatic life, the Division has strict requirements for the use of flocculants. Please address the items below
regarding the use of flocculants. [15A NCAC 02H .0502(a)(4); 15A NCAC 02H .0506(b)(2)]
a. Flocculants cannot be approved unless water quality standards cannot be met after all appropriate
physical Best Management Practices (BMPs) have been implemented at the site. Please describe why
the proposed sediment dewatering bag, mechanical dewatering device, and turbidity curtains will not
be adequate. Please include in the discussion why the project design cannot be modified or relocated
to include only physical BMPs.
3
b. Please include a plan describing which flocculants will be used and how they will be applied. Please
include any steps taken to ensure that safe concentrations are not exceeded.
c. A sediment basin or similar structure is required between the application point of flocculants and
surface waters. Additionally, flocculants cannot be applied directly to surface waters. Please indicate in
the plan where flocculants will be applied and any BMPs located relative to this point.
d. Any proposed flocculants will need to be reviewed by the Division Aquatic Toxicity Branch to determine
the product’s safe application rate. Attached is a list of approved flocculants previously reviewed by the
Division. If your product is not listed, please submit the product’s label, application instructions, and
Material Safety Data Sheet for evaluation. Also attached is some general information on requesting
confidential treatment of trade secret information to be exempt from public record disclosure
requirements. From experience, confidential treatment can make it difficult to approve a flocculant for
use.
Pursuant to Title 15A NCAC 02H .0502(c), the applicant shall furnish all of the above requested information for the
proper consideration of the application. Please provide your response by September 29, 2023. If all of the requested
information is not received, the Division will be unable to approve the application and it will be denied as incomplete.
The denial of this project will necessitate reapplication to the Division for approval, including a complete application
package and appropriate fee.
Please let me know if you have any questions.
Regards,
Joey
Joey Winston
Environmental Specialist II, Division of Water Resources
North Carolina Department of Environmental Quality
Office: (828) 296‐4685 | Cell: (828) 785‐9171
NEW: joey.winston@deq.nc.gov
DEQ is updating its email addresses to @deq.nc.gov in phases from May 1st to June 9th.
Employee email addresses may look different, but email performance will not be impacted.
Email correspondence to and from this address may be subject to the North Carolina Public Records Law and may be disclosed to third parties by an authorized
state official.