WQ0042579_Staff Report_20210916

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State of North Carolina
Division of Water Resources
Water Quality Regional Operations Section
Environmental Staff Report
Quality
To: ❑ NPDES Unit ® Non -Discharge Unit Application No.: W00042579
Attn: Lauren Plummer Facility Name: Mulberry Branch WRF
From: Bryan Lievre
Wilmington Regional Office
Note: This form has been adapted from the non -discharge facili . staff report to document the review of both non -
discharge and NPDES permit applications and/or renewals. Please complete all sections as they are gpplicable.
I. GENERAL AND SITE VISIT INFORMATION
1. Was a site visit conducted? ® Yes or ❑ No
a. Date of site visit: 6/23/2021 (w/ 6/30/21 follow up)
b. Site visit conducted by: Bryan Lievre, Morella Sanchez -King & Tyler Benson (& Patrick Mitchell)
c. Inspection report attached? ® Yes or ❑ No
d. Person contacted: Tim Webb and their contact information: [phone] ext.
e. Driving directions: 349 Forest St Ext., Shallotte, NC 28470. From Wilmington: US Hwy 17S then right onto
Frontage Rd, right onto Forest St Ext NW and facility will be on left
2. Discharge Point(s): N/A
Latitude: Longitude:
Latitude: Longitude:
3. Receiving stream or affected surface waters: N/A — Mulberry Branch
Classification:
River Basin and Subbasin No. Lumber River Basin, Stream Index 15-25-2-7
Describe receiving stream features and pertinent downstream uses:
II. PROPOSED FACILITIES: NEW APPLICATIONS
1. Facility Classification: Grade II Biological (Please attach completed rating sheet to be attached to issued permit)
Proposed flow: 750,000 gallons per day
Current permitted flow: NA
2. Are the new treatment facilities adequate for the type of waste and disposal system? ® Yes or ❑ No
If no, explain:
3. Are site conditions (soils, depth to water table, etc) consistent with the submitted reports? ® Yes ❑ No ❑ N/A
If no, please explain:
4. Do the plans and site map represent the actual site (property lines, wells, etc.)? ® Yes ❑ No ❑ N/A
If no, please explain:
5. Is the proposed residuals management plan adequate? ® Yes ❑ No ❑ N/A
If no, please explain:
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6. Are the proposed application rates (e.g., hydraulic, nutrient) acceptable? ® Yes ❑ No ❑ N/A
If no, please explain:
7. Are there any setback conflicts for proposed treatment, storage and disposal sites? ❑ Yes or ® No
If yes, attach a map showing conflict areas.
8. Is the proposed or existing groundwater monitoring program adequate'? ® Yes ❑ No ❑ N/A
If no, explain and recommend any changes to the groundwater monitoring program:
9. For residuals, will seasonal or other restrictions be required'? ❑ Yes ® No ❑ N/A
If yes, attach list of sites with restrictions (Certification B)
Describe the residuals handling and utilization scheme:
10. Possible toxic impacts to surface waters: NA
11. Pretreatment Program (POTWs only):
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IV. REGIONAL OFFICE RECOMMENDATIONS
1. Do you foresee any problems with issuance/renewal of this permit? ® Yes or ❑ No
If yes, please explain: See below
2. List any items that you would like the NPDES Unit or Non -Discharge Unit Central Office to obtain through an
additional information request:
Item Reason
Please See Section V
3. List specific permit conditions recommended to be removed from the permit when issued:
Condition Reason
4. List specific special conditions or compliance schedules recommended to be included in the permit when issued:
Condition Reason
5. Recommendation: ® Hold, pending receipt and review of additional information by regional office
❑ Hold, pending review of draft permit by regional office
❑ Issue upon receipt of needed additional information
❑ Issue
❑ Deng-ggg,e5t,4te reasons: )
6. Signature of report preparer: �ti�
Signature of regional supervisor: 74249nBEo37443E...
Date: 9/16/2021
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V. ADDITIONAL REGIONAL STAFF REVIEW ITEMS
Staff from WiRO along with some assistance from Patrick Mitchell (WSRO) have performed a cursory review of the
approximately 2,205 pages within the permit modification application, dated 6/2/2021. In correspondence, dated
6/28/2021, a request was made to provide a more organized permit application and make the application specific to this
project, without information specific for the Shallotte WWTF Modification (Permit Application WQ0000798). As a
result of the request, the applicant submitted a revised permit modification application with approximately 2,333 pages,
dated 7/24/2021. Although a cursory review of the later permit application was also performed, the document was found
to still contain a substantial amount of information relevant to the proposed Shallotte WWTF application and an
inordinate amount of time was required to ascertain information relevant information regarding this project.
With the review provided, please see the comments below:
1. Plan Sheet G4 depicts two 16 inch influent lines without any depiction of these lines being reduced prior to the
influent flow meters. As illustrated in Plan Sheet M2, the line from US Hwy 17 will be reduced from 16 inches to
12 inches prior to the flow meter. In addition, Plan Sheets, C14, C16 and C26 indicate that the other influent line
will be 12 inches. Please revise Plant Sheet G4 to reflect the proper pipe sizes or explain.
2. A Combination Box is depicted within Plan Sheets G4 and G5, prior to the proposed Headworks. It is assumed
that this is the same structure that is labelled as the 6' x 6' Mixing Well in Plan Sheet M1 and the Mixing Box on
Plan Sheet M3. Section III. of the Design Calculations indicates that the Combination Box will be part of the
Headworks, but also indicates that "The Combination Box will be a circular concrete manhole like structure... ".
Please revise information submitted to utilize the same nomenclature and revise the Design Calculations or plans
to reflect the same structure or explain otherwise.
3. The revised application package dated July 24, 2021 included a Unit Process Summary provided within the
Executive Summary which indicates that Pump Station No. 1 will be equipped with one low flow capacity pump
capable of 300 gpm at 32.4 ft TDH and two pumps with a combined peak capacity of 1,650 gpm at 47.4 ft TDH.
However, Item V. e. of the application indicates that the pump station will be equipped with three pumps each
capable of 1,650 gpm at 47.4 ft TDH. The Engineering Calculations indicate that three of the same pumps will be
provided with variable frequency drives. However, the pump curve and the subsequent tabulated information
indicate that the combined flow of two pumps will be approximately 1,650 gpm. Please update Item V. e. to
document the required capacity of each pump or revise the calculation information to clearly reflect flow for each
pump.
4. The revised application package dated July 24, 2021 included a Unit Process Summary provided within the
Executive Summary which indicates that Pump Station No. 2 will be equipped with one low flow capacity pump
capable of 520 gpm at 42.6 ft TDH and two pumps with a combined peak capacity of 1,302 gpm at 82.2 ft TDH.
However, Item V. e. of the application indicates that the pump station will be equipped with three pumps each
capable of 1,302 gpm at 82.2 ft TDH. No information could be located in the Engineering Calculations to
simulate this pump station. Please update Item V. e. to document the required capacity of each pump and provide
calculations to illustrate the proper operation of this pump station.
5. The peak inflow to the system appears to be greater than the ability of Pump Station No. 2 operating by itself.
Please describe anticipated operations and explain how an overflow situation is anticipated to be prevented at the
Influent Pump Station. Note that some of these instructions may be recommended to be placed within the
specifications, if warranted.
6. It is believed that the total dynamic head listed for one of the pumps listed for PS No. 7 within Item V. e. of Form
HRIS 06-16 may be incorrect. Please check and revise or explain the listed TDH of 107 feet on the form.
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7. Please discuss the need and purpose(s) for the 12 inch bypasses around each of the influent flowmeters and
combination box.
8. Design Calculations must be signed and sealed by a North Carolina Licensed Professional Engineer. Please V
revise.
9. The Soils and Hydrogeologic Site Analysis at the Shallotte Site, prepared by Edwin Andrews and Associates,
Inc., dated January 2018 provided justification for the installation of the high -rate infiltration basins and
groundwater lowering system. The report indicated the recovery of an estimated 816,172 gallons per day from
the system surrounding Basins A and B and the recovery of 397,540 gpd from the system surrounding Basin C.
Information could not be located that discusses the chemistry of the water that will be discharged into the nearby
wetlands, or the potential impacts of the water chemistry on receiving water bodies. This proposal shall include
estimated effluent concentrations for parameters that describe the quality of the groundwater discharge water, and
provide a discussion of the effects of these parameters on receiving water bodies. The discussed parameters shall
include at a minimum:
a. Nutrients, including a discussion or model on how nutrients will affect downstream surface water
quality of Mulberry Branch;
b. Iron, which is common to shallow groundwater, which may cause an issue with iron bacteria blooms in
receiving waters;
c.
d. BO BOD; and,
e. Turbidity.
10. Please explain how the recovered groundwater will be disposed after draining to the two 30 feet long sections of
24-inch diameter, 16-gauge, corrugated metal pipe, as depi d within Plan Sheet D2.
In regards to a review of the hydrogeological information, Patrick Mitchell provided comments, as noted below.
Below are the items that I noted from review of the soils report and related portions of the Southport application package.
These items either require additional information be provided or the applicant's consultants need to clearly point out the
location of items in the application packages that they submitted. There are some similar issues with this application as to
the Shallotte application. It would probably be quicker for the applicant and for us if they would simply put the requested
information together and send it in, and not to resubmit a huge application with more info then we are requesting, IMO.
This project also created some confusion with the hydrogeologist & soil scientist providing information and data from
previous project site evaluation (some unrelated to this project) which made it difficult to determine if minimum
evaluation criteria specific to this proposed project is present. Again, I am not saying with 100% confidence that the info
is not present somewhere in the multiple reports, maps and data, just that I cannot find it or it is not clear, and in some
cases there are even some conflicting information that was provided between prior project reports.
A. I was unable to determine the following items related to the soils evaluation and hydraulic conductivity
measurements in the application package that was submitted:
o Was there a sufficient number of hydraulic conductivity measurements conducted for each soil series
mapped within the proposed infiltration basins? I realize they plan to remove restrictive horizons, but
there are contrasting soils present within the proposed areas which may have more restrictive layers
present. V
It is critical that the restrictive horizons be removed to ensure system to function properly. Request a
written response that clearlv tells us how manv measurements were taken for each soil series present and
a map that clearly shows us where all Ksat measurements were conducted within the proposed irrigation
area related to the soils mapped in this area. � V
Also, I recommend issuing the permit for construction only. A schedule should be included in the permit
requiring LSS certification be completed following construction to confirm proposed loading rates are
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still acceptable and that confining layers were removed. Particularly on the western half of proposed
Basin A and the northern midsection of Basin B. The operation permit should only be issued if/once the
post -construction evaluation and certifications are completed.
o Was a complete soil profile description provided for each hydraulic conductivity measurement point to a
sufficient depth below the measurement point? Request a complete soil profile description be provided f
each hydraulic conductivity measurement point.
o Were the hydraulic conductivity measurements run until they reached a steady state for each test
conducted within each restrictive horizon for each soil series? Request field measurements and a
summary of measurements for each soil series present in the proposed irrigation area.
B. Eviu,.,.._- - soles was described in the reports contained in the application package. The reports also suggest
that these "sink ho e s conduits to the Castle Hayne aquifer" as "a portion of the flow from the
proposed basins leads to towar s ne aquifer". Request explanation for how direct conduits will be
proposed basins.
C. Vegetative screens need to be maintained to help prevent dust from adjacent farming activities from potentially
clogging the infiltration basins. This may be an item the WiRO can follow up on during construction to ense
basins are protected.
Please request that this information either be provided or that the applicant provide a written response to each item and
clearly point us to this information in the existing application. If information is provided, please request that this specific
information be clearly provided without resubmitting the entire package. This information is required to determine if the
minimum required data and sufficient data has been provided in the application. Unfortunately, the Division's Soil
Scientist Evaluation Policy does not provide minimum expectations or guidance for high -rate infiltration basins, but it can
still be used as a guide for minimum expectations for soil borings and Ksat measurements.
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