NC0078131_Inspection_20180705

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.: NC0078131
Attn: Brianna Young,Compliance and Expedited Permitting Unit Facility name: Brown Blvd.WTP
From: Scott Vinson
Washington Regional Office
Note: This form has been adapted from the non-discharge facility staff report to document the review of both non-
discharge and NPDES permit applications and/or renewals. Please complete all sections as they are applicable.
RECEIVED/DENR/DWR
I. GENERAL AND SITE VISIT INFORMATION
1. Was a site visit conducted? ® Yes or❑No JUL 1 6 2018
a. Date of site visit: 7/5/2018 Water Resources
Permitting Section
b. Site visit conducted by: Scott Vinson
c. Inspection report attached? ® Yes or❑No
d. Person contacted: David Hemenway and their contact information: [phone] ext.
e. Driving directions: Located on Brown Blvd. at the intersection with Webb Blvd., Havelock,NC.
2. Discharge Point(s):
Latitude: 34.8599 Longitude: -76.8936
3. Receiving stream or affected surface waters: UT to Shop Branch prior to Hancock Creek
Classification: SC; Sw,NSW Index No.: 27-115-3
River Basin and Subbasin No.: Neuse River Basin&03-04-10
Describe receiving stream features and pertinent downstream uses: The WTP discharges to the roadside
ditch that runs south the length of Brown Blvd. before emptying into the receiving stream which is a fresh
water canal system (UT to Shop Branch) that runs about 2 miles from the discharge point before entering
Shop Branch. Shop Branch is a tidal salt water and protected for secondary recreation such as fishing.
boating, and other activities involving minimal skin contact; fish and noncommercial shellfish
consumption; aquatic life propagation and survival; and wildlife. These are Nutrient Sensitive Waters
which need additional nutrient management due to being subject to excessive growth of microscopic or
macroscopic vegetation.
II. PROPOSED FACILITIES: NEW APPLICATIONS - n/a
III.EXISTING FACILITIES: MODIFICATION AND RENEWAL APPLICATIONS
1. Are there appropriately certified Operators in Charge(ORCs)for the facility? ® Yes ❑No ❑N/A
ORC: David Hemenway Certificate#: PC-1, 28581 Backup ORC: Jacquelyn Acha Certificate#:PC-1, 1001046
2. Are the design, maintenance and operation of the treatment facilities adequate for the type of waste and disposal
system? ® Yes or❑ No
If no, please explain:
FORM: WQROSSR 04-14 Page 1 of 4

Description of existing facilities: The WTP's backwash discharge enters a new 450,000 gallon settling basin with
coned bottom and rotating scrapper arm prior to be pumped to the secondary 63,000 gallon settling/polishing
basin with floating decanter prior to being discharged. Dechlor tablets are no longer used. The sodium sulfite
tablets have been replaced with liquid Captor as the new dechlorination method with a small shed housing the
stored liquid, pumps and meters. Solids from the bottom of both settling basins are pumped in a slurry to one of
six(6) new drying beds. Dried solids are then hauled to the landfill for final disposal.///The potable water side
of the plant consists of four(4)water supply wells, aeration basins, oxidation, six(6) greensand filters, four(4)
ion-exchange water-softners and a 1,000,000 gallon potable water storage tank. Chemicals used on the potable
water side include, bleach,zinc orthophosphate, sodium permanganate, and ammonium sulfate.
Proposed flow: 0.271 MGD
Current permitted flow: n/a
Explain anything observed during the site visit that needs to be addressed by the permit, or that may be important
for the permit writer to know(i.e.,equipment condition, function, maintenance, a change in facility ownership,
etc.)
3. Are the site conditions(e.g., soils,topography, depth to water table, etc)maintained appropriately and adequately
assimilating the waste? ® Yes or❑No
If no, please explain:
4. Has the site changed in any way that may affect the permit(e.g., drainage added,new wells inside the compliance
boundary, new development, etc.)? ®Yes or❑No
If yes, please explain: A new 450,000 gallon settling tank, 6 new drying beds and a change in dechlor method
warrents changing the wastewater treatment system within the permit.
5. Is the residuals management plan adequate?. ® Yes or❑No
If no, please explain:
6. Are the existing application rates(e.g., hydraulic,nutrient) still acceptable? ❑ Yes or n No ®N/A
If no, please explain:
7. Is the existing groundwater monitoring program adequate? ❑ Yes ❑No ®N/A
If no, explain and recommend any changes to the groundwater monitoring program:
8. Are there any setback conflicts for existing treatment, storage and disposal sites? ® Yes or❑No
If yes, attach a map showing conflict areas. There may be setback conflicts with the placement of the six(6)new
drying beds. I have requested that the ORC send verification as to the minimum 50' setback from the property
line and 100' setback from any habitable residence or place of public assembly. The new drying beds are near the
southern edge of the property line located between the existing water tower and cell phone tower.
9. Is the description of the facilities as written in the existing permit correct? [' Yes or®No
If no, please explain: a new 450,000:gallon settling basin,the existing 63,000 gallon settling basin, new liquid
Captor replaces the dechlor tablets, and six(6)new drying beds are the result of recent additions added.
10. Were monitoring wells properly constructed and located? ❑ Yes ❑No ®N/A
If no, please explain:
11. Are the monitoring well coordinates correct in BIMS? ❑Yes ❑No ®N/A
If no, please complete the following(expand table if necessary):
12. Has a review of all self-monitoring data been conducted(e.g., DMR,NDMR,NDAR, GW)? ® Yes or❑No
Please summarize any findings resulting from this review: There have been numerous NOVs sent for TSS limit
exceedances which have now stopped as of March 2018 with the construction and operation of the new
450,000gal. settling basin in conjunction with the existing 63,000gal. basin and drying beds.
Provide input to help the permit writer evaluate any requests for reduced monitoring, if applicable.
13. Are there any permit changes needed in order to address ongoing BIMS violations? ❑ Yes or®No
If yes, please explain: None other than the wastewater treatment description to include the new settling tank and
drying beds.
FORM: WQROSSR 04-14 Page 2 of 4

14. Check all that apply:
n No compliance issues [' Current enforcement action(s) ❑ Currently under JOC
®Notice(s)of violation ❑ Currently under SOC ❑ Currently under moratorium
Please explain and attach any documents that may help clarify answer/comments(i.e.,NOV,NOD, etc.)
If the facility has had compliance problems during the permit cycle,please explain the status. Has the RO been
working with the Permittee?Yes, and it appears with the eDMRs submitted from March through June,that the
facility's TSS problem has been taken care of with the$$3.1M improvements added. Is a solution underway or in
place? Yes.
Have all compliance dates/conditions in the existing permit been satisfied? ® Yes ❑No ❑N/A
If no, please explain:
15. Are there any issues related to compliance/enforcement that should be resolved before issuing this permit?
Yes ®No ❑ N/A
If yes, please explain:
16. Possible toxic impacts to surface waters: This Water Treatment Plant has consistently failed it's Toxicity testing
since October of 2015 with only one exception(Oct.2016). This could be addressed with a Special Condition
within the permit renewal.
17. Pretreatment Program(POTWs only): n/a
IV. REGIONAL OFFICE RECOMMENDATIONS
1. Do you foresee any problems with issuance/renewal of this permit? ❑ Yes or Z No
If yes, please explain:
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
Setback distance of new I have already emailed the ORC to request information to help determine
Drying Beds. compliance with setback rules for the new drying beds that have recently been
added to the facility.
3. List specific permit conditions recommended to be removed from the permit when issued:
Condition Reason
None
4. List specific special conditions or compliance schedules recommended to be included in the permit when issued:
Condition Reason
Modified Acute Toxicity This Water Treatment Plant has consistently failed its Toxicity testing since
Monitoring to address October of 2015. This should be addressed with a modified Special Condition
ongoing Failure results within the permit renewal.
FORM: WQROSSR 04-14 Page 3 of 4

5. Recommendation: ® Hold, pending receipt and review of additional information by regional office
/1 Hold, pending review of draft permit by regional office
❑ Issue upon receipt of needed additional information
❑ Issue
❑ Deny(Please st.> reasons: )
6. Signature of report preparer: •_
Signature of regional supervisor: .I
Date: 1 Ct— 16
V. ADDITIONAL REGIONAL STAFF REVIEW ITEMS
None.
FORM: WQROSSR 04-14 Page 4 of 4

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United States Environmental Protection Agency
Form Approved
EPA Washington,D C 20460 OMB No 2040-0057
Water Compliance Inspection Report Approval expires 8-31-98
Section A National Data System Coding(i.e,PCS)
Transaction Code NPDES yr/mo/day Inspection Type Inspector Fac Type
1 IN I 2 El 3 I NC0078131 111 12 1 18/07/05 117 18 [ j 19 Ls I 201 l
211 11 1 1 11 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 L 1 1 1 p6
Inspection Work Days Facility Self-Monitoring Evaluation Rating B1 QA — Reserved
67I I 7° 1
1 71 1 I 72 1 N I 731 1 174 7511 11 1 I 1 1 180
Section B Facility Data
Name and Location of Facility Inspected(For Industrial Users discharging to POTVV,also include Entry Time/Date Permit Effective Date
POTW name and NPDES permit Number) 10 30AM 18/07/05 14/09/01
Brown Blvd WTP
Exit Time/Date Permit Expiration Date
Brown Blvd
12 45PM 18/07/05 18/06/30
Havelock NC 28532
Name(s)of Onsite Representative(s)/Titles(s)/Phone and Fax Number(s) Other Facility Data
///
David Robert Hemenway/ORC/252-444-6420/
Jacquelyn G Acha/ORC/252-444-6420/
Name,Address of Responsible Official/Title/Phone and Fax Number
Contacted
David Hemenway,PO Box 368 Havelock NC 28532/ORC/252-444-6420/
No
Section C Areas Evaluated During Inspection(Check only those areas evaluated)
• Permit • Operations&Maintenance • Records/Reports • Self-Monitoring Program
• Sludge Handling Disposal • Facility Site Review II Effluent/Receiving Waters
Section D Summary of Finding/Comments(Attach'additional sheets of narrative and checklists as necessary)
(See attachment summary)
Name(s)and Signature(s)of Inspector(s) Agency/Office/Phone and Fax Numbers Date
Scott A Vinson WARO WQ//252-946-6481 Ext 208/
Signature of Management Q A Reviewer Agency/Office/Phone and Fax Numbers Date
EPA Form 3560-3(Rev 9-94)Previous editions are obsolete
Page# 1

V
NPDES yr/mo/day Inspection Type (Cont.) 1
31 NC0078131 I11 121 18/07/05 117 18 LI
Section D Summary of Finding/Comments(Attach additional sheets of narrative and checklists as necessary)
DWR-WQROS staff member, Scott Vinson, visited site on July 5, 2018 to perform a compliance
evaluation as well as to review the permit for the upcoming renewal. The facility has recently finished
(February 2018) upgrades to add a larger 450,000g settling tank as well as 6 new sand drying beds.
The facility has also changed from dechlor tablets to liquid captor as a means to dechlorinate the
effluent discharged The permit is currently being renewed and will need to be revised to show the
upgrades.
Overall the facility looked good and was well maintained.
The records were spot checked and for the periods of June 2016, May 2017 and March 2018, the
records, bench sheets, lab results and reported eDMRs were accurate and in order.
A new 450,000 gallon settling tank has been added in addtion to the existing 63,000 gallon tank which is
now used as a finishing/polishing tank after instal settling in the larger tank is allowed to occur. The
smaller tank has a decant skimmer used to discharge the effluent water. The sludge slurry from both
tanks are pumped to one of the new six (6) drying beds then onto the landfill for final disposal of solids.
The facility has changed from using dechlor tablets to liquid Captor to dechlorinate the effluent prior to
discharge.
ORC- David Hemenway, Cert#28581, PC-1
Backup ORC -Jacquelyn Acha Cert.#1001046, PC-1
Page# 2

Permit: NC0078131 Owner-Facility Brown Blvd WTP
Inspection Date: 07/05/2018 Inspection Type Compliance Evaluation
Permit Yes No NA NE
(If the present permit expires in 6 months or less). Has the permittee submitted a new ❑ ❑ 0 0
application?
Is the facility as described in the permit? ❑ • 0 ❑
#Are there any special conditions for the permit? • 0 ❑ 0
Is access to the plant site restricted to the general public? • ❑ ❑ ❑
Is the inspector granted access to all areas for inspection? I ❑ ❑ ❑
Comment The facility has recently finished (February 2018) upgrades to add a larger 450,000g settling
tank as well as 6 new sand drying beds. The facility has also changed from dechlor tablets
to liquid captor as a means to dechlorinate the effluent discharged. The permit is currently
being renewed and will need to be revised to show the upgrades.
Operations & Maintenance Yes No NA NE
Is the plant generally clean with acceptable housekeeping? • ❑ ❑ ❑
Does the facility analyze process control parameters,for ex: MLSS, MCRT, Settleable • ❑ ❑ ❑
Solids, pH, DO, Sludge Judge, and other that are applicable?
Comment: The analysis performed by the facility on the effluent are TRC, pH & DO.
Record Keeping Yes No NA NE
Are records kept and maintained as required by the permit? MI ❑ ❑ ❑
Is all required information readily available, complete and current? • ❑ ❑ ❑
Are all records maintained for 3 years(lab. reg. required 5 years)? • ❑ 0 0
Are analytical results consistent with data reported on DMRs? • ❑ ❑ LI
Is the chain-of-custody complete? • ❑ 0 ❑
Dates,times and location of sampling •
Name of individual performing the sampling •
Results of analysis and calibration •
Dates of analysis U
Name of person performing analyses •
Transported COCs •
Are DMRs complete do they include all permit parameters? • ❑ LI ❑
Has the facility submitted its annual compliance report to users and DWQ? ❑ LI • ❑
(If the facility is=or>5 MCD permitted flow) Do they operate 24/7 with a certified operator ❑ ❑ U ❑
on each shift?
Is the ORC visitation log available and current? • ❑ ❑ ❑
Is the ORC certified at grade equal to or higher than the facility classification? • ❑ ❑ ❑
Page# 3

Permit NC0078131 Owner-Facility* Brown BlvdWTP
Inspection Date: 07/05/2018 Inspection Type Compliance Evaluation
Record Keeping Yes No NA NE
Is the backup operator certified at one grade less or greater than the facility classification? • El El ❑
Is a copy of the current NPDES permit available on site? • ❑ ❑ ❑
Facility has copy of previous year's Annual Report on file for review? El El • ❑
Comment ORC-David Hemenway, Cert#28581, PC-1
Backup ORC-Jacquelyn Acha Cert.#1001046, PC-1
Equalization Basins Yes No NA NE
Is the basin aerated? ❑ ❑ I ❑
Is the basin free of bypass lines or structures to the natural environment? • ❑ ❑ ❑
Is the basin free of excessive grease? • ❑ ❑ ❑
Are all pumps present? •. ❑ ❑ ❑
Are all pumps operable? • ❑ 0 El
Are float controls operable? • ❑ ❑ ❑
Are audible and visual alarms operable? • ❑ ❑ ❑
#Is basin size/volume adequate? • El ❑ ❑
Comment: A new 450,000 gallon settling tank has been added in addtion to the existing 63,000 gallon
tank which is now used as a polishing tank with a decant skimmer prior to discharging the
effluent water. The sludge slurry from both tanks are pumped to the 6 new drying beds for
drying and then onto the landfill for final disposal of solids.
De-chlorination Yes No NA NE
Type of system? Liquid
Is the feed ratio proportional to chlorine amount(1 to 1)? • ❑ ❑ p
Is storage appropriate for cylinders? ❑ ❑ • ❑
• #Is de-chlorination substance stored away from chlorine containers? • ❑ ❑ ❑
Are the tablets the proper size and type? ❑ El IN ❑
Comment. The facility has also changed from using dechlor tablets to liquid Captor to dechlorinate the
effluent prior to discharge.
Are tablet de-chlorinators operational? ❑ ❑ • 0
Number of tubes in use'?
- Comment
Effluent Sampling Yes No NA NE
Is composite sampling flow proportional'? ❑ IN ❑ ❑
Is sample collected below all treatment units'? • ❑ 0 ❑
Page# 4

Permit. NC0078131 Owner-Facility: Brown Blvd WTP
Inspection Date: 07/05/2018 Inspection Type: Compliance Evaluation
Effluent Sampling Yes No NA NE
Is proper volume collected'? • 000
Is the tubing clean'? • 000
#Is proper temperature set for sample storage (kept at less than or equal to 6.0 degrees • ❑ ❑ ❑
Celsius)?
Is the facility sampling performed as required by the permit(frequency,sampling type U 000
representative)?
Comment The sampling is done by time/volume method because there is no steady discharge of
effluent The effluent Is discharged in batches almost daily, and can be held in the new
larger tank if needed
The facility has a new effluent sampler which is refrigerated to 4C on day of inspection
At the time of inspection, facility was not discharging.
Drying Beds Yes No NA NE
Is there adequate drying bed space'? • 000
Is the sludge distribution on drying beds appropriate? U ❑ ❑ ❑
Are the drying beds free of vegetation'? • ❑ ❑ ❑
#Is the site free of dry sludge remaining in beds'? U ❑ ❑ ❑
Is the site free of stockpiled sludge'? 11000
Is the filtrate from sludge drying beds returned to the front of the plant? U ❑ ❑ ❑
#Is the sludge disposed of through county landfill'? U ❑ ❑ ❑
#Is the sludge land applied'? 0 • 00
(Vacuum filters) Is polymer mixing adequate'? ❑ ❑ • ❑
Comment The facility has 6 new drying beds One is currently in use with 3-6 inches of drying solids
on top The facility will remove sludge periodically and haul to the local landfill for final
disposal.
Upstream / Downstream Sampling Yes No NA NE
Is the facility sampling performed as required by the permit(frequency,sampling type, and • 000
sampling location)?
Comment
Page# 5

CITY OF HAVELOCK\ WTP BACKWASH SOLIDS HANDLING PROJECT
DESIGN MEMORANDUM
1.0 INTRODUCTION: The design for the WTP Backwash Solids Handling Project adheres to
the plan set forth in the preliminary engineering report with minor modifications for
improvement and positive change to the project. One positive change is having the effluent
flow by gravity under differential head pressure rather than a pressurized flow driven by
pumps. The design memorandum generally follows the NC DEQ \ DWI Bid and Design
Document Submittal Form. The commentary endeavors to present material covering primary
and incidental elements in a logical sequence to explain the design with associated questions,
investigations, calculations and engineering decisions as shown by the plans and
specifications for the Havelock WTP Backwash Solids Handling Project.
2.0 PROJECT DESCRIPTION: The project includes a 450,000 gallon circular pre-stressed
concrete waste settling basin with 60-foot diameter and 20.5-foot sidewall height plus six
sand-drying beds with each having a width of 20-feet and length of 53 feet. The facility
includes two pump stations, one is a 3.5 HP, 250 GPM suction-lift solids pump station with
fiber-glass house, piping and control panel; the other is a 3.0 HP, 150 GPM submersible
under drain pump station with 6-foot diameter wet-well and 5'0 diameter check-valve vault.
The de-chlorination unit includes a 6'0 x 4'0 fiberglass building with power, lights, heat and
ventilation for two (2) peristaltic pumps and chemical storage plus an injector/static mixer in
a 5'0 diameter vault for feeding calcium-thiosulfate into the effluent pipeline. Other
equipment includes a composite sampler, two (2) 8-inch mag-meters in 5'0 x 6'0 vaults plus
five (5) motor operated valves. Another project requirement is retrofit of an existing
rectangular basin (32' x 20' x 14') that includes installation of a floating decanter.
Associated work for the project includes electrical/control conduit, wire, lighting and various
fixtures plus additions to existing SCADA system. All site-work including demolition,
excavation, installation of all yard-piping, fittings, valves and appurtenances, installation of
driveway and fence plus incidental work and subsidiary obligations including
erosion/sediment control and storm-water management as inherent parts of the project.
3.0 PURPOSE: The purpose for the WTP Backwash Solids Handling Project is to design
and construct a backwash wastewater residuals facility to receive filter-backwash and
softener-regeneration-backwash wastewater from the existing 2.8 MGD water treatment
plant that utilizes greensand filters and ion-exchange softeners to produce finish drinking
water for the City of Havelock, North Carolina. The effluent discharge from the
backwash wastewater residuals facility is to meet requirements of the existing NPDES
Permit NC0078131 —effective September 21, 2014 through June 30, 2018. See Exhibit I—
NPDES Permit
4.0 GOALS: Produce Quality Effluent for Discharge
Reduce Volume of Solid Residuals for Disposal
Minimize Power Consumption
Maximize Options for Operation
Minimize Labor Requirement for Operation
Page 1 of 17

5.0 OBJECTIVES, ELEMENTS and FEATURES: The design utilizes a batch-decant
process to separate residual solids and liquid. Design for the solid-stream complements
disposal at an off-site landfill. Design for the liquid-stream is discharge meeting
requirements of the existing NPDES Permit that includes a TSS Daily Maximum Limit of
45 mg/L and TSS Monthly Average Limit of 30 mg/L.
The basic function of the project is removal of residual solids and residual liquid from
the site; that function is achieved by three primary elements of design. The first is a
circular settling basin (BASINsETTLE) for batch processing of the backwash wastewater
from the water treatment plant and the second is a relatively small rectangular polishing
basin (BASINpoLISH) that receives supernatant-decant from the BASINsETTLE The third
element is Sand Drying-Beds that reduces volume of iron oxide and manganese oxide
solids for off-site disposal.
The proposed BASINsETTLE is a circular concrete basin with diameter equal to 60-foot and
straight-sidewall height equal to 20.5 vertical feet. The BASINpoLISH is a retrofit-
conversion of an existing structure currently receiving backwash wastewater from the
water treatment plant. The conversion includes a floating-decanter and motor-operated
valves for control of the batch-decant process. Other design items for the project include
two (2) pump stations, effluent metering, de-chlorination, effluent sampling and related
piping plus necessary power and control with additions to existing SCADA.
5.1 SOLIDS-STREAM: The BASINsETTLE and batch-settling decant method for separation of
solids from liquid includes various design features; the key feature is a rotating scraper
mechanism with an integral center-feed pipe and center-well with baffles to facilitate
removal of residual precipitate-solids from bottom of the BASINsETTLE. The design calls
for a Solids Pump-Station to convey residual precipitate-solids from the BASINsETTLE to
Sand Drying-Beds and a Sand-Bed Underdrain Pump-Station to convey liquid from the
Sand Drying-Beds back to the BASINsETTLE. Periodically, the iron and manganese
residual solids shall be transported from the Sand Drying-Beds to an off-site landfill for
appropriate disposal.
In addition to receiving flow from the BASINsETTLE, the piping design allows the Solids
Pump-Station to receive settled-solids flow from the BASINpoLISH Opening the drain-line
from the BASINpOLISH to convey residual solids to the Solids Pump-Station and Sand
Drying-Beds is an infrequent as necessary event.
In regard to the Sand-Bed Underdrain Pump-Station, normal operation would have the
under-drain pump convey liquid flow from the Sand-Drying Beds to the BASINsETTLE. An
optional mode-of-operation allows the operator to manually open/close valves and direct
liquid flow from the Sand Drying-Beds to the BASINpoLISH•
5.2 LIQUID-STREAM {supernatant-decant-effluent}: The BASINsETTLE includes six (6) pipes
for supernatant to exit the basin. The single-point HIGH-LEVEL OUTLET is an
overflow/telescope valve that liquid will exit when it reaches overflow-level. If water-
Page 2 of 017

4
level in the BASINsETTLE rises above the overflow/telescope valve, then liquid will flow
from the BASINSETTLE through the BASINSETTLE BASINPOLISH to the DISCHARGEOUTLET•
Typically, the BASINsETTLE overflow-level would be set to allow 2'0 of freeboard above
normal high water-level (HWLN); however, the operator can select a different overflow-
level and high water-level (HWL). The overflow/telescope valve outlet can be used as a
manual decant mechanism for the five vertical-feet of liquid below normal high water-
level(HWLN).
The single-point MID-LEVEL OUTLET is a motor-operated-valve (open/close) (MOV-1 0/C
normally-close). It is located eleven feet below normal high water-level (HWLN) and
opens upon the operator choosing to allow the supernatant-decant to flow through the
MID-LEVEL OUTLET.
The four-point LOW-LEVEL OUTLET is a set of four-pipes located just above the precipitate-
solids zone at a low elevation in the supernatant-decant-liquid zone of the BASINsETTLE.
A motor-operated-valve (open/close) (MOV-2 0/C normally-close) located on the
common collection-pipe for the low-level set-of-pipes opens upon the operator choosing
to allow the supernatant-decant to flow through LOW-LEVEL OUTLET.
The operator can choose any of the three levels — HIGH-LEVEL, MID-LEVEL or LOW-LEVEL
and allow the supernatant-decant to flow from the BASINsETTLE. Typically, the operator
will utilize either the MID-LEVEL OUTLET or LOW-LEVEL OUTLET for the supernatant-decant
process. Whichever outlet is chosen, all flow from the BASINSETTLE to the BASINPOLISH
reaches a common pipeline with a motor-operated-valve (flow-control) (MOV-3 FCV
normally-open) located at entrance and adjacent to the BASINPOLIsx•
In regard to retrofit-conversion for the BASINPOLISH,'the existing rectangular structure
includes two chambers; one has an 1 x w x h dimension 28' x 24' x 14' and the other has
dimension is 4' x 24' x 14'; there are three existing 10-inch wall-pipes with valves that
can allow water to pass from one chamber to the other. The valves are scheduled for
demolition to have one 24' x 32' x 14' hydraulic chamber for the BASINPOLISH. The key
feature of the proposed BASINPOLISH is a floating-decanter that provides mechanism for
top-water effluent-flow to exit the BASINPOLISH•
Design flow entering the BASINPOLISH and passing through flow-control valve MOV-3 enters
bottom of the BASINPOLISH. A pressure sensor/transducer monitors water level in the
basin to allow direction from SCADA for the flow-control valve. The flow-control valve
will modulate as necessary to maintain water level in the BASINPOLISH at an elevation less
than or equal to an operator set-point. The floating-decanter and pipe system
configuration for the facility will keep normal operation low-water level (LWL) above a
fixed elevation and allow any latent particulate to settle in bottom of the BASINPOLISH.
In addition to the basin water-level signal being used by SCADA to modulate flow-
control valve MOV-3, the same signal is used by SCADA to control a motor-operated-
valve (open/close) (MOV-4 0/C normally-open) at exit from the BASINPOLISH. When the
supernatant-decant and effluent-discharge process is not in progress, MOV-3 and MOV-4
at entrance and exit of the BASINPOLISH are open. Under this normally open condition, any
Page 3 of 017

unanticipated flow from the overflow/telescope valve in the BASINsETTLE will pass through
the BASINpoLISH and continue to the DISCHARGEouTLET.
The normal operation for supernatant-decant and effluent-discharge process begins with
direction from the operator to allow action. Three (3) motorized valves are keys to the
operational process; the first valve is (MOV-1 0/C or MOV-2 0/C normally-close) at exit
from the BASINsETTLE. Whichever outlet is chosen by the operator for flow from the
BASINsETTLE — the motor-operated valve moves to open. The second valve is (MOV-3
FCV normally-open) adjacent and located at entrance to the BASINpoLISH—it remains open
and modulates as necessary to limit high-water-level(HWL) in the BAS1NpoLISH• The third
valve is (MOV-4 O/C normally-open) adjacent to the basin and located on pipe that exits
from the BASINpoLISH—it moves to close and remains in that position until water-level in
the BASINpoLISH rises from fixed low water-level (LWL) to operator set-point high-water-
level(HWL).
When water-level reaches HWL in the BASINpoLISH, MOV-4 on pipe at exit from the
BASINpoLISH moves to open. The effluent flow exiting the BASINpoLISH during the normal
operation for supernatant-decant and effluent-discharge process flows through pipeline
and other design features including a mag-meter for measuring effluent, de-chlorination
and an effluent sampler in route to the DISCHARGEoUTLET•
The normal operation for supernatant-decant and effluent-discharge process continues until
cessation of flow from the BASINsETTLE. The supernatant in the BASINsETTLE ceases to flow
upon reaching operator set-point for decant water-level in the BASINsETTLE and either MOV-1
or MOV-2 at respective exit from the BASINsETTLE moves from open to close. With no flow
into the BASINpoLISH, its water level and the floating-decanter descend to a rest-position at
fixed low water-level (LWL) in the BASINpoLISH• With floating-decanter in rest-position at
fixed low water-level (LWL) in the BASINpoLISH, the two motor operated valves, MOV-3 and
MOV-4 at entrance and exit of the BASINpoLISH, move to full-open.
As shown by the flow schematic, a bypass decant operation is possible by having flow by-
pass the BASINpoLISH• The fifth motor operated valve (MOV-5 FCV normally-open) is located
on a common pipeline that allows flow control for both normal decant operation and bypass
decant operation. During normal decant operation with water level in the BASINpoLISH at
32.00 MSL, MOV-5 could reduce flow-rate to a rate less than approximately 1000 GPM.
During bypass decant operation with water level in the BASINsETTLE at high water-level
(HWL) 40.00 MSL, MOV-5 could reduce flow-rate to a rate less than approximately 1600
GPM. MOV-5 would modulate in response to operator set-point and flow-rate measured by
the effluent flow meter with both parameters in the control system utilizing SCADA.
6.0 DESIGN LOAD
Exhibit II — Wastewater Data Calculation and Summary shows loading most relevant to
sizing of the primary feature of the solids handling facility—the BASINsETTLE.
Page 4 of 017

-4
6.1 DESIGN LOAD - INFLUENT HYDRAULIC FLOW: The design hydraulic loading for the
backwash wastewater residual facility is a direct function of the existing water treatment
plant design capacity with its operational mode for filter-backwash and softener-
regeneration-backwash.
FILTERS: The existing water treatment plant is capable of producing 2.8 MGD of finish-
water by utilizing four (4) softeners and two (2) filter trains each with three (3) filters. Each
of the six (6) filters undergoes a nine-step filter-backwash once every 24-hours. The design
raw water flow-rate through each filter is 324 GPM with all six in operation and 389 GPM
with 5 filters in operation and one in backwash. The current condition of the well-pumps and
filter pumps has the raw water flow-rate(s) through each filter respectively 183 GPM and
220 GPM. With current average daily water production approximately 1.0 MGD,the current
raw-water flow-rate is less than the design rate, and not causing issue in regard to finish-
water production. Current pressure-drop-across-the-filter just prior to backwash is 2.5 PSI
which is much less than the maximum allowable pressure-drop-across-the-filter of 10 PSI.
Execution of filter-backwash before reaching maximum allowable pressure-drop-across-the-
filter can promote efficient operation of the filter and extend service-life of the filter media.
Based on observation of pressure-drop and current raw water flow-rate, estimate of pressure-
drop-across-the-filter just prior to backwash for design raw-water flow-rate equal to 324
GPM through each filter is 7.8 PSI and less than the maximum allowable pressure drop.
Table 8-I - Summary of Filter-Backwash Wastewater from one filter follows:
Table 8-I: Summary of Filter-Backwash Wastewater
ACTION TIME QBW-FLOW TOTAL
de-pressurize 1 minute 450 GPM 450 gallon
drain-down 5 minute 450 GPM 2,250 gallon
Air 2 minute 0 GPM 0 gallon
air/water 3 minute 450 GPM 1,350 gallon
slow-refill 2 minute 450 GPM 900 gallon
Backwash 10 minute 1,360 GPM 13,600 gallon
bed-settle 2 minute 0 GPM 0 gallon
Rinse 3 minute 339 GPM 1,017 gallon
• 29 minute 19,567 gallon
The total filter-backwash wastewater generated is 6 x 19,567 gallons or 117,402 GPD and
the process requires 6 x 29 minutes equals 174 minutes or 2.9 hours/day.
SOFTENERS: An operator set-point has a softener-regeneration-backwash event for each
softener occur after n-gallons of water pass through the softener. At any given time with
both filter trains on-line, six (6) filters and all four (4) softeners could be processing water or
three (3) softeners processing water while one (1) softener undergoes softener-regeneration-
Page 5 of 017

backwash. With only one filter train and three (3) filters on-line, the softeners rotate as
necessary to ensure two (2) softeners are always processing water.
The softener mode-of-operation based on gallons of flow includes a changeable independent
set-point for each softener and fluctuating daily flows dependent on variable demand from
the water system. The quantity of softener-regeneration-backwash wastewater is less
predictable than for filters with mode-of-operation based on a fixed time.
However, with average operator set-point flow for the softeners equal to 325,000 gallons and
accounting for increase in flow for each of three (3) softeners when one (1) softener
undergoes softener-regeneration backwash; there could be an average of 81/2 softener-
regeneration-backwashes per day. A single four-step softener-regeneration backwash action
for one softener takes 78 minutes and generates over 20,000 gallons of softener-regeneration
backwash wastewater. Table 8-II - Summary of Softener-Regeneration-Backwash
Wastewater from one softener follows:
Table 8-II: Summary of Softener-Regeneration-Backwash Wastewater
ACTION TIME QBW-FLOW TOTAL •
slow rinse 21 minute 66 GPM 1,386 gallon
fast rinse 27 minute 451 GPM 12,177 gallon
Regeneration 20 minute 101 GPM 2,020 gallon
Backwash 10 minute 471 GPM 4,710 gallon
78 minute 20,293 gallon
The design total softener-regeneration-backwash wastewater generated is 8.5 x 20,293
gallons or 172,490 GPD and the process requires 8.5 x 78 minutes equals 663 minutes or
11.0 hours /day. {Note: The softener-regeneration-backwash mode-of-operation is further
explained in discussion of influent constituents.}
As shown by tables, the maximum flow-rate for backwash wastewater flowing from the
water treatment plant to the backwash-wastewater basin — BASINSETTLE is 1,360 GPM during
filter backwash and the minimum flow-rate is 66 GPM during softener-regeneration-backwash.
Approximately 14 hours per day is spent on backwash activity and the grand total of filter-
backwash plus softener-regeneration-backwash wastewater is (117,402 GPD + 172,490 GPD)
equals 289,892 GPD — say 290,000 GPD. The design hydraulic loading for the backwash
wastewater residual facility with flow from filters and softeners in the WTP is 290,000 GPD
6.2 DESIGN LOAD —EFFLUENT HYDRAULIC FLOW: When utilizing the batch-decant process, the
normal operation for supernatant-decant process would preferably occur when the basin was
quiescent and would not transpire when flow was entering the basin or during a quiescent
time when particles are settling in the basin. The Iron and Manganese Removal Handbook—
Page 6 of 017

Second Edition (2015); AWWA when describing the batch-settling-decant method makes
statement that follows:
"Generally the filter-backwash wastewater from an iron and manganese pressure filter will
settle in approximately 3 hours, after which the decant quality is generally less than 1-NTU.
After settling period is complete, the supernatant flows to the plant influent or a local
waterway."
The clarifier with rotating scraper mechanism having integral center-feed pipe and baffled
center-well is specifically designed to minimize disturbance when flow is entering the basin.
However, if one chose to decant when there is no-flow into the basin and decant only after a
three hour period of no-flow; there could be only seven (7) hours available for supernatant-
decant process. With daily outflow equal daily inflow, the average effluent flow over seven
hours would be {290,000 gal/ [24 hr—(14 hr+ 3 hr) x 60 min/hr]} or 690 GPM. The design
minimum overall-average effluent flow-rate is 690 GPM and actual overall average effluent
flow-rates should be greater than 690 GPM.
6.3 DESIGN LOAD — INFLUENT CONSTITUENTS: The constituent loading for the backwash
wastewater residual facility is a function of the water treatment plant design capacity with its
operational mode for filter-backwash and softener-regeneration-backwash plus solids in the
raw water passing through the filters and the brine used to regenerate the softeners. The
water treatment plant receives raw water from the Castle Hayne Aquifer by means of four (4)
wells with two (2) wells on the WTP Site and two (2) remotely located with respective
straight-line distances approximately 2,000 and 2,900 feet from the WTP. The raw water
from the Castle Hayne Aquifer in this small area is relatively consistent over time and space
with negligible short-term variations in constituents and water quality.
6.4 INFLUENT CONSTITUENTS \FILTER-BACKWASH WASTEWATER: As shown in the Preliminary
Engineering Report, the City of Havelock's raw water data for the Year 2014 shows iron
concentration minimum equal to 2.00 mg/L; maximum 3.69 mg/L and the average 2.68
mg/L. The design concentration of iron in the raw water is 3.0 mg/L.
Iron in the raw water is oxidized during water treatment and filtration to have Fe(OH)3 such
that 1 mg/L of soluble iron in the raw water oxidizes into 1.91 mg/L of residual solids. The
existing water treatment plant is capable of producing 2.8 MGD. The design quantity of iron
in the raw water would be (3.0 ppm x 8.34 lb/gal x 2.8 MGD) or 70.1 lb /day and design
quantity of oxidized iron residual solids from the filter-backwash wastewater is 1.91 x 70.1
lb/day or 133.9 lb/day.
In regard to manganese, raw water data for the Year 2014 shows manganese concentration
minimum equal to 0.051 mg/L; maximum 0.298 mg/L and the average 0.137 mg/L. The
design concentration of manganese from the raw water is 0.150 mg/L.
The manganese in the raw water is oxidized during water treatment and filtration to have
Mn(OH)2 such that 1 mg/L of soluble manganese in the raw water oxidizes into 1.61 mg/L of
residual solids. With the existing water treatment plant capable of producing 2.8 MGD, the
Page 7 of 017

design quantity of manganese in the raw water would be (0.150 ppm x 8.34 lb/gal x 2.8
MGD) or 3.50 lb /day and design quantity of oxidized manganese residual solids in the filter-
backwash wastewater is 1.61 x 3.5 lb/day or 5.64 lb/day.
The grand total of oxidized iron and manganese residual solids is 133.9 lb/day + 5.64 lb/day
equals 139.54 lb/day, or 140 lb/day of residual solids from the filter-softener backwash
wastewater equal to 289,892 GPD — say 290,000 GPD. The design concentration of total
suspended solids (TSS) in the combination of filter-backwash wastewater and softener-
regeneration-backwash wastewater is [140 lb/day / (8.34 lb/gal x 0.290 MGD)] equal to 57.9
mg/L or say 58.0 mg/L. {Note: A negligible quantity of suspended solids is expected in the
softener-regeneration-backwash wastewater.}
6.5 INFLUENT CONSTITUENTS \ SOFTENER-REGENERATION-BACKWASH WASTEWATER: The water
treatment plant produces water to achieve its target hardness for the finish-water by blending
filter-softener-process water that has zero hardness with filter process water that has the
same hardness as the raw water. The ratio can vary, but the typical blend for the existing
water treatment plant is 85%filter-softener-process water and 15%filter process water. The
design water production rate is 2.8 MGD or 1944 GPM of finish-water meaning the blend
would utilize (0.15 x 1944 GPM) or 292 GPM of filter process water and (0.85 x 1944 GPM)
or 1652 GPM of filter-softener process water to produce the finish-water with a target
hardness selected for the WTP.
The raw water data for Year 2014 shows hardness varying from 193 to 290 with average
equal to 247. The design number for the raw water hardness is 290 and the target for
finished-water hardness is between 45 and 60.
HARDNESS REMOVAL — The softeners remove grains of hardness at a given softener
removal-rate equal to 17.1 grains /gallon and require periodic regeneration to maintain that
removal rate. The total hardness removal requirement per day equals [1652 GPM x 1440
min x (290/ 17.1)] / 1000 or 40,344 K-grain.
SOFTENER CAPABILITY — The given exchange capacity of the softener resin varies
depending on type and manufacturer of the resin plus condition and age of the resin in the
softener. A given softener exchange capacity of 20 K-grain/CF is typical and reasonable for
the Havelock WTP. With average volume of resin for each of four softeners equal to 288
CF, the total hardness removal capability equals [4 x 288 CF x 20 K-grain/CF)] or 23,040 K-
grain/regeneration-cycle.
REGENERATION CYCLE — The softener-regeneration-cycles equals hardness removal
requirement divided by hardness removal capability or 40,344 K-grain / 23,040 K-grain
equals 1.75 cycle /day or one (1) softener regeneration for each softener every (24 hr/ 1.75)
or 13.7 hours and/or one (1) softener regeneration for each softener every [(1652 /4)x 13.7 x
60] or 339,478 Gallon. The design regeneration-cycle is an operator set-point appropriately
less than the regeneration-cycle. Each softener has a changeable set-point. Based on
current set-points, the design average regeneration-cycle flow for the water treatment plant
softeners is 325,000 Gallon. With the existing water treatment plant capable of producing
2.8 MGD (1944 GPM), and considering time that each softener experiences increased flow
Page 8 of 017

1
while one softener is •off-line to backwash the design average number of softener-
regeneration-backwashes /day is approximately 8.5 generating 172,490 GPD of softener-
regeneration-backwash wastewater.
SOFTENER-REGENERATION-BACKWASH WASTEWATER SALINITY — The softener-
regeneration removes calcium and magnesium on the resin and replaces that calcium and
magnesium with sodium. The manufacturer of the softener and the resin concur on
requirements for regeneration that includes using 6.0 lb of salt (NaCl) for each cubic foot of
resin. The total amount of salt would be (6.0 LB /CF x 288 CF) or 1,728 LBSALT. The salt
solution is conveyed by the brine pumps to the softener in a 10% brine solution with a flow-
rate equal to 101 GPM for 20 minutes.
The brine solution flowing through the softener for 20 minutes with flow-rate equal to 101
GPM generates a total of 2,020 gallons of brine with 1,728 lb of salt in the wastewater from
each softener-regeneration backwash. The salt is a dissolved solid contributing to the
quantity of total dissolved solids (TDS) in the backwash wastewater. Each softener-
regeneration-backwash generates 20,293 gallons of softener-regeneration-backwash
wastewater including 2,020 gallons of brine with 1,728 lb of salt. The total softener-
regeneration backwash wastewater generated in one day is 8.5 x 20,293 GAL/regeneration or
172,490 GPD with salinity equal to [(8.5 x 1,728 LBSALT) / (8.5 x 20,293 gal x 8.34 LBWATER
/gal)] x 100 which equates to 172,490 gallons of a 1.0% salt solution/day.
When the softener-regeneration backwash wastewater is combined with the filter-backwash
wastewater the mix becomes {(8.5 x 1,728 LBSALT / [(8.5 x 20,293 gal) + (6 x 19,567 gal)] x
8.34 lb/gal} x 100 equals a 0.6% solution saltwater.
7.0 DESIGN ELEMENTS
The existing backwash wastewater process consists of a rectangular waste holding basin with
overall dimension of 32' x 24' x 14' and approximate operational capacity 63,000 gallons. It
has two chambers; one is a primary holding chamber and the other has two pumps that
operate alternately conveying effluent to a discharge vault with diameter and height equal to
5'0. The effluent flows from the basin through a meter and tablet feeder to the discharge
vault and a 10-inch pipe before entering a drop inlet.
The waste holding basin is being retrofitted to become a polishing basin. The pumps, meter
and tablet feeder are being supplanted by the proposed project which includes demolition and
abandonment of the discharge vault. The design elements being sized for the project include
the following:
➢ WASTE SETTLING BASIN
➢ PIPELINE,FITTINGS,VALVES AND APPURTENANCES
➢ FLOATING DECANTER
➢ DECHLORINATION FACILITY
➢ EFFLUENT METER
➢ BACKWASH METER
Page 9 of 017

➢ SAND-DRYING BEDS
➢ SOLIDS PUMP STATION
➢ UNDERDRAIN PUMP STATION
7.1 FILTER-SOFTENER BACKWASH WASTEWATER BASIN(BASINsETTLE) STRUCTURE: The primary
feature of the backwash-wastewater residual facility is the BASINsETTLE. The BASINsETTLE
provides the basin structure for a batch-settling method to process 117,402 GPD of filter-
backwash wastewater with its iron oxide and manganese oxide suspended solids plus
172,230 GPD of softener-regeneration-backwash wastewater with dissolved solids in a
solution with salinity approximately 1.0%.
The design calls for a basin that contains a one-day volume of filter-backwash-wastewater
and softener-regeneration-backwash wastewater plus a 15% buffer plus volume to store 4-
days of settled-solids. The BASINsETTLE shown in Figure 7.1 includes an operational volume
as follows:
One-Day Volume— 290,000 Gallon(289,632)
Buffer— 49,000 Gallon (48,730)
SUBTOTAL— 339,000 Gallon(338,362)
Settled-Solids— 70,000 Gallon (70,492)
TOTAL— 409,000 Gallon(408,362)
The BASINsETTLE design allows iron and manganese particulate to continuously settle out-of-
the-filter-backwash wastewater. The design with supernatant-decant zone volume approximately
339,000 gallons and appropriate mode-of-operation provides a minimum of three (3) consecutive
hours for settling with no flow into the BASINSETTLE. The precipitate-solids zone at the basin
bottom has a design volume of 70,000 gallons to hold a variable concentration of precipitate-
solids. The solids settle and compress as a rotating scraper mechanism moves material to a
hopper-sump with discharge pipe for flow to the solids-pump station. The Solids Pump-
Station conveys solution of residuals to the dewatering system—Sand-Drying Beds.
WASTEWATER SETTLING BASIN: The design for the 450,000 gallon wastewater settling basin calls
for a cylindrical pre-stressed concrete basin with a slope-bottom (1v:12H) to its center having
dimensions and elevations as follow:
DIAMETER 60.0 FT
SIDE-WALL HEIGHT 20.5 FT {w/operational water depth 18.5 VF}
TOP-OF-WALL 42.00 MSL
HIGH-LEVEL OUTLET 40.00 MSL one 8-inch exit with manual telescoping valve
MID-LEVEL OUTLET 29.17 MSL one 8-inch exit with motor-operated MOV-1 (0/C)
LOW-LEVEL OUTLET 24.00 MSL four 6-inch exits with motor-operated MOV-2(0/C)
BASE OF CENTER PIER 19.17 MSL one 20-inch center inlet pipe
Page 10 of 017

The pre-stressed concrete basin shall include certified structural design, calculations and
drawings that include consideration of the soils report, local conditions and applicable codes.
Buoyancy forces will be addressed by means of pressure relief valve design from the
engineer certifying the design of the basin. See Exhibit III—Soils Report
7.2 ROTATING SCRAPER MECHANISM W/ CENTER FEED AND BAFFLE EQUIPMENT: The rotating
scraper mechanism and other basin features facilitate processing of the liquid and solid
streams to enter and exit the wastewater settling basin. The equipment features follow:
Mechanism Material—Painted Carbon Steel
Drive Motor—0.5 HP for collector drive w/overload device
plus local alarm light, local and remote control, plus run signal to SCADA
Scraper for settled-solids
Center feed-well with baffles
Stationary walkway with handrails
See Exhibit IV—Rotating Scraper Mechanism
7.3 POLISHING BASIN (BASINPOLrsH): The plan for retrofit of the existing waste holding basin
turns it into a polishing basin; the work includes demolition of existing pipe, valves and
pumps and installation of new pipe plus a stainless-steel floating-decanter. The design
utilizes the floating decanter to optimize performance with fixed dimension of the existing
rectangular structure. The floating decanter removes upper-most water throughout the
decant-operation. No water exits the basin when decanter ascends from low-water-level to
the high-water-level, water exits the basin with the decanter at high-water-level and
continues to exit as decanter descends from high-water-level to low-water-level. With the
decanter at low-level in the BASINPOusH, one can remove all of the liquid above low-level
outlets in the BASINsETTLE• The existing structure to serve as the polishing basin has
dimensions as follow:
DIMENSION 32' x 24' x 14'
OPERATIONAL DEPTH 12.0 FT
DECANT DEPTH 8.5 FT
TOP-OF-WALL 34.00 MSL
OVERFLOW-WATER-LEVEL 33.00 MSL
HIGH-LEVEL OUTLET 32.00 MSL
LOW-LEVEL OUTLET 23.50 MSL
BOTTOM 20.00 MSL
7.4 FLOATING-DECANTER: The T-shape, stainless-steel floating-decanter has a 10-inch diameter
and connects to exit pipe with a swivel joint fitting that allows it to ascend and descend
Page 11 of 017

through its range of motion with maximum from horizontal centerline being 60°. See Exhibit
V—Floating Decanter
7.5 MOTORIZED-VALVES: The design calls for five (5) motor-operated valves. Three (3) of these
are on-off valves—one eight-inch, one ten-inch and one twelve-inch. The other two are flow
control valves with with modulating actuators—one eight-inch and one 12-inch valve.
7.6 EFFLUENT AND BACKWASH FLOW METER FLOW-METER: The backwash flow-meter is
measuring backwash wastewater from the filters and softeners as it passes through a common
pipeline to the BASINsETTLE with range of seven different flow-rates between 0 - 1360 GPM.
The associated velocity range through the 8-inch backwash meter is 0—8.7 FPS.
a �
The effluent flow-meter is measuring effluent flow from the BASINsETTLE and BASINPOLisH to
the DISCHARGEouTLET with range of flow-rates from 0 — 1500 GPM and corresponding
velocity range 0—9.6 FPS.
The normal service velocity range for an eight-inch mag-meter is 0 — 39 FPS with
corresponding flow range 0 — 6100 GPM. The preferred service range is 2 — 20 FPS with
corresponding flow range 313 — 3100 GPM. All of the anticipated flows are within the
normal service range for the meter(s). For each and both the backwash meter and effluent
meter, the design selection is an 8-inch mag-meter with transmitter that will communicate
with SCADA. See Exhibit VI—Magnetic Flow-Meter
7.7 DECHLORINATION
7.7A BUILDING, STORAGE TANK PUMPS, AND POWER/CONTROL PANEL: The dechlorination unit
includes a 6'0 x 4'0 pre-fabricated fiberglass building with power, lights, heat and
ventilation. It is to house a electrical distribution panel plus two peristaltic pumps and
chemical storage. The pumps deliver calcium-thiosulfate to a nearby injector mixer to ensure
dechlorination of effluent leaving the premises. See Exhibit VII—Dechlorination
7.7B INJECToR/MIxER: An injector-mixer will be installed on the 12-inch effluent pipeline in a 5'0
diameter vault. The calcium-thiosulfate is injected into the effluent pipeline by the static
mixer. It is made of stainless steel and includes a 1-inch duty inlet connection for injecting
de-chlorination chemical. See Exhibit VII—Dechlorination
7.7C VAULTS: Vaults are provided for various items including the injector/mixer, two (2) magnetic
flow-meters and a check valve. See Exhibit VIII—Bouyancy Calculation— Vaults
7.8 EFFLUENT SAMPLER
The automatic composite effluent sampler is described in the specifications. It will take
samples when flow is present in the effluent line and keep composite sample in a climate
controlled sample storage compartment. The unit is,approximately 44" x 44" with height
equal to 50-inches. See Exhibit VII—Dechlorination
Page 12 of 017

V
7.9A SAND DRYING-BEDS: The total volume of the sand drying beds is approximately equal to
volume of the solids precipitate zone in the BASINsETTLE. As particles continuously settle to
the bottom of the BASINsETTLE,the lowest layers undergo concentration and consolidation; the
mix thickens and it is periodically pumped to the sand-drying beds. The design area of each
bed is 1,060 SF and each will hold 1,590 CF of liquid-solid mix. With six sand-beds the total
volume is 71,359 gallon and approximately equal to 70,492 gallon which is the volume of the
solids-precipitate-zone in the BASINsETTLE.
The normal operation for the BASINsETTLE would have only part of thickened-mix
periodically sent to the sand-drying beds. The operator would have the solids pump station
convey thickened-mix from bottom of the BASINSETTLE to the sand-drying bed and allow time
for solids to settle before directing water through the telescoping valve(s) to the underdrain
pump station for return to the BASINsETTLE. The schedule and details for periodic conveyance
of solids-in-solution to the solids pump station and decanting top-water to the underdrain
pump station to allow dewatering by the sand beds is an activity that requires visual
observation and oversight by the operator.
One operational scenario would pump approximately 17,300 gal /week or 69,300 gal /month
from bottom of the settling basin to the sand drying beds by filling one drying bed every 5
days which equates to filling each of the drying beds once a month. Under this mode-of-
operation, the process could continue each month until ready for disposal.
Based on typical sand-drying bed performance; removal of solids from the sand drying beds
could transpire every six-months with depth of solids equal to approximately 3-inches. In
that case the volume of residual solids for loading and hauling is 1590 CF of residual solids
for disposal every six-months. As with loading the sand-drying beds, the schedule and
details for unloading the sand-drying beds plus hauling and disposal of residual solids is an
activity that requires observation and judgment by the operator.
7.9B SOLIDS PUMP-STATION: The solids-pump flow-rate is relevant to loading from the filter-
backwash wastewater with hydraulic design load equal to 117,400 GAL /DAY. The filter-
backwash wastewater includes 15% of 117,400 or 17,610 GAL/DAY of solids that settle into
the precipitate-solids zone of the BASINsETTLE. However, normal operation would not have
the pump station operate every day. The solids-pump station will periodically pump settled
solids to the sand-drying beds with quantity determined by the operator. Considerations for
the pump-rate include pipe diameter relevant to velocity for conveyance of liquid with
particulate plus effort to minimize labor requirements for operation. The solids-pump design
flow-rate is 250 GPM and its velocity through a six-inch pipe is 2.8 FPS. The flow-rate
allows the operator to pump the volume of one sand bed in 46 minutes or volume of six sand
beds in approximately 41/2 hours. The operator could elect to periodically pump more or less
thickened-mix on any given day; how often and how much pumping is an operational
decision dependent on evaluation of residuals in the precipitate-solids zone and the sand
beds. The solids-pump calculations and rationale for selection of 3.0 horsepower suction-lift
pump are shown in Exhibit IX—Solids Pump Station.
7.9c UNDERDRAIN PUMP-STATION: Similar to the solids pump-station, the under-drain pump flow-
rate is relevant to hydraulic loading equal to 17,610 GAL /DAY liquid-solid mix in the
BASINsETTLE. The underdrain pump station receives filtrate from the underdrain pipes and
Page 13 of 017

intermittently receives top-water from the sand-drying beds. The pump operates whenever
water-level in its wet-well rises to a PUMP-ON set-point and continues until water-level in the
wet-well falls to a PUMP-OFF set-point.
After the sand-drying bed receives flow from the solids pump station, solids settle to bottom
of the mix. At appropriate time, the operator utilizes telescoping valve(s) to allow water into
the underdrain pump station wet-well. The time required for optimal settling of solids in the
sand beds before directing water through the telescoping valve is a determination made based
on visual inspection, experience and judgment by the operator. The under drain-pump design
flow-rate is 150 GPM and its velocity through a 4-inch pipeline is 3.8 FPS. The pump-rate
allows pumping of water from one sand bed in less than 11/2 hour at a time selected by the
operator. The underdrain pump calculations and rationale for selection of 3.5 horsepower
submersible pump are shown in Exhibit X— Underdrain Pump Station.
8.0 HYDRAULICS for PROCESS FLOW
The flow calculations with worksheets and sketches for proposed flows are shown in Exhibit
XI—Hydraulic Calculation and Summary that cover backwash wastewater from the WTP to
the BASINSETTLE, supernatant-effluent flow from the BASINsETTLE to the BASINpoLISH to the
DISCHARGEoUTLET plus residual-solids flow from the BASINSETTLE to the Sand-Beds,
residual-liquid flow from the Sand-Beds to the BASINsETTLE and related optional flows.
The design hydraulic calculations primarily use the Hazen-Williams Formula and continuity
equation with some evaluations using the Manning Formula. Evaluation of various flows
was done with excel worksheets and other calculations.
The majority of process flows under consideration are either pressure flow driven by head
differential or pressure flow driven by pumps; headloss calculations for these flows utilize
the Hazen-Williams Formula as follows:
Hazen-Williams—HL= .002083 {(100 Q/C)' 852/D4 8655] L
HL is headloss (FT-HD), Q is a flow-rate (GPM), C a roughness coefficient-of-friction, D is
diameter of pipe (INCH); L is length of pipe (FT). Typically, C can vary between 100 and
150 depending on type, age and condition of the pipe material.
Evaluation of flow through an existing 18-inch storm-water pipe considers flow with both the
Hazen-Williams Formula and the Manning Formula in concert with the Continuity Equation
as follows:
Manning—V= (1.49 /n) RH2I3 s1/2 and RH=A Pw
V is velocity in feet per second (FPS), n a roughness coefficient-of-friction, RH is the
hydraulic radius equal to cross-section area(SF) of flow divided by the wet perimeter (FT) of
flow; S slope of pipe or channel ft,,/ fth. Typically, n can vary between 0.010 and 0.030 for
pipes, 0.025 and 0.045 for canals and 0.025 and 0.150 for streams. With velocity (V) and
area (A)known one can calculate the flow-rate (Q) with continuity equation.
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Continuity—Q =V A
Q is flow-rate in cubic-feet per second (CFS), V is velocity in feet per second (FPS) and A is
cross-sectional area-of-flow in square feet (SF). Q-GPM is equal to Q-CFS x (7.48 gal/CF) x
(60 sec/min); 1 CFS equals 448.80 GPM.
•
8.1 PRIMARY FLOWS: The proposed backwash wastewater residual process facility includes four
(4) primary flows through pipelines between structures utilizing differential head in
categories that follow:
Q100 backwash flow from distribution system to WTP filters to BASINsETTLE
Q200 backwash flow from distribution system to WTP softeners to BASINsETTLE
Q300 supernatant-effluent flow from BASINsETTLE to BASINPOLisx
Q400 supernatant-effluent flow from BASINsETTLE or BASINPOLrsn to DISCHARGEouTLET
8.2 Q100 AND Q200: Water flowing from the distribution system to the filters for backwash and
filter backwash wastewater flow to the BASINsETTLE is Q100. Similar flow relevant to the
softeners is Q200.
The filter-backwash and softener-regeneration-backwash wastewater from the water
treatment plant flows through a 10-inch pipeline in the yard and beneath the basin floor to a
20-inch pipe for entry into the BASINsETTLE. The tank has a diameter equal to 60-feet and
sidewall height equal to 20.50 vertical feet; flow enters a center-well with 12-foot diameter
and baffle system located at center of the scraper mechanism coinciding with the center of
the BASINSETTLE•
The filter-backwash operational plan for the water treatment plant has water from the
distribution system flow through the backflow prevention device and provide backwash-
water for filters in the WTP. The three (3) operational wastewater flow-rates are 339 GPM,
450 GPM and 1360 GPM. The backwash operation for the filters causes only a minimal
increase in head for backwash wastewater flow to the proposed BASINsETTLE and available
head is adequate for backwash of the filters (and softeners} in the WTP. With flow equal to
1360 GPM, the design calculations show the proposed additional pipeline has a friction
headloss of 4.6 FT-HD and the BASINsETTLE structure increases static head 6 FT-HD. The total
increase in head for the proposal is 10.6 FT-HD.
The available head from the elevated tank at its low water-level (LWL) and high water-level
(HWL) is respectively 110 and 140 FT-HD. In comparison the 7.5 FT increase in head from
current operation appears negligible. However, to confirm adequate available head, design
consideration is given a chosen filter with associated pipe and fittings for flow-path that
could experience the greatest friction headloss — Filter 06 with Qmax equal to 1360 GPM.
The headloss calculation for flow-path through Filter 06 indicates no adverse hydraulic
consequence for Qmax and the flows from on-site point in the distribution system to the
BASINsETTLE•
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The softener-regeneration-backwash operational plan is similar to the filters in regard to
water flow. The softener regeneration-backwash is a four-step process with one being brine-
regeneration and other three being two rinses and one backwash. The four (4) flow-rates
during softener regeneration-backwash process are 66 GPM, 101 GPM, 451 GPM and 471
GPM. All are less than filter backwash flow equal to 1360 GPM.
With the lower flow-rates, headloss is less for softener backwash flows than for greater filter
backwash flows. The outcome of headloss calculation for worst case Filter 06 with flow
equal to 1360 GPM indicates lesser filter and softener backwash flows will not suffer adverse
effect of headloss through flow path to the BASINSETTLE. See Exhibit XII — Hydraulic
Calculation and Summary—Backwash Wastewater from WTP to the Basin Settle
8.3 Q300 /Q300-400 /Q400 \ NORMAL DECANT OPERATION FOR SUPERNATANT- EFFLUENT-
DISCHARGE: Normal operation for the supernatant-effluent-flow process consists of
supernatant flowing from BASINSETTLE to BASINPOLISH to DISCHARGEOUTLET• The process
begins with flow from the BASINSETTLE filling the BASINPOLISH; it continues with un-interrupted
flow from the BASINSETTLE to BASINPOLISH to DISCHARGEOUTLET; and concludes with flow
from the BASINPOLISH draining to the DISCHARGEoUrLET.
One of the hydraulic calculations depicts normal decant operation from BASINSETTLE for
290,000 gallons and 338,000 gallons of supernatant. During the normal decant operation, it
takes about one-half hour for water to reach high-water-level in the BASINPOLISn. Then a
flow control valve limits water-level in the BASINPOLISH such that inflow equals outflow for
the BASINPOLISH. With water level in the BASINPOLISH at 32.0 MSL and elevation of the
DISCHARGEouTLET 22.1 MSL effluent flow is approximately 986 GPM(2.2 CFS).
As water level in the BASINSETTLE descends the flow rate decreases to 0 GPM. With 290,000
gallons of effluent flowing from the BASINSETTLE in approximately six hours, the overall
. average flow-rate equal to 795 GPM (1.8 CFS) and one could decant all 338,000 gallons of
the supernatant from the BASINSETTLE in approximately 8 hours with overall average flow-rate
equal to 693 GPM (1.5 CFS). Both of these flow-rates for normal decant operation are equal
or greater than minimum design average effluent rate of 690 GPM (1.5 CFS). See Exhibit XIII
—Hydraulic Calculation and Summary—Normal Decant Operation
8.4 Q400 \ TEMPORARY BYPASS DECANT OPERATION: The flows to the DISCHARGEOUTLET are
categorized as a series of flows Q400. Q401 is normal decant flow from the BASINPOLISH;
Q402 is temporary bypass flow from the BASINSETTLE.
In addition to normal operation utilizing the BASINPOLISH, the design provides an option for a
temporary by-pass decant operation. The operator can manually open/close valves to utilize
a temporary by-pass that would allow liquid-stream {supernatant-effluent} from the
BASINSETTLE flow directly to the DISCHARGEouTLET. The by-pass is a short-term option available
whenever the BASINPOLISH is out-of-service for cleaning and maintenance. All flow through the
temporary bypass flows through the effluent flow meter, dechlorination injector/mixer and the
composite effluent sampler.
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Whether flow to the DISCHARGEouTLET is from the BASINPOLisu by {normal decant operation}
or directly from the BASINsETTLE {bypass decant operation), design for supernatant-effluent-
discharge flow from the facility is such to meet requirements of the existing NPDES Permit
NC0078131. See Exhibit XIV—Hydraulic Calculation and Summary— Temporary Bypass Decant
Operation
9.0 CLOSING COMMENT
As shown by Exhibit XV — Process Flow Schematic, the proposed flow has backwash
wastewater travel first to the waste settling basin and secondly to the waste polishing basin.
In a manner similar to the existing system, the effluent flow continues through the effluent
flow-meter, dechlorination and sampling before to discharge into McCotter Canal.
The additional electrical load for the proposed rotary scraper mechanism and the two (2)
small pump stations and is minimal compared to entire electrical load for the entire water
treatment plant. See Exhibit XVI—Electrical Load Summary
The current estimate of construction cost is $1,930,000 with project cost including contingency
$2,610,000. See Exhibit XVII—Opinion of Probable Cost
•
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