masterplan finalreport submitted

8/10/2019 MasterPlan FinalReport Submitted

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Roanoke Rapids Sanitary District

Distribution System Master Plan

Project Number 31144-000

July 2010


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan iH&S Project No. 31144-000

EXECUTIVE SUMMARY

This report for the Roanoke Rapids Sanitary District (District) documents the

Distribution System Master Plan and Water Audit. The purpose of this project

was to study past and current water use in the District and predict futuredemands. Using the Districts hydraulic model, we identified current and future

deficiencies and recommended improvements.

The purpose of the water audit was to quantify water losses in the distribution

system. The water audit results showed that the non-revenue water was 32

percent by volume of the total water supplied for the 2007-2008 fiscal year.

Average and maximum day demands in 2008 were 5.13 million gallons per day

(mgd) and 8.08 mgd, respectively. Projected average and maximum day

demands for the year 2030 including new wholesale customers, were 6.9 mgd

and 10.9 mgd, respectively. The design capacity of the existing water treatment

plant (12 mgd) is sufficient to meet the projected demands; however, restrictions

that currently limit the plant to 10 mgd will need to be eliminated.

Our evaluation showed system storage was adequate for existing and future

demands, but firm pump capacity was deficient. We recommend a new 4,400

gpm or 6.3 mgd pump that is efficient in the range of 235 to 255 feet of totaldynamic head.

The Districts hydraulic model was used for assessing existing hydraulic

conditions and for simulating the future conditions. Deficiencies were identified

and the model was used to study alternatives to correct existing problems and

meet future demands.

We further assessed the condition of the distribution system by conducting field

tests and interviews with District staff. Master meter tests revealed that the

master meter at the WTP was under-registering by 7.0 to 9.2 percent which is

approximately 139 million gallons annually. Hydraulic grade line tests showed

several locations where closed valves are likely. C-factors tests showed that the

unlined cast iron pipes in the system have lost about 70 percent of their original


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan iiH&S Project No. 31144-000

capacity due to tuberculation. We used these tests and fire flow tests to update

the model to give more accurate hydraulic results. The model then was used to

estimate available fire flows throughout the entire distribution system. Many

areas were shown to have inadequate fire protection. Using the model and the

Districts mapping records, as well as pipe replacement, pipe repair, and valve

status records, we prioritized pipes in need of rehabilitation and recommended

new pipes to provide adequate fire flows. The annual budget required to

rehabilitate all the unlined cast iron pipes within the next twenty years is

approximately $375,000. Pipe rehabilitation is critical for the District as a means

to improve water quality and hydraulic capacity. Restoring or improving hydraulic

capacity improves fire protection. Pipe rehabilitation is also an important step

toward water conservation as it can greatly reduce water losses by decreasing

leakage and the number of main breaks. Decreasing main breaks reduces the

risk to public safety.

Roanoke Rapids Sanitary District plans to begin selling water to the Town of

Weldon in the near future. Using the hydraulic model, we evaluated pressures,

available fire flows, and water quality assuming three possible meter locations.

Based on this analysis, we recommend supplying the Town of Weldon from the

12-inch water line at the intersection of Country Club Road and US 158.

This report also recommends operational and capital improvements to the

distribution system for improved pressures and water age with the proposed

Weldon connection. Operational improvements can improve water quality.

A capital improvement plan (CIP) was created to prioritize new pipes for fire

protection as well as new transmission mains to improve hydraulic performance.

The first phase of proposed improvements total approximately $1.6 million. To

supply the Town of Weldon with 2 mgd, the next phase of improvements total

$1.07 million. The third phase of improvements to supply projected growth by the

year 2030 total $0.5 million.


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan iiiH&S Project No. 31144-000

TABLE OF CONTENTS

EXECUTIVE SUMMARY ....................................................................................... i

TABLE OF CONTENTS ....................................................................................... iii

TABLE OF FIGURES ........................................................................................... vi

TABLE OF TABLES ............................................................................................. ix

1 Introduction ................................................................................................. 1-1

1.1 Scope of WorkWater System Master Plan ........................................ 1-1

1.2 Scope of Work - Water Audit ................................................................ 1-3

1.3 Background Information ........................................................................ 1-3

1.3.1 Tanks and Pump Stations .............................................................. 1-4

1.3.2 Existing Model Update ................................................................... 1-6

1.4 Purpose ................................................................................................ 1-7

2 Water Requirements ................................................................................... 2-1

2.1 Population Projections .......................................................................... 2-1

2.1.1 Historical Population Records ........................................................ 2-1

2.1.2 District Meter Count........................................................................ 2-1

2.1.3 County Population Projections ....................................................... 2-3

2.1.4 District Population Projections ........................................................ 2-6

2.2 Water Demands .................................................................................... 2-7

2.2.1 Historical Water Production ............................................................ 2-7

2.2.2 Needed Fire Flows ......................................................................... 2-9

2.2.3 Historical Water Billing ................................................................... 2-9

2.2.3.1 Historical Industrial Billing Records ........................................ 2-112.2.3.2 Historical Wholesale Billing Records ..................................... 2-12

2.2.3.3 Historical Domestic Demand.................................................. 2-14

2.2.4 Conservation Measures ............................................................... 2-15

2.2.5 Recent Water Use ........................................................................ 2-16

2.3 Demand Projections and Water Requirements ................................... 2-17

2.3.1 Assumptions for Projections ......................................................... 2-17

2.3.2 Water Requirements Summary .................................................... 2-20

3 Storage and Pump Evaluation .................................................................... 3-1

3.1 Storage Requirements .......................................................................... 3-13.1.1 Elevated Storage ............................................................................ 3-1

3.1.2 Emergency Storage........................................................................ 3-3

3.2 Pumping Evaluation .............................................................................. 3-3

3.2.1 WTP Pump Recommendations ...................................................... 3-4

3.2.2 Becker Pump Station ...................................................................... 3-4

4 Hydraulic Modeling ..................................................................................... 4-1


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan ivH&S Project No. 31144-000

4.1 Modeling Scenarios .............................................................................. 4-1

4.2 Design Criteria ...................................................................................... 4-2

4.2.1 Pressure ......................................................................................... 4-2

4.2.2 Head Loss and Velocities ............................................................... 4-2

4.2.3 Fire Flows ....................................................................................... 4-3

4.2.4 Tank and Pump Performance ........................................................ 4-4

5 Condition Assessment ................................................................................ 5-1

5.1 Field Tests ............................................................................................ 5-1

5.1.1 Master Meter Test .......................................................................... 5-1

5.1.2 Hydraulic Gradient Tests ................................................................ 5-4

5.1.3 C-Factor Tests ............................................................................. 5-10

5.1.4 Fire Flow Tests ............................................................................. 5-14

5.1.4.1 Fire Flow Test Number 5 ....................................................... 5-17

5.1.4.2 Fire Flow Test Number 10 ..................................................... 5-17



5.2 Other Methods of Condition Assessment ........................................... 5-20

5.2.1 Pipe Age and Material .................................................................. 5-20

5.2.2 Main Breaks: Replacement and Repairs ...................................... 5-22

5.2.3 Valve Status ................................................................................. 5-22

5.2.4 Available Fire Flows ..................................................................... 5-26

5.2.5 Pressure ....................................................................................... 5-26

6 Analysis and Recommendations ................................................................. 6-1

6.1.1 Town of Weldon Connection2010 .............................................. 6-1

6.1.1.1 Recommended Weldon Connection ........................................ 6-4

6.1.2 Hydraulics with Future Demands ................................................... 6-5

6.1.2.1 Recommendations to Improve Tank Performance................... 6-7

6.1.2.2 Recommendations to Improve Fire Flows ............................. 6-11

7 Water Quality Analysis ................................................................................ 7-1

8 Infrastructure Renewal ................................................................................ 8-1

8.1 Likelihood of Failure .............................................................................. 8-2

8.1.1 Scoring Likelihood of Failure .......................................................... 8-2

8.2 Consequence of Failure ........................................................................ 8-3

8.2.1 Scoring Consequences .................................................................. 8-4

8.3 Available Fire Flow ............................................................................... 8-5

8.4 Risk ....................................................................................................... 8-5

8.5 Prioritization and Rehabilitation ............................................................ 8-7

9 Capital Improvement and RehabilitaTion Plans .......................................... 9-1


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan vH&S Project No. 31144-000

9.1 Capital Improvement Plan..................................................................... 9-1

9.1.1 Right of Way and Permitting Issues ............................................... 9-7

9.1.2 Funding Opportunities .................................................................... 9-8

9.1.2.1 North Carolina Rural Economic Development Center .............. 9-9

9.1.2.2 NCDENR Public Water Supply Section ................................... 9-9

9.1.2.3 United States Department of Agriculture (USDA) RuralDevelopment Center ............................................................................. 9-10

9.1.2.4 North Carolina Clean Water Management Trust Fund ........... 9-11

9.1.2.5 Funding References .............................................................. 9-11

9.2 Rehabilitation Plan .............................................................................. 9-12

Appendix A Water Audit .................................................................................... a

Appendix B Water Audit Grading Matrix ............................................................ g

Appendix C Manufacturers Pump Curves ......................................................... o


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan viH&S Project No. 31144-000

TABLE OF FIGURES

Figure 1-1: Roanoke Rapids Sanitary District Water Distribution System .......... 1-5

Figure 2-1: Historical County Populations .......................................................... 2-2

Figure 2-2: Historical Meter Count ..................................................................... 2-2

Figure 2-3: Traffic Analysis Zone (TAZ) Population Densities ........................... 2-4

Figure 2-4: Population Growth between 2000 and 2007 (from TAZ Data) ......... 2-5

Figure 2-5: District Average Day Demand and Maximum Day Demand 1998to 2009 ......................................................................................................... 2-8

Figure 2-6: Estimated Needed Fire Flows Based on Zoning ............................ 2-10

Figure 2-7: Historical Water Billed and Produced by RRSD ............................ 2-11

Figure 2-8: Historical Industrial Water Usage .................................................. 2-12

Figure 2-9: Historical Wholesale Water Sold and Contractual AgreementRanges ....................................................................................................... 2-13

Figure 2-10: Recent Per Capita Demand ......................................................... 2-14Figure 2-11: Percentage of Domestic, Wholesale, and Industrial Water

Produced in 2009 ....................................................................................... 2-16

Figure 2-12: Anticipated Population Growth Areas for Residential andCommercial Customers in RRSD ............................................................... 2-18

Figure 2-13: Areas for Industrial Growth .......................................................... 2-19

Figure 2-14: Water Requirements and WTP Capacity ..................................... 2-21

Figure 5-1: Velocity Profile for 20-inch Pipe ....................................................... 5-2

Figure 5-2: Hydraulic Grade Line Test 1, WTP to Rapids Tank ......................... 5-5

Figure 5-3: Hydraulic Grade Line Test 2, WTP to Becker Farm Tank ................ 5-6

Figure 5-4: HGL 1-A and 1-B, Calibration Results ............................................. 5-8

Figure 5-5: Pipes with Possible Closed Valves near 11 thStreet Ball Park ......... 5-9

Figure 5-6: HGL 2, Calibration Results .............................................................. 5-9

Figure 5-7: Hydraulic Grade Line, WTP to Craige Street ................................. 5-12

Figure 5-8: Gaston Road 12-Inch Pipe Fittings Removed in 2008 ................... 5-13

Figure 5-9: Fire Flow Test Locations ................................................................ 5-15

Figure 5-10: Fire Flow Test 5 Results - Pipes with Possible Closed Valve ...... 5-18

Figure 5-11: Fire Flow Test Number 12 ........................................................... 5-19

Figure 5-12: Estimated Pipe Installation Dates ................................................ 5-21

Figure 5-13: Pipes Repaired since 2002 .......................................................... 5-23

Figure 5-14: Pipes Replaced since 2002 ......................................................... 5-24

Figure 5-15: Broken, Leaking, or Hard to Turn ValvesOctober 2009 ........... 5-25

Figure 5-16: Available Fire Flows with Existing System ................................... 5-27

Figure 5-17: Deficient Fire Flows with Existing System ................................... 5-28

Figure 6-1: Possible Town of Weldon Connections ........................................... 6-3


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan viiH&S Project No. 31144-000

Figure 6-2: Pipes with Diameters 12-inch and Larger in Main Pressure Zone ... 6-6

Figure 6-3: Tank Levels Under Varying Supplies to Weldon .............................. 6-7

Figure 6-4: 2030 Peak Hour Pressures without Improvements .......................... 6-8

Figure 6-5: Average Daily Tank Levels with Tank Connection Alternatives ....... 6-9

Figure 6-6: Proposed Route for Improvements to Tank HydraulicConnections................................................................................................ 6-10

Figure 6-7: Deficient Fire Flow on Jackson Street Between 5 thand 6thStreets ........................................................................................................ 6-12

Figure 6-8: Deficient Fire Flows on 8 thand 9thStreets ..................................... 6-13

Figure 6-9: Deficient Fire Flow at Industrial Area at Monroe Street ................. 6-15

Figure 6-10: Fire Flow Improvement near Recommended WeldonConnection ................................................................................................. 6-17

Figure 6-11: Fire Flow Improvements near I-95 Interchange ........................... 6-18

Figure 6-12: Hales Branch Subdivision Deficient Fire Flows ........................... 6-20

Figure 6-13: West End Deficient Fire Flows and RecommendedImprovements ............................................................................................. 6-22

Figure 6-14: Fire Flow Improvements - Ransome Street Area ......................... 6-24

Figure 6-15: Fire Flow ImprovementVirginia Ave ......................................... 6-25

Figure 6-16: Fire Flow ImprovementsMitchell Street .................................... 6-26

Figure 6-17: Fire Flow ImprovementsTown of Gaston ................................. 6-28

Figure 7-1: Existing System Modeled Tank Water Levels with CurrentOperations .................................................................................................... 7-2

Figure 7-2: Existing System Tank Water Age Improvements ............................. 7-3

Figure 7-3: Existing System Tank Levels with Proposed OperationalImprovements ............................................................................................... 7-5

Figure 7-4: Existing System Average Water Age ............................................... 7-7

Figure 7-5: Existing System Average Water Age Using Becker Tank PumpStation with Current Operations .................................................................... 7-8

Figure 7-6: Existing System Average Water Age Using ProposedOperations .................................................................................................. 7-10

Figure 7-7: Existing System Average Water Age Using ProposedOperations with Becker Pump Station ........................................................ 7-11

Figure 7-8: Tank Water Age Improvements Due to Weldon Connection ......... 7-12

Figure 7-9: 2010 System Water Age with Supply to Weldon (Using CurrentOperations without Becker Tank Pump Station) ......................................... 7-13

Figure 7-10: 2010 System Water Age with Supply to Weldon Using ProposedOperations (without Becker Tank Pump Station) ........................................ 7-14

Figure 8-1: Bi-Directional Distribution Matrix of Overall Risk ............................. 8-5

Figure 8-2: Pipe Failure Risk ............................................................................. 8-6

Figure 8-3: Deficient Fire Flow Comparison after Rehabilitation ........................ 8-8


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan viiiH&S Project No. 31144-000

Figure 9-1: Capital Improvements ...................................................................... 9-6

Figure A-1: M36 Water Balance Terms ................................................................. a

Figure A-2: RRSD Water Audit Reporting Worksheet ........................................... b

Figure A-3: July 2007June 2008 RRSD Water Balance .................................... c

Figure A-4: Water Loss Control Planning GuideWater Audit Data ValidityScore ............................................................................................................... e

Figure A-5: Water Loss Control Planning GuideGeneral Guidelines for Settinga Target ILI ....................................................................................................... f


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan ixH&S Project No. 31144-000

TABLE OF TABLES

Table 1-1: Existing Water Distribution System Pumps ....................................... 1-4

Table 1-2: Existing Water Distribution System Tanks ........................................ 1-6

Table 2-1: County Population Projections .......................................................... 2-3

Table 2-2: Projected RRSD Populations ............................................................ 2-6

Table 2-3: District ADD, MDD, and Peaking Factors 1998 to 2008 ................... 2-8

Table 2-4: Projected Populations and Water Demands ................................... 2-21

Table 3-1: Water Distribution System Storage Evaluation ................................. 3-2

Table 3-2: Pump Capacity Evaluation ................................................................ 3-4

Table 4-1: Needed Fire Flows for One- and Two-family Residences .............. 4-3

Table 5-1: Master Meter Test ............................................................................. 5-3

Table 5-2: Hydraulic Grade Line (HGL), Calibration Results ............................. 5-7

Table 5-3: Summary of Loss of Head Tests ..................................................... 5-11

Table 5-4: Fire Flow Test Results .................................................................... 5-16

Table 5-5: Model Calibration with Fire Flow Test Results ................................ 5-16

Table 8-1: Likelihood of Failure Weighting ......................................................... 8-3

Table 8-2: Consequence of Failure Weighting ................................................... 8-4

Table 9-1: Recommended Immediate Improvements (Phase 1) to ProvideAdequate Fire Flow ...................................................................................... 9-2

Table 9-2: Recommended Phase 2 Improvements(to Supply Town of Weldon) ......................................................................... 9-5

Table 9-3: Recommended Phase 3 Improvements(to Supply 2030 Demands) ........................................................................... 9-5

Table 9-4: Rehabilitation Plan .......................................................................... 9-14


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Roanoke Rapids Sanitary DistrictDistribution System Master Plan 1-2H&S Project No. 31144-000

4) Evaluate Storage and Pump Capacities

a) Calculate storage needs and compare with existing tank capacities

b) Determine pump requirements and compare with existing pump capacity

c) Recommend additional storage and pump capacity if needed

5) Model Critical Conditions

a) Add new 12-inch pipe to Gaston and new booster pump station at Becker

Village Tank

b) Review model calibration

c) Evaluate existing conditions

d) Model supply to Weldon

e) Identify improvements for deficient fire flows

f) Model future conditions to check for deficiencies

g) Evaluate alternatives for improvements

h) Run extended period simulations to check pump and tank performance

6) Model Water Quality

a) Develop water age predictions

b) Investigate methods of decreasing water age

c) Evaluate water quality impacts of proposed improvements

7) Develop Capital Improvement Plan

a) Present preliminary recommendations to the District and respond to

review comments

b) Prioritize proposed improvements

c) Organize construction projects and estimate costs

d) Suggest funding opportunities

e) Explore right of way and permit issues

8) Prepare Final Report

a) Write draft report

b) QA/QC and technical review

c) Respond to District review comments and submit final report

d) Deliver hydraulic model to the District as an EPANET data file


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1.2 Scope of Work - Water Audit

1) Test water plants master meter

2) Analyze production records and billing records

3) Prepare audit as described in AWWA Manual M36 using AWWA software4) QA/QC and technical review

5) Present the water audit results to the District

1.3 Background Information

Roanoke Rapids Sanitary District (RRSD or the District) is located along

Interstate 95 in eastern North Carolina about five miles south of the Virginia

border. The District comprises an area of approximately 15.6 square miles. The

Districts water distribution system includes roughly 120 miles of pipe (6-inch

diameter and larger), that supply more than 9,000 water customers. It includes

parts of both Halifax County and Northampton County, all of the City of Roanoke

Rapids and Town of Gaston, and parts of the Town of Weldon.

Raw water is taken from Roanoke Rapids Lake which is an impoundment on the

Roanoke River. Water flows by gravity (or is pumped under certain hydraulic

conditions) to the water treatment plant (WTP) located west of NC Hwy 48 on the

north side of the City of Roanoke Rapids.

The water distribution system was originally built by Rosemary Manufacturing

Company to supply the needs of its cloth and paper mills. RRSD was formed in

1931 and in 1933 took over part of the water distribution system and expanded it.

This included the construction of the 11 thStreet elevated tank. A second elevated

tank was built on Rapids Street in 1951 and, according to a 1963 RRSD water

distribution system study, the distribution system was greatly expanded to the

east, south, and west in 1957. The District expanded to the north in 1977 when a

12-inch transmission main was installed to supply the Town of Gaston. Further

growth in the 1970s and 1980s included construction of the Becker Farm Tank

in 1987.


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Figure 1-1 shows the existing RRSD water distribution system with city and

county boundaries.

1.3.1 Tanks and Pump Stations

The District has four pumps at the WTP as summarized inTable 1-1.A secondpump station located at the Becker Farm Tank was under construction at the

start of this project and is discussed in detail in Chapter3.

The District has two ground storage tanks used as clearwells at the WTP and

four elevated storage tanks located throughout the distribution system as shown

inFigure 1-1 and detailed inTable 1-2.Two additional tanks, the Roanoke-Davie

tank and the I-95 tank are owned by Halifax County. However, these tanks are

directly connected to RRSD pipes and directly influence the Districts operations.

Table 1-1: Existing Water Distribution System Pumps

PumpNo.

PumpName

PumpType

WTPLocation

RatedCapacity

(gpm)

RatedCapacity

(mgd)

TDH(ft)

Power(hp)

1PacoPump

HorizontalSplit Case

InsideFinished

Water Pump

Station

3,000 4.3 250 250

2Fairbanks

MorsePump

HorizontalSplit Case

InsideFinished

Water PumpStation

2,200 3.2 320 250

3Fairbanks

Morse400

VerticalTurbine

OutsideFinished

Water PumpStation

4,400 6.3 273 400

4

Diesel

Pump

Vertical

Turbine

DieselEngine

PumpStation

3,000 4.3 200 630

Note: Another vertical turbine pump (10 mgd, 310 TDH, 700 hp) was removed from service inJune,2009.

Manufacturers pump curves for pumps 1, 2, and 3 are shown in Appendix C.


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Table 1-2: Existing Water Distribution System Tanks

Tank Name Capacity (mg)Overflow

Elevation (ft)Head Range

(ft)

Elevated

Gaston 0.20 302 20Rapids Street 0.50 330 34.5

11th Street 0.50 330 40

Becker 0.50 320 37

Roanoke / Davie* 0.50 325 30

I-95* 0.25 325 26.5

Ground

Rectangular WTP Clearwell 1.25 97 12

Circular WTP Clearwell 2.00 97 12

Notes: * Owned by Halifax County, but directly connected to RRSD system

1.3.2 Existin g Model Update

The existing model was provided by RRSD. The model was updated and

calibrated in 2007 by Highfill Infrastructure Engineering in a report titled Water

Distribution System Model Update and Calibration.

We updated the model by adjusting C-factors, pipe configurations, and minor

losses at the WTP. We also added details showing the placement of pumps and

pipes at the plant. Using aerial photographs and a yard drawing of the WTP, we

arranged the pumps and piping to more clearly represent the system.

Additionally, the 2007 model had very large minor losses for the piping at the

WTP. We updated the minor losses for these pipes to reflect the actual valves

and fittings shown on plant drawings.

The Districts model did not include pipes with diameters smaller than 6 inches,

as pipes that are smaller than 6-inches are often not included in hydraulic models

to save computer memory and calculation time. In most cases, system hydraulics

are not significantly affected by omitting small-diameter piping, however; to better


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calibrate the model, we added some small-diameter pipes (more than 3 miles)

where needed for this project.

The total system demands in the model were also updated based on 2008 billing

and production records. Domestic demand allocation, which is the placement ofeach individual residential and commercial demand based on detailed billing

records, however, was not changed from the existing model.

1.4 Purpose

In this report, we have studied elements regarding the past and current public

health, water use, water quality, and fire protection in the District and have made

predictions about future water demands. Using the Districts hydraulic model, we

identified current and future deficiencies in these elements associated with the

distribution system and recommended corrective improvements.

The purpose of the recommended improvements is to improve water

conservation, water quality, and hydraulic capacity with the ultimate goal of

protecting public health, safety, and the environment.


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2 WATER REQUIREMENTS

This chapter discusses Task 3 of the Water System Master Plan. The goal of

Task 3 was to estimate future water requirements by projecting future population

and water demands. The impacts of conservation were also evaluated. Ameeting with the District was held on September 17, 2009 to review preliminary

projections and discuss fire flow requirements. Final projections were included in

a January 21, 2010 technical memo and are summarized in this chapter.

2.1 Population Projections

As shown inFigure 1-1,the District falls within two North Carolina counties.

Northampton County includes the Town of Gaston in the northern part of the

District. The rest of the District is in Halifax County.

2.1.1 Historic al Popu lation Record s

Determining the population of the District based on census data is complicated

because it falls in two counties and includes all or part of three municipalities

(City of Roanoke Rapids, Town of Gaston, and Town of Weldon as shown in

Figure 1-1).

Historical county populations were relatively unchanged between 1980 and 2008,

as shown inFigure 2-1.

2.1.2 Distr ict Meter Coun t

To obtain a more clear view of the population inside the District boundary, we

reviewed water meter records.

Meter records were examined to identify the trend over the last ten years as

shown inFigure 2-2.The total population of Roanoke Rapids and Gaston, which

cover much of the Districts area, is shown in comparison. These population

estimates were provided by the state demographer.

A linear regression of the meter data shows a trend of 49 new meters per year.

This corresponds to supplying about 120 additional people per year assuming

2.42 people per meter based on the average household size in the City of

Roanoke Rapids from the 2000 census.


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Figure 2-1: Historical County Populations

Figure 2-2: Historical Meter Count

-

10,000

20,000

30,000

40,000

50,000

60,000

70,000

1950 1960 1970 1980 1990 2000 2010 2020

CountyPopulation

Year

Northampton Halifax


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2.1.3 County Popu lat ion Project ions

Projecting the population supplied by the District is also difficult because it falls

within several political and planning boundaries. The state demographer makes

County population projections starting from the last census (2000) as shown in

Table 2-1.Projections for Halifax and Northampton Counties both decrease by a

small percentage over the next twenty years.

Table 2-1: County Population Projections

Populations Halifax County Northampton County

Census 2000 57,374 22,086

2010 Projection 55,053 21,045

2020 Projection 54,232 20,885

2000 to 2020 % Decrease 5.5% 5.4%

Annual % Decrease 0.3% 0.3%

Current municipal populations are estimated by the state demographer, but

municipal projections are not made. Some areas in North Carolina have

projections for Traffic Analysis Zones (TAZ). TAZ data near the District is

available through the Upper Coastal Plain Council of Governments. However, it

only provides year 2000 and current population estimates. Population projections

for the area are not currently available.

TAZ data shows the location of existing population in the District more precisely,

as shown by the population densities inFigure 2-3.TAZ data also includes

population estimates which allow us to note the population growth between 2000

and 2007 as shown inFigure 2-4.


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Figure 2-4: Population Growth between 2000 and 2007 (from TAZ Data)


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2.1.4 Distr ict Popu lation Projection s

Even though the state demographer predicts County populations will decrease,

and municipal populations have declined by approximately 400 people in the past

seven years, the number of water meters in the District has increased over the

same time period (Figure 2-2). This implies that the population supplied by the

District is increasing because the District service area has grown, or people are

moving into areas of the District not within city limits. Part of the increase in the

number of meters could be new meters used for irrigation, but the TAZ

population estimates show an overall increase in population inside the District

service area between 2000 and 2007 (Figure 2-4).

Because of the population growth observed in the TAZ estimates, it is reasonable

to assume that the increase in water meters denotes an increase in housing and

growth in population. The meter trend corresponds to population growth of

approximately 120 people per year, which is the basis forTable 2-2.

Table 2-2: Projected RRSD Populations

Year Population Projection

2008 19,290

2010 19,530

2020 20,710

2030 21,900


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Figure 2-5: District Average Day Demand and Maximum Day Demand 1998to 2009

Table 2-3: District ADD, MDD, and Peaking Factors 1998 to 2008

Year ADD MDD MDD/ADD

1998 4.58 8.40 1.83

1999 4.65 7.59 1.63

2000 5.15 8.49 1.65

2001 4.58 9.19 2.01

2002 4.63 7.59 1.64

2003 4.40 6.30 1.43

2004 4.10 6.15 1.50

2005 5.08 6.88 1.362006 5.34 7.81 1.46

2007 5.53 7.66 1.38

2008 5.13 8.08 1.57

2009 5.18 7.11 1.37

1.831.63

1.65 2.01

1.64

1.43 1.50

1.36

1.46 1.381.57

1.37

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

WaterProduction(mgd)

YearADD MDD MDD/ADD


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Figure 2-5 also shows the ratio of MDD to ADD for each year. This ratio was

especially high in 2001 due to usage by a textile mill. The mill, however, went out

of business in early 2004, so such large peaks are not expected in the future.

Since 2004, the largest ratio of MDD to ADD was 1.57 in 2008. This ratio was

used to estimate future maximum day demands for domestic and wholesale

customers.

2.2.2 Needed Fire Flow s

The water system master plan involves designing pipes and storage tanks to

deliver fire flows. To do this, we estimated needed fire flows throughout the

District. Zoning data from Halifax County, Northampton County, City of Roanoke

Rapids, and Town of Weldon identified the type of land use in an area, and

needed fire flows were estimated based on this information, as shown inFigure

2-6.We assumed 3,500 gpm for industrial zones, 2,500 gpm for commercial

zones, 1,500 for multi-family residential zones, 1,000 gpm for single-family

residential zones, and 750 for agricultural residential zones. These fire flows are

recommended by the International Conference of Building Officials (ICBO, 1997).

2.2.3 Historic al Water Bil l ing

Water billing records have remained relatively constant over the last few years as

shown inFigure 2-7.Production records are shown for comparison. The

prominent decline in water billing starting in about 2000 was due to large

industrial customers curtailing their water use. Water billed has remained steady

since 2003. These steady demands show that population growth was

compensated by conservation. However, also important to note is the difference

between water produced and water billed starting in 2005. This is likely due to

water loss in the system such as leaks or other unbillable water use.


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Figure 2-6: Estimated Needed Fire Flows Based on Zoning


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Figure 2-7: Historical Water Billed and Produced by RRSD

2.2.3.1 Historical Industrial Billing Records

Roanoke Rapids has historically been home to paper and textile mills. Two large

textile mills closed, one in 1997 and another in 2004. There has been a generaldecline in the textile industry in North Carolina in recent years. Free trade

regulations and price competition from developing countries has triggered a

steady relocation of the textile industry from the Carolinas to overseas

production. However, the District still has three major industrial users (one textile,

one paper, and one power supply industry). The historical water consumption of

each large industrial user is shown inFigure 2-8.A steep drop in water used by

two of the industries occurred in 1997.

Industrial maximum day demands were based on the historical billing records

shown inFigure 2-8.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0

50,000

100,000

150,000

200,000

250,000

Jan-97

Jan-98

Jan-99

Jan-00

Jan-01

Jan-02

Jan-03

Jan-04

Jan-05

Jan-06

Jan-07

Jan-08

Jan-09

Jan-10

Jan-11

sage/Production(g

d)

Usage/Production(1000gallonspermonth)

Month-Year

Water Produced Water Billed


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Figure 2-8: Historical Industrial Water Usage

2.2.3.2 Historical Wholesale Billing Records

The District sells water wholesale to Northampton and Halifax Counties. Water

sold since 1990 is shown inFigure 2-9.Water sold wholesale is also commonly

called exported water because it is used in another distribution system.

The District has maintained purchase agreement contracts with Northampton and

Halifax Counties since 1986 and 1981, respectively. Contract limits are shown

onFigure 2-9.Northampton Countys purchase agreement was amended in

2002. Since that time, the average annual volume sold has more than doubled.

The average amount of water purchased by both counties has continued to

slowly increase as shown inFigure 2-9.

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

Jan-9

0

Jun-9

1

Oct-9

2

Mar-9

4

Jul-9

5

Dec-9

6

Apr-9

8

Aug-9

9

Jan-0

1

May-0

2

Oct-0

3

Feb-0

5

Jul-0

6

Nov-0

7

Mar-0

9

Aug-1

0

Dec-1

1

Usage(mgd)

Month-Year

Dominion Co-Gen

Halifax Linen

Kapstone Paper


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Figure 2-9: Historical Wholesale Water Sold and Contractual Agreement Ranges

Current Contract Min

Current Contract Max

Current Contract Min

Current Contract Max

Original Contract Range

Original Contract Range

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Jan-9

0

Jan-9

1

Jan-9

2

Jan-9

3

Jan-9

4

Jan-9

5

Jan-9

6

Jan-9

7

Jan-9

8

Jan-9

9

Jan-0

0

Jan-0

1

Jan-0

2

Jan-0

3

Jan-0

4

Jan-0

5

Jan-0

6

Jan-0

7

Jan-0

8

Jan-0

9

Jan-1

0

Jan-1

1

Jan-1

2

Usage(mgd)

Month-Year

Historical Wholesale Demand

Halifax County

Northampton County


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2.2.3.3 Historical Domestic Demand

We analyzed domestic demand by determining per capita water use. We

calculated per capita use by dividing total domestic use by the population

supplied. We determined the total domestic use from historical billing records.

We estimated the population supplied by multiplying the number of meters by the

Census 2000 official estimate of 2.42 persons per household for the City of

Roanoke Rapids. The calculated gallons per capita per day (gpcd) are shown in

Figure 2-10 for years 2003 to 2008. The per capita demand decreased

significantly in 2004 because of conservation, which is discussed in the next

section. Since 2004, annual per capita demand has averaged 82 gpcd.

The per capita demand shown in the chart includes small commercial users such

as restaurants, car washes, etc. but not non-revenue water.

Figure 2-10: Recent Per Capita Demand

93

8382

80

85

79

70

75

80

85

90

95

2003 2004 2005 2006 2007 2008

GallonsPerCapitaPe

rDay

Year


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2.2.4 Cons ervation Measures

House Bill 1215 was ratified by the North Carolina General Assembly in 2002.

The Bill contains a number of provisions related to water conservation and water

supply planning, motivated by North Carolinas experience with the extreme

drought of 2002 and a heightened awareness to focus more attention on

assuring adequate water supply for future needs.

House Bill 1215 dealt with two types of water conservation. The first type was

conservation necessary on a short-term basis during droughts or other

emergency situations. The second type was year-round water use efficiency. The

bill directed the Department of Environment and Natural Resources (DENR) to

pursue voluntary measures and incentives that increase long-range water useefficiency.

Roanoke Rapids Sanitary District responded by adopting a set of Water Shortage

Regulations in 2003 that addressed both conservation measures necessary on a

short-term basis during droughts and year-round water use efficiency guidelines

for its customers.

Conservation is evident from per capita demand trend.Figure 2-10 shows a clear

decrease in per capita demand between 2003 and 2004.

AsFigure 2-10 shows, per capital demand has stabilized since 2004 varying from

85 to 79 gpd. This report assumes conservation will continue in the future.


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2.2.5 Recen t Water Use

The percentage of water produced for each type of consumption is shown in

Figure 2-11 for 2009.

Figure 2-11: Percentage of Domestic, Wholesale, and Industrial WaterProduced in 2009

Domestic

(Residential and

Commercial

Customers)

29%

Dominion Co-Gen

(Industrial)

3%

Halifax Linen

(Industrial)

2%

Kapstone Paper

(Industrial)

5%

Halifax County

(Wholesale)

31%

Northampton

County (Wholesale)

7%

Unmetered

23%

2009


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2.3 Demand Projections and Water Requirements

After examining historical production and billing trends as described above, this

section describes demand projections and future water requirements.

2.3.1 Ass ump tions for Project ions

In order to project water use, we made assumptions based on our study of

historical trends. Assumptions for projections are summarized below.

a) Domestic water use of 85 gallons per person per day

b) Population increase of approximately 120 people per year based on metertrend

c) Domestic growth areas are shown inFigure 2-12,based on discussions withDistrict staff

d) Halifax County maximum day demand for the design year is equal to theircurrent contractual maximum.

e) Northampton County maximum day demand increases to 0.75 mgd by designyear

f) The Town of Weldon will receive a maximum of 2.0 mgd by 2010 and willincrease its supply from the District by 10% by the design year

g) For domestic, industrial, and wholesale demand, a maximum day peakingfactor of 1.57 was used

h) Industrial consumption will increase by 10 percent by the design year for each

of the three existing industrial customers

i) Water demand for new industries will increase the total industrial demand by10 percent by the design year

j) Industrial growth will occur in areas outside Roanoke Rapids city limits, butinside the District boundary as shown inFigure 2-13.This was based ondiscussions with District staff

k) Peak hour demand multiplier is 1.3 for domestic, wholesale, and industrialwater users based on diurnal measurements made for the Districts InitialDistribution System Evaluation in 2007

l) Design fire flow is 3,500 gpm, which is equivalent to 5.04 mgd


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Figure 2-12: Anticipated Population Growth Areas for Residential andCommercial Customers in RRSD


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Figure 2-13: Areas for Industrial Growth


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2.3.2 Water Requirements Summary

A summary of projected water requirements is shown inTable 2-4.

A water audit (Appendix A) was part of the Water Distribution System Master

Plan. Because the water audit revealed a notable amount of non-revenue water,a percentage for water loss was added to estimate total system demands. For

future years, we assumed that the percent of water loss would decrease over

time as infrastructure is renewed or repaired.

Maximum day plus fire was the critical (largest) design flow for RRSD (15.9 mgd

in 2030). Maximum day demands by 2030, 10.9 mgd, do not exceed the water

treatment plants rated capacity of 12.5 mgd. However, District staff indicates that

the plant cannot currently achieve the rated capacity and estimate a maximum

treatment rate of 10 mgd.

The limitations on plant capacity need to be addressed before the maximum day

supply to the Town of Weldon can begin as shown inFigure 2-14. Figure 2-14

shows historical and predicted average and maximum day demands compared to

plant capacity.


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Table 2-4: Projected Populations and Water Demands

Water Requirement 2010 2020 2030

Population Supplied 19,530 20,710 21,900

Domestic Consumption (mgd) 1.66 1.76 1.86

Industrial Use (mgd) 0.55 0.60 0.65

Wholesale Demand (mgd) 3.10 3.44 3.78

Non-Revenue Water (%) 20% 15% 10%

Non-Revenue Water (mgd) 1.06 0.87 0.63

Total Average Day Demand (mgd) 6.37 6.67 6.92

Maximum Day Demand (mgd) 10.0 10.5 10.9

Maximum Day Plus Fire (mgd) 15.0 15.5 15.9

Peak Hour Demand (mgd) 13.0 13.7 14.2

Note: See Section 3.1 for water requirement assumptions

Figure 2-14: Water Requirements and WTP Capacity

WTP Rated

Capacity

Average Day

Historical

Maximum Day

Historical

WTP ExistingEstimated Capacity

Predicted

Average Day

Predicted

Maximum Day

0

2

4

6

8

10

12

14

1995 2000 2005 2010 2015 2020 2025 2030

WaterProduction(mgd)

Year

Begin to Export

Water to Town

of Weldon


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3 STORAGE AND PUMP EVALUATION

Two important components of RRSDs water distribution system are storage and

pumping. The storage and pumping capacities must be adequate for existing and

future water requirements. Storage and pumping capacities were evaluated forexisting and future conditions as described in this chapter.

3.1 Storage Requirements

Storage serves three purposes in a water system: it supplements production

during fires, equalizes demand on a daily basis, and supplies the system during

emergencies (for a limited period of time).

3.1.1 Elevated Sto rage

Fire storage provides fire flows while the WTP supplies maximum day demand.

For the worse case, we assumed a fire flow of 3,500 gpm for which the American

Water Works Association (AWWA) recommends a design duration of 3 hours.

Assuming a 3,500 gpm fire flow for 3 hours, the corresponding volume is 0.63

million gallons for the fire storage requirement.

Equalizing storage allows water to be pumped at a constant rate. Storage

depletes when demand is above average and fills when below average. The

amount of storage required depends on how much the demand varies. The

variation in demand over a 24-hour period is called the diurnal curve. A diurnal

curve was previously calculated from tank level data in a 2007 report titled

Water Distribution System Model Update and Calibration by Highfill

Infrastructure Engineering. This diurnal curve was examined, and the calculated

equalizing requirement was 8 percent of the total water used in a day. The

equalizing requirement is therefore 0.85 mg currently, 0.90 mg for 2020 and 0.94

mg for 2030 as shown in Table 3-1.

Equalizing storage and fire storage are usually combined to evaluate elevated

storage. The elevated storage requirement was compared with existing elevated

storage capacity to determine if more storage is needed.


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Table 3-1: Water Distribution System Storage Evaluation

Units 2008 2010 2020 2030

Equalizing Storage

Percent from diurnal curve 8% 8% 8% 8%

Maximum Day mgd 8.08 10.03 10.51 10.90

Storage Needed mg 0.64 0.79 0.83 0.86

Fire Storage

Design Fire Flow gpm 3,500 3,500 3,500 3,500

Duration hrs 3 3 3 3


Emergency Storage

Percent to Meet State Regulations 50% 50% 50% 50%

Average Day mgd 5.13 6.37 6.67 6.92


Total Storage Requirement

Elevated Storage mg 1.27 1.42 1.46 1.49Emergency Storage mg 2.57 3.18 3.34 3.46

Existing Storage Capacity

Gaston mg 0.15*

Rapids Street mg 0.50

11th Street mg 0.50

Becker mg 0.50

Rectangular WTP clearwell mg 1.25 (0)

Circular WTP clearwell mg 2.00

Roanoke / Davie mg 0.50

I-95 mg 0.25

Total mg 5.65 (4.4)

Elevated Storage Summary

Required (Fire plus Equalizing) mg 1.27 1.42 1.46 1.49

Existing Capacity mg 1.65 1.65 1.65 1.65

Surplus Storage mg 0.38 0.23 0.19 0.16

Emergency Storage Summary

Required (by State) mg 2.6 3.2 3.3 3.5

Existing Capacity mg 5.65 5.65 5.65 (4.4) 5.65 (4.4)

Surplus Storage mg 3.08 2.47 2.31 (1.1) 2.19 (0.9)

Notes:WTP clearwells and County-owned tanks were not relied upon for equalizing or fire storage,

but could be used in an emergency. The District is considering removing the rectangularWTP clearwell from operation due to its aging condition. Surplus emergency storagewould be 0.9 mg by 2030 in this case, as shown above in parentheses.

* Gaston tank rated at 200,000 gallons but operating capacity closer to 0.15 mg


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As shown in Table 3-1, there is sufficient elevated storage both now and for 2030

(surplus of 0.16 mg and 2.19 mg, respectively).

3.1.2 Emergency Storage

Emergency storage supplies water when the normal sources are interrupted.Emergency storage requirements are typically compared to the total elevated

and ground storage available in a system.

According to the Rules of Governing Public Water System published by the North

Carolina Department of the Environment, Health and Natural Resources,

combined elevated and ground storage of finished water shall be a minimum of

one-half a days supply of the average annual daily demand. This would be 3.18

mg for 2010 and 3.46 mg for 2030 as shown in Table 3-1.

Existing elevated and ground storage is 5.65 mg in total, or 4.4 mg if the

rectangular clearwell is taken out of service. In either case, there is sufficient

emergency storage currently and for 2030 projected demands. Therefore, RRSD

meets the current and the future requirements for emergency storage.

3.2 Pumping Evaluation

The firm capacity of the pumps at the water plant must meet maximum day

demands.Table 3-2 appears to show the existing pumps are adequate for

current and future conditions. Firm capacity is defined as the rated capacity with

the largest pump out of service (the Fairbanks Morse 400 hp pump in this case).

All pumps need to be taken offline occasionally for repairs and/or maintenance,

which means the remaining pumps in service must have enough capacity to

meet demand.

However, the diesel pump is not intended for regular use but as an emergency

pump, should power be lost at the WTP. Excluding the diesel pump, the firm

capacity is only 7.5 mgd, which is deficient.


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Table 3-2: Pump Capacity Evaluation

million gallons per day (mgd) 2008 2010 2020 2030

Maximum Day Demand 8.08 10.03 10.51 10.90

Total Pump Capacity 17.4 17.4 17.4 17.4

Firm Pump Capacity 11.1 11.1 11.1 11.1

Pump Capacity Deficit - - - -

*Firm Pump CapacityNo Diesel 7.5 7.5 7.5 7.5

*Pump Capacity DeficitNo Diesel 0.60 2.5 3.0 3.4

*Assumes: Diesel pump (No. 4) is for emergency and short-term use only. Both inside pumpstation pumps cannot be operating at the same time.

3.2.1 WTP Pump Recomm endat ions

We recommend a new pump with the same rated flow as Pump 3 (4,400 gpm or

6.34 mgd). The required head of a new pump was estimated by running the

model under various demand conditions. Based on these results, we recommend

a pump that is efficient in the range of 235 to 255 feet of total dynamic head.

We also recommend testing Pump 2 (inside Fairbanks Morse) to determine the

wire-to-water efficiency for evaluating its replacement. This pump is nearly 60

years old and was designed for a TDH nearly 100 feet higher than existing

conditions. This pump may be operating at low efficiencies. Measuring its

efficiency would allow calculation of the time it would take to recover replacement

costs through reduced power costs.

3.2.2 Beck er Pump Station

There is a new duplex pump station (completed November 2009) at the Becker

Tank. The pumps were originally designed to pump 1,050 gpm at 70 TDH, but

during factory testing each was able to pump 1,400 gpm. However; variable

frequency drives (VFDs) will automatically limit flow to 1,200 gpm.

There are two main purposes for the Becker Pump station. The main goal is to

pull water out of the Becker Tank, because this tank is 10 feet lower than the

Rapids Street and 11thStreet Tanks, and the altitude valve closes to prevent


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overflows. Consequently, the Becker Farms tank historically has gone for weeks

with little change in water level (little tank turnover). Inadequate tank turnover can

cause water quality problems. The second objective of this pump station is to

help deliver water south to Halifax County if demands rise with a new industrial

park currently under development.

District staff controls the pump station at the WTP, at the operator's discretion,

with flow rate as an adjustable parameter. VFDs are programmed to allow pumps

to run between 350 and 1200 gpm. There will be an automatic shut-off when the

tank level drops to half full, thus maintaining a reserve for fire protection. The

altitude valve on Becker tank can be controlled remotely enabling the operators

to postpone filling the tank until system demands have dropped.


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4 HYDRAULIC MODELING

The hydraulic model was used for condition assessment by showing existing

hydraulic conditions, and for examining the future conditions. Deficiencies were

identified and the model was used to design improvements by studyingalternatives to correct existing problems and meet future demands. This chapter

explains the way in which the model was used and the criteria for assessing

modeling results. Results and recommendations are presented in the following

chapters.

4.1 Modeling Scenarios

First, we modeled existing conditions for average day, maximum day, and peak

hour demands to identify existing problems. Future demand scenario pressure

problems and fire flow deficiencies were identified and alternatives were tested in

the model to find the most efficient improvements that met design criteria. Peak

hourly demands were used to evaluate system pressures because these

demands represent the worst-case condition, with respect to pressure, that

customers would experience. Maximum day demand plus fire demands could

result in lower pressures, but fires are less common and the locations that would

experience low pressure are highly dependent on the location and size of the fire.Average day conditions were used to examine water age as a surrogate for water

quality. Average day demand conditions were used to evaluate water age

because these demands represent the worst-case condition for water quality as

velocities are lower and therefore water age higher.

This hydraulic model used two types of simulations. The first type, steady state,

analyzed one moment in time. Steady state simulations were used to help size

pipes and pumps. The second type, extended period simulations, evaluate pumpand tank performance over time as well as water age.


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4.2 Design Criteria

We compared the models predicted performance with design criteria for :

1. Pressures at the nodes

2. Head losses and velocities in the pipes

3. Fire flows

4. Tank and pump performance

4.2.1 Pressure

There are generally three design criteria for pressures: maximum pressure,

minimum pressure during peak hour, and minimum pressure during a fire flow.

Generally, maximum pressures should be no greater than 150 psi which is the

nominal pressure rating of some distribution system piping and fittings. Some

utilities require pressure-reducing valves on the service lines to individual

customers when pressures exceed 80 psi.

The minimum pressure during peak hour refers to minimum pressure at

customers taps during the highest demand. This value is typically in the range of

30-50 psi and ensures that there is adequate pressure to second story fixtures.

The minimum pressure during fire flows, as recommended by the National Fire

Protection Association (NFPA), is 20 psi. This pressure is the minimum pressure

anywhere in the distribution system. The value of 20 psi is used because it

prevents backflow or groundwater contamination and provides head for

overcoming the friction losses in the hydrant branch, hydrant, and suction hoses

to the pumper truck during a fire.

4.2.2 Head Lo ss and Velocit ies

In general, a distribution system is considered to be deficient if the following

conditions are predicted:

1. Velocities greater than 5 ft/sec

2. Head losses greater than 5 ft/1,000 ft (about 10 psi per mile)


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When designing larger pipes (16-inch or greater) the goal is to keep head losses

less than 2 ft/1,000 feet (about 5 psi per mile).

Head losses and velocities exceeding the criteria can indicate excessive loss of

energy, which might require additional pumping. They are not absolute limits,because even though the operating costs can be substantial over the life of the

pipe, it must be compared to the capital cost of new pipes to correct the deficient

piping. It is important to note that as velocity increases, pipe head losses

increase exponentially. As velocities approach 10 ft/sec, the potential exists for

other problems, such as water hammer, to emerge.

4.2.3 Fire Flow s

Table 4-1 summarizes needed fire flows for one-and two-family residences as

recommended in the AWWA Manual of Practice on Distribution System

Requirements for Fire Protection.

Table 4-1: Needed Fire Flows for One- and Two-family Residences

Distance Between Buildings (ft) Needed Fire Flow (gpm)

More than 100 500

31-100 750

11-30 1,000

Less than 11 1,400

At 20 psi

In the model, nodes on pipes with diameters less than 6 inches were not

considered for fire flow analysis because fire hydrants are only allowed on

pipelines that are 6-inches or larger, according to the Rules Governing Public

Water Systems by the NC Department of Environment and Natural Resources.


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4.2.4 Tank and Pump Performance

Elevated storage tanks supply water for short periods of peak demand and

should remain at least half full to maintain a reserve for fire protection or other

emergencies.

Tanks by themselves do not produce water to supply a distribution system

because the net flow over 24 hours is zero. The 24-hour average demand must

be supplied by the WTP and purchased supplies. WTP capacity plus purchased

water must be equal to or greater than the maximum day demand of a water

distribution system.

Pump operations must ensure that the tanks cycle (fill and empty) enough to

prevent excessive water age and thus ensure good water quality. General criteriafor pump operations is to allow the tank levels to drop as much as possible while

still providing adequate fire flow and emergency storage. The larger the range in

water level for each tank, the lower water age will be.


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5 CONDITION ASSESSMENT

The condition of the distribution system was assessed in three ways. The first

was by performing field tests. The second was by examining RRSD records and

interviewing District staff to deduce the age and condition of the pipes. The thirdwas running the hydraulic model under existing demands and operations to

determine pressures and available fire flows system-wide.

5.1 Field Tests

Field tests help show the general condition of the existing piping system. These

tests serve three purposes:

1. Produce input data needed for the hydraulic model

2. Obtain information for calibrating the model

3. Check for unusual conditions such as closed valves or mapping errors

Four types of tests were performed for this master plan. They included a master

meter test, hydraulic gradient tests, C-factor or loss of head tests, and fire flow

tests. These tests were used to further validate the model, which was last

calibrated in 2007, and check for any unusual conditions as discussed below.

5.1.1 Master Meter TestA meter test compares master meter registration to flow rates measured by

another instrument. Our meter tests compare meter registration to pitot tube

measurements of the flow in a pipe, rather than simply checking electronic

calibration of a transducer. Many meters, including the D istricts master meter at

the WTP, have a primary device (a Venturi tube in this case), and a secondary

element, such as a differential pressure transducer, which converts the physical

output to an electronic signal. An inaccurate primary device causes meter error

even if the secondary element is calibrated correctly.

The master meter test was conducted on September 15, 2009. It compared the

meter totalizer for the 20-inch pipe leaving the WTP to pitometer flow

measurements. Pitometers are pitot tubes that are inserted into a pipe through a

corporation tap which the District installed prior to testing. Flowing water


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produced a differential pressure between the upstream and downstream orifices

of the pitot tube. Water velocities were calculated from the measured differential

pressures. The average velocity was determined by conducting a velocity profile

along the vertical diameter of the 20-inch pipe, as shown byFigure 5-1. The

profile has a typical bullet shape for velocities within a pipe. The inside diameter

was measured with a pipe caliper. The area of the pipe was calculated from the

diameter, and the flow rate was determined by multiplying the area of the pipe by

the average velocity.

Figure 5-1: Velocity Profile for 20-inch Pipe

Table 5-1 shows the results of the meter test. The 20-inch meter was tested for

five different flow rates. The different flow rates were achieved by running

various pump combinations.

0

2

4

6

8

10

12

14

16

18

20

0.5 1.5 2.5 3.5 4.5

Distanc

efromBottom-inches

Velocity - feet per second

Average Maximum Minimum


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Table 5-1: Master Meter Test

Description Results

Location Roanoke Rapids WTP

Name BIF Series 41969Meter Size 20 X 13.318Multiplier 1,000,000

Gauging Point DataPipe Size - inches 20

Inside Diameter - inches 20.250Velocity Factor 0.706

Test Date - 2009 September 15

Test Number: 1

2 3 4 5Totalizer Registration- gal 0.062 0.078 0.145 0.087 0.117*Elapsed Time - minutes 29.71 29.97 30.43 16.05 19.86Pump(s) In Use:

No. 1: PACO X X XNo. 2: Inside FM XNo. 3: Outside 400 HP X X X

Pitometer Flow - mgd 2.87 4.03 7.44 8.57 9.35Master Meter Flow - mgd 3.01 3.75 6.86 7.81 8.48

Totalizer Error 4.6% -7.0% -7.8% -8.9% -9.2%

Notes: * Control valve to Gaston closed during test. Negative sign indicates meter is under-registering flow

Flow outside design range of meter. Test disregarded.

The lowest flow showed the meter was over-registering. This flow was outside

the design range of the meter, so the result was disregarded. The next four flow

rates consistently indicated the meter was under-registering between 7.0% and

9.2%. This is a significant inaccuracy.

We recommend contacting the master meter manufacturer or supplier to adjust

the primary and/or secondary metering element to agree with measured flows.

We also recommend that all system master meters have their primary devices

tested annually to verify their performance.


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Remaining field tests and the water audit (Appendix A) accounted for the under-

registering meter when flow rates were used in calculations.

5.1.2 Hydrau l ic Gradient Tests

Hydraulic gradient is the change in hydraulic grade line (HGL) with distance.The HGL is the ground elevation plus water pressure expressed in feet.

Hydraulic gradient tests consist of simultaneous flow and pressure

measurements along trunk mains between the water plant and tanks. Plotting

measured HGLs versus distance shows where head loss occurs along

important trunk mains. Comparing measured HGLs and flows with model

predictions is a method of calibrating the model.

Two hydraulic gradient tests were performed for this study. Test 1 traced the

hydraulic gradient from the WTP to Rapids Street Tank. The test also

measured HGLs at two sites along the 20-inch pipe in Henry Street. The test

was conducted for two conditions: with a large flow from the water plant

(HGL 1-A) and with a fire hydrant flowing at 11 thStreet (HGL 1-B) as shown in

Figure 5-2.Test 2 traced the hydraulic gradient from the WTP to Becker Farm

Tank with large flow from the water plant as shown inFigure 5-3.

TheTable 5-2 shows the results from the HGL field tests compared to the

model results. The locations of the measurements are shown inFigure 5-2

andFigure 5-3 for reference.

To match the model to the measurements for HGL 1, we had to assume

several valves were closed as shown inFigure 5-4.For HGL 1-A, the model

calibration indicates that a 12-inch valve is closed on 8 thStreet between

Wilson Street and Rapids Street Tank. Valve status records indicate a broken

valve in that area. Due to the age of the system, valves that are broken in the

closed position are not surprising. We recommend locating the closed valve

and repairing or replacing it as soon as possible to improve fire flow

availability.


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Figure 5-2: Hydraulic Grade Line Test 1, WTP to Rapids Tank


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Figure 5-3: Hydraulic Grade Line Test 2, WTP to Becker Farm Tank


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Table 5-2: Hydraulic Grade Line (HGL), Calibration Results

Location Distance (ft)MeasuredHGL (ft)

CalibratedModel HGL (ft)

HGL 1-A

WTP - 350 352

Henry Street & 1st Street 3,500 345 345Franklin Street & 5th Street 6,400 340 340

Bolling Road & Wilson Street 8,300 340 340

Rapids Street Tank 10,500 327 327

HGL 1-B

WTP - 335 333

Henry Street & 1st Street 3,500 330 330

Franklin Street & 5th Street 6,400 327 327

Henry Street & 8th Street 8,800 325 327

Franklin Street & 11th Street 11,100 304 305

HGL 2

WTP - 354 353311 Carolina Street 5,300 339 339

Carolina Street & 8tStreet 8,200 335 335

11th Street Tank 10,800 322 322Kelly Street & Long Circle 15,600 313 312

Old Farm Road 20,900 306 306

Becker Farm Tank 22,100 305 305

Notes

The Gaston control valve was open during all HGL tests. Pumps 1 and 3 operating. Measured = 8.49 mgd, model = 8.37 mgd (1.4 % difference).Pump 3 operating, hydrant flow on 11thStreet was 460 gpm (measured and model)Pumps 1 and 3 operating. Measured = 8.68 mgd, model = 8.57mgd (1.3% difference).

For HGL 1-B, the model calibration indicates that two valves are closed near

the location of the flowing hydrant on 11thStreet (near the ball park).Figure

5-5 shows the most likely locations of these closed valves. Again, we

recommend locating the closed valves and repairing or replacing them as

soon as possible to improve fire flow availability.

For HGL 2, only minor modifications to the modelsroughness coefficients

and elevations were made to calibrate the predicted HGLs with the field

measurements. Results are shown inTable 5-2 andFigure 5-6.Notable is the

steep loss in head between 8thStreet and 11thStreet. This loss is due to a

restriction in the system as water flows through 16-inch pipes until it reaches

10thStreet where the pipe sizes reduce to 8-inches until reaching the 11th

Street Tank.


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Figure 5-5: Pipes with Possible Closed Valves near 11 thStreet Ball Park

Figure 5-6: HGL 2, Calibration Results

WTP

11thStreet

Tank

KellySt&Long

Circle

BeckerFarmTank

280

290

300

310

320

330

340

350

360

0 5,000 10,000 15,000 20,000 25,000

HGL-feet

Distance - feet

Calibrated Model Measured


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District staff notes that the Roanoke Rapids Fire Department, approximately ten

years ago, had inadequate fire flow in the area during a fire at the Heilig-Meyers

Furniture Store, likely due to the hydraulic constriction.

5.1.3 C-Facto r TestsC-factor tests, also called loss of head tests, determine the friction coefficient C

in the Hazen-Williams equation. This equation relates head loss to the flow in a

pipe with the coefficient, a smoothness indicator. A typical coefficient of a new

pipe is 140. Computer models need accurate C-factor data to simulate hydraulic

performance.

Each test consisted of measuring flow, head loss and pipe length, and calculating

the coefficient for a known pipe diameter. Flow was measured using a hydrant

pitot blade or a meter at the water plant. Head loss was measured using digital

pressure gauges connected to hydrants on the upstream and downstream ends

of the test section. The length of the test section was measured using a

measuring wheel or scaled from the hydraulic model

Table 5-3 shows the results of the loss of head tests. Not surprisingly for an

unlined pipe installed before 1935, the C factor along Roanoke Avenue was low

(43) indicating the interior of the pipe is tuberculated and head losses are high.

The pipe segments tested along 2ndStreet and 10thStreet were installed around

1947 based on available maps of the distribution system and hydrant dates.

Lined pipe did not become predominant for most water distribution systems until

after World War II. Although these pipes were installed around 1947, shortly after

World War II ended, the results of the C-factor test make it clear that the two test

segments were unlined cast iron based on their low C-factors (Table 5-3). The

low C-factor indicates significant tuberculation and high head losses. We

assumed other pipes installed in 1947 were also unlined.

We attempted to conduct a C-factor test on one of the pipes near the WTP. This

was not possible because the valves in the yard of the WTP were inoperable.

Therefore, the test was cancelled.


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Figure 5-7: Hydraulic Grade Line, WTP to Craige Street

This pipe is most likely lined ductile iron and a C-factor of at least 120 was

expected. A photograph of 45-degree bend removed in 2008 confirms that the

interior of the pipe is fairly smooth as shown inFigure 5-8. Figure 5-8,however,also shows an expansion coupling from the same pipeline removed in the same

year. The coupling was highly tuberculated indicating the C factor could be much

lower. The pipe condition was inconsistent from these photographs. We

recommend investigating this section of pipe by installing taps for pressure and

flow measurements.

GastonMeter

SouthSideofBridge

HydrantonCraige

295

300

305

310

315

320

325

330

335

340

0 1,000 2,000 3,000 4,000 5,000 6,000

Head(elevation+pressurein

feet)

Distrance from Gaston Meter (ft)

Model

Measured (+)

Measured

Measured (-)

Calculated C-factor

ranges from 13 to 44

Calculated C-factor ranges

from 33 to 113

Assumed C-factor of 120


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Figure 5-8: Gaston Road 12-Inch Pipe Fittings Removed in 2008

45-Degree Bend

Expansion Coupling


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5.1.4 Fire Flow Tests

Fire flow tests show the strengths and weaknesses of the system at particular

test locations and the test measurements can be used to calibrate models.

Figure 5-9 shows the location of fire flow tests we performed for the District.

A fire flow test consists of measuring the static pressure with the hydrants closed,

then opening a nearby hydrant and measuring the residual pressure and the flow

rate.

Table 5-4 summarizes the fire flow test results. The table shows the location of

the test, and static and residual pressures of the test hydrant. The table also

shows the flow during the test and the available flow at 20 psi, which is the

lowest acceptable pressure in a water system.

Estimated needed fire flows, which depend on land use (types and sizes of

buildings) are shown inFigure 2-6 and are also included inTable 5-4. Only one

location was deficient because the needed flow exceeded the available flow.

Improvements to reinforce these areas are discussed in a later chapter.

The fire flow tests were also used for further model calibration as shown in Table

5-5.Minor model adjustments were made to elevations and C-factors in most

cases. All fire flow tests were within 3 psi of model predictions except for one.Fire flow tests which indicated unexpected conditions are discussed in detail

below.


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Figure 5-9: Fi

masterplan finalreport submitted

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