WESTERN CARY WATER STORAGE TANK

Town of Cary

Preliminary Engineering Report

Progress MeetingJune 8, 2015

Agenda

• Preliminary Engineering Report Recap– Hydraulic Model Evaluation– Western Cary Booster Pump Station– Western Cary Elevated Storage Tank– Water Main Improvements– Pressure Zone Boundary Connections– Opinion of Probable Cost

• Next Steps– Finalize Preliminary Engineering Report– Begin Design

WESTERN CARYHYDRAULIC MODEL EVALUATION

Western Pressure Zone Boundary Revisions– Reconfigure 30- and 42-inch

transmission mains from Cary/Apex Water Treatment Facility to both feed CPZ

– Remove Davis Drive PRV– Install new PRV on 30-inch main

along Hwy 55 north of Jenks Rd– Open valves along current WPZ/CPZ

boundary– Modify or abandon existing

connections along new pressure zone boundary

– Install 12” WL from Hwy 55 to Roberts Rd

Waterline Improvement Phasing– 2016

• CPZ-1 (in design)• WPZ-12 (20”) north of Western Cary Tank to existing

12”• WPZ-23 (12/16”) Green Level West (developer driven)• Nwy 55 north of Lewey Dr (12”)• Kit Creek Road (12”)• Roberts Road (12”)

– 2025• WPZ-18 (12”) White Oak Church (developer driven)• WPZ-22 (12”) Green Level Church/Roberts Rd

(developer driven)• Parallel 20” on Hortons Creek Rd

– Build-Out• Morrisville Parkway (12/16”)• WPZ-14 (12”) McCrimmon Pkwy• WPZ-19 (16”) Parallel on Green Level Church Rd• WPZ-16 (16”) Carpenter Fire Station Rd gap

Emergency Scenarios

1. 36” CPZ Break (east of Hwy 55)– Can keep CPZ EST from draining empty and maintain pressures through build-out

2. 42” Jenks Rd Break– 2016: Can keep CPZ EST from draining empty and maintain pressures– 2025: CPZ EST empty in approximately 20 hours– Build-out: CPZ EST empty within first few hours

3. Carpenter Tank Out-of-Service– Jenks Rd & Hwy 55 PRV open during peak hour demands to avoid pressure

<50 psi along Hwy 55

4. 42” Jenks Rd Break and Carpenter Tank Out-of-Service– Pump continuously from WPZ to CPZ via Western Cary ground storage tank– 2016 & 2025: Can keep CPZ elevated tanks from draining empty and

maintain pressures (ADD)– Build-out: CPZ EST’s empty in approximately 72 hours (ADD)

WPZ Storage Requirements by Planning Period

*Chatham demands included only for build-out

Storage Factor 2016 2025 Build-out

Equalization 20% of MDD 0.7 1.3 2.4

Fire Flow 3,500 gpm x 3 hours 0.6 0.6 0.6

Emergency* 40% of Summer ADD 1.1 1.9 3.6

Total Storage Required 2.4 3.8 6.6

• The Town currently has 2.0 MG of storage in the Carpenter EST

• In order to meet future demands, the Town decided that the Western Cary EST should be 2.0 MG in volume

Western Cary Tank Improvements

• New 2 MG Elevated Storage Tank– Composite and Hydropillar to be bid

• New Booster Pump Station– Engineer design with pre-manufactured concrete building

• New Waterline– Hortons Creek Road– Good Hope Church Road– Roberts Road

• Pressure Zone Boundary Connections– Modify 3 connections for emergency use– Remove 12 existing connections

WESTERN CARYELEVATED STORAGE TANK

Western Cary Elevated Storage Tank

• Western Cary EST will store equalization, fire flow, and emergency water for WPZ and well as supplement peak demands in the CPZ

• Three infrastructure improvements were considered:– Elevated storage tank– Elevated and ground storage tank– Combined elevated and ground storage tank

• The Town decided to move forward with the design of an elevated storage tank

Western Cary Elevated Storage Tank Style

Style CostMulti-Leg $5.4M

Pedesphere $7.2M Composite $3.9M to $4.5M

Fluted Column $4.5M to $4.7M

• The Composite and Fluted Column (Hydropillar) styles will both be bid.

Western Cary Elevated Storage Tank Operation

• WPZ– The Western Cary EST will float on the WPZ.

• CPZ– The Western Cary BPS will pump out of the Western Cary EST and into the CPZ during periods of high demand.

• Emergency Operation – The Western Cary EST can be continually pumped into the CPZ while the WPZ High Service Pumps meet the WPZ demands.

WESTERN CARY BOOSTER PUMP STATION

Western Cary Booster Pump Station Usage

• Western Cary Booster Pump Station (BPS) will be utilized to facilitate turnover in the Western Cary EST and aid in meeting high demands in the CPZ

• As demand increases in the WPZ, the need to pump out of the Western Cary EST for water age reasons decreases

• During emergency operation the Western Cary BPS will provide continuous transfer of water from the WPZ into the CPZ

Booster Pump Station Operation

Demand Scenario

WPZ Demand (mgd) Daily Operation Western Cary Tank

Average Water Age

2016 ADD 2.2None 7.9 days

8 hours per day 4.6 days

2016 MDD 3.6 5 hours per day 4.0 days

2025 ADD 3.9 None 4.8 days

Build-out ADD 7.4 None 3.7 days

• Pump run times are based solely on keeping water age under 5 day threshold • Assumes pumping rate of 1,800 gpm

Proposed Pump Characteristics

Equipment Description

Pump Type Canned Vertical Turbine

Number of Pumps 3

Flow per Pump (gpm) @ Design Point 900

Total Head (ft) @ Design Point 125

Efficiency (%) @ Design Point 84

Motor Horsepower 50

Pump Manufacturer Fairbanks Morse

Pumping Summary

Pumping Scenario

Flow Rate (gpm)EQ Volume High

Water LevelEQ Volume Low Water

Level Tank Low Water Level

1 Pump Operation 1,050 1,000 720

2 Pump Operation 2,000 1,850 1,350

3 Pump Operation 2,800 2,600 1,900

• All pumps will run off of variable frequency drives and the third pump will be designed to turn on in emergency scenario

• Summary of flow rates at 100% operating speed for different pumping scenarios is provided in table below

WESTERN CARYWATER MAIN IMPROVEMENTS

Water Main Improvements

• Three separate water main improvement recommendations were identified during hydraulic model efforts:– CPZ Connection– WPZ Connection– Roberts Road Improvements

CPZ Connection – Good Hope Church Road• Approximately 3,200 feet

of 16-inch waterline along Good Hope Church Road from the Western Cary EST and BPS site into the CPZ

• Includes trenchless crossings of the CSX railroad, Saunders Grove Lane, and Morrisville Carpenter Road

WPZ Connection – Hortons Creek Road Extension• Approximately 4,200 feet of 20-

inch waterline along a portion of NC-55 ROW and then cross country along a proposed Unnamed Collector Road and future Hortons Creek Road extension

• Includes trenchless crossings of NC-55 and open-cut underneath an existing NC-540 bridge

Roberts Road Improvements

• Approximately 1,800 feet of 12-inch waterline from the NC-55 and Jenks Road intersection to Roberts Road

• This waterline will eliminate the 30-inch diameter dead-end on NC-55 that would otherwise be created with the pressure zone boundary modification

WESTERN CARYPRESSURE ZONE BOUNDARY CONNECTIONS

Pressure Zone Boundary Connections

• Connections were divided into two categories:– Non-Emergency – Connections that will be abandoned and

create a permanent separation between the WPZ and CPZ– Emergency – Connections will act as a semi-permanent barrier

and will utilize a PRV so that in emergency scenarios, the Town could open the connection and allow water to flow from the CPZ into the WPZ

• Remove existing WPZ and CPZ pressure zone boundary PRVs

Waterline Modifications

• 3 Emergency Connections– 3 PRVs– 4 Hydrants/Blowoffs– 1 Isolation Valve– Waterline

• 12 Non-Emergency Connections – 10 Isolation Valves– 3 Tees/Elbows– 3 Hydrants– Waterline

WESTERN CARYCONCEPTUAL OPINION OF PROBABLE CONSTRUCTION COST

Opinion of Probable Construction Cost – Hydropillar Style Tank

Opinion of Probable Construction Cost – Composite Style Tank

WESTERN CARYQUESTIONS?

Emergency Scenario 136-inch CPZ feed east of Hwy 55 out of service

• Assume 36-inch for CPZ-1• Assume max day demand• Can keep CPZ elevated tanks from draining empty and

maintain pressures through build-out

Emergency Scenario 242-inch Jenks Rd Pipe out of service

• Assume max day demand• Pump continuously from WPZ to CPZ via Western Cary

ground storage tank– One ground storage pump on in 2016– Two ground storage pumps on in 2025, build-out

• 2016: Can keep CPZ elevated tanks from draining empty and maintain pressures

• 2025: CPZ elevated tanks empty in approximately 20 hours• Build-out: CPZ elevated tanks empty within first few hours

Emergency Scenario 3Carpenter Tank out of service

• Assume average day demand• Jenks Rd & Hwy 55 PRV open during peak hour demands to

avoid pressure < 50 psi along Hwy 55

Emergency Scenario 442-inch Jenks Rd Pipe & Carpenter Tank out of service• Assume average day demand• Pump continuously from WPZ to CPZ via Western Cary

ground storage tank• 2016 & 2025: Can keep CPZ elevated tanks from draining

empty and maintain pressures (ADD)• Build-out: CPZ elevated tanks empty in approximately 72

hours (ADD)

• Results similar to Emergency Scenarios 2 and 3

Western Cary Booster Pump Station Design

• Three pump station design options were considered for the Western Cary BPS– EST Column Design – Placing pump station inside of EST column with

separate building for electrical equipment. Option was eliminated by the Town and therefore costs were not developed

– Pre-packaged Design – Use of a pre-packaged pump station designed and built off-site

– Engineer Designed – Design of pump station would be by CDM Smith specifically to meet the project needs

Pump Station Design Construction Cost ($)

Pre-packaged $790,000

Engineer $815,000

• The Town decided the Western Cary BPS should be designed by CDM Smith

Western Cary Booster Pump Station Building

• Three building options were considered for Western Cary BPS– Pre-Packaged Building – Building supplied by manufacturer of pre-

packaged pump station– Pre-Manufactured Building – Steel or concrete panels designed off-site

and erected around pump station– Built On-site Building – Design of building would be by CDM Smith

specifically to meet the project needs

Building Design Capital Cost ($)Pre-Packaged $530,000

Pre-Manufactured Steel $425,000Concrete $605,000

Built On-site $543,000

• The Town decided the Western Cary BPS should be housed inside of a Pre-manufactured concrete building