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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