Seven Corners Tank

Replacement

Council Work Session

City of Falls Church

January 17, 2017

Seven Corners Tank Replacement

Why is a new tank needed?

What alternatives have been

considered?

What are the benefits of a

new tank?

Next steps

Seven Corners TankWillston Tank

Seven Corners Area Water Service

Willston Pumping Station

Former City of Falls Church Water Service Area

Water Pressure in Seven Corners Area

History of low pressures

History of insufficient storage

Some areas of low fire flow

Some small projects implemented in effort to improve pressure to some areas

Prior recommendations consistently recommended higher hydraulic gradeline (and by definition taller tank)

Replace Seven Corners Tank to match Willston (approx. 50 feet taller)

Expand the Willston zone and construct a new tank

Water Quality in Seven Corners Area

Recurring issues with maintaining a chlorine residual in distribution system

Several operational changes implemented to mitigate but problems persist

Issues a direct result of water age in Seven Corners tank

Water age is a direct result of hydraulic limitations of the Seven Corners tank

Additional Challenges

Insufficient storage in Willston zone for current

demands

Identified in 1997 Master Plan and subsequent

studies

Previous CIP’s planned to address

Challenges with land acquisition for new tank site

Storage, fire flow and pressure issues will be

exacerbated with proposed redevelopment

Seven Corners Tank

Redevelopment in Seven Corners Area

What has changed?

Able to more comprehensively address pressure and water quality issues in Seven Corners area

Review issues/challenges in perspective of larger system integration

Eliminate large “dead end” configuration of Seven Corners area

Raise the target service pressure for high ground areas

Larger customer base to support needed system improvements

Fairfax Water’s Recommendation

Replace Seven Corners tank with a taller tank on existing site

Create new, higher pressure zone to encompass existing Seven Corners and Willston

Construct a pumping station in base of tank

Eliminate Willston Tank and Pumping Station

Reduce long term maintenance expenses through consolidation of facilities

Eliminate “dead-end” configuration of Seven Corners area distribution system

Seven Corners Tank Replacement

1.25 MG of storage

Pumping station within tank

base

Est. cost: $10.75 Million

Increase service pressures by 10

to 25+ psi

Improve fire flows

Address water quality concerns

Support redevelopment of area

Seven Corners Tank Replacement

Fairfax Water owns the land

Site has been used for water storage since 1961

Site is centrally located within area it will serve

Minimizes improvements to transmission system

to supply the tank

Required easements for construction are

temporary in nature

Alternatives Considered

Conversion of Seven Corners tank to pumped

storage

Replacement of Willston tank

Construct new tank on Fire Station property

Construct new tank on School property

Conversion of Seven Corners to

Pumped Storage Cannot be accomplished on

existing site

Requires acquisition of additional land resulting in permanent impacts to adjacent property(ies)

Eden Center, Cemetery, Koons

Requires additional transmission mains

Creates operational/water quality issues elsewhere in the system

Excluding land acquisition, estimated cost of $14.4 Million

Existing Seven Corners Tank Site

Required Water Main

Construct New Willston Tank

Requires land acquisition (cost unknown) Existing site unable to accommodate a larger tank

No available vacant parcels

Requires construction of new tank ($8.5 Million)

Requires new pumping station ($5.2 Million) Located on existing Seven Corners site

Existing Willston PS and easement too small

Requires additional transmission ($2.3 Million)

Excluding land acquisition estimated cost of $15.9 Million

Existing tank Site

Site previously Identified for new tank

Willston Tank Alternative

Additional Required Transmission for Willston

New Pumping Station4,500 linear feet of 24-inch water main

New Willston Tank

County School and Fire Station Sites

Seven Corners Fire Station

Bailey’s Upper Elementary School

County Sites

Not owned by Fairfax Water

Fully utilized or plans to expand

– no room for a tank

Tank at Fire Station would have

to be 25 feet taller than Seven

Corners

Sites would require additional

transmission mains

Seven Corners Fire Station

Baileys Upper Elementary

Fairfax Water’s Proposed

Replacement of Seven Corners Tank Least cost alternative at $10.75 Million

Improves service for existing customers in Seven Corners and Willston areas Addresses long-standing pressure issues in Seven Corners area

Addresses long-standing storage deficiency in Willston pressure zone

Addresses water quality issues

Provides storage capacity and pressure to support contemplated redevelopment

Least construction disturbance to community

Consolidates number of water facilities required to provide service – improves operational efficiency

Only alternative that does not require permanent land acquisition on private property

Customers Benefitting from Proposed Tank

Hydrant Fire Flow Improvements with New Tank

Proposed Seven Corners Tank

Tysons TankProposed Seven Corners Tank

Tysons Central Development

KOONS

EDEN CENTER

Temporary Construction Easement

Pedestal

Bowl

OAKWOOD CEMETERY

COW

Existing Tank

Next Steps

City consideration of zoning code amendment to allow for consideration of Seven Corners tank replacement

Continue discussions with adjacent property owners

Easement negotiation/acquisition

Continue discussions with City staff regarding temporary arrangements for City radio

Develop preliminary design drawings for applications to City and conduct community meetings

Questions?