Typical Water Project Construction Stages

Typical construction durations shown are approximate. Actual duration may vary dependent on existing conditions, site-specific road/traffic conditions, and weather conditions.  For updated current information on when construction will occur in your specific area, please contact the Project Engineer, City of Palo Alto, Water, Gas, Wastewater Engineering.

FAQs for Construction of Major Capital Improvement Projects

Water Project Stages

CONSTRUCTION PHASE

DESCRIPTION

TYPICAL DURATION

Site Mobilization

Contractor moves equipment and material near the construction area or to their storage yard. Contractor marks the boundaries of the area for underground Service Alert (USA).

1 - 2 working days

USA / Survey

Underground Service Alert (USA) and City Survey Crew marks out existing utilities and proposed water main alignment on the street pavement with spray paint.

2 - 5 working days

Sawcutting

The Contractor sawcuts existing pavement as marked by the survey crew.

1 - 3 working days

Excavation

The Contractor removes pavement and excavates soil to prepare for installation of a new water main and services.

1 - 3 working days

New Water Main, Services Installation, and Existing Services Reconnection

The Contractor performs a system tie-in to an existing water main, closes tie-in valve, and begins laying new main and service connection points along the new water main alignment. Note: Your service is not connected to the new system at this stage of the construction.

2 - 6 working days

New water main pressure test 

To assure tightness at pipe joints and fittings, the Contractor performs hydrostatic pressure tests on the new water main.  Water mains are pressurized with potable water using pressure at lowest elevation in the system at 150 psi.  The pressure is being maintained constant for 4-hour period by adding makeup water.  After 4-hour period is completed, the pressure shall remain steady within 5% (7.5 psi) of a target 150 psi test pressure for one hour.

For a typical city block: 6 to 8 hours

Fill new main with water for disinfection & bacteriological Test

System tie-in valve is opened to fill the installed system with water. A liquid disinfectant (chlorine) is injected into the charged system to kill any pre-existing microbial organisms. The new water main will stay chlorinated for at least 24 hours and then flushed until chlorine concentration decreases to 1ppm.  Then water samples will be gathered and taken to a laboratory for analysis.  The Contractor will be required to perform two consecutive 24-hours apart bacteriological (Coliform) tests.

Less than 1 hour

Water test results back in 1-2 working days

Service Transfer Connections

Once the Bacteriological Test has passed and written passing results are submitted, the Contractor begins connecting your service line to the new water main.

0.5 - 3 hours per service (this entails an individual water service interruption)

Backfilling

Contractor fills and compacts the ground openings with backfill material as the new main is installed.

Performed concurrently with the new main and services installation and connection

Install Temporary Pavement or "Cutback" 

Temporary cold asphalt mix is placed on the backfilled area to temporarily restore the roadway service. If your street is concrete, steel plates will be placed on top of the trench in order for the concrete base to cure, prior to final restoration.

Performed concurrently with the new main and service installation, connection, and backfill

Final Pavement Restoration 

The Contractor removes temporary asphalt pavement, steel plates, and restores pavement and all surface improvements to the preconstruction condition

1 - 3 days per block 

Final cleaning

The Contractor sweeps the street affected by the project and removes USA markings.

1 - 2 days per block

 New water main connection to existing water distribution system

 New Water mains will be tied into water distribution system within 24 hours following the acceptance of the bacteriological tests' results.

 1-2 days


Last Updated: Oct 3, 2017
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