To:
From:
Re:
G. Motion:
Attachments:
Discussion:
City of Nashua, Public Works Division
Board of Public Works Meeting Date: June 22, 2017
Noelle Osbome, Piant Operations Supervisor
Wastewater Department
Change Order #2 - Siphon Covers Installation project
To approve Change Order #2 for the installation of new siphon and manhole covers
project to William P. Davis Excavation, LLC, of Portsmouth, NH in amount of
$16,617.50. Funding will be through: Department: 169 Wastewater — Account
Classification: 54 Property Services.
Change Order 2
The vortex structure at the wastewater treatment facility is designed to dissipate energy in
the wastewater flow where the Salmon Brook Interceptor meets the South Merrimack
Interceptor. The vortex structure consists of an 8-foot diameter top section and a lower 4-
foot diameter section that extends over 30 feet deep. Upon original installation of the
vortex, the access manhole was not centered over the vortex, leaving no access to clean
the vortex. A new, larger opening centered over the vortex structure is needed.
The new concrete top slab will have a centered hatch opening and built-in safety grate.
William P. Davis Excavation, who completed the work for the siphon cover upgrades
project, was requested to put together a cost proposal for a new top slab on the vortex.
Davis Excavation is ideally situated for this work from their experience with the
installation of new hatch and safety grates during the siphon cover upgrades project.
Davis Excavation was awarded the siphon project in January 2017 in the amount of
$49,875. Change order 1 for the installation of new bolts to replace the existing stripped
bold on covers increased the contract amount by $4,996.20 to a new total amount of
$54,871.20. This change order is in the amount of $16,617.50 brings the new total
contract amount to $71,488.70.
Davis Excavation has satisfactorily completed the siphon cover installation project within
the project schedule and on budget. Their costs are considered reasonable and they will
be able to start in timely manner when requested to do so by the Wastewater Department.
