Underground Construction - November 2021 - 36

MANHOLE REHABILITATION
SPECIFICATION TIPS
By NASSCO Member Karol Giokas, PE - RJN Group, Inc.
NASSCO has elevated and standardized the
approach for inspecting sewer assets, both
sewers using Pipeline Assessment Certification
Program (PACP™) standards and structures
using Manhole Assessment Certification Program
(MACP™) standards. However, once a structure
inspection has been performed, how do you get to
a rehabilitation program and develop specifications
for bidding?
Gathering Attribute Data
Assuming that the inspection and attribute data
collection were performed using MACP standards,
the data needed for developing a specification is
readily available and includes:
* Structure ID number
* Address and rough location description-road,
highway, easement, field
* Surface and cover type
* Structure depth, size, shape, and wall material
* Chimney height
Adhering to MACP standards is highly
recommended for creating a homogenous
dataset for assets systemwide and across various
inspection crews or contractors. One additional
piece of requisite asset data, floodplain status,
comes from FEMA floodplain maps. Once you
have acquired all of this information, you can begin
to build your rehabilitation plan.
Rehabilitation Determination
Several considerations must be addressed to
narrow down the field of available rehabilitation
options before the process advances further:
* Are there specific rehabilitation methods that
the owner does or does not want to use?
* Are there scheduling restrictions?
* What work will be contracted versus selfperformed
by the owner?
* What items will be considered incidental-e.g.,
mobilization, traffic control, bypass pumping,
restoration, testing, etc.?
* What is the desired warranty?
* Will work be phased or completed in one
contract?
With these questions answered, initial rehabilitation
methods can be developed and then grouped by
type or location into a project that fits within the
owner's budget.
Typical manhole rehabilitation methods include:
* Adjustment or replacement of frame and cover
* Chimney seals
* Lining for either structural rehabilitation or
chemical protection
* Chemical grouting for inflow and infiltration (I/I)
* Repair or replacement of the bench and trough
Additional options include the installation of barrel
sections, complete manhole replacement, or
performing O&M work such as cleaning or root
removal.
Preliminary rehabilitation recommendations may
require adjustment based on additional external
factors, such as being located within a brick
driveway, state highway, or floodplain. Manholes in
a 100-year flood zone have requirements to raise
the rim elevation above the base flood elevation or
install a bolted frame or sealing cover.
Some items will be incidental to the cost of an
existing bid item. For example, for sewers under
15 inches in diameter, bypass pumping will likely
be incidental. For larger sanitary sewers, bypass
pumping is often listed as a separate line item.
Underground Construction - November 2021

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