### **ITEM D-751 MANHOLES, CATCH BASINS, INLETS AND INSPECTION HOLES**

DESCRIPTION

**751‑1.1**  This item shall consist of construction of manholes, catch
basins, inlets, and inspection holes, in accordance with these
specifications, at the specified locations and conforming to the lines,
grades, and dimensions shown on the plans or required by the Engineer.

MATERIALS

**751-2.1 BRICK.**  The brick shall conform to the requirements of ASTM
C 32, Grade SM.

**751-2.2 MORTAR.**  Mortar shall consist of one part portland cement
and two parts sand.  The portland cement shall conform to the
requirements of ASTM C 150, Type I.  The sand shall conform to the
requirements of ASTM C 144.

**751-2.3 CONCRETE.**  Plain and reinforced concrete used in structures,
connections of pipes with structures, and the support of structures or
frames shall conform to the requirements of Item P‑610.

**751-2.4 PRECAST CONCRETE PIPE MANHOLE RINGS.**  Precast concrete pipe
manhole rings shall conform to the requirements of ASTM C 478.  Unless
otherwise specified, the risers and offset cone sections shall have an
inside diameter of not less than 36 inches (90 cm) nor more than 48
inches (120 cm).

**751-2.5 CORRUGATED METAL.**  Corrugated metal shall conform to the
requirements of AASHTO M 36.

**751-2.6 FRAMES, COVERS, AND GRATES.**  The castings shall conform to
one of the following requirements:

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  **a.**  Gray iron castings shall meet the requirements of ASTM A 48,
  Class 30B and 35B.

  **b.**  Malleable iron castings shall meet the requirements of ASTM A
  47. 

  **c.**  Steel castings shall meet the requirements of ASTM A 27.

  **d.** Structural steel for grates and frames shall conform to the
  requirements of ASTM A 283, Grade D.

  **e.** Ductile iron castings shall conform to the requirements of ASTM
  A 536.

  **f.** Austempered ductile iron castings shall conform to the
  requirements of ASTM A 897.
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All castings or structural steel units shall conform to the dimensions
shown on the plans and shall be designed to support the loadings,
aircraft gear configuration and/or direct loading, specified.

Each frame and cover or grate unit shall be provided with fastening
members to prevent it from being dislodged by traffic but which will
allow easy removal for access to the structure.

All castings shall be thoroughly cleaned. After fabrication, structural
steel units shall be galvanized to meet the requirements of ASTM A 123.

**751-2.7 STEPS.**  The steps or ladder bars shall be gray or malleable
cast iron or galvanized steel.  The steps shall be the size, length, and
shape shown on the plans and those steps that are not galvanized shall
be given a coat of bituminous paint, when directed.

CONSTRUCTION METHODS

**751-3.1 UNCLASSIFIED EXCAVATION.**

**a.**  The Contractor shall do all excavation for structures and
structure footings to the lines and grades or elevations, shown on the
plans, or as staked by the Engineer.  The excavation shall be of
sufficient size to permit the placing of the full width and length of
the structure or structure footings shown.  The elevations of the
bottoms of footings, as shown on the plans, shall be considered as
approximately only; and the Engineer may order, in writing, changes in
dimensions or elevations of footings necessary to secure a satisfactory
foundation.

**b.** Boulders, logs, or any other objectionable material encountered
in excavation shall be removed. All rock or other hard foundation
material shall be cleaned of all loose material and cut to a firm
surface either level, stepped, or serrated, as directed by the Engineer.
All seams or crevices shall be cleaned out and grouted. All loose and
disintegrated rock and thin strata shall be removed. When concrete is to
rest on a surface other than rock, special care shall be taken not to
disturb the bottom of the excavation, and excavation to final grade
shall not be made until just before the concrete or reinforcing is to be
placed.

**c.** The Contractor shall do all bracing, sheathing, or shoring
necessary to implement and protect the excavation and the structure as
required for safety or conformance to governing laws. The cost of
bracing, sheathing, or shoring shall be included in the unit price bid
for the structure.

**d.** Unless otherwise provided, bracing, sheathing, or shoring
involved in the construction of this item shall be removed by the
Contractor after the completion of the structure. Removal shall be
effected in a manner that will not disturb or mar finished masonry. The
cost of removal shall be included in the unit price bid for the
structure.

**e.** After each excavation is completed, the Contractor shall notify
the Engineer to that effect; and concrete or reinforcing steel shall be
placed after the Engineer has approved the depth of the excavation and
the character of the foundation material.

**751-3.2 BRICK STRUCTURES.**

**a. Foundations.** A prepared foundation shall be placed for all brick
structures after the foundation excavation is completed and accepted.
Unless otherwise specified, the base shall consist of reinforced
concrete mixed, prepared, and placed in accordance with the requirements
of Item P-610.

**b. Laying Brick.** All brick shall be clean and thoroughly wet before
laying so that they will not absorb any appreciable amount of additional
water at the time they are laid. All brick shall be laid in freshly made
mortar. Mortar that is not used within 45 minutes after water has been
added shall be discarded. Retempering of mortar shall not be permitted.
An ample layer of mortar shall be spread on the beds and a shallow
furrow shall be made in it that can be readily closed by the laying of
the brick. All bed and head joints shall be filled solid with mortar.
End joints of stretchers and side or cross joints of headers shall be
fully buttered with mortar and a shoved joint made to squeeze out mortar
at the top of the joint. Any bricks that may be loosened after the
mortar has taken its set, shall be removed, cleaned, and relaid with
fresh mortar. No broken or chipped brick shall be used in the face, and
no spalls or bats shall be used except where necessary to shape around
irregular openings or edges; in which case, full bricks shall be placed
at ends or corners where possible, and the bats shall be used in the
interior of the course. In making closures, no piece of brick shorter
than the width of a whole brick shall be used; and wherever practicable,
whole brick shall be used and laid as headers.

**c. Joints.** All joints shall be slushed with mortar at every course,
but slushing alone will not be considered adequate for making an
acceptable joint. Exterior faces shall be laid up in advance of backing.
Exterior faces shall be back plastered or pargeted with a coat of mortar
not less than 3/8-inch (9 mm) thick before the backing is laid up. Prior
to pargeting, all joints on the back of face courses shall be cut flush.
Unless otherwise noted, joints shall be not less than 1/4-inch (6 mm)
nor more than 1/2-inch (12 mm) wide and whatever width is adopted shall
be maintained uniform throughout the work.

**d. Pointing.** Face joints shall be neatly struck, using the weather
joint. All joints shall be finished properly as the laying of the brick
progresses. When nails or line pins are used the holes shall be
immediately plugged with mortar and pointed when the nail or pin is
removed.

**e. Cleaning.** Upon completion of the work all exterior surfaces shall
be thoroughly cleaned by scrubbing and washing down with water and, if
necessary to produce satisfactory results, cleaning shall be done with a
5% solution of muriatic acid which shall then be rinsed off with liberal
quantities of clean fresh water.

**f. Curing and Cold Weather Protection.** In hot or dry weather, or
when directed by the Engineer, the brick masonry shall be protected and
kept moist for at least 48 hours after laying the brick. Brick masonry
work or pointing shall not be done when there is frost in the brick or
when the air temperature is below 50 F (10 C) unless the Contractor has
on the project ready to use, suitable covering and artificial heating
devices necessary to keep the atmosphere surrounding the masonry at a
temperature of not less than 60 F (15 C) for the duration of the curing
period.

**751-3.3 CONCRETE STRUCTURES.**  Concrete structures shall be built on
prepared foundations, conforming to the dimensions and form indicated on
the plans.  The construction shall conform to the requirements specified
in Item P‑610.  Any reinforcement required shall be placed as indicated
on the plans and shall be approved by the Engineer before the concrete
is poured.

All invert channels shall be constructed and shaped accurately so as to
be smooth, uniform, and cause minimum resistance to flowing water.  The
interior bottom shall be sloped downward toward the outlet.

**751-3.4 PRECAST CONCRETE PIPE STRUCTURES.**  Precast concrete pipe
structures shall be constructed on prepared or previously placed slab
foundations and shall conform to the dimensions and locations shown on
the plans.  All precast concrete pipe sections necessary to build a
completed structure shall be furnished.  The different sections shall
fit together readily, and all jointing and connections shall be cemented
with mortar.  The top of the upper precast concrete pipe member shall be
suitably formed and dimensioned to receive the metal frame and cover or
grate, or other cap, as required.  Provision shall be made for any
connections for lateral pipe, including drops and leads that may be
installed in the structure.  The flow lines shall be smooth, uniform,
and cause minimum resistance to flow.  The metal steps that are embedded
or built into the side walls shall be aligned and placed at vertical
intervals of 12 inches (300 mm).  When a metal ladder replaces the
steps, it shall be securely fastened into position.

**751-3.5 CORRUGATED METAL STRUCTURES.**  Corrugated metal structures
shall be constructed on prepared foundations, conforming to the
dimensions and locations as shown on the plans.  The structures shall be
prefabricated.  standard or special fittings shall be furnished to
provide pipe connections or branches of correct dimensions.  The
connections or branches shall be of sufficient length to accommodate
connecting bands.  The fittings shall be welded in place to the metal
structures.  When indicated, the structures shall be placed on a
reinforced concrete base.  The top of the metal structure shall be
designed so that either a concrete slab or metal collar may be attached
to which can be fastened a standard metal frame and grate or cover. 
Steps or ladders shall be furnished as shown on the plans.

**751-3.6 INLET AND OUTLET PIPES.**  Inlet and outlet pipes shall extend
through the walls of the structures for a sufficient distance beyond the
outside surface to allow for connections but shall be cut off flush with
the wall on the inside surface, unless otherwise directed.  For concrete
or brick structures, the mortar shall be placed around these pipes so as
to form a tight, neat connection.

**751-3.7 PLACEMENT AND TREATMENT OF CASTINGS, FRAMES, AND FITTINGS.** 
All castings, frames, and fittings shall be placed in the positions
indicated on the plans or as directed by the Engineer, and shall be set
true to line and to correct elevation.  If frames or fittings are to be
set in concrete or cement mortar, all anchors or bolts shall be in place
and position before the concrete or mortar is placed.  The unit shall
not be disturbed until the mortar or concrete has set.

When frames or fittings are to be placed upon previously constructed
masonry, the bearing surface or masonry shall be brought true to line
and grade and shall present an even bearing surface in order that the
entire face or back of the unit will come in contact with the masonry. 
The unit shall be set in mortar beds and anchored to the masonry as
indicated on the plans or as directed and approved by the Engineer.  All
units shall set firm and secure.

After the frames or fittings have been set in final position and the
concrete or mortar has been allowed to harden for 7 days, then the
grates or covers shall be placed and fastened down.

**751-3.8 INSTALLATION OF STEPS.**  The steps shall be installed as
indicated on the plans or as directed by the Engineer.  When the steps
are to be set in concrete, they shall be placed and secured in position
before the concrete is poured.  When the steps are installed in brick
masonry, they shall be placed as the masonry is being built.  The steps
shall not be disturbed or used until the concrete or mortar has hardened
for at least 7 days.  After this period has elapsed, the steps shall be
cleaned and painted, unless they have been galvanized.

When steps are required with precast concrete pipe structures, they
shall be cast into the sides of the pipe at the time the pipe sections
are manufactured or set in place after the structure is erected by
drilling holes in the concrete and cementing the steps in place.

When steps are required with corrugated metal structures, they shall be
welded into aligned position at a vertical spacing of 12 inches (300
mm).

In lieu of steps, prefabricated ladders may be installed.  In the case
of brick or concrete structures, the ladder shall be held in place by
grouting the supports in drilled holes.  In the case of metal
structures, the ladder shall be secured by welding the top support and
grouting the bottom support into drilled holes in the foundation or as
directed.

**751-3.9 BACKFILLING.**

**a.**  After a structure has been completed, the area around it shall
be filled with approved material, in horizontal layers not to exceed 8
inches (200 mm) in loose depth, and compacted to the density required in
Item P‑152.  Each layer shall be deposited all around the structure to
approximately the same elevation.  The top of the fill shall meet the
elevation shown on the plans or as directed by the Engineer.

**b.**  Backfilling shall not be placed against any structure until
permission is given by the Engineer.  In the case of concrete, such
permission shall not be given until the concrete has been in place 7
days, or until tests made by the laboratory under supervision of the
Engineer establish that the concrete has attained sufficient strength to
provide a factor of safety against damage or strain in withstanding any
pressure created by the backfill or the methods used in placing it.

**c.**  Backfill shall not be measured for direct payment.  Performance
of this work shall be considered on obligation of the Contractor covered
under the contract unit price for the structure involved.

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> **When structures are located within the runway safety area, POFA,
> RPZ, etc., the elevation of the structures shall be set to meet the
> grading requirements of these areas.**

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**751-3.10 CLEANING AND RESTORATION OF SITE.**  After the backfill is
completed, the Contractor shall dispose of all surplus material, dirt,
and rubbish from the site.  Surplus dirt may be deposited in
embankments, shoulders, or as ordered by the Engineer.  The Contractor
shall restore all disturbed areas to their original condition.

After all work is completed, the Contractor shall remove all tools and
equipment, leaving the entire site free, clear, and in good condition.

METHOD OF MEASUREMENT

**751-4.1**  Manholes, catch basins, inlets, and inspection holes shall
be measured by the unit.

BASIS OF PAYMENT

**751-5.1**  The accepted quantities of manholes, catch basins, inlets,
and inspection holes will be paid for at the contract unit price per
each in place when completed.  This price shall be full compensation for
furnishing all materials and for all preparation, excavation,
backfilling and placing of the materials; furnishing and installation of
such specials and connections to pipes and other structures as may be
required to complete the item as shown on the plans; and for all labor
equipment, tools and incidentals necessary to complete the structure.

Payment will be made under:

Item D‑751‑5.1 Manholes---per each

Item D‑751‑5.2 Catch Basins---per each

Item D‑751‑5.3 Inlets---per each

Item D‑751‑5.4 Inspection Holes---per each

MATERIAL REQUIREMENT

ASTM A 27 Steel Castings, Carbon, for General Application

ASTM A 47 Ferritic Malleable Iron Castings

ASTM A 48 Gray Iron Castings

ASTM A 123 Zinc Coating (Hot-Dip) on Iron and Steel Hardware

ASTM A 283 Low and Intermediate Tensile Strength Carbon Steel Plates,
Shapes, and Bars

ASTM A 536 Ductile Iron Castings

ASTM A 897 Austempered Ductile Iron Castings

ASTM C 32 Sewer and Manhole Brick (Made from Clay or Shale)

ASTM C 144 Aggregate for Masonry Mortar

ASTM C 150 Portland Cement

ASTM C 478 Precast Reinforced Concrete Manhole Sections

AASHTO M 36 Zinc Coated (Galvanized) Corrugated Iron or Steel Culverts
and Underdrains

**END OF ITEM D-751**

**Intentionally Left Blank**

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