At the request of the Engineer a complete set of computations,
in a tabular form, indicating depths and velocities at minimum, average
and maximum daily waste flows for the different sizes of sewers proposed.
Size, type, class, thickness and pressure rating of sewers shall be
as shown on the approved plans.
6.0.1.
Depth. In general, sewers shall be sufficiently deep so as to receive
sewage from the first floor of all places served by the sewers and
to prevent freezing. Minimum cover of sanitary sewers shall be 42
inches, unless approved otherwise.
6.0.2.
Slope. All sewers shall be designed and constructed to give mean
velocities, when flowing full, of not less than 2.0 feet per second.
The following are the minimum slopes which should be provided; however,
slopes greater than these are desirable.
|
Sewer Size
|
Minimum Slope in Ft. per 100 Ft.
| |
|---|---|---|
|
8 inch
|
0.40
| |
|
10 inch
|
0.28
| |
|
12 inch
|
0.22
| |
|
14 inch
|
0.17
| |
|
15 inch
|
0.15
| |
|
16 inch
|
0.14
| |
|
18 inch
|
0.12
| |
|
21 inch
|
0.10
| |
|
24 inch
|
0.08
| |
|
27 inch
|
0.067
| |
|
30 inch
|
0.058
| |
|
36 inch
|
0.046
|
|
Sewers should be laid with uniform slope between manholes. Sewers
on 20 per cent slope or greater shall be anchored securely with concrete
anchors spaced no more than 36 feet center to center.
|
6.0.3.
Sizing. New sewer systems shall be designed on the basis of an average
daily per capita flow of sewage of not less than 100 gallons per day.
Generally, the main, trunk and outfall sewers shall be designed to
carry, when running full, not less than 250 gallons daily per capita
contributions of sewage, exclusive of sewage or other waste flow from
industrial plants. The Engineer may modify these minimum flow conditions
as required by system performance or modeling of future flows in the
system.
No sewer shall be less than 8 inches in diameter. Sewer taps
and laterals shall not be less than 6 inches in diameter. Cleanouts
shall be a minimum of 6 inches in diameter.
Sanitary sewers shall be constructed of the following pipe unless
otherwise approved by the Engineer. At cover depths less than 10 feet,
any of these pipe types may be used. At cover depths greater than
10 feet, SDR 35 PVC pipe shall not be used. At cover depths greater
than 15 feet, no PVC pipe may be used.
6.1.1.
Reinforced Concrete Pipe. Reinforced Concrete sewer pipe and fittings
for sewers shall be minimum Class III. Interior shall be lined with
Permite PCS-9043 Type II or approved equal.
6.1.2.
PVC Pipe (Gravity). Polyvinyl chloride plastic pipe and fittings
for gravity sanitary sewers shall be Type PSM SDR-35 or SDR-26 in
accordance with ASTM D-3034 and F-679.
Pipes and fittings shall have integral molded bells for bell
and spigot type joints with elastomeric ring gaskets providing a water
tight seal. Gaskets shall be certified by the manufacturer to be chemically
immune to normal sewage and sewer gas and the gasket design arrangement
on the bell shall be approved by the Engineer.
All pipe fittings shall be molded or otherwise made as one piece
integral units.
Adapters as furnished by the pipe manufacturer shall be used
to connect PVC pipe to all other type of pipes of fittings.
PVC pipe shall not be used in any system which may receive industrial
waste or materials with temperatures greater than 140 degrees F.
6.1.3.
Ductile Iron Pipe. Ductile iron pipe for gravity sewers and sewage
force mains shall be pressure class 150-350, and shall conform to
AWWA/ANSI C150/A21.5. Interior shall be lined with Protecto 401, TNEMEC
Series 431 Perma-Shield PL, or approved equal. Pipe fittings shall
be mechanical joint Class 250 conforming to ANSI Specification Asl.10
(AWWA C-110) for short body cast iron fittings.
6.1.4.
High Density Polyethylene Pipe (HDPE). HDPE pipe for sewage force
mains shall be 160 psi working pressure, DR11 (DR9 for 4" diameter
and smaller), and shall conform to ASTM D-1248 and ASTM D-3350. Fittings
shall be molded or fabricated with ends to match system piping.
Unless specifically directed otherwise by the Engineer, not
more than 100 feet of trench shall be opened ahead of the pipe laying
work of any one crew, and not more than 100 feet of open ditch shall
be left behind the pipe laying work of any one crew. Watchmen or barricades,
lanterns and other such signs and signals as may be necessary to warn
the public of the dangers in connection with open trenches, excavation
and other obstructions, shall be provided by and at the expense of
the contractor. Conformance to all state highway requirements shall
be the responsibility of the contractor when encroachment on highway
right-of-way is necessary.
When directed by the Engineer, only one half of street crossings
and road crossings shall be excavated before placing temporary bridges
over the side excavated for the convenience of the traveling public.
All backfilled ditches shall be maintained in such a manner that they
will offer no hazard to the passage of traffic. The convenience of
the traveling public and property owners abutting shall be taken into
consideration. All public or private drives shall be taken into consideration
and shall be promptly backfilled or bridged at the direction of the
Engineer. Excavated materials shall be disposed of so as to cause
the least interference, and in every case the disposition of materials
shall be satisfactory to the Engineer. Trenches in which pipes are
to be laid shall be excavated in open cut to the depths shown on the
approved plans, cut sheets or as specified by the Engineer. Where
rock is encountered, is shall be removed to a minimum depth of four
(4) inches below the pipe bells.
Unless specifically authorized by the Engineer, trenches shall
be in no case excavated or permitted to become wider than 2 feet 6
inches plus the nominal diameter of the pipe at the level of or below
the top of the pipe. If the trench does become wider than 2 feet 6
inches at the level of or below the top of the pipe, special precautions
may be necessary, such as providing compacted granular fill up to
the top of the pipe or providing pipe with additional crushing strength
as determined by the Engineer after taking into account the actual
trench loads that may result and the strength of the pipe being used.
The contractor shall bear the cost of such special precautions as
necessary.
Trenches shall be kept free of water during the laying of the
pipe and until the pipeline has been backfilled. Removal of water
shall be at the contractor's expense.
All sanitary sewer pipes shall be laid using bedding of #9 crushed
stone placed to a minimum depth of four inches (4") below the bottom
of the pipe barrel. Unstable soil shall be stabilized by over-excavating
to allow a layer of #3 crushed stone below the four inches (4") of
#9 bedding.
The laying of the sewer pipe in finished trenches shall be commenced
at the lowest point so that the spigot or tongue ends point in the
direction of flow. Jointing of pipes shall follow the manufacturer's
recommended procedures.
Contractors may use a laser instrument to set the grades on
sewer lines in lieu of using a grade string and batter boards set
from grade stakes. In using such an instrument, the contractor shall
be responsible for maintaining grades and elevations as called for
on the drawing profiles, and any variances found shall be corrected
by the Contractor at his expense.
All pipe lengths shall be laid with ends properly jointed and
true to line and grade as approved by the Engineer. They shall be
joined to form a sewer with a smooth and uniform invert. Supporting
of pipe shall be as set out hereinbefore under "Pipe Bedding" and
in no case shall the supporting of pipe on blocks be permitted.
Branches, fittings and specials for sewer lines shall be provided
and laid as and where directed by the Engineer or shown on the plans.
Before each piece of pipe is lowered into the trench, it shall
be thoroughly inspected to insure it is clean. Each piece of pipe
shall be lowered separately unless special permission is given otherwise
by the Engineer. No piece of pipe or fittings which is known to be
defective shall be laid or placed in the lines. If any defective pipe
or fitting shall be discovered after the pipe is laid, they shall
be removed and replaced with a satisfactory pipe or fitting. In case
a length of pipe is cut to fit in a line, it shall be so cut as to
leave a smooth end at right angles to the longitudinal axis of the
pipe and a repair type coupling used as a splicing device.
When installation is stopped for any reason, the exposed ends
of pipes shall be closed with a plug fitted into the pipe bell, so
as to exclude earth or other material, and precautions taken to prevent
flotation of pipe by runoff into trench.
In cases where storm sewers, gas lines, water lines, telephone
lines, and other utilities, or other underground structures are encountered,
they shall not be displaced unless necessary, in which case they shall
be replaced in as good condition as found as quickly as possible.
Any lines or underground structures damaged in the construction shall
be replaced at the contractor's expense, unless in the opinion of
the Engineer, such damage was caused through no fault of the contractor.
The contractor shall notify the utility companies prior to excavation
adjacent to their facilities.
The contractor's attention is further directed to Section 1.4
for additional requirements.
Where unstable material is encountered or where the depth of
excavation in earth exceeds six feet, the sides of the trench or excavation
shall be supported by substantial sheeting, bracing or shoring in
accordance with applicable regulations. Adequate and proper shoring
of all excavations, and design and fabrication of all sheeting and
shoring systems shall be the entire responsibility of the Developer.
Care shall be taken to avoid excessive backfill loads on the
completed pipelines and the requirements that the width of the ditch
at the level of the crown of the pipe be not more than two feet six
inches plus the nominal diameter of the pipe shall, as set out in
Section 6.2, be strictly observed.
All backfilling shall be accomplished in accordance with the
details shown on Standard Drawings.
When directed by the Engineer, the contractor shall add water
to the backfill material or dry out the material when needed to attain
a condition near optimum moisture content for a maximum density of
the material when it is compacted. The contractor shall obtain a compaction
of the backfill of at least 95 per cent of standard (ASTM D 698) Procter
density.
Where required by the Engineer, impervious check dams shall
be installed in pipeline trenches to prevent migration of groundwater
along the pipe. At a minimum, these check dams shall be installed
at any crossing of a creek or stream, and at one thousand foot (1000')
intervals along any run of pipe.
Before final acceptance, the contractor will be required to
level off all trenches or to bring up the level of the surrounding
terrain. The contractor shall also remove from roadways, rights-of-way,
and/or private property all excess earth or other materials resulting
from construction.
In the event that pavement is not placed immediately following
trench backfilling in streets and highways, the contractor shall be
responsible for maintaining the trench surface in a level condition
at proper pavement grade at all times.
In all cases walking or working on the completed pipelines,
except as may be necessary in compacting or backfilling, will not
be permitted until the trench has been backfilled to a point one foot
above the top of the pipe. The filling of the trench and the compaction
of the backfill shall be carried on simultaneously on both sides of
the pipe in such a manner that the completed pipeline will not be
distributed and injurious side pressures do not occur.
6.7.1.
Method "A" Backfilling in Open Terrain. Backfilling of pipeline trenches
in open terrain shall be accomplished in the following manner:
The lower portion of the trench, from the pipe bedding to a
point 6 inches above the top outside surface of the pipe shall be
backfilled with No. 9 crushed stone. This material shall be placed
in 6" layers along each side of the pipe taking care to keep the level
of fill on each side of the pipe equal. Compaction shall be accomplished
by hand-tamping or by approved mechanical methods. Upon approval of
the Engineer, crushed stone, fine gravel, or sand may be used as backfill
in lieu of compacted earth.
The upper portion of the trench above the compacted portion
shall be backfilled with material which is free from large rock. Incorporation
of rock having a volume exceeding eight (8) cubic inches is prohibited.
Backfilling this portion of the trench may be accomplished by any
means approved by the Engineer. The trench backfill shall be heaped
over or leveled as directed by the Engineer.
6.7.2.
Method "B" - Backfilling Under Sidewalks, and Unpaved Driveways.
The entire trench shall be backfilled with No. 9M crushed stone.
6.7.3.
Method "C" - Backfilling Under Streets and Paved Driveways. The lower
portion of the trench, from the pipe bedding to a point six inches
(6") below the bottom of the pavement or concrete sub-slab shall be
backfilled with No. 9 crushed stone or fine gravel.
The upper portion of the trench, from a point 6 inches below
the base of the pavement or concrete, shall be backfilled with a base
course of dense graded aggregate. At such time that pavement placement
is accomplished, the excess base course shall be removed as required.
The testing of sewage force mains and gravity sewers shall be
accomplished by the contractor in accordance with the procedures listed
hereinafter.
6.8.1.
Sewage Force Mains. On all projects involving the installation of
sewage force mains, the finished work shall comply with the provisions
listed below, or similar requirements which will insure equal or better
or better results:
a.
Leakage in pipelines, when tested under pressure of 50 psi in excess
of normal operating pressures, shall not exceed 50 gallons per 24
hours per inch of diameter per mile of pipe.
b.
Where practicable, pipelines shall be tested between line valves
or plugs in lengths of not more than 1500 feet.
c.
Pipelines shall be tested before backfilling at joints except where
otherwise required by necessity, local ordinance or public convenience.
d.
Duration of test shall be not less than two hours where joints are
exposed and not less than 24 hours where joints are covered.
e.
Where leaks are visible at exposed joints and/or evident on the surface
where joints are covered, the joints shall be retightened or relayed,
and leakage minimized, regardless of total leakage as shown on test.
f.
All pipe, fittings and other materials found to be defective under
test shall be removed and replaced at the contractor's expense.
g.
Lines which fail to meet tests shall be repaired and retested as
necessary until test requirements are complied with.
h.
Where nonmetallic joint compounds are used pipelines should be held
under normal operating pressure for at least three (3) days before
testing.
6.8.2.
Gravity Sanitary Sewer Lines. On all projects involving installation
of sanitary sewer lines, the finished work shall comply with the provisions
listed below or similar requirements which will insure equal or better
results:
a.
After collecting and/or outfall lines or system have been brought
to completion, and prior to final inspection, the contractor will
be required to clean all dirt, debris and trash from lines and manholes.
b.
All lines or sections of lines that are found to be laid improperly
with respect to line or grade, that are found to contain broken or
leaking sections of pipe, or are obstructed in such a manner that
they cannot be satisfactorily corrected otherwise, shall be removed
and replaced at the contractor's expense.
c.
The contractor shall lay sewer lines, including house connections
so that the ground water filtration shall not average more than 200
gallons per inch of pipe diameter per 24 hours per mile of sewer.
The length of the main sewers shall be used in making the foregoing
computation even though the house connections (from the main sewer
to the property line) should be in place and included as a part of
the system when infiltration is measured. This requirement may be
applied to a portion of the contract work, such as the sewers in a
separate drainage area or to a single section of the line between
two manholes.
d.
Prior to acceptance, all sewers
shall be tested for leakage. Leakage shall conform to ASTM C-828,
as follows:
i.
Contractor shall flush and clean the line prior to testing to wet
the pipe surface and clean out debris. Contractor shall plug all outlets.
ii.
Calculate the test time for the section in accordance with the
Technical Manual.
iii.
Plug and brace the plugs in all openings in test section.
iv.
Add air until the internal pressure is raised to approximately
4 psi gage. Allow the pressure to stabilize, and start the test. Record
the drop in pressure for the est time. If the pressure drops more
than 1.0 psi gage during the test time, the line has failed the test.
Report test results to the Engineer.
e.
In order to test for infiltration, the Engineer may also require
exfiltration tests on each section of pipe between manholes after
it has been laid out but prior to backfilling of joints. Exfiltration
tests shall be conducted by plugging the lower end of the section
of sewer to be tested and filling the sewer with water to a point
approximately five feet above the invert at the lower end and at least
one foot above the pipe at the upper end, observing for leakage at
all joints and measuring the amount of leakage for a given interval
of time. Exfiltration shall not exceed 110 per cent times the infiltration
limits set out hereinbefore. All observed leaks shall be corrected
even though exfiltration is within the allowable limits. Exfiltration
tests will normally be required for flat sections of sewer that are
expected to be below the wet season, ground water table.
f.
To test for infiltration, the Engineer may also require that the
contractor plug the open ends of all lines at the manhole so that
measurements may be made at each section of the sewer line. This infiltration
test will not be made until the sewer line is completed, and the contractor
will be required to correct all conditions that are conducive to excessive
infiltration and may be required to relay such sections of the line
that may not be corrected otherwise. All observed leaks shall be corrected
even though infiltration is within allowable limits.
Manholes shall be installed at the end of each line, at all
changes in grade, size or alignment, at all intersections, and at
distances not greater than 400 feet (500 feet for 18-inch or larger
sewers).
Drop pipes shall be provided for any sewer entering a manhole
at an elevation 24 inches or more above the manhole invert. Drop manholes
shall be constructed with an outside drop connection, where practical.
The entire outside drop connection shall be encased in concrete.
Manholes shall be constructed to the form and dimensions shown
on the approved plans Manholes shall be constructed as per the Standard
Drawings. They shall be constructed on 3500 psi concrete foundations.
Minimum manhole diameter shall be 48 inches.
All connections to manholes or other structures shall be made
using a chemical resistant rubber compression diaphragm, precast into
the manhole. Diaphragms shall meet the requirements of ASTM C-923.
6.9.1.
Standard Manholes. The standard manhole shall be six feet or more
in depth, measured from the base of the cover frame to the top of
the concrete footing and shall be of cone type, top construction as
shown on the Standard Drawings.
6.9.2.
Shallow Manholes. The shallow manholes shall be less than six feet
in depth, measured from the base of the cover frame to the invert
of the effluent pipe and shall be of flat top construction as shown
on the Standard Drawings. Manholes shallower than four (4) feet from
the bench to the top of the frame and lid shall replace the flat concrete
top with East Jordan catalog No. V-7048, or Neenah Foundry catalog
No. R-1740-F with access lid in the center of the casting.
6.9.3.
Plastic Adjusting Rings. Plastic adjusting rings shall be round,
injection molded high density polyethylene (HDPE) adjustment rings
as manufactured by LADTECH, Inc. or approved equal, and shall be traffic
rated AASHTO HS-20. Adjustment rings shall be molded from 100% recycled
material.
6.9.4.
Precast Concrete Cones. Precast concrete cones shall be concentric,
of the size and shape shown on the plans, and shall conform to the
ASTM C478.
6.9.5.
Manhole Inverts. Manhole inverts shall be formed from 3500 psi concrete
as shown on Exhibit.[1] Curved invert shall be constructed of concrete, as shown,
and shall form a smooth, even half-pipe section as shown. The inverts
shall be constructed when the manhole is being built using prefabricated
forms.
The excavation shall be kept free of water while the manhole
is being constructed and the manhole shall not be backfilled until
inspected by the Engineer.
[1]
Editor's Note: The Exhibits are included as an attachment to this chapter.
6.9.6.
Manhole Frames and Covers. Unless otherwise approved manhole castings
shall consist of cast iron frames and 22 - 3/4 inch diameter covers,
weighing not less than 300 pounds per frame and cover, dimensioned
as shown on the plans. Manhole covers must sit neatly in the rings,
with contact edges machined for even bearing and tops flush with ring
edge. They shall have sufficient corrugations to prevent slipperiness.
The lids shall have two pick holes about 1-1/4 inches wide and 1/2
inch deep with 3/8 inch undercut all around. Lids on sanitary sewer
manholes must not be perforated.
6.9.7.
Drops into Standard Manholes. Drops into standard manholes shall
be built as per the Standard Drawings. Internal drops are permissible
as shown on the Standard Drawings.
6.9.8.
Manhole Testing. All manholes shall be subjected to a vacuum test
in accordance with ASTM C1244, except as specified otherwise herein.
Manholes shall be tested after installation with all connections in
place, and shall include testing of the seal between the frame and
the concrete cone, slab or grade rings. A vacuum of at least ten inches
of mercury (10" Hg) shall be drawn on the manhole. The manhole shall
be considered to pass the test if the vacuum reading does not drop
more than one inch Hg (from 10" to 9" Hg) during the minimum test
time. Minimum test time is based on manhole diameter and manhole depth,
as specified in the applicable Technical Manual.
Approved taps shall be installed on the public sewer for all
house or building connections at locations established by the developer's
engineer. At least one connection shall be provided for each platted
lot. The contractor shall lay the service laterals from this point
to the property line, or easement line. The developer shall place
a cap on the end of the service lateral and use a metallic marker
with PVC pipe and cap around it for protection. This marker should
be even with the ground. The developer is not required to install
the tee and cleanout, unless so directed by the Engineer during plan
review.
Sanitary sewer tap clean-outs and service connections shall
be installed in accordance with the plans and details by a qualified
plumber. Clean-outs shall be 6-inch minimum in diameter and have cast
iron covers installed according to the standard drawings.
Each separate dwelling structure, commercial building or industrial
building shall be provided with a separate service lateral. All connections
which service single family dwellings shall be not less than 6 inch
in diameter pipe. All connections which service multi-family dwellings,
or commercial and industrial buildings shall be sized based on occupancy
or use. Trenching, pipe installation and backfilling shall conform
to the requirements set out herein. All open ends of service laterals
shall be sealed with a standard PVC plug or cap, with compression
joints compatible with the pipe.
Service laterals shall be PVC (polyvinyl-chloride) sewer pipe,
ASTM D-3034, latest revision, or ductile iron pipe, AWWA specification
C-151 cement lined, and shall meet requirements of the state plumbing
code. Any part of a service lateral that is located within five (5)
feet of a water service pipe shall be constructed with ductile iron
pipe, unless the service lateral is at least one (1) foot deeper in
the ground than the water service line. Ductile iron pipe may be required
where the service lateral is exposed to damage or stoppage by tree
roots. Ductile iron pipe shall be used in filled or unstable ground,
in areas where the cover over the service lateral is less than three
(3) feet, or in areas where the sewer is subject to vehicular or other
external loads.
Under normal conditions service laterals shall be laid on a
slope of not less than two percent (approximately 1/4 inch per foot).
A minimum grade of one percent may be used with the approval of the
Engineer.
The tapping of service laterals into manholes on the newly constructed
sewers will not be permitted, except as permitted by the Engineer.
Where it is necessary to do so, the invert of the service lateral
shall not be higher than a point three inches below the top of the
bench in the manhole and suitable trough shall be provided in the
bench to prevent the accumulation of solids on the bench. If necessary,
a standard drop connection shall be provided for a house service that
is tapped into a manhole.
The installation of service laterals shall follow immediately
or be concurrent with the construction of the main sewer.
Connection to existing gravity sewer lines shall be made where
indicted on the plans. All connections to existing sewers shall be
performed by HWU personnel, with costs to be borne by the developer
in accordance with utility standard operating procedures.
6.12.1.
Concrete Sidewalks, Curbs and Gutters. Where concrete sidewalks,
curbs or gutters are cut or disturbed during the construction work,
they shall be removed to limits as directed by the Engineer, and shall
be replaced in fully as good or better condition than that which existed
prior to the contractor's operation.
When replacing concrete sidewalks, existing sidewalk shall be
removed to the edge of the next panel. The developer shall install
1/2 inch premolded full-depth expansion material at the exposed edges
of existing concrete, and at intervals not to exceed 40 feet.
Sidewalk shall be formed, poured and cured in conformance with
Section 4.2 of these specifications. Curbs and Gutters shall be formed,
poured and cured in conformance with Section 4.3 of these specifications.
6.12.2.
Concrete Pavement. Where Portland Cement concrete streets, alleys
and driveways are removed, they shall be reconstructed to the original
lines and grades and in such manner as to leave all such surfaces
in fully as good or better condition than existed prior to the operation.
The existing concrete paving shall be sawed or cut to straight
edges 12 inches outside the edges of the trench or removed to an existing
joint as directed by the Engineer.
Concrete pavement shall be formed, poured and cured in conformance
with Section 3.5 of these specifications.
6.12.3.
Bituminous Highway, Street and Driveway Replacement. The contractor
shall replace those sections of existing alleys, streets and driveways
which have been removed during construction. He shall reconstruct
same to the original lines and grades and in such manner as to leave
all such surfaces in fully as good or better condition than that which
existed prior to his operation.
Prior to trenching, the pavement shall be scored or cut to straight
edges at least 12 inches outside each edge of proposed trench to avoid
unnecessary damage to the remainder of the paving. Edges of the existing
pavement shall be recut and trimmed to square, straight edges after
the pipeline has been installed and prior to placing the new base
and pavement.
Backfilling the trench shall be in accordance with the previous
section on backfilling trenches. Base course for the paving shall
be Dense Graded Aggregate and shall be placed in accordance with section
3.4 to a depth equal to the existing base course, but not less than
6 inches in streets and alleys, and 4 inches in driveways.
Pavement shall be replaced in conformance with Section 3.4 of
these specifications.
Concrete cradle, anchors or encasement of sewer lines and/or
fittings are discouraged and shall only be placed where shown on the
plans, required by the specifications, or as directed by the Engineer.
Concrete shall be Class "B" and shall be mixed sufficiently wet to
permit it to flow under the pipe to form a continuous bed. In consolidating
concrete, care shall be taken not to disturb the grade or line of
the pipe or injure the joints. See standard drawing.
6.14.1.
Horizontal Separation. Sewers should be laid at least 10 feet,
horizontally, from an existing or proposed water main. Should local
conditions prevent a lateral separation of 10 feet, a sewer may be
laid closer than 10 feet to the water main if:
6.14.2.
Vertical Separation. Whenever sewers must cross under water
mains, the sewers shall be laid at such an elevation that the top
of the sewer is at least 18 inches below the bottom of the water main.
When the elevation of the sewer cannot be buried to meet the above
requirements, the sewer line shall be reconstructed with ductile iron
pipe for a distance of 10 feet on each side of the water line. One
full length of water main shall be centered over the sewer so that
both joints will be as far from the sewer as possible.
Existing mail boxes, drainage culverts, clothes line posts,
fences, and the like shall not be disturbed unless necessary, in which
case, they shall be replaced in as good condition as found as quickly
as possible. Existing materials shall be reused in replacing such
facilities when materials have not been damaged by the contractor's
operations. Existing facilities damaged by the contractor's operations
shall be replaced with new materials of the same type at the contractor's
expense.
Casing pipe shall be steel, plan end, coal tar enameled, mill
coated inside and out. The steel pipe shall have welded joints and
be at least 18 foot lengths. The wall thickness of the pipe shall
be at least 1/4 inch.
Upon completion of the installation of the sewer pipes and appurtenances,
the contractor shall remove all debris and surplus construction materials
resulting from the work. The contractor shall grade the ground along
each side of the pipe trench in a uniform and neat manner leaving
the construction area in a shape as near as possible to the original
ground line.
Unless otherwise specified by the Engineer, all graded areas
shall be left smooth and sown with a mixture of grasses at a rate
of not less than 100 pounds per acre. Seed mixture shall be as specified
in Section 2.9. When final grading has been completed, the area to
be seeded shall be fertilized with number 12-12-12 fertilizer at a
rate of 1000 lbs. per acre. Agricultural limestone shall be added
at a rate of 3 tons per acre. After the fertilizer and agricultural
limestone have been distributed, the contractor shall disc or harrow
the ground to thoroughly work the fertilizer into the soil. The seed
shall then be broadcast either by hand or by approved sowing equipment.
After the seed has been distributed, the contractor shall then lightly
cover the seed by use of a drag or other approved device. All seed
shall be certified. The seeded area shall then be mulched with clean,
weed-free straw to a depth of approximately 2 inches. Any necessary
reseeding or repairing shall be performed by the contractor prior
to final acceptance.
When sodding is required, it shall be so laid that no voids
occur between strips. Weed roots shall be removed as the sod is laid,
and the finished surface shall be true to grade even and equally firm
at all points. Well screened topsoil shall be lightly sprinkled over
the sodded areas and shall be raked to insure sealing the sod joints.
The sodded areas shall be thoroughly watered.
