HomeMy WebLinkAboutCorrespondence Miscellaneous 4/4/2006
Apr. 4, 2006 4:25PM
DEQ EUGENE
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No. 1254 P. 1
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State of Oregon
DEPARTMENT OF ENVIRONMENTAL QUALITY
FAX Transmittal Memorandum "
No. of Pages: d...
Date: If 'l.{ / 0),
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To:
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From; W-~ c...--1 ;;,. 1
EUGENE OFFICE
Dept. of Enviromnental Quality
1102 Lincoln St., Suite 210
Eugene, OR 97401
Company or Department:
Phone:
Phone:
(541)___. ____
(541) 686.7551 ,
FAX:
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Message: 0
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APPENDIX A
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SEWER PIPELINES
.1) MINIMUM REQUIREMENTS FOR
SEWER - PIPELINES (2) GUIDELINES FOR SEWER PIPELINES
(a) Caoacitv: (a) Caoacity:
Sewers shall be of such diameter as to (A) Collection sewers should be designed for
pass without overflow, bypass, or back the ultimate development of the tributary
flow onto damageable property of a user areas as determined by master sewerage
the design peak flow including sewage and land use plans of the owner.
and intiltration. All unavoidable inflow
fram roaf. surface. fooring, foundation, (B) The design of sewers should be based upan
or other graundwater. or surface water initial and ultimate tlows. Flows should be
saurces shall be excluded from capacity broken' down into domestic, industrial, and
allowance. in ti ltration! in flow fractions. A peaking
factor should be applied to domestic and
industrial fractions.
(C) Domestic tlows should be between 50 and
100 gallons per capita per day (gpcd).
Peaking factors should be between 1. 8 and
4.0. Infiltration allowance should be
normally less than 2,CXlO gallons per acre
per day; any greater allowance should be
justified. Any significant intlow allawance
should be justified.
(0) The minimum diameter,Of sewers should
be 8 inches far maintenance purpases.
Short nonextendable 6 inch sections ,Of up "
to 250 feet are permissible.
(E) Replacement sewers should be designed
commensurate with flow conditions.
(b) Velocity: (b) Velocitv:
Sewers shall be designed to have a' (A) Sewers should be laid on a gradient which
velocity to "self clean" or transport will produce a mean velocity, when flow-
constituent solids to the treatment facility ing full or half full, of at least (2) two feet
or the owner shall periodically service per second, based upon the Manning for-
sewers to flush, transport, or remove mula with" n", the coefficient of rough-
solids from sewers with minimal ness. valued at 0.013. r
velocity .
(B) Sewers with minimal flow such as upper
OAR52 A-I (September, 1981) .
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(c) Waterti!!htness:
Completed sewer construction shall
result in limited infiltrationlexfiltration
through pipe walls, joints, fittings, and
connection fittings, etc., andno inflow.
The limit shall be consistent with the
pipe and manhole materials and with
what is obt.ainable at the time by the
construction industry on representative
jobs for the same type of construction
using high quality materials and state-of-
. the-art methods of workmarrship. All
completed sewer lines in new work shall
be tested for watertighmess using either
recognized air or water testing require-
ments and procedures.
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:
reaches of laterals or those sewers serving
few dwellings should be steepened and/or
. reduced in diameter to approach a (2) two
feet per second selfcleaning velocity.
Actual flows during initial years of use
should be carefully'evaluated in this
regard.
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(C) Force mains and inverted siphons should
be designed for (3) three feet per second at
average flows.
(D) The minimum gradient for 8 inch sewers
should be no less than 0.4 percent
regardless of pipe material.
(E) The minimum gradient for 6 inch sewers
should be no less than 0.6 percent,
. preferably 0.75 percent.
(F) The flow channel(s) through manhole bases
should be smooth .and conform to the shape
and slope of the inlet sewer(s).
(G) Intersecting sewers, sewer connections,
etc., should be made without causing
backup into the smaller sewer. For
intersecting unequal sized sewers in
manholes, the elevation at 0.8 of full depth
of flow in each sewer should match.
(c) Waterti!!hmess:
(A) Watertighmess begins with good material
and finally depends upon sound field
practices. Good inspection and tests
should be supplemented with an initial
television inspection after trench backfilling
is complete. Since many defects do not
appear initially. an eleventh month final
inspection should be performed where that
capability is available and determined
necessary to obtain acceptable in-place
work. If only one television inspection is
considered, the eleventh month inspection
is recommended. .
(B) Exfiltration testing or the low pressure air
test for sanitary sewers should be a pres-
0AR52
A-2 (September, 1981)
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sure at least 6 feet greater than the
groundwater conditions which the sewer is
subject to at test time.
(C) Pipe materials, joints, fittings, and
appurtenances should be selected for their
watertight capabilities.
(D) Acceptance or performance standards
should not necessarily be uniform for all
pipe materials since average testing results
with good workmanship for work will vary
depending upon pipe materials. The range
of allowable exfiltrationlinfiltration for
work acceptance should be between 50 and
200 gallons per day per inch-of-diameter
per mile (gpdidm). Nonporous
(non-airpermeable) pipe should sustain
pressure for twice the computed time for
the same one pound per square inch (ps'i)
air pressure drop required by the air test.
Test sections should be from manhole-to-
manhole or about 700 feet maximum,
(E) The watertightness of all building sewers'
should conform to the State Plumbing Code
and' be tested without exception.
(F) Manholes should be water tested for
exfiltration during construction and/or
visually inspected during first wet weather
season after construction for intiltration.
Leaks should be promptly repaired.
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(G) Curved sewers should be as watertight as
other sewers and be tested. While not
recommended, horizontal/vertical curves at
times may be allowed but should be limited
in use. When used, the minimum radius of
curvature should be not less than 200 feet
and the maximum computed joint opening
no more than 3/8 inch. Complete and
accurate records should be kept of the
exact location of such curved sewers for
future reference. Reasonable field control
should be exercised to not compound joint
deflections and compromise watertightness.
0AR52
A-3 (September, 1981)
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(d) Structural Stren~h:
The completed installation including the
excavated trench, the pipe, the bedding,
and the pipe zone materials shall resist
imposed loads from backfill, impact, and
live loads (construction and design)
without pipe failure through crushing,
loss of watertightness; settlement, or
significant capacity loss.
(e) Abilirv to Pass Solids: .
Sewer systems shall be free of
depressions, sharp edges, roughness,
side sewer projections, obstructions,
restrictions, displaced "0" rings, etc.,
which can cause solids to accumulate or
deposit.
0AR52
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(d) Structural Stren~h:
(A) Bedding material should be placed full
trench width from at least 4 inches under
to spring line of all pipe for a leveling
course and proper pipe support. Hand
shaping of the native trench bottom for
rigid pipe is not recommended but may be
allowed, if appropriate, and uniform pipe
support can be obtained and gradel
alignment can be maintained.
(B) Cantilevering of nonreinforced rigid pipe at
manholes should be limited to the least
distance practicable to make a flexible
connection. A flexible joint should be
within 12 inches of manhole for smaller
pipe sizes. A ~econd flexible joint should
be provided within 4 feet of the manhole.
(C) Where cover from top of pipe to finished
grade is less than 36 inches, special design
and/or construction requirements should be
considered including, but not limited to,
raising finish grade, increasing class of
pipe and/or pipe bedding, use of ductile
iron, concrete encasement and restriction
of construction equipment from travel over
partially backfilled trench.
(e) Abilirv to Pass Solids:
(A) New sewers should be thoroughly flushed
and visually inspected for accumulated
. debris prior to use.
(B) Building sewer connections should be made
with fittings which prevent any projection
into the main sewer. The main sewer
should not be cracked, crushed, or
otherwise damaged in making taps. All
taps should be watertight.
(C) A tolerance for vertical deviation from true
grade line should be plus or minus 0.02
feet. Depressions for solids deposition
should be avoided. Similarly, the
horizontal tolerance for deviation from line
should be plus or minus 3/8 inch.
A-4
(September, 1981)
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(f) Durability:
(A) The materials and details of
construction shall provide an in-
place sewerage system which will
resist corrosion of the pipe and
manhole materials caused by any
source or condition. Any corrosive
effect shall be consistent with the
. design life of the sewer.
(B) Resistance to erosion of surfaces by
grit, high velocity flow, etc., shall
be addressed if appropriate.
(C) Temperature effect upon
thermoplastic materials shall be
appropriate.
(g) Stability:
(A) Line and Grade: Horizontal
alignment and vertical grade of in-
place sewers upon construction
completion and construction
acceptance shall be relatively
stable.
Design considerations, construction
specifications, inspections, etc.,
shall preclude pipe settlement,
shifting,. or flotation such that
capacity, watertightness structural
integrity, ability to pass solids,
maintainability, etc., are not
compromised either at construction
or any later time.
(B) Diameter: Rigid, flexible and
.
(D) Drop manhole piping should be easily
maintained, self cleaning or able to
'~.overtlow" into the manhole. Pressure
sewer piping cD'llnections, flow measuring
devices, etc., in manholes should be
designed to not obstruct flow.
(E) Flow channels in manholes should slope at
least 0.1 feet from inlet to outlet.
(f) Durability:
(A) Sewers should be constructed of materials
resistant to or protected from biological
degradation, acid and alkaline solutions,
normal sewer temperature variations,
abrasion and industrial wastes (where
applicable), or other harmful service
conditions which may exist in the sewerage
system.
Velocities over 15 feet per second in
sewers should have special consideratio
for erosion control.
ta
(A) Appropriate foundation stabilization or
soils should be employed in unstable soils.
Back fill should be in small lifts and
compacted uniformly to specified density
along and around the pipe.
(B) The Soil Class and density for bedding and
pipe zone materials should be carefully
selected and then compacted in the field to
the required in-place density.
PVC and ABS composite sewer pipe
should be deflection tested upon
construction completion prior to acceptance
with an approved nine blade go-no-go
gauge. Initial deflection at construction
completion should be no more than the
following:
0AR52
A-5
(September, 1981)
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semitlexible pipes tend to lose
minimum inside diameter if not
designed andJodnstalled properly.
Design considerations, construction
specifications, field inspections,
etc., shall preclude diameter loss
such that capacity, watertightness,
structural integrity, ability to pass
solids, maintainability, etc., are not
compromised either at construction
or any later time.
(h) Ooeration. Maintenance. and SafelY:
Sewer systems require periodic. and
unscheduled maintenance for sustained
. operation. Designs shall conform to
requirements of the sewage works owner
for manhole construction, spacing, size,
details and easements. All parts of the
sewerage system shall be readily
accessible. The minimum inside bottom
diameter of manholes shall be 42 inches.
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(i) pye (ASTM 0-3034) sewer pipe
should detlect no more than 4 to 5
percent bas~ upon inside base
diameters of 7.76,9.71, 11.56
and 14.14 inches for 8, 10, 12, and
15 inch nominal pipe respectively.
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(ii) ABS (ASTM 0-2680) composite
sewer pipe should deflect no more
thaa 2 to 3 percent based upon inside
average diameters of 7.75, 9.75,
11. 75 and 14.75 inches for. 8, 10, 12,
and 15 inch nominal pipe re-
spectively.
(C) Sewers on slopes over 25 percent should be
evaluated for slippage or pipe bedding
depending upon soil type, groundwater
presence, construction conditions, etc.
Appropriate anchors should be provided if
necessary .
(h) Ooeration. Maintenance. and SafelY:
(A) Access to the sewer by the sewer owner is
essential to perform maintenance tasks.
Easements should be granted along the
sewer I ine to the system owner for any
sewer for emergency repai rs. Manholes
and cleanouts are necessary for routine
access. Strucrures should not be located
over sewers.
(B) Owners should review own procedures,
equipment, construction standards, etc., for
sewer maintenance. Requirements of the
owner should be obtained by designers
upon start of sewer design since the owner
must assume all future maintenance.
Stricter standards of the owner should
prevail if in conflict with these guidelines.
(C) General Manhole/Cleanout Standards for
Sewers :
(I) The minimum inside bottom diameter
should be no less than 48 inches.
The least inside dimension may be
reduced 38 inches where an integral
0AR52
(September, 1981)
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A-6
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insige drop is acceptable to the
owner. No more than one inside
drop should be installed in a
manhole:
(Ii) Minimum cover opening diameter
should be 22 inches.
(iii) Manholes should be located at:
(l) Every change in grade or
alignment of sewer.
(II) Every point of change in size
or elevation of sewer.
(III) Each intersection or junction '
of sewers.
(IV) Upper end of a lateral sewer.
(V) At intervals of 500 feet or less
except for 24 inch and larger
sewers .
(iv) Cleanouts should not be substituted
for manholes except at the upper end
of lateral sewers 250 feet or less in
length.
(v) Channel width and depth should be
equal pipe diameter. Manhole base
ledges should be sloped to drain at
least I in 12.
(vi) Access to manholes may be by port-
able ladder. Manhole rungs and
in-place ladders which are subject to
considerable' corrosion and sliming
are not recommended.
(vii) Where free fall of sewage into a
manhole exceeds 24 inches from inlet
pipe invert to manhole invert, an
approved drop manhole should be
used.
0AR52
A-7
(Seprember, 1981)
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(D) Inverted Siohons:
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Inverted siphons should include at least two
pipe lines of such size and hydraulic gra-
dient as to maintain a velocity of at least 3
feet per second in one pipe under c'ondi-
tions of average dry weather flow. Control
manholes must be provided at both ends of
the inverted siphon line. The inlet and
outlet details shall be so arranged that the .
normal flow is diverted to either barrel so
that the other barrel may be removed from
service for maintenance.
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(i) Seoaration of Water and Sewer Lines:
(I) Seoaration of Water and Sewer Lines:
Protection of the water supply, be it
distribution system, production facilities
or source is not only prudent but
mandatory and absolutely necessary.
(A) Parallel Water and Sewer Lines:
(i) Sewer lines should conform to
Figure A-I.
Sanitary sewers and appurtenances
thereto shall not physically connect to a
public or private potable water supply
system so as to permit the passage of
any sewage or polluted water into the
potable supply.
(ii) Common trench construction for
water and sewer should be avoided
where practical. Where used, the
minimum pipe separations of Figure
A-I should be maintalned.
Sewer construction shall not disturb,
degrade, or decrease the watertightness
of any existing water supply line.
(B) Vertical Seoaration at Crossin!!s of Water
and Sewer Lines:
No special precautions should be necessary
where top of sewer line is at least 1.5 feet
below bOllom of waterline and adequate
structural protection for each line is
provided.
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(C) ExceDtions: Use of Pressure Pice Materials
for Sewer Line:
(I) Where the above horizontal or verti-
cal separations cannot be maintained,
the following pressure pipe materials
should be used in ,addition to what-
ever waterline improvements or
reconstruction that may be advisable
or required for protection of water.
The use of these pressure pipe
materials from manhole-to-manhole
is encouraged to avoid discontinuity
0AR52
A-8
(September, 1981)
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of materials.
(I) . Ductile iron pipe, class 50,
ANSI Standard A21.51
(AWWA C-151) with either
Push-on or mechanical rubber
gasket joints in accordance
with ANSI Standard A2Ul
(AWWA-Cll I).
(II) PVC pressure pipe, ASTM
0-2241, SDR 32.5, (125 psi)
with rubber-gasket joint in
accordance with UNI-Bell
Plastic Pipe Association
recommended Standard
Specification UNI-B-l for a
pressure-joint assembly.
(III) Asbestos-Cement pressure
pipe, class 100. ASTMC-296
(A WW A C-400) wirh rubber-
ring gaskets in accordance
wirh ASTM 0-1869.
(IV) High densiry polyethylene pipe
(Driscopipe 1000) PE 3406,
minimum SDR 32.5, wirh butt
fused joints.
(\I) Orher materials approved by
the State Health Division.
(ii) At crossings requiring pressure pipe
materials, the following should apply
with one standard length of special
pressure pipe centered over the
waterline in all cases:
S'2Jld2rd ~Iinimum Layiq .
Pipe Pipe' Leo~Lb Eacb Side
Material of Waterlin~:".
L=lLb Cr~5iDg:i;,':..;:: .
Ductile leon I 18 Feet I 18 Feet I
PVC 10 Feet I 20 Feet
A.&:.to....ccment lJ Feet 19 Feet
High.Deruiry I 38 Feel 19 Feet
Polyethylene
0AR52
A-9
(September, 1981)
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(D) Soil Restoration at Crossin!!s:
Soil removed in sewer line trench
construction at waterline crossings where
sewer crosses over water should be
replaced in all areas to as near natural
densities as possible through mechanical
compaction to restore any natural resis-
tance to groundwater movement which did
exist prior to construction. Soil should
include no rocle fragments over 1-112 inch
in the pipe zone.
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(E) Well Protection:
No sewer pipe should be laid less than 50
feet from any well without specific Health
Division approval. Pressure pipe materials
should be used to protect wells where
minimum setbacks are not obtainable or
where additional protection is required as
determined by the State Health Division.
(F) PiDe Testin!!:
Whenever a pressure pipe material is used
for any of the above purposes of separa-
tion, an appropriate pressure test should be
conducted on the pressure pipe to confirm
watertightness. Test pressures should be
no less than 15 psig where use will be for
a gravity sewer and higher where use will
be for a pressure sewer (force main).
(G) Other Exceptions should be resolved jointly
with the water purveyor and the State
Health Division.
0AR52
(Seprember, 1981)
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