HomeMy WebLinkAboutResolution 894ft
17,
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Attest:
RESOLUTION NO. 894
CITY OF ORONO
ON-SITE SEWAGE TREATMENT SYSTEM
DESIGN MANUAL.
ADOPTED AS THE STANDARD PRACTICES AND
REQUIRED SPECIFICATIONS FOR THE CON-
STRUCTION, REPAIR OR ALTERATION OF
ANY ON-SITE SEWAGE TREATMENT SYSTEM
WITHIN THE CITY OF ORONO
February 15, 1978
Adopted on the
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DESIGN MANUAL INDEX
Page
PART I:
DEFINITIONS
2
PART II:
SUBMITTALS REQUIRED FOR APPROVAL
Section
.l
New System Construction ....................
7
Section
2,Existing
System Repair or Alteration .......
7
Section
3
Subdivision Applications ...................
8.
Section
4
Innovative Systems .........................
8
PART III:
SITE EVALUATION
Section
1
General ....................................
9
Section
2
Drainfield'Site Conditions .................
10
Section
3
Soil Borings ...............................
16
Section
4
Percolation Testing ........................
17
PART IV:
STANDARD SYSTEM DESIGN
Section
1
General ......... ..................... .......
19
Section
2
Standard System Design .....................
20
PART V:
CONSTRUCTION AND MATERIAL SPECIFICATIONS
Section
1
Construction Procedures ..... .................22
Section
2
Building Sewers-..*, ......... o .............
23
Section
3
Septic Tanks ...............................
24
Section
4
Distribution of Effluent ...................
31
Section
5
Dosing of. -Effluent ........................
34
Section
6
Drainfields or Soil Treatment Area .........
37
Section
7
Holding Tanks ..............................
40
Section
8
Innovative Shallow Trench or Bed Subsurface
Soil Treatment and*Sewage Disposal System ..
42
Section
9
Innovative Mound Systems ...................
45
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f
PART I: DEFINITIONS
For the purpose of these regulations, certain terms or'words
used herein shall be interpreted as follows: the word "shall"
is mandatory,'the words "should," and "may" are permissive. All
distances unless.otherwise specified shall be measured horizontally.
"ADMINISTRATOR" That person charged by the City Council with
the enforcement of the On -Site Sewage Treatment Code.
"AEROBIC TANK" Any sewage tank which utilizes the principle of
oxidation in the decomposition of sewage by the introduction of
air into. the sewage.
[ "ALTERNATIVE SYSTEM" An individual sewage treatment system
employing such methods and devices presented in Sections 8
fand 9 of this Manual.
"BAFFLE" A device installed in a septic tank for proper operation
P P P P
o the tank, and to provide maximum retention of solids. Includes
l} vented tees and submerged pipes in addition to those devices that
are normally called baffles.
[ "BEDROCK" That layer of parent material which is consolidated
and unweathered.
!� "BEDROOM" Any room within a dwelling that, in the judgement -of the
administrator, might reasonably be used as a sleeping room, including
r but not limited to rooms designated as den, office, or study.
1 BUILDING DRAIN"That part of the lowest piping of the drainage
system which receives the da.schrge from soil, waste, and other
drainage pipes inside the walls of the building and conveys it
to the building sewer beginning at least one foot outside the
building footings.
"BUILDING SEWER" Thaty
art of the drainage s stem which extends
P g
from the end of the building drain and conveys its discharge to
[ an individual on-site sewage treatment system. Adequate•cleanouts
shall be provided as per the State Plumbing Code.
"CAPACITY The liquid volume of a sewage tank using inside
imensions below the outlet.
i "CESSPOOL" An underground pit into which raw household sewage
or other untreated liquid waste is discharged and from which .the
liquid seeps into the surrounding soil.
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• "CLERK" The Clerk of the City of Orono.
"CODE" The On -Site Sewage Treatment Code. •
"COUNCIL" The Council of the City of Orono.
"DISTRIBUTION PIPES" Perforated pipes or agricultural drain
tiles that are used to distribute sewage tank effluent in a
soil treatment system.
"DOSING" Dosing is the periodic application of effluent to
the soil absorption area.
"DISTRIBUTION DEVICE" A device which is used to distribute
sewage tank effluent to the distribution pipes,*including but
not limited to distribution boxes, drop boxes, and valve boxes.
"DOSING DEVICE" A pump, siphon, or other device that is used to
ischarge sewage tank effluent from the dosing chamber into the
-�^ distribution device or pipes in`intermittent quantities.
:'DOSING CHAMBER" (or pump pit or wet well) A tank or.separate
compartment following the sewage tanks which serves as a reservoir
for the dosing device.
"DWELLING UNIT" OR "RESIDENCE" Any building or portion thereof
or place used or intende to a used by human occupants as a
single family unit.
"EQUAL DISTRIBUTION" The distribution of sewage effluent equally
over the entire soil absorption area.
"EXISTING SYSTEM". "Any individual sewage treatment system after
instal ation.
"FILTER MATERIAL" Clean rock, crushed igneous rock or similar
insoluble, dura a and decay -resistant material free from dust,
sand, silt, or clay.
"FLOOD PLAIN" - Lands-, which are subject to flooding. This
includes a 1. areas including all marshes, wetlands, swamps,-
drainageways, lakes, and watercourses as more specifically
defined in Section 31.800 and sequel of Zoning Code.
"GREYWATER" Liquid waste from any source except toilet waste
and surface water runoff.
Ll
• "HOLDING TANK" A water tight tank for storage of sewage until
it can be transported to an off -site -point of disposal.
"IMPERMEABLE" With regards to bedrock, a bedrock having no
cracks or crevices and having a vertical permeability less
than one inch in 24 hours shall be considered impermeable.
With -regard to soils, a soil horizon or layer having a vertical
permeability less than one inch in 24 hours shall be considered
impermeable.
"INDIVIDUAL ON-SITE SEWAGE TREATMENT SYSTEM" A sewage treatment
system including the building sewer, septic tanks, and soil
absorption area, or part thereof, serving a dwelling or any
building or place, which utilizes soil treatment and disposal.
"MOTTLING" A soil condition of chemical oxidation and reduction
activity, appearing as. splotchy patches of red, brown, orange
and grey.
"MOUND SYSTEM" A on-site sewage treatment system where the
soi treatment area is built above the -existing ground.
"NEW SYSTEM" Any individual on-site sewage treatment system
. -to be installed, constructed,.altered, or repaired.
"OFFICIAL SOIL MAP" The Orono Soil Development Guide Map
prepared by the Hennepin'County Soil Conservation District and
available at the City Hall for reference).
"PERCOLATION RATE" The time rate of drop of a water surface in
a test hole as specified in the Code.
"_PLASTIC LIMIT" A soil moistur--e content below which the soil
maybe manipulated for purposes of installing a soil treatment
system, and above which manipulation will cause compaction and
puddling. The standard method -of determining the plastic limit
is specified in American Association of State.Highwa_y Officials
(AASHO) Designation: #T-90-61.
"PRESSURE DISTRIBUTION SYSTEM" A
of a pumping chamber and properly
equal distribution.
distribution system consisting
sized pumps and pipe to accomplish
"SAND" A soil texture composed •by weight of at least 25 percent
o very coarse and medium particles varying in size from two to
0.25 mm, less than 50 percent of fine or very fine sand ranging
in size between 0.25 and 0.50 mm, and no more than ten percent
of particles smaller than 0.05 mm.
• --4
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"SEEPAGE PIT" An underground pit into which a sewage tank
discharges sewage and from which the sewage seeps into the
surrounding soil through the bottom and openings in the side
of the pit.
"SEPTAGE" Those solids and liquids removed during periodic
maintenance of a septic tank or aerobic tank, or which are
removed from a holding tank. ,
"SETBACK" The shortest separation distance measured horizontally.
"SEWAGE" Any greywater or toilet waste. This does not include
ooting and roof drainage.
( "SEWAGE TANK EFFLUENT" That liquid which flows from a septic
i or aerobic tank under normal operation..
t^ "SEPTIC TANK" Any watertight, covered receptacle designed and
` constructed to receive the discharge of sewage from a building
sewer, to separate solids from liquid, to digest organic matter,
and to store solids through a period of detention, and to allow
the clarified liquids to discharge to a soil treatment area.
• "SITE" The proposed on-site sewage treatment system area.
"SLOPE" The ratio of vertical rise or fall to horizontal
distance.
"SOIL -BORING" Any type of excavation capable of revealing in
detail, textural characteristics of soils penetrated.
"SOIL'CLASSIFICATION" Where soil particle sizes or textures
t_ are specified, t ey refer to the Guide for USDA Soil Textural
Classification, attached in this document as Figure 1.
"PERMEABILITY" The rate of water infiltration into the soil
expressed as a rate (inches per hour).
"SOIL TREATMENT AREA" An area where sewage tank effluent is
treated and isposed of below the ground surface by filtration
�- and percolation through the soil, and also by evapotranspiration.
"STANDARD SYSTEM" An individual on-site sewage treatment system
employing septic tanks and the_soil treatment area commonly known
as drainfields.
."TOILET WASTE" Fecal matter, urine, toilet paper and any water
used for flushing.
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"VALVE BOX" Any device.which can stop septic tank effluent from
owing to a portion of the soil treatment area. Includes, but
is not limited to caps or plugs on distribution or drop box outlets,
divider boards, butterfly valves, gate valves or -other mechanisms.
"WATERTABLE" The highest elevation in the soil where all voids
are it ed with water, as evidenced by presence of water or soil
r mottling or other information.
"SEASONALLY HIGH WATERTABLE" The temporary or perched depth of
-soil which is saturated during a season, a temporary period of
time, or as a temporary condition.
"NORMAL (or ORDINARY) HIGH WATER MARK" A mark -delineating the
igest water level which has been maintained for a sufficient
` period of time to leave evidence upon the landscape. The normal
high water mark is commonly that point where the natural vegetation
i changes from predominantly aquatic to predominantly terrestrial.
"WATERTIGHT" Constructed so that water cannot get in or out except
through the outlet or inlet piping.
16
PART II - SL%11TTA1,S REQUIRED FOR APPROVAL
OSECTICN 1 - NE19 SYSTEM CONSTRUCTION
At the time of filing an application for a building permit for any work requiring a
new on-site sewage treatment system, or an installation permit application for a
I new system to serve an existing structure, the applicant shall provide a site• evalua-
tion report confirming that a conforming system can be installed and maintained on
the property. Information required:
1. Completed application form.
2. Plot plan including primary and alternate drainfield areas.
f 3. Site evaluation report:
l 4. Design plans and specifications.
•SECTION 2 - EXISTING SYSTEM REPAIR OR ALTERATION
*At the time of' 'filing an application to repair or alter any existing.
on-site sewage treatment system, the applicant shall provide a site evalu-
ation report confirming the existing conditions and the extent of the
proposed alterations. Non -conforming systems must be made fully conforming.
Conforming systems must remain conforming. Information required:
i
1.-• Completed application form.
2. Plot plan locating the existing septic tank(s) and drainfield area(s)
and indicating the location of all percolation tests and soil borings.
3.. Copy of the current compliance inspection report for the existing
system.
4. Site evaluation report. Incases involving the construction of a
new.drainfield area, the evaluation report shall include 2 soil
borings and 4 percolation tests. In cases involving the addition
of new drainfield laterals to an existing drainfield, at least
one soil boring shall be taken in the proposed area. The City may
require 2 or more percolation tests depending upon the soil
classification series or.test boring results.
S. Design plans and specifications.
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SECTION 3 - SUBDIVISION APPLICATIONS
At the time of filing for preliminary plat approval, the developer shall
provide a site evaluation report confirming that each building site
has sufficient suitable soil for on-site sewage
treatment. Submittals required:
1. Plot plan which shall be a copy of the preliminary plat.drawing
showing all existing structures, wells, and drainfield systems
and all proposed building sites, well locations, primary and alternate
drainfield locations.
2. Site evaluation report which shall
three (3) soil borings and six (6)
building site of less than 5 acres.
tabulate date from at least
percolation tests on each proposed
3. Copy of the current compliance inspection report for each existing
on-site system within the subdivision boundaries.
4. Where the site evaluation shows slopes in excess of 12%, percolation
rates slower than 60 minutes per inch, ground water table less than
5 feet deep or soil classification requiring innovative system
• design, the site'evaluation report shall also indicate specific
system design specifications as normally required for construction
permit applications.
SECTION 4 - INNOVATIVE SYSIBIS
Applications for innovative system installation variances shall include all the data
required for standard system applications, plus any additional data necessary to
establish the acceptability of the proposal. Such data would normally include case
histories of similar installations, manufacturer's literature, independent test
results and engineering .reports .
•
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PART III - SITE EITALUATION
•SECTION 1 - GENERAL
1. Site Evaluator: A site evaluator for purposes of this manual is a person who
is a geologist, soil scientist, registered professional engineer experienced
in soils engineering, or who has had at least four years of combined academic
training and field experience in soils analysis.
2. Evaluation Report: Proposed sites for all on-site sewage treatment. system
construction or alteration shall be fully explored, evaluated and reported to
the City by a qualified site evaluator. The City of Orono shall be notified
at least 24 hours prior to any soil boring or percolation testing so that an
inspector may be present at the site. The location of all soil borings or
percolation tests shall be indicated on the plans and certified by -the site'
evaluator. No soil testing shall be undertaken when'the soils are frozen.
3. Description of Site Evaluation Report. Each report shall include a plot plan
and supporting data.
a. Plot Plan: A scale drawing of the entire lot showing the following:
(1) All property.lines and lot dimensions.
(2) All existing and proposed structures.
(3) _All existing_or proposed well locations, or water supply piping.
(4) Relative elevations of house,.lot corners and diainfield areas.
(5) Slope of ground at"drainfield sites by contour lines or direction
arrows and slope percentages.
(6) Location of all percolation test holes and soil borings with
identifying symbols and relative ground elevations of each.
(7) Primary drainfield area identified - this area shall include at
least 2 soil borings and 4 percolation tests.
(8) Alternate drainfield area identified - this area shall include
at least 1 soil boring and 2 percolation tests.
(9) Distance from primary and alternate drainfield areas to property
lines, well locations, and any lake, stream, marsh or drainage
channel within 75 ft. of any part of the system.
b. Site Evaluation Report: The supporting data recording the information
gathered by on-site soil analysis including:
(1) Log of all soil borings keyed to the plot plan showing diameter
and depth of hole, soil profile and ground water conditions.
(2) Log of all percolation tests keyed to the plot plan showing
diameter and depth of hole, soil -profile, percolation rate
expressed in minutes per inch and ground water conditions if
encountered.
(3) Descri tion of the testing methods and equipment used.
(4) Date(s of of
and name of evaluator.
IV
SECTION 2 - DRAINFIELD SITE CONDITIONS
1. STANDARD SYSTEMS. The City will review applications for standard
on-site sewage treatment system designs provided each site meets
the following minimum conditions necessary for proper functioning
of such systems:
a. Lot Size: The lot shall have an adequate area for -all. existing
and expected improvements in addition to areas of soil suitable
for'the installation of two on-site sewage treatment systems,
known as the "primary drainfield site" to be used initially,
and the "alternate drainfield site" to be used should the primary
site ever fail. In all cases,.at least 10,000 square feet of
suitable soil and slope shall be identified within each lot'
as dedicated for drainfield use.
b. Soils: The following soil classification series shall in
most.cases be considered suitable for installation of standard
systems:
Anoka - AnB, AnC Hayden - HbB, HcC2
Braham - B+B, B+C Lester - LrB, LrC, ,LsC2
• Burnsville-- BuB,.BuC, BxB, BxC
c. Percolation Rate': The percolation -rate must be faster than
60 minutes per inch and slower than 0.5 minutes per inch.
.d. Depth to Groundwater or Seasonally Saturated Horizons: For
proper functioning of this system -the minimum depth to groundwater
or seasonally saturated condition-s.shall be more than 5 feet.
e. Flooding Hazard: There must be no hazard of flooding in.the
area where these systems are installed.
f. Slope: The land slope in the area proposed for the soil absorption
field shall not be greater than 12%.
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• 2. INNOVATIVE SYSTEMS. The City Engineer will review innovative
system designs where minimum site conditions are not acceptable
for standard system installation. Applications shall be made
according to the Variance Section of the Code.
a. Lot Size: The lot shall have an adequate area for all existing
_and expected improvements in addition to areas of soil suitable
for the installation of two on-site sewage treatment systems,
known as the "primary drainfield site" to be used initially,
and the "alternate drainfield site" to be used should the
primary site ever fail. In all cases, the area dedicated for
drainfield use shall be identified on the plot plan with sufficient
soil and slope data to ensure proper -design. -
b. Flooding Hazard: There must be no hazard of flooding in the
area'where these systems are installed.
C, Shallow Trench Systems: This system is intended for areas of
moderately high ground water table depth where percolation rates
are in the normal range.
1. Percolation Rate: The percolation rate must be faster than
. 60 minutes per -inch and slower than 0.5 minutes per inch.
2. Depth to Groundwater or Seasonally Saturated Horizons: For
proper functioning of this system the minimum depth to
groundwater or seasonally saturated conditions shall be
more than 3 feet.
3. Slope: The land slope in the area proposed for the soil
absorption'field shall not be greater than 12%.
4. Position on the Landscape: The system shall be installed
on level areas, on top of rises on convex slopes, on sides
of rises on plane. The systems shall not be installed in
depressions, swales, or drainageways.
5. Soils: The following soil classification series shall
..in most cases be considered unsuitable for the installation
of standard systems, but acceptable for a properly designed
shallow trench system:
Hayden - HbB, HcC2
LeSueur - LtB
Nessel - NeB
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d. Mound Systems, Type 1: This system is intended for areas of
moderately high ground watertable depth where percolation rates
are slow.
1. Percolation Rate: The percolation rate in 12 inches or
more of natural surface soil shall be faster than 60 minutes
- per inch and the percolation rate in subsoil and/or substratum
shall be faster than 120 minutes per inch.
2. Depth to'Groundwater or Seasonally Saturated Horizons: The
depth to groundwater shall be greater than 3 to 4 feet if
the percolation rate is 60 to 120 minutes per inch and 2 to
3 feet with a percolation rate 30 to 60 minutes per inch.
-12
3. Slope: The land slope in the area being considered for
installation of the system -shall not be greater than 6%.
4. Position on the Landscape: The system shall be installed
.on level areas, on top of rises on convex slopes or on
sides of rises on plane. The systems shall not be installed'
in depressions, swales or drainageways.
5. Soils: The following soil classification series shall in
most cases be considered unsuitable for the installation of
standard systems, but acceptable for a*properly designed
mound system;
Cordova - Co
Dalbo - D1A
Dundas - Du -
Erin - EnB
Kilkenny
Lester - LsC2
Lerdal - LmB
Minnetonka - Mt
Shields. - Sh
Shorewood - SwA, SwB
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e. Mound Systems, Type 2: This system is intended for areas of
extremely permeable soils.
1. Percolation Rate: The percolation rate must be faster than
60 minutes per inch and may be faster.than 0.5 minutes
per inch.
2. Depth to Groundwater or Seasonally Saturated Horizons: For
proper functioning of•this system the minimum depth to
groundwater or seasonally saturated conditions shall be
more than 3 feet.
3. Slope: The land slope in the area being considered for
installation of the system shall not be greater than 6%.
4. Position.on the Landscape: The system shall be installed
on level areas, on top of rises on convex slopes or on
sides of rises on plane. The systems shall not be installed
in depressions, swales or drainageways.
5.. Soils: The following soil classification series shall
in most cases be. considered.unsuitable for the installation
• of*standard systems, but -acceptable for a properly designed
mound system: j
An6ka AnB
Braham B+B
Burnsville - BuB, BxB
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1 •
f. Steep Slope Limitations: Steep slopes occurring in many soil
classification series present severe limitations due to side
hill seepage and unusual design features or construction
technique. '
1. The following soil classification series indicating slopes
of 6% - 18% shall in most cases be considered unsuitable
for the installation of standard systems without special
design considerations:'
Anoka - AnC Heyder - HID, HeD
Braham - B+C, B+D Hayden - HbD, HcD2
Burnsville - BuC, BuD, BxC Kilkenny - KkC, KkD,
Dalbo - D1C K1C211 K1D2
Erin - EnC, EnD, ErC2 Lester - LrD, LsD2
2. The following soil classification series indicating slopes
in excess of 18% shall in most cases be considered urisuitable
for the installation of any drainfield area:
Braham - B+D Heyder - HIE
Burnsville - ' BuD Kilkenny - Kke.
• Erin - EnE, EsF Lester - LrE
Hayden - HbE, HcE2, HdF Salida - SaE
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0
g. Disturbed Soil Limitations: Disturbed soils present unusual
design limitations due to unpredictable soil characteristics.
Extensively detailed site and soil evaluation is required for
consideration of any drainfield area on the following soil
classification series:
Cut - Cu Borrow pit - BoBp
Fill- Fd Gravel pit - GP,
h. Severely Restrictive Soils: Lowland and marshy soils present
extremely severe limitations for any drainfield installation
due to high ground water table depths, flooding hayards and
extremely slow percolation rates. Every reasonable effort
must be made to preclude these soils from consideration for
drainfield installation.
Where such -soils must be considered 'due to existing lot con-
figurations, the proposed designs shall be carefully engineered
and could be expected to include methods such as complete soil
replacement mounding, and other innovations. The City Engineer
must approve all such designs and thq City is under no obligation
to approve any drainfield on these soils.
Any drainfield approved for installation on these soils shall
be subject to the metering of.water inflow, and regular ground
water quality testing. Certificates of Compliance shall be
issued on a one-year renewable substandard system basis and may
be revoked at any time that ground water quality is found to
be deteriorating. _
The following.soil classification series fall within this
restrictive category:
Glencoe - Gc Marsh - Ma
Hamel Loam - Ha Peaty Muck - Pa, Pm
Lake Beaches - Lc, Ld '
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SECTION 3 - SOIL BORINGS
Soil Borings at least-8 feet deep (S feet below the bottom of any
proposed drainfield trench) shall be taken to determine soil types and
water table information. For new systems, at least 2 borings shall be
made within the primary drainfield area'and at least one boring within
,the alternate drainfield area.' For drainfield additions to existing
'systems, at least one soil boring is required.
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SECTION 4 - PERCOLATION TESTING
Percolation testing shall be done on -all proposed drainfield sites to
help determine the natural absorption capability of the soil. For new
systems, at least 4 percolation tests shall be -made within the primary
drainfield area and at least 2 percolation tests within the alternate
drainfield area. For drainfield additions to existing systems, at
least two percolation tests should be made in the expansion area.
Percolation Test Procedure:
1.
Type of Test Hole
1
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SECTION 4 - PERCOLATION TESTING
Percolation testing shall be done on -all proposed drainfield sites to
help determine the natural absorption capability of the soil. For new
systems, at least 4 percolation tests shall be -made within the primary
drainfield area and at least 2 percolation tests within the alternate
drainfield area. For drainfield additions to existing systems, at
least two percolation tests should be made in the expansion area.
Percolation Test Procedure:
1.
Type of Test Hole
A hole with horizontal dimensions of six inches and vertical
si.des�shall be dug or bored to the depth of the proposed
absorption trench.
2.
Preparation of Test Hole
The bottom and sides of the hole shall be carefully scratched
with a knife blade or sharp pointed instrument to remove any
smeared soil surfaces and to provide a natural soil interface
•
into which water may percolate..' All loose material shall be
removed from the hole and two (2)* inches of coarse sand or
Ane gravel shall be added to protect the bottom from scouring.
and sediment.
3.
Saturation and Swelling of the Soil
The hole shall'be carefully filled with clear water ta_a minimum
depth -of twelve (12) inches over the gravel. Water shall be
kept in the hole for at least four (4) hours, and preferably
overnight, by refilling if necessary, or by supplying a surplus
reservoir of water, such as in -an automatic siphon. In sandy
soils containing little or no clay, the swelling procedure shall
not be required and the test may be made as described under
Item.2diiD3 after the water from one filling of the hole has
completely seeped away.
4.
Percolation Rate Measurement -
With the -exception of sandy soils, percolation rate measurements
shall be made on the day following the procedure described
under Item (C) above and as follows: A percolation rate data
sheet shall.be kept and submitted for each test.
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Figure 7
• USDA TEXTURAL CLASSIFICATION OF SOILS
0 0 0 0 0 ''o
COMPARISON OF PARTICLE SIZE SCALES
Sieve Openings in Inches U. S. Standard Sieve Numbers
3 2 ] 3- ' : 4 10 20 40 Gn 200
ap o
IFIE0
F
GRAVEL
SAND
SILT OR CLAY
1. Coarse Fine
USDA
GRAVEL' _
SILT
CLAY
Ftne
Sell
CIA,
Coarse
Coarse
►{colts
Fine fine
IFIE0
F
GRAVEL
SAND
SILT OR CLAY
1. Coarse Fine
Coarse H cdtum F,ne
III I LLL_!____ I 1 111 1 1 1 I
—18
GRAVEL OR STONE
SAND
SILT — CLAY
AASHO
Codrse
meottra
Fine
Coarse
Ftne
Sell
CIA,
III I LLL_!____ I 1 111 1 1 1 I
—18
PART IV. - STA?�'DW SYST N DLSIM
SECTION 1 - MNERAL
�• 1. DESI�I BASED QN SITE EVALUATIM: The engineered design and layout'of system
components shall account for the proposed flow and actual soil absorption
capabilities and site conditions determined by the site evaluation.
2. SYSTE14 DESIGNER: The system designer should be the site evaluator or a person
i with similar training including a geologist, soil scientist, registered pro-
fessional engineer experienced in soils engineering, or who has had at least
four years of combined academic training and field experience in septic system
design.
3. DESIGN PLANS AND SPECIFICATIGNS; The system layout and design specifications
t shall be 'consistent with the standards and requirements of this manual. The
data submitted for review shall include the following:
a. Proposed flow rate into the system expressed in gallons *per day, or in
number of bedrooms for residential systems.
b. Proposed drainfield absorption area required to handle the expected flow,
based upon the requirements in this Design ?-Manual, expressed in square
feet of absorption area.
'`- c. Capacity and type of proposed septic tanks.
d. Sketch of proposed system layout showing building served, septic tanks,
• distribution line, distribution boxes, dosing pumps if used, and number,
width, length and layout of absorption trenches.
�- e. Sketch section of drainfield area showing depth and width of trenches,
size and amount of filter material, size and type of drainage pipe, and
' extent of cover.
f. Any additional data or drawings necessary to depict and construct the pro-
posed system,- particularly -if the proposal is an innovative system.
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SECTIO] 2 - STANDARD SYSTEM DESIGN
•1. SEPTIC TANKS
3
a. Each single family residence shall be equipped with two (2) septic tanks.
The first tank shall be not less than 1000 gallon capacity and the second
tank not less than 750 gallon capacity. For better operating efficiency,
it is highly recommended, but not mandatory, that the second tank be of
1000 gallon capacity. With two tanks of differing sizes, the first tank
shall be the larger of the two:
b. The liquid capacity of a septic tank serving an establishment other than
a single family residence shall be sufficient to provide a sewage deten-
tion period of not.less than 36 hours'din,the tank for flows less than
1,500 gallons per day, but in no instance shall the liquid capacity be
less than 1000 gallons. For flows greater than 1,500 gallons per day,
the.minimum liquid capacity shall equal 1,125 gallons plus 75 percent of
the daily sewage flow rate, which shall be'determined by measurement or -
estimated from data provided by the applicant.
c. Septic tanks shall be placed so that access is convenient for the removal
of liquids and accumulated; solids. _. The _tanks -shall-be- placed -.on -firm and..
settled soil capable of bearing the weight of the tank and its contents.
DISTRIBUTION B()X: A distribution box with a removable cover and of sufficient size
to accommodate the necessary field .lateral lines shall be constructed at the head
of each disposal field. A standard box of 16" diameter shall have no more than four
(4) outlet pipes. A separate distribution box shall be used on each level of any
multi-level drainfield area.
SOIL ABSORPTION AREA REQUIRBEM: Final treatment and disposal of sewage tank
effluent shall be -by means of soil absorption.
a. All treatment areas shall be setback the following horizontal distances
from the features given below:
Minimum
Setback
Feature_ Distance (Feet)
Property Lines, Buildings and
Buried Pipes Distributing -
Water Under Pressure 20
Water Supply Wells or Buried
Water Suction Pipes 75
Lakes, Streams.and Wetlands 75
-20
b. The required soil treatment area shall be determined by the results of
the site evaluation and the design flow into the system.
The minimum soil treatment area required for any dwelling unit shall
be as follows:
Perc Rate Primary Field Alternate Field
1/2 to 30 MPI 600 Sq. Ft. 600 Sq. Ft
30 to 60 MPI d 800 Sq. Ft. 800 Sq. Ft.
The minimum soil treatment area required for multiple residential units
shall consist of the, sum of the areas required for each individual unit
multiplied by the number of units.to provide for primary and alternate
site.
Trench and bed size based upon flow rates shall be as follows:
4- Percolation Rate Per Gallon of Required Soil Treatment
(Minutes per Inch) Mlaste Per Day (b) Area Per Bedroom
. .... .............
(Square Feet) (a) -(e)
Faster than ,1/2 - -
1/2 to 5 - 0.83 125
6 to 15 1.27 190
16 to 30 1.67 250
[J 31 to 45 2.00 300
• 46 to 60 2.20 330
[ J (1) Area requirements as determined from table shall be provided in
both the primaiy and alternate sites.
t (2) When treatment system design -is based on gallons of waste per
day, the required treatment area may be reduced for trenches
only, by the following percentages: 20 percent for 12 inches
of filter material below the distribution pipe; 35 percent for
18 inches; and` 40. percent for 24 inches. • The filter material
shall completely encase the disposal pipes to a depth of at
C least one inch.
(3) Soil is unsuitable for a standard system if the percolation rate
is faster than 1/2 minute per inch or slower than 60 minutes per
inch. See Variance section for alternative systems that may be
considered. -
' 4. ABSORPTION TRENCH REQUIRDEM: The trench beds shall be not less than 18 inches
nor more than 36, inches wide. Trenches and beds shall not be more than 100 feet
I in length. The size and minimum, spacing requirement
s for treatment trenches is
as follows:
Width at Bottom
iIn Inches
Effective Absorption
Area in Square Feet
`Per Lineal 'Feet
1.3
2.0
2.5
3.0
-2
1-inimum Spacing of
Lines, Center to
Center, In Feet
6.0
6.5
7.0
7.5
{ 18
24
I_
30
36
Effective Absorption
Area in Square Feet
`Per Lineal 'Feet
1.3
2.0
2.5
3.0
-2
1-inimum Spacing of
Lines, Center to
Center, In Feet
6.0
6.5
7.0
7.5
`PART V - OONSTRUCTIQV AND MkTERIAL SPECIFICATIONS
�SECTICN 1 - CONSTRUCHON PROCEDURES
M
1. PROTECT ABSORPTIQN AREAS: Proposed drainfield absorption areas shall be identified
and marked off on the lot at the time of the site evaluation and prior to any
construction or grading occurring in the area. The drainfield area shall remain
undisturbed until drainfield construction is commenced. No vehicular traffic should
-be allowed in the drainfield area either before or after drainfield installation.
2. FAVORABLE MATHER REQUIRED: Drainfield absorption area or trench construction must
not proceed if the area is wet or has had rain within 48 hours. Once construction
'commences, it should proceed to completion without interruption unless rain or
ground moisture causes the trench sides to smear or the ground to compact under the
equipment. No construction shall occur in frozen ground. Rain or snow should not
be allowed to acevumilate on uncovered trenches.
3. EQUIPMENT RESTRIMONS: Equipment used for drainfield construction shall be chosen
to cause minimum compaction of surface soil. Tracked equipment is preferred over
wheeled equipment. Trenching equipment is best sized to produce the required
trench width in one pass to reduce smearing. Trench -side scarifying is important
and must be -done either with the trench -cut, -or by hand following the cut. .
4. INSPECTION NOTICE: The City of Orono shall be notified at least 24 hours in
advance of any septic system construction start, and shall also*be notified when
construction recommences after having been stopped for 24 hours or longer.
-22
e
-23' .
1•
•
,
SECTION 2: BUILDING SEWERS
1.
The building sewer, and all piping to the point where
the disposal field begins, shall be of water tight
piping and joints. Joints between this piping and
other appurtenances of the system shall be water tight.
-The use of perforated pipe or its equivalent is prohibited.
2.
No building drain or building sewer shall be less than
four inches in diameter.
3.
The buried or concealed portion of any building sewer,
building drain or branch thereof shall be located at
least 20 feet from any well shall be constructed of
cast iron pipe with air tested joints. The air test
should be made by attaching an air compressor or test
apparatus to a suitable opening and closing all other
inlets or outlets to the sewer and/or drain under test
by means -of -prop;er --testing-plugs;—Air- -shall be forced
Into the system until there is uniform pressure of five
pounds per square inch in the section being tested.
The system'shall be considered satisfactorily air
tested'if the pressure therein remains constant for 15
minutes without the addition of air. -
•
4:'
The portions of any buried sewer more than 50 feet from
a well shall be *constructed of cast-iron, vitrified
clay, cement -asbestos, concrete or other City approved
pipe material.
5.
All joints between -pipes and fittings in the building
sewer shall have water tight and root tight joints and
'
shall be air . tested.- Portland cement mortar joints
"
shall not be allowed. 'mines shall provide a.grade of
not less than one-eighth inch per foot. All changes. of
grade shall be by means of long sweep ells. Where -long
sweep ells are not used and where the direction changes
by more than 22-1/2 degrees, accessible cleanouts shall
be provided.
-23' .
SECTION 3: SEPTIC TANKS
1. Materials
�- a.• General: All tanks, regardless of material or method
I of construction shall be:
(1) Watertight -
(2) So designed and .constructed as to withstand all
lateral earth pressures under saturated soil
( conditions with the tank empty.
(3) So designed and.constructed as to withstand a
(; minimum of seven feet of saturated earth cover
above the tank top.
�^ In addition, the following specifications apply to specific
materials as -indicated.
lb. Precast Concrete Tanks
(1) Precast concrete tanks shall be constructed of at
least a-4,000 psi (pounds per square inch) core
• test, air entrained concrete mix.
I. (2) Precast concrete tanks shall be cured to at least
a seven-day strength before installation.
T
C. Fiberglass & Plastic Tanks
- Fiberglass and plastic tanks shall be designed and
L constructed to meet the general requirements outlined
above.'-
Block-or
bove.Block-or Sectional Tanks•
i (1) Rectangular Blocks.
(a), Rectangular blocks shall be laid on an
�- approved bottom. Block shall be at least
eight inches thick, constructed of•a 4,000
Psi core test concrete mix, and cured to a
28 -day strength before installation.
(b) Rectangular blocks shall be laid either with
mortar joints or filled cores.
-24
f
I
T
(c) There shall be at least two coats of 1/4
inch thick concrete plaster placed on the
inside of the block tank. There shall be
at least two hours elapsed time between
coats. The plaster coat shall start at
the bottom course and work up.
(2) Circular Block Tanks
Circular blocks shall be carefully placed on an
approved bottom. Circular blocks shall be at
least -two inches thick and constructed of a 4,000
psi core test concrete mix, cured to a 28 -day
strength before. installation.
There shall be at least two coats of 1/4 inch
thick .concrete plaster placed on the inside of
the block tank. There shall be at least two
hours elapsed time between coats. The plaster
coat shall start at the bottom course and work up.
(3) Sectional Tanks
(4)
A sectional tank shall have an entire section
cast as an integral unit.'
A sectional tank shall have two :or more sections
and shall have a6 least one joint below the level
of the outlet invert of the tank. Sectional
tanks shall have an integrally cast bottom, or
shall be laid on an approved bottom.
The -joint or joints shall be permanently sealed
so.as to,be watertight.
Bottoms
Any tank not having an integrally cast bottom
shall not be installed when the watertable is
closer than,three inches to the bottom of the
excavation.
If the bottom is poured -in-place concrete, it
shall be at least four inches thick and extend
to at least four inches outside the tank wall.
A concrete mix of at .least one part cement,
two parts washed sand and three parts washed'
rock shall be -mixed before placement in the
excavation.
.-25
L.
r'
e.
If a starter ring is used, it shall be constructed
of a 4,000 psi core test concrete mix, cured to a
seven-day strength before installation. It shall
extend at least one inch beyond the tank wall, or
be cast integrally with the bottom section.
A sectional tank not having an integrally precast
bottom shall have a four inch thick bottom poured
within the tank -walls.
(5) Any tank cover not integrally cast with the tank
shall be so installed that the joint with the tank
sidewall is permanently sealed so as to be water-
tight. ,
All covers shall be so.designed and constructed
as to withstand a minimum of seven feet of saturated
earth cover above the tank top.
Inlet and Outlet Device Materials
(1) Inlet and outlet devices shall be sanitary -tees,
or baffles constructed of acid resistant,concrete,
acid resistant fiberglass or plastic.
(2) Sanitary.tees shall be glued to the inlet or outlet
pipes. Baffles shall be integrally cast with the.
tank, affixed with a permanent waterproof adhesive
or affixed with stainless steel connectors, top
and bottom.
f. Other Materials _
Tanks or baffles of any material other than those -
outlined above shall not be used except as approved
by the City Engineer..
2. Design
All tanks, regardless of material or method of construction, -shall
conform to the following -design criteria:
a. The liquid depth of any septic tank or compartment
thereof shall be not less than 30 inches. A liquid
depth greater than six and one-half feet shall not
-be considered in determining tank capacity.
b. 'No tank or compartment thereof shall have an inside
horizontal dimension less than 24 inches:
=26
E
C. Inlet and outlet connections of the tank thereof shall
be submerged by means of vented, sanitary tees or
baffled. •
d. The space in the tank between the liquid surface and
the top of the inlet and -outlet baffles or sanitary
tees shall be not less than 20 percent of the total
required liquid capacity, except that in horizontal
cylindrical tanks this space shall be not less than 15
percent of the total 'required liquid capacity.
e. The inlet baffle or sanitary tee shall extend at least
six inches but not more than 20 percent of the total
liquid depth below the liquid surface and at least oiie
inch above the crown of the inlet sewer.
f. The outlet baffle or sanitary tee and the baffles or
sanitary tees between compartments shall extend below
the liquid surface a distance equal to 40 percent of
the liquid depth except that the penetration of the
indicated'baffles or sanitary tees for horizontal
cylindrical tanks shall be 35 percent of the total
liquid depth. They also shall extend above the liquid '
surface as -required in d. above. In no case shall
they extend less than six inches above the liquid
surface.
,g. There shall be at least one inch between the underside
of the top of the tank and the highest point of the
-inlet and -outlet devices.
h. The inlet invert shall be not less than three inches
above the outlet invert.
i. The inlet and outlet shall be located opposite each
other along the axis of maximum dimension. The
horizontal distance between the nearest points of the
inlet and outlet devices shall be at least four feet.
j. Sanitary tees shall be at least four inches in diameter.
Inlet baffles shall be no less than six inches or no
more than 12 inches measured from the end of the inlet
pipe to the nearest point on the baffle. Outlet baffles
shall be six - inches measured from beginning of the outlet
pipe to the nearest point on the baffle.
I,
•
•
k. Access to the septic tank shall be as follows:
There shall be one or more manholes, at least 20
inches least diameter, and located within six feet
of all walls of the tank: The manhole shall extend
I
through the cover to a point within 12 inches but
no closer than six inches below finished grade.
(.The
manhole cover shall be covered with at least
SIX inches of earth.
(
There shall be an inspection,pipe of at least four
i,
inches diameter or a manhole over both the inlet and
outlet devices. The inspection pipe shall extend through
f
the cover and be capped flush.or above finished grade.
1i
A downward projection of the center line of the
inspection pipe shall be directly in line with the
r
center line of the inlet or outlet device.
t
1. Compartmentation of single tanks:
l
(1) Septic tanks larger than 3,000 gallons and
fabricated as a single unit shall be divided
into two or more compartments.
(2) When a septic tank is divided intotwocompart-
ments, not less than one half nor more than
C,
two-thirds of.the total volume shall be in the
first compartment.*
(
1.
(3) When a septic tank is divided into three or
more compartments, one-half of the total
(
volume shall be in the first compartment and
1,
the other half equally divided in the 'other
compartments . ' , . s
I
(4) Connections between compartments -shall be
submerged by means of vented tees or baffled
j
so as to obtain effective retention of scum
1;
and sludge. Thesubmergence of the outlet
device of each compartment shall be as
specified in Section f. above.
• (5) Adequate venting must be provided between
'
compartments by•vented tees or baffles or
►.
by an opening of at least 50 square inches
near the top of the compartment wall.
!.
(6) Adequate access `to each compartment shall be
provided by one or more manholes, at least
1
20.inches least dimension, and located within
1.:
six feet of all walls,of the tank. The manhole
shall extend through the cover to a point within
12 inches but no closer than six inches below
t_
finished grade.
f .
-28
(7) Where more than one tank is used to obtain the
required liquid volume, the tanks shall be
connected in series.
(8) No more than four tanks in series can be used
to obtain the required liquid volume.
(9) The first tank shall be no smaller than. any
subsequent tanks in series.
3. Aerobic Tanks
a. Aerobic tank treatment systems shall comply with the
following design requirements:
(1) The treatment system including each individual
unit or compartment shall be easily accessible
for inspection and maintenance and shall be
provided with secured covers.
(2) The raw sewage flow from the dwelling. shall be
intercepted by a trash trap prior to its entering
the aeration compartment. The trash trap shall
have a net holding capacity of not less than 20
percent of the average daily flow. The invert
level to the trap shall be above the liquid level
and discharge directly into the trap. The outlet
from the trap to the aeration compartment shall be
deep baffled or equipped with a.tee or long ell.
(3) The trash trap shall, be readily accessible for
inspection and effective cleaning and shall be so
-constructed as to prevent unaiuthorized entry.
(4) The aeration compartment shall have a minimum
holding capacity of .five hundred.gillons or one
hundred twenty gallons per bedroom, whichever
is greater.
(5)• The method of aeration shall be accomplished by
mechanical aeration, diffused air, or both. The
method used shall maintain aerobic conditions
at all times.
-29
(6) The settling compartment shall have a minimum
net holding capacity equal to twenty •percent
of the volume of the aeration compartment. The -
design shall provide for effective settling and
continuous return of settled sludge to the
aeration compartment.
b.* A minimum of one year warranty and an initial two
year- service contract which specifies regular inspection
calls and effluent quality checks shall be provided as
a part of the purchase agreement.
C. All other features of the aerobic tanks not specifically
mentioned above shall comply with National Sanitation
Foundation. Standard No. 40.
•
1,49
SECTION 4: DISTRIBUTION OF EFFLUENT
A. By Gravity Flow Over The Soil Treatment Area
1. Level Ground
Where the elevation difference of the ground surface
does not exceed 28 inches in any direction within the
soil treatment area; the sewage tank effluent may be
directed to the soil treatment area through a system
of interconnected distribution pipes or trenched in
a continuous system. The bottom of the trenches and
distribution pipes shall be constructed on a relatively
level grade,.not to exceed six inches difference in
elevation.
2. Slightly Sloping Ground*
Where the elevation difference of the ground surface
exceeds 28 inches in any direction within the soil
treatment area, the sewage tank effluent may be
distributed -by a distribution box provided the final
ground surface elevation of the lowest trench is at
least one foot higher than the outlet inverts of'the
distribution box.
(a) Distribution Box
(1) The distribution box shall be precast
concrete with a removable cover and shall be
constructed of durable materials not subject
to excessive corrosion or decay. The minimum
inside dimension shall be at least ten inches
-" unless the box is to 'be used' as a valve `box.
Then each outlet shall have at least eight
inches of sidewall space and the side of -any
outlet shall be at least six inches from any
corner.
(2) The inverts of all,outlets shall be at'the
same elevation as measured from a liquid
surface in the bottom of the box.
(3) The inlet invert shall be at least one inch
above the outlet inverts.
(4) The outlet inverts shall be at least four
inches above the distribution box floor.
-31
ti
•
1,49
SECTION 4: DISTRIBUTION OF EFFLUENT
A. By Gravity Flow Over The Soil Treatment Area
1. Level Ground
Where the elevation difference of the ground surface
does not exceed 28 inches in any direction within the
soil treatment area; the sewage tank effluent may be
directed to the soil treatment area through a system
of interconnected distribution pipes or trenched in
a continuous system. The bottom of the trenches and
distribution pipes shall be constructed on a relatively
level grade,.not to exceed six inches difference in
elevation.
2. Slightly Sloping Ground*
Where the elevation difference of the ground surface
exceeds 28 inches in any direction within the soil
treatment area, the sewage tank effluent may be
distributed -by a distribution box provided the final
ground surface elevation of the lowest trench is at
least one foot higher than the outlet inverts of'the
distribution box.
(a) Distribution Box
(1) The distribution box shall be precast
concrete with a removable cover and shall be
constructed of durable materials not subject
to excessive corrosion or decay. The minimum
inside dimension shall be at least ten inches
-" unless the box is to 'be used' as a valve `box.
Then each outlet shall have at least eight
inches of sidewall space and the side of -any
outlet shall be at least six inches from any
corner.
(2) The inverts of all,outlets shall be at'the
same elevation as measured from a liquid
surface in the bottom of the box.
(3) The inlet invert shall be at least one inch
above the outlet inverts.
(4) The outlet inverts shall be at least four
inches above the distribution box floor.
-31
•
(5) Each drainfield trench line shall'be
connected separately to the distribution ,
box and shall not be subdivided.
(6) When sewage tank effluent is delivered
to.the'distribution box by pump, either
- a baffle wall shall be installed in'the
' distribution box or the pump discharge
shall. be directed against a wall or side
I
of the box on which there is no outlet.
The baffle .shall be secured to the box
_
and shall extend at least one inch above
the top of the inlet flow line.
t-
`
3. Sloping Ground
(a) 'Where the elevation difference of the ground
surface exceeds 28 inches in any direction `
within soil treatment area and a distribution
box cannot be used as specified in item A-2.
above, a drop box shall be installed at the head
end of each lateral line. Connections between
drop boxes shall be*by watertight pipes.
` •
(b) Drop Boxes
�-
(1) The drop box shall be watertight and constructed
of precast concrete. The minimum inside
dimension shall be at least ten inches, unless
C
the box is to. be used .as a valve box. Then
each outlet shall -have at least eight inches
of sidewall space and the side of 'any outlet
C-
shall be at, least six inches from any corner.
(2) The invert of the inlet pipe shall be at
least one inch higher than the invert of the
outlet pipe to the`next trench.
[_
(3) The invert of the outlet pipe to the next
trench shall be at least two inches higher
than the invert of the outlet pipe of the
!.
trench in which the box'is located..
(4) When sewage tank effluent is delivered to the,
{.
drop box by a pump, the pump discharge shall
be directed. against a wall or side of the box
on which there is no'outlet.
- --32
Z
(5) The drop box shall have a removable cover
either flush or above finished grade or
covered by no more than six inches of soil.
B. By
Pressure Flow Over The Soil Treatment Area
-1.
Distribution pipe laterals used in trenches or beds for
pressure flow distribution shall be 1-1/4 inch diameter
pipe.
2.
A row of holes 3/16 to 1/4 inch in diameter shall be
C
spaced 36 inches apart in a straight line along the
axis of the pipe and laid to discharge downward.
[
3..,
Laterals shall be spaced no further than 20 inches
from a trench or bed wall.
4.
Laterals shall be spaced no further than 40 inches
li
ap art .
[-
5.
Laterals shall be no longer than 50 feet.
6.•
*Laterals shall be connected to a header pipe which
[
is at least 1-1/2 inch and no more than 3 inches
•
diameter.
SECTION 5: DOSING OF EFFLUENT
A. Dosing Chamber
1. The dosing,chamber shall be watertight and constructed
of sound and durable materials not subject to excessive
corrosion or decay.
2. There shall be one or more manholes, at least 20 inches
least dimension and preferably located directly above
the dosing device. -The manhole shall extend through
the dosing chamber cover to final grade and shall be
so constructed as to prevent unauthorized entry.,
3. The size of the effluent dose shall be determined by
design -of the soil treatment unit but in no case shall
the dosing chamber be -sized to provide a dose of less
than 75 gallons.
B. Dosing Devices For Gravity Distribution
1. A pump or siphon shall deliver the dose to the soil
treatment unit for gravity distribution over the
soil treatment area.
2. For systems for dwellings, the dosing device shall
discharge at least 600 gallons per hour but no more
than 2700 gallons per hour.
3. For other establishments, the dosing -device should
discharge at a rate at least ten percent greater than
the water supply -flow rate but no faster than'the rate
at which effluent will flow out of the distribution
..,box; drop box or valve box.
4. If the dosing device is a siphon, a maintenance inspection
shall be made every -six months and a report shall -be
filed with the administrator. The siphon shall be
maintained in proper operating condition.
S. If the dosing device is a pump, it .shall be cast iron
.or bronze fitted and with stainless steel screws or
constructed of other sound, durable and corrosion-'
resistant materials.
-34
0
6. Where the soil treatment area is at a higher -elevation
than the pump, sufficient dynamic head shall be provided
for both the elevation difference and friction loss.
7. Where the dosing device is a pump, an alarm device shall
be installed to warn of pump failure. For dwellings,
there. -should be reserve- storage volume equal to one
day's sewage flow based on the amounts specified for
number of bedrooms at 150 gallons per bedroom per
day. For other establishments, reserve' capacity
should be based on the nature of the facility, but in
no case shall it be less than 25 percent of the daily
sewage flow.
C. Dosing Devices For Pressure Distribution .
1. The dosing device shall be a pump which is cast iron
or bronze fitted and with stainless'steel screws or
constructed of sound, durable and corrosion -resistant
materials.
2. The pump discharge capacity shall be at least 30 gallons
'per minute for a three-bedroom or smaller dwelling. and
an additional ten gallons per minute for each bedroom
above three. For otherestablishments, the pump dis-
charge shall be ten gpm for each 200 gallons per day of
-sewage flow or 30 gallons per minute, whichever is
greater.
3. The pump discharge head shall be at least five feet
greater than the head required to overcome pipe
friction losses and the'elevation difference between
-the pump and the distribution device.
4.• The quantity of effluent delivered for each pump cycle
shall be equal to 25 'percent of one day's sewage flow
or 200 gallons, -whichever is greater.
5. An alarm device shall be installed to warn of pump
failure. For dwellings there should be reserve storage
volume equal to one days sewage flow based on the amounts
specified for number of bedrooms at 150 gallons per
bedroom per day.: For other establishments, reserve
capacity should be based on the nature of the facility,
but in no case shall it be less than 25 percent of the
daily sewage flow.
-35
D. Dual Field
1. Dual field systems shall be sized, designed, and
constructed as set forth above for standard systems
excpet as follows:
r' •
(a) The soil treatment area shall be divided into two
or more parts. This may be done by having:
(1) Two or more sets of trenches, or
(2) Two or more beds at least ten feet apart,
each having 1/2 the total area, or
(3) One bed, divided into two, or more parts by a
vertical barrier, parallel to the direction
of the distribution pipes. The barrier shall
extend from the bottom of the excavation up
to the level of the.tops of the disposal
pipes.' The barrier shall be constructed of
clay soil, concrete blocks laid=with mortar,•
.fiberglass, approved'plastic or other approved
impermeable materials.
(b) Alternating soil .treatment areas shall be connected
to a valve box outlet, with design and construction
being the same as a distribution box. ,
.1
r
t
SECTION
6: DRAINFIELDS OR SOIL TREATMENT AREA
I A. Location '
1.
On slopes in excess of 12 percent the soil profile
shall be carefully evaluated in the location of the
`
proposed soil treatment area and downslope to identify
_
the presence of layers that may cause sidehill seepage.
In no case shall. a trench be located within 15 feet of
such a layer surfacing on the downslope.
2.
Bed construction shall be limited to areas having
I
natural slopes of less than six percent.
(� B. Design
and Construction
- 1.
The bottom of trenches and beds shall be at least four '
feet above the watertable or bedrock.
2.
The trenches shall be not less than 18 inches nor more
fthan
36 inches wide. Any trench wider than 36 inches
shall.be considered a bed.
[; 3.
Trenches and beds shall be. not more than 100 feet in
length.
4.
The bottom of the trench or bed excavation shall be
level.
[, 5.
The bottom and sides of the trench or bed excavation
to the level of the filter material shall be scarified
_
to remove smears left by the construction equipment and
_
footprints. All loose material shall be removed from
.the excavation. The bottom of the excavation shall not -
be driven on after scarification.
6.
When the soil percolation rate at the bottom of the
trench or bed is slower than 15 minutes per inch, no
vehicle or .excavator shall be allowed to drive on after
scarification.
7.
There shall'be a layer of at least six but no more than
.24 inches of filter material in the bottom.of the
trenches and beds.
'. 8.
Where disposal trenches are constructed*within ten feet
of trees six inches or larger in diameter, or dense
shrubbery, or where it -can reasonably be anticipated
that such vegetation will be present 'during the
expected life of the system, at least 12 inches of
filter material shall be placed beneath the distribution
pipe.
=37
•
LET
9. Distribution pipe used in trenches or beds for
gravity flow distribution shall be materials allowed
by the State Plumbing Code, and at least four inches
in diameter and constructed of sound and durable
material mot subject to corrosion or decay or to loss
of strength under -continuously wet conditions.
(a) Agricultural drain the shall be in 12 -inch
lengths and laid with 1/4 inch open joints'on
grade boards. All open joints shall be protected
on top by -strips of asphalt -treated building paper
at least ten inches long and three. to six inches
wide or by other acceptable means.
.(b) Perforated plastic pipe shall be laid with one
row of perforations on the•bottom. Perforations
shall be at least 1/2 inch in diameter and spaced
no farther than 36 inches apart.
(c) Other devices may be used to distribute sewage
tank effluent over the soil treatment area after
City approval.
10. The distribution pipes shall be laid level or on a
uniform slope away from the sewage tank of no more
than four.inches per 100 feet.
11. The distribution pipes in beds shall be uniformly
spaced no more than five feet apart and not less
than 30 inches from the side walls of the bed.
12. The filter material shall completely encase the
disposal pipes to a depth of at least one inch.
13. The filter material shall be covered with untreated
building paper or a two-inch layer of hay -or straw
or similar, approved permeable materials.
14: The trenches or beds shall be backfilled with the
excavated material and slightly crowned -above
finished.grade to allow for settling. The .backfill
shall not be compacted to a density greater than that
of the original soil.
15. The minimum depth of cover over the distribution pipes
shall be at least eight inches.
1
16. The maximum depth of cover over the distribution pipes
shall be no more than 36 inches and preferably 24
inches.
i 17. A grass cover shall be established over the soil
I treatment area.
-39
•
SECTION 7: HOLDING TANKS
A. General
Holding tanks shall be considered for replacement systems only
if there are no other alternatives and it can be shown that
their -installation will eliminate a public health or pollution
hazard.
B. Construction
A holding tank shall be constructed of the same materals and by
the same procedures as those specified for watertight septic
tanks. ,
C. Access '
A cleanout pipe of at least six inches diameter shall extend to
the ground surface and be provided with seals to prevent odor
and to exclude insects and vermin. A manhole of at least 20
inches -least dimension shall extend through the cover to a point'
within 12 inches, but no closer 't1tan six inches below finished
grade. The manhole cover shall*be covered with at least six
inches' of earth. -
D. Depth of Bury
The tank shall be protected against flotation under high water -
table conditions. This shall be achieved by°weight of tank,
earth anchors or shallow bury depths.
E. Capacity _ ..
(1) For a dwelling the size shall be 2,000 gallons or x400
gallons times the number of bedrooms, whichever is'
= greatest.
(2) For.permanent structures other than dwellings, the
capacity shall be based on measured flow rates or
estimated flow rates. The tank capacity shall be
at least five times the daily flow rate..
F. Location _
Holding tanks shall be located:
(1) In an area readily accessible to .the pump truck under
' all weather conditions.
10 (2) As specified for septic tanks.
7:-40
4 f
(3) Where accidental spillage during pumping will not
create a nuisance.
G. Water Meter
A water meter shall be.required with all holding tanks to
measure-the flow to all plumbing fixtures except the outside
sillcocks.. Readings shall be submitted at least quarterly,
to the pumper and the City. Readings shall be used to.
I establish the amount of sewage.pumped and hauled.
H. Contract
A contract for disposal and treatment of the sewage wastes
shall be maintained by-the homeowner or pumper and a copy
rshall be given to the City.
I. Accidental Overflow"
Hg
oldin tanks shall be monitored to minimize the chance-of
faccidental sewage overflows. Techniques such as visual
I observation.,•warning lights or bells, or regularly scheduled.
pumping shall be used. For institutional use, a positive
( warning system shall be installed which allows 25 percent
1: reserve capacity after actuation.
! -41
i •
SECTION 8: INNOVATIVE SHALLOW -TRENCH -OR BED SUBSURFACE SOIL
TREATMENT AND SEWAGE DISPOSAL SYSTEM
A. Applicability
1. Percolation Rate - The percolation rate must be faster
t an 60 minutes per inch.
.2. Depth to Groundwater - Depth to groundwater or seasonally
saturated area must a greater than three feet..
3. Flood Hazard - There must be no, flooding hazard.
4. S1T ope - The land slope in the area being considered for
installation of the system must not be greater than 12%.
5. Position on the Landscape - The system shall be installed
on level areas, on top o rises on convex slopes, on
sides of rises on plane. The systems shall not be
installed in depressions, swales, or drainage -ways.
B. Trench Depth
The trenches or beds shall be installed to a depth not to exceed
:12 inches.
C. Trench Dimensions
General requirements and dimensions of the seepage trenches are
as follows:.
1. 'The bottom of the seepage trench shall be 'level.
2. Seepage trench excavations shall'be 2 to 3 feet in
width. The absorption area of a seepage trench shall
be computed by using the bottom area only and shall
conform to the standards given in the Code.
3.' Trench excavations shall be spaced at least 10 feet
ap art .
4'. -The individual laterals shall not be over 100 feet
long.
5. All other requirements of drainfield trenches as of
Section 6 apply.
D. Seepage -Beds
Seepage beds shall meet the requirements of a seepage trench
except that the excavation is more than 3 feet wide -and has
more than one distribution line. Distribution' lines in a
seepage bed shall be uniformly spaced no more than 6 feet
apart and no less than 3 feet apart and no more than 3 feet
from the sidewall.
.42
• E. Distribution of Sewage
A pressure distribution system shall be utilized to provide
equal distribution of the sewage effluent over the entire soil
absorption area.
F. Pressure System
The pressure distribution system shall consist of a pumping
chamber, pump of adequate size to deliver the effluent through
the system, and 1 to 1-1/2 inch PVC pipe for the distribution
laterals.
G. Piping
Distribution piping shall be 1 to 1-1/2 inch ASTM approved PVC
pipe with 1/4•inch holes drilled ever -y-30 inches. The holes
shall be drilled in accordance with the procedure indicated
in mound package•#1 - Section 9.
H. Pipe Laid
The distribution pipe shall -be laid in continuous straight
or curved lines.
I. Pipe Laid
L The distribution pipe shall be laid level for proper distribution
of the effluent.
CJ. Aggregate
A minimum of 12 inches of clean, graded rock in similar aggregate
ranging in size from 1 to 2-1/2 inches shall be laid into the ,
trench or bed below the distribution pipe and such aggregate shall
extend at least 2 inches over.the top of the distribution pipe.
The aggregate shall be covered with untreated building paper or T
.2 inches of marsh hay or equal.
K. Backfill _
The soil backfill shall be 12-18 inches over the top for the
distribution piping. The soil shall be an unconsolidated loam.
The soil shall be mounded to allow for settling.. (See Figure -2).
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-44 -
SECTION 9: INNOVATIVE MOUND SYSTEMS
A. Applicability
'. 1.
Percolation Rate - The percolation rate in 12 inches
i
or more of natural surface soil shall be faster than
I
60 minutes per inch and the percolation rate in sub-
soil -and/or -substratum shall -be faster --than 120 minutes
per 'inch.
2.
Depth to Groundwater - The depth to groundwater shall
be greater than 3 to -4 feet if the percolation rate is
I
60 to 120 minutes per inch and 2 to 3 feet with a
percolation rate 30 to 60.minutes per inch.
3.
Flood Hazard - There shall be no hazard of flooding
-
within t e area considered for installation of the
system.
4.
Slloo e_ - The land slope in the area being considered
of r installation of the system shall not be_,greater
[ ,
-than 6%. '.
5.
Position on the Landscape - The system shall be in-
stalled on level areas, on top of rises on convex ,
slopes -or on sides of rises on plane. 'The systems shall
not be'installed in depressions, swales or drainageways.
B. General Requirements of Mound Systems '
C1.
Below the sand layer there shall be at least one layer
*of soil, either natural or fill, at least 12 inches
r -
-thick, which has a percolation rate slower than five
!_r
minutes per inch- (loamy sand) .
2.
Wherever.possible mounds shall be located on flat areas
:or crests of slopes. Mounds shall not be located on
natural - slopes of more than three percent if the
percolation,rate is slower than 60 minutes per inch to
a depth of at least 24 inches below the sand layer.
3.
Mounds shall not be located on slopes exceeding six
percent if the soil percolation rate is slower than
30 minutes per inch to.a depth of. at least 24 inches
below the sand layer.
4.
Mounds shall not be located on natural slopes exceeding
12 percent under any soil percolation. rate.conditions.
5.
The bottom area.of the filter material shall be sized
the basis of 125 feet bedroom or 0.83
on square per
square feet per gallon of waste per day.
-45
-46
{ 6.
In no case shall the width of'the filter material
in a single bed exceed ten feet.
.
7.
A rubber tired tractor may be used for plowing or
disking but in no•case shall a rubber tired tractor
be used after the surface preparation is completed.
A _crawler—or track:_typ_e -_tractor_-shall-be used for
1 '
mound construction.
;! 8.
The discharge pipe from the pump to the mound area
shall be installed prior to soil'surface preparation.
The trench shall be carefully backfilled and compacted
�
o
to prevent seepage of effluent.
-
a 9.
Soil Surface Preparation:
t --
(a) The total area selected for the mound,, including
jf
the dikes shall be plowed with•a mold board plow to
a depth of -at least eight 'inches. Furrows shall
run perpendicular to the direction of slope. All
[
frrows shall be -thrown uphill and there•shall be
no dead furrow under the mound. The soil shall be
;-
plowed only when the moisture content of a
;[
fragment eight inches below the surface is below
•
the plastic limit.
j(b)
'In soilspercolation rates faster than
` t
.having
15 minutes per inch (sandy loam) in the top
eight inch depth, disking may be used for
surface preparation as a substitute for plowing.
(c) Mound construction shall proceed immediately
after surface preparation is completed.
E- 10.
A minimum of twelve -inches of soil defined as sand shall
be.placed where the filter material is to -be located.
"
A crawler tractor with a blade shall be used to move
the sand into place. At least six inches of sand
shall be kept under the tracks to minimize compaction
of the plowed layer. The sand layer upon which the
.filter• material ,is placed shall be, level.
11.
A depth of at least nine inches of•filter material shall
.be placed over the bed area below the distribution
-pipe.
-46
.•
L
i.
, • ,fir xt!
12. Distribution of effluent over the filter material
shall be by one and one fourth inch diameter
perforated pipe under pressure from a manifold.
13. At least two inches of filter material shall be
placed over the lateral or distribution pipes.
14. --Straw--or-marsh hay -to-an-uncompa-cted-depth---of. three --
to four inches shall be placed over the filter
material.
15. Construction vehicles shall not be allowed on the
filter material until backfill is placed.
16. Sandy loam soil shall be placed on the filter material
to a depth of one foot in the center of the mound
and to a depth�of six inches at the sides.
17.. A maximum of two ten -foot wide beds may be installed
side by'side in a single mound'if the soil percolation
rate is between five and 60 minutes per inch to a
depth of at least 24 inches below the sand layer.
The beds shall be separated by four feet of sand.
18. When two beds�are installed side by side the sandy
loam fill at the center of the mound shall be 18
inches deep and six inches deep at -the sides. ,
19. Six inches of topsoil shall be placed on the fill
material over the entire area of the mound.
20.: A grass cover shall be established over the entire
area of the mound.
21. No shrubs shall be planted on the top of the mound.
.. Shrubs ' may be placed at the foot and side slopes of
the mound.
22. The side -slopes on the mound shall be no steeper
than three to one.
23. Whenever mounds are located on slopes a diversion
shall be constructed immediately upslope from the
mound to intercept and direct runoff.
-A7
y
y
0
0 24. A pump shall be used as specified in Section 5B.
C�
25. Pressure Distribution:
(a) Perforation holes shall be three -sixteenths to
one-fourth inch in diameter drilled in a
straight line along the length of the pipe.
Hole spacing shall be 36 inches. Holes shall
be drilled straight into the pipe and not at
an angle.
(b) The perforated pipe laterals shall be connected
to a two-inch diameter manifold pipe with the
ends capped. The laterals shall be spaced no
further than 40 inches on center and no further
than 20 inches -from the edge of the filter
material.
(c) The perforated pipe laterals shall be installed
level with the perforations downward.
(d) The manifold pipe shall be connected to the
supply pipe from the pump. The manifold shall
be sloped toward the supply pipe from the pump.
26. Additional Construction Procedures-:
(a) Additional construction procedures and methods
can be found in the mound packages available
from City Hall.
BU -11