The location and installation of each individual sewage disposal system or other means of disposal shall be such that, with responsible maintenance, it will function in a satisfactory manner and will not create a nuisance or discharge into any watercourse of the commonwealth. In determining a suitable location for the system, consideration shall be given to the size and the shape of the lot, slope, natural and adjusted drainage, existing and known future water supplies, depth to groundwater, presence of impervious material, soil classifications and reserve area. No disposal works construction permit, as described in § 223-2, shall be issued until a representative of the approving authority has:
A.
The purpose of the deep observation hole is to determine
the character of the soil in the leaching area and specifically to
determine the groundwater elevation and the presence of impervious
material. On any lot, in the area to be used for leaching, except
as noted below, there will be at least two observation holes, plus
any additional number which, in the opinion of the approving authority,
will be necessary to determine the consistency (or lack thereof) of
the character of the soil. The observation holes shall be examined
to a depth of at least four feet below the bottom of the proposed
leaching facility but in no case shall be lower than 10 feet, unless
this depth is unattainable because of bedrock, etc. The groundwater
elevation should be determined when the groundwater is at its maximum
elevation.
B.
Exception. In cases where three or more contiguous
single-family uses are being examined at the same time by the same
engineer, the requirement of two deep observation holes per lot is
reduced to one deep observation hole per lot, provided that the character
of the soils remains consistent in the opinion of the approving authority.
The deep observation holes shall be conducted in the area to be used
for leaching on each lot.
The purpose of the percolation test is to determine
the suitability of the soil at the leaching elevation and to a depth
of four feet below this elevation. In cases where the soil varies
with depth as indicated by the deep observation holes, percolation
tests at various elevations may be required by the approving authority.
A.
At least two percolation tests shall be performed
at the site of each disposal area in the soil to be used for leaching.
Additional tests will be required where the soil structure varies
or where large disposal areas are required. Percolation tests can
be performed at any time of the year.
B.
Percolation tests, as prescribed in this section,
shall be performed, at no expense to the approving authority, by a
registered professional engineer. All percolation tests shall be performed
in the presence of a representative of the approving authority. The
cost of labor and equipment necessary to dig observation holes and
the provision of water for the performance of percolation tests shall
not be at the expense of the approving authority.
C.
Percolation tests shall not be made in holes that
have remained open to the atmosphere for more than three days, nor
shall they be made in frozen soil. Percolation tests may be performed
when the elevation of the soil to be tested is below the frozen soil
layer.
D.
Percolation tests shall not be made in filled ground unless the requirements of § 223-20 have been made.
E.
The minimum leaching area to be installed shall be determined from the following table, with the estimated sewage flow as determined in accordance with § 223-16. The slowest percolation rate obtained shall govern leaching area requirements.
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Leaching Area Requirements1, 4, 6, 7, 8
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|---|---|---|---|---|
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Sidewall Area2, 9
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Percolation Rate
(minutes per inch)
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Square Feet Per Gallon
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Gallons Per Square Foot
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Bottom Area3
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|
0.0 to 10.0
|
1.0
|
1.00
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|
15.0
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1.5
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0.67
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20.0
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2.0
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0.50
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25.0
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2.5
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0.40
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|
30.0
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3.0
|
0.33
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Over 30.05
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Unsuitable
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NOTES:
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1 Leaching fields: see Article XV.
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2 Sidewall area is
the pervious vertical interface of the excavation for the leaching
facility below the invert elevation of the inlet, or the lowest invert
elevation of the distribution line.
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3 Bottom area will
not be considered as part of the leaching facility without prior approval
of the Board of Health.
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4 Systems for more
than 2,000 gallons per day shall not be installed where the percolation
rate is slower than 20 minutes per inch.
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5 Soil with a percolation
rate over 30 minutes per inch is considered impervious and, therefore,
unsuitable for the subsurface disposal of sewage.
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6 Garbage grinders
are not allowed.
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7 Sewage systems
to be constructed in fill must be designed according to the percolation
rate of the underlying original soil.
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8 See Illustrations
A and B (on file in the Town offices).
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9 Minimum allowable
square footage by the Southborough Board of Health is 450 square feet
of sidewall area only.
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A.
Prepare test hole into the proposed leaching strate,
within the disposal area, of 12 inches in diameter with vertical sides,
18 inches deep.
B.
Establish a fixed point at the top of the test hole
from which all measurements can be taken.
C.
Scratch the bottom and sides of the test hole to remove
any smeared soil surfaces. Either add two inches of coarse sand to
protect the bottom from scouring or insert a board or other impervious
object in the hole so that water may be poured down or on it during
the filling operation.
D.
Carefully fill the hole with clear water to a minimum
depth of 12 inches and maintain the water level by adding water as
necessary for the purpose of soil saturation, but in no case less
than 15 minutes after first filling the hole.
E.
After saturation, if the water level drops to a depth
of nine inches in less than 30 minutes, measure the length of time
in minutes for it to drop from a depth of nine inches to a depth of
six inches. If the rate is erratic in the opinion of the approving
authority, the hole shall be refilled and soaked until the drop per
increment of time is steady. The time for the level to drop from a
depth of nine inches to a depth of six inches divided by three will
be the percolation rate in minutes per inch.
F.
If the initial three-inch drop requires more than
30 minutes (rate equal to more than 10 minutes per inch), the soil
shall be saturated by filling the hole to the top and maintaining
it full for at least four hours. The soil shall then be permitted
to swell overnight so that the soil conditions will approach those
which exist during the wettest season of the year. After the overnight
swelling period, the test shall be made again by filling the hole
to a twelve-inch depth and maintaining that level for 15 minutes,
letting the level drop to nine inches, then timing the drop between
nine inches and six inches. The time elapsed between nine inches and
six inches, divided by three shall be the percolation rate.
G.
In certain soils, particularly coarse sand, the soil
is so pervious as to make the percolation test as described above
difficult, impractical and meaningless. Therefore, at the discretion
of the approving authority, the test, as described above, may be waived,
and a rate of two minutes per inch can be assumed, provided that at
least 24 gallons of water is added to the percolation hole within
15 minutes and it is impossible to obtain a liquid depth of nine inches
or the percolation rate is faster than 30 seconds per inch.
Subsurface sewage disposal systems shall be
located in an area where there is at least a four-foot depth of naturally
occurring pervious soil below the entire area of the leaching facility.
The naturally occurring pervious soil shall have a percolation rate
less than or equal to 30 minutes per inch, or 20 minutes per inch
for systems over 2,000 gallons per day, and the four-foot stratum
must be free of impervious material, such as layers of clay, silt,
subsoil or loam.
No disposal facility shall be closer than the
distances stated to the components listed in the following table.
The distance shall be increased where required by conditions peculiar
to a location.
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Distances1, 2
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|---|---|---|---|---|
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Component
|
Septic Tank
(feet)
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Leaching Facility
(feet)
|
Building Sewer
(feet)
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Privy
(feet)
|
|
Well or suction line
|
50
|
1001
|
—3
|
1001
|
|
Water supply line (pressure)
|
—4
|
—4
|
—4
|
—4
|
|
Property line
|
10
|
10
|
—
|
30
|
|
Cellar wall or in-ground swimming
pool
|
10
|
20
|
—
|
30
|
|
Surface water supplies (reservoirs
or tributaries to reservoirs), including open and subsurface drains
|
502, 5
|
1001, 2, 5
|
—5
|
1001, 2, 5
|
|
Watercourses
|
252, 5
|
502, 5
|
—
|
502, 5
|
|
Subsurface drains
|
25
|
25
|
—
|
25
|
|
Leaching catch basin or dry well
|
—
|
25
|
—
|
—
|
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Downhill slope (measured from the
top of the leaching facility)
|
150 times the slope (expressed as
a fraction) (See Illustrations A, B, C, on file in Town offices.)
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NOTES:
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1 One hundred
feet is a minimum acceptable distance, and no variance shall be grated
for a lesser distance, except with prior written approval of the Department
of Environmental Quality Engineering.
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2 All distances
shall be measured from the average of the mean annual flood elevation
in inland areas and from mean high water in coastal areas.
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3 Ten feet
if constructed of durable corrosion-resistant material with water
tight joints or 50 feet if any other type of pipe is used.
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4 It is
suggested that the disposal facilities be installed at least 10 feet
from the 18 inches below water supply lines. Wherever sewer lines
must cross water supply lines, both pipes shall be constructed of
Class 150 pressure pipe and should be pressure tested to assure watertightness.
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5 The applicant
should be aware of his obligation to comply with the requirements
of the Wetlands Protection Act. MGL c. 131, § 40.
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