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A. Application
A grit and oil separator,
hereinafter called a Particle Separator, shall be installed where outdoor
parking and paved areas are being drained or otherwise as required by BWSC.
It is emphasized that the use of
Particle Separators does not eliminate the need for oil separators in indoor
parking garages as detailed in requirement 11 of BWSC’s Site Plan Data for
Sewers. In addition, separate requirements apply at gas stations and where fuel
oil is being handled.
B. Design Criteria
| 1. |
When the total area being drained is
less than 7,500 square feet, a BWSC Standard Type 5 Catch Basin incorporating an
effective oil trap shall be installed on the drain line before it connects to
the public sewer system. The outlet from the catch basin shall be at least 1
foot below the standing water elevation to allow for an accumulation of trapped
oil. See Attached
BWSC Standard Details
B-01g Catch Basin
with Oil-Trap Outlet. |
| 2. |
Where the total area being drained
is greater than 7,500 square feet, but less than 30,000 square feet, a Particle
Separator having a total storage of not less than 1,000 gallons shall be
installed on the drain line before it connects to the public sewer
system. See Attached
BWSC Standard Details
B-11a – Typical
in Line Particle Separator.
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| 3. |
Where the total area being drained
is greater than 30,000 square feet, but less than 40,000 square feet, a Particle
Separator having a total storage of not less than 1,500
gallons shall be installed on the drain line before it connects to the
public sewer system. See attached
BWSC
Standard Details B-11b - Typical in Line Particle Separator.
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| 4. |
Where the total area being drained
is greater than 40,000 square feet, a Particle Separator having a total storage
volume as determined by the following capacity requirements shall be installed
off-line to avoid large flows and re- suspension of settled particles. See
Attached
BWSC
Standard BWSC Details B-11c – Typical Off-Line Particle Separator. |
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Capacity Requirements |
| i. |
Particle Separators shall be
designed to detain and treat a storm with an intensity of 1 inch/hour. |
| ii. |
To allow for deposition of
sediment within the Particle Separator, only one-half of the volume should
be used for detention purposes. |
| iii. |
The objective is to remove fine
sand particles and larger particles that are retained by a 100 sleeve or
0.15 mm screen. To achieve this objective, a minimum detention time of 60
seconds is required. |
| iv. |
The minimum capacity shall be
1,500 gallons. |
| v. |
If Particle Separator capacity
exceeds 3,000 gallons, a three-compartment unit shall be installed. |
C. General
Conditions
| 1. |
All baffles shall be tightly
sealed at sidewalls and at the roof so as to prevent the escape of oil. |
| 2. |
Roof drains should by pass the
Particle Separator and discharge directly to a storm or combined sewer. This
will reduce the size of the Particle Separator required and result in more
effective use of the unit that is installed. |
| 3. |
The Particle Separator shall be
located in such a position that it is accessible at all times for routine
maintenance or the emergency removal of oil or chemical spills. |
| 4. |
Particle Separators shall be
inspected and cleaned frequently and at a minimum twice annually. Floating
oil and sediment (or any hazardous material found therein) shall be removed
by a properly licensed contractor and disposed of in accordance with State
and Federal Regulations. |
| 5. |
If a large oil spill occurs, the
oil that is retained in the Particle Separator shall be removed immediately. |
| 6. |
If a spill of any chemical
substance or hazardous material occurs, every possible effort shall be made
to retain the spill within the Particle Separator and have it removed and
disposed of in a proper manner. |
| 7. |
BWSC reserves the right to enter
and inspect the condition, test the contents and monitor the operation of
any Particle Separator that discharges to the public sewer system. |
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