First Defense
®
Operation and Maintenance Manual
First Defense
®
Operation and Maintenance Manual
Hydro International
(Stormwater), 94 Hutchins Drive, Portland ME 04102
Tel: (207) 756-6200 Fax: (207) 756-6212 Web: www.hydro-int.com
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II. Model Sizes & Configurations
The First Defense
®
inlet and internal bypass arrangements are available in several model sizes and configurations. The components
of the First Defense
®
-4HC and First Defense
®
-6HC have modified geometries as to allow greater design flexibility needed to
accommodate various site constraints.
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III. Maintenance
Overview
The First Defense
®
protects the environment by removing a wide range of pollutants from stormwater runoff. Periodic removal of
these captured pollutants is essential to the continuous, long-term functioning of the First Defense
®
. The First Defense
®
will capture
and retain sediment and oil until the sediment and oil storage volumes are full to capacity. When sediment and oil storage capacities
are reached, the First Defense
®
will no longer be able to store removed sediment and oil. Maximum pollutant storage capacities are
provided in Table 1.
The First Defense
®
allows for easy and safe inspection, monitoring and clean-out procedures. A commercially or municipally owned
sump-vac is used to remove captured sediment and floatables. Access ports are located in the top of the manhole.
Maintenance events may include Inspection, Oil & Floatables Removal, and Sediment Removal. Maintenance events do not require
entry into the First Defense
®
, nor do they require the internal components of the First Defense
®
to be removed. In the case of
inspection and floatables removal, a vactor truck is not required. However, a vactor truck is required if the maintenance event is to
include oil removal and/or sediment removal.
Maintenance Equipment Considerations
The internal components of the First Defense
®
-HC have a centrally located circular shaft through which the sediment storage sump
can be accessed with a sump vac hose. The open diameter of this access shaft is 15 inches in diameter (Fig.3). Therefore, the nozzle
fitting of any vactor hose used for maintenance should be less than 15 inches in diameter.
Determining Your Maintenance Schedule
The frequency of clean out is determined in the field after installation. During the first year of operation, the unit should be inspected
every six months to determine the rate of sediment and floatables accumulation. A simple probe such as a Sludge-Judge
®
can be
used to determine the level of accumulated solids stored in the sump. This information can be recorded in the maintenance log (see
page 9) to establish a routine maintenance schedule.
The vactor procedure, including both sediment and oil / flotables removal, for a 6-ft First Defense
®
typically takes less than 30 minutes
and removes a combined water/oil volume of about 765 gallons.
Table 1.
First Defense
®
Pollutant Storage Capacities and Maximum Clean out Depths
First
Defense
®
Model
Number
Diameter
Oil Storage
Capacity
Oil Clean Out
Depth
Maximum Sediment
Storage Capacity
1
Recommended Sediment
Clean-out Capacity
Volume
Depth
Volume
Depth
(ft / m)
(gal / L)
(in / cm)
(yd
3
/ m
3
)
(in / cm)
(yd
3
/ m
3
)
(in / cm)
FD-4
4 / 1.2
180 / 681
<23.5 / 60
1.3 / 1.0
33 / 84
0.7 / 0.5
18 / 46
FD-4HC
191 / 723
<24.4 / 62
FD-6
6 / 1.8
420 / 1,590
<23.5 / 60
3.3 / 2.5
37.5 / 95
1.6 / 1.2
18 / 46
FD-6HC
496 / 1,878
<28.2 / 72
NOTE
1
Sediment storage capacity and clean out depth may vary, as larger sediment storage sump volumes are provided when required.
First Defense
®
Components
1. Built-In Bypass
2. Inlet Pipe
3. Inlet Chute
4. Floatables Draw-off Port
5. Outlet Pipe
6. Floatables Storage
a.
Fig.3 The central opening to the sump of the First Defense
®
-HC is 15 inches in diameter.
15-in Maintenance Access
b.
1
2
3
4
5
6
7
8
(not pictured)
Fig.2a) First Defense
®
-4 and First Defense
®
-6; b) First Defense
®
-4HC and First Defense
®
-6HC, with higher capacity dual internal
bypass and larger maximum pipe diameter.
All First Defense
®
models include the internal components that are designed to remove and retain total suspended solids (TSS),
gross solids, floatable trash and hydrocarbons (Fig.2a - 2b). First Defense
®
model parameters and design criteria are shown in
Table 1.
7. Sediment Storage
8. Inlet Grate or Cover
