Hydroworks Hydroguard HG 4 Manual

Hydroworks®Hydroguard
Operations & Maintenance Manual
Version 1.5

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Introduction
The Hydroguard is a state of the art hydrodynamic separator. Hydrodynamic separators
remove solids, debris and lighter than water (oil, trash, floating debris) pollutants from
stormwater. Hydrodynamic separators and other water quality measures are mandated
by regulatory agencies (Town/City, State, Federal Government) to protect storm water
quality from pollution generated by urban development (traffic, people) as part of new
development permitting requirements.
As storm water treatment structures fill up with pollutants they become less and less
effective in removing new pollution. Therefore it is important that storm water treatment
structures be maintained on a regular basis to ensure that they are operating at optimum
performance. The Hydroguard is no different in this regard and this manual has been
assembled to provide the owner/operator with the necessary information to inspect and
coordinate maintenance of their Hydroguard.
Hydroworks®HG Operation
The Hydroworks HG separator is unique since it treats both high and low flows in one
device, but maintains separate flow paths for low and high flows. Accordingly, high flows
do not scour out the fines that are settled in the low flow path since they are treated in a
separate area of the device as shown in Figure 1.
The HG separator consists of three chambers:
1. an inner chamber that treats low or normal flows
2. a middle chamber that treats high flows
3. an outlet chamber where water is discharged to the downstream storm system
Under normal or low flows, water enters the middle chamber and is conveyed into the
inner chamber by momentum. Since the inner chamber is offset to one side of the
structure the water strikes the wall of the inner chamber at a tangent creating a vortex
within the inner chamber. The vortex motion forces solids and floatables to the middle of
the inner chamber. The water spirals down the inner chamber to the outlet of the inner
chamber which is located below the inlet of the inner chamber and adjacent to the wall of
the structure but above the floor of the structure. Floatables are trapped since the outlet
of the inner chamber is submerged. The design maximizes the retention of settled solids
since solids are forced to the center of the inner chamber by the vortex motion of water
while the outlet of the inner chamber draws water from the wall of the inner chamber.
The water leaving the inner chamber continues into the middle chamber, again at a
tangent to the wall of the structure. The water is then conveyed through an outlet baffle
wall (high and low baffle). This enhances the collection of any floatables or solids not
removed by the inner chamber. Water flowing through the baffles then enters the outlet
chamber and is discharged into the downstream storm drain.

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Figure 1. Hydroworks HG Operation –Plan View
During high flows, the flow rate entering the inner chamber is restricted by the size of the
inlet opening to the inner chamber. This restriction of flow rate into the inner chamber
prevents scour and re-suspension of solids from the inner chamber during periods of
high flow. This is important since fines, which are typically considered highly polluted,
are conveyed during low/normal flows.
The excess flow is conveyed directly into the middle chamber where it receives
treatment for floatables and solids via the baffle system. This treatment of the higher flow
rates is important since trash and heavier solids are typically conveyed during periods of
higher flow rates. The Hydroworks HG separator is revolutionary since it incorporates
low and high flow treatment in one device while maintaining separate low and high flow
paths to prevent the scour and re-suspension of fines.
Figure 2 is a profile view of the HG separator showing the flow patterns for low and high
flows.

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Figure 2. Hydroworks HG Operation –Profile View
The HG 4i is an inlet version of the HG 4 separator. There is a catch-basin grate on top
of the HG 4i. Water flows directly into the inner chamber of the HG 4i through the catch-
basin grate on top of the structure. The grate is oversized to allow maintenance of the
entire structure. A funnel that sits underneath the grate on the top cap of the concrete
itself directs the water into the inner chamber during normal flows and the middle
chamber during high flows. Figures 3 and 4 show the flow paths for the HG 4i separator.
The inlet funnel is sloped towards the corner inlet and hence the wall of the inner
chamber. Water moves in a circular direction in the inner chamber since water enters
tangentially along the wall of the inner chamber due to the sloping funnel.
Water continues moving in a circular motion (vortex) through the rest of the structure
(through the middle chamber and baffle wall) until it is discharged from the separator.

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During periods of peak flow the water will
back up from the corner inlet and overflow
into two side overflow troughs which
discharge directly into the middle chamber.
These overflow troughs are covered from
the surface such that water cannot directly
fall through them (i.e. water must back up
to enter the overflow troughs).
Accordingly this funnel provides the same
separate flow paths for low and high flow
as the other Hydroguard separators.
The whole funnel is removed for inspection
and cleaning providing.
Figure 3. Hydroworks HG 4i Normal Flow Path
Figure 4. Hydroworks HG 4i Peak Flow Path

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Inspection
Procedure
Although all parts of the Hydroguard should be inspected, inspection and maintenance
should focus on the inner and middle chambers since this is where the pollutants
(floatable and sinking) will accumulate.
Floatables
A visual inspection can be conducted for floatables by removing the covers and looking
down into the separator. Multiple covers are provided on Hydroworks HG units to access
all areas of the separator (The HG 4 will have a single larger 32” (800mm) cover due to
the lack of space for multiple 24” (600mm) covers). Separators with an inlet grate (HG4i
or custom separator) will have a plastic funnel located under the grate or on the top cap
of the concrete that must be removed through the frame prior to inspection or
maintenance. If you are missing a funnel please contact Hydroworks at the numbers
provided at the end of this document.
TSS/Sediment
Inspection for TSS build-up can be conducted using a Sludge Judge®, Core Pro®,
AccuSludge® or equivalent sampling device that allows the measurement of the depth of
TSS/sediment in the unit. These devices typically have a ball valve at the bottom of the
tube that allows water and TSS to flow into the tube when lowering the tube into the unit.
Once the unit touches the bottom of the device, it is quickly pulled upward such that the
water and TSS in the tube forces the ball valve closed allowing the user to see a full core
of water/TSS in the unit. The unit should be inspected for TSS through each of the
access covers. Several readings (2 or 3) should be made at each access cover to
ensure that an accurate TSS depth measurement is recorded.
Frequency
Construction Period
The HG separator should be inspected every two weeks and after every large storm
(over 0.5” (12.5 mm) of rain) during the construction period.
Post-Construction Period
The Hydroworks HG separator should be inspected during the first year of operation for
normal stabilized sites (grassed or paved areas). If the unit is subject to oil spills or
runoff from unstabilized (storage piles, exposed soils) areas the HG separator should be
inspected more frequently (4 times per year). The initial annual inspection will indicate
the required future frequency of inspection and maintenance if the unit was maintained
after the construction period.

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Reporting
Reports should be prepared as part of each inspection and include the following
information:
1. Date of inspection
2. GPS coordinates of Hydroworks unit
3. Time since last rainfall
4. Date of last inspection
5. Installation deficiencies (missing parts, incorrect installation of parts)
6. Structural deficiencies (concrete cracks, broken parts)
7. Operational deficiencies (leaks, blockages)
8. Presence of oil sheen or depth of oil layer
9. Estimate of depth/volume of floatables (trash, leaves) captured
10. Sediment depth measured
11. Recommendations for any repairs and/or maintenance for the unit
12. Estimation of time before maintenance is required if not required at time of
inspection
A sample inspection checklist is provided at the end of this manual.
Maintenance
Procedure
The Hydroworks HG unit is typically maintained using a vacuum truck. There are
numerous companies that can maintain the HG separator. Maintenance with a vacuum
truck involves removing all of the water and sediment together. The water is then
separated from the sediment on the truck or at the disposal facility.
In instances where a vacuum truck is not available other maintenance methods (i.e.
clamshell bucket) can be used, but they will be less effective. If a clamshell bucket is
used the water must be decanted prior to cleaning since the sediment is under water
and typically fine in nature
The local municipality should be consulted for the allowable disposal options for both the
water and sediments removed from the Hydroguard prior to any maintenance operation.
Once the water is decanted the sediment can be removed with the clamshell bucket.
Maintenance of a Hydroworks HG unit will typically take 1 to 2 hours based on a vacuum
truck and longer for other cleaning methods (i.e. clamshell bucket).
Frequency
Construction Period
A HG separator can fill with construction sediment quickly during the construction period.
The Hydroguard must be maintained during the construction period when the depth of

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TSS/sediment reaches 30”(750 mm). It must also be maintained during the construction
period if there is an appreciable depth of oil in the unit (more than a sheen) or if
floatables other than oil cover over 50% of the open water surface on the inlet side of the
outlet baffle wall.
The HG separator should be maintained at the end of the construction period, prior to
operation for the post-construction period.
Post-Construction Period
The Hydroguard was independently tested by Alden Research Laboratory in 2008. A
HG6 was tested for scour with initial sediment loads of 4.6 ft3and 9.3 ft3. The results
from these tests were almost identical. Therefore, the 9.3 ft3sediment load was used as
50% of the maximum sediment depth for maintenance in the calculation of the
maintenance interval for the HG6 separator based on the NJDEP maintenance equation.
Maintenance Interval (months) = 3.565 x (Sediment Storage) / (MTFR x TSS Removal)
Maintenance Interval (HG6) = 3.565 x 9.3 / (1.81x 0.60) = 30 months
All values (flow, sediment storage) can be scaled by the surface area making the
sediment depths and maintenance intervals equal for all separators.
The separator was loaded with the sediment in the inner chamber and middle chamber
with the majority of sediment (80%) located in the inner chamber. The inner chamber for
area represents approximately 44% of the separator surface area. The inner chamber is
4 ft (1200 mm) in diameter in the HG6. Therefore the 50% sediment depth for the HG6 in
the inner chamber would be:
9.3 ft3x 0.80 / (3.14 x 4 ft2) x 12 in/ft = 7.1 inches (175 mm)
Accordingly the 100% sediment volume would represent 14.2”(350 mm) of sediment
depth in the inner chamber.
The HG separator must be maintained if there is an appreciable depth of oil in the unit
(more than a sheen) or if floatables other than oil cover over 50% of the open water
surface on the inlet side of the outlet baffle wall. It should also be maintained once the
accumulated TSS/sediment depths are greater than 14”(350 mm) in the inner chamber.
For typical stabilized post-construction sites (parking lots, streets) it is anticipated that
maintenance will be required annually or once every two years. More frequent or less
frequent maintenance will be required depending on individual site conditions (traffic
use, stabilization, storage piles, etc.). The long term maintenance frequency can be
established based on the maintenance requirements during the first several years of
operation if site conditions do not change.

Please call Hydroworks at 888-290-7900 or email us at [e-mail] if you have
any questions regarding the Inspection Checklist. Please fax a copy of the completed checklist
to Hydroworks at 888-783-7271 for our records.
HYDROGUARD INSPECTION SHEET
Date
Date of Last Inspection
Site
City
State
Owner
GPS Coordinates
Date of last rainfall
Site Characteristics Yes No
Soil erosion evident
Exposed material storage on site
Large exposure to leaf litter (lots of trees)
High traffic (vehicle) area
Hydroguard Yes No
Incorrect access orientation ***
Obstructions in the inlet or outlet *
Missing internal components **
Improperly installed internal components **
Improperly installed inlet or outlet pipes ***
Internal component damage (cracked, broken, loose pieces) **
Floating debris in the separator (oil, leaves, trash)
Large debris visible in the separator *
Concrete cracks/deficiencies ***
Exposed rebar **
Water seepage (water level not at outlet pipe invert) ***
Water level depth below outlet pipe invert “
Routine Measurements
Floating debris depth < 0.5” (13mm) >0.5” 13mm) *
Floating debris coverage < 25% of surface area > 25% surface area *
Sludge depth < 14”(350mm) > 14”(350mm) *
* Maintenance required
** Repairs required
*** Further investigation is required

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