20200579 Ver 1_StormTrap Maintenance Manual_20200511

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Katie Merritt
Initial Review Completed Date 05/12/2020
Mitigation Project Submittal - 5/11/2020
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Rebecca Stubbs, PE
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Wilson
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STORMTRAP MAINTENANCE MANUAL

1. Introduction

Regular inspections are recommended to ensure that the sys tem is functioning as designed.
Please call your Authorized StormTrap Representative if you have questions in regards to the
inspection and maintenance of the StormTrap system. Prior to entry into any underground
storm sewer or underground detention systems, appropriate OSHA a nd local safety
regulations and guidelines should be followed.

2. Inspection Schedules for Municipalities

StormTrap Stormwater Management Systems are recommen ded for inspection whenever the
upstream and downstream catch basins and stormwater pipes of the stormwater collection
system are inspected or maintained. This will economize the cost of the inspection if it is done
at the same time the Municipal crews are visiting the area.

3. Inspection Schedules for Private Development

StormTrap Stormwater Mangement Systems, for a private d evelopment, are recommended
for inspection after each major storm water event. At a minimum, until a cleaning schedule
can be established, an annual inspection is recommended. If in spected on an annual basis,
the inspection should be conducted before the stormwater season begins to be sure that
everything is functioning properly for the upcoming storm season.

4. Inspection Process

Inspections should be done such that at least 2-3 days has lapsed since the most recent rain
event to allow for draining. Visually inspect the system at all manhole locations. Utilizing a
sediment pole, measure and document the amount of silt at each manhole location (Figure
1). Inspect each pipe opening to ensure that the silt level or any forei gn objects are not
blocking the pipes. Be sure to inspect the outlet pipe(s) because this is typically the smallest

pipe in the system. It is common that most of the larger materials will be coll ected upstream
of the system in catch basins, and it is therefore important at time of inspections to check
these structures for large trash or blockages.

Remove any blockages if you can during the inspection process only if you can do so safely
from the top of the system without entering into the system. Do not go into the system
under any circumstances without proper ventilation equipment and training. Pass any
information requiring action onto the appropriate maintenance personnel if you c annot
remove the blockages from above during the inspection process. Be sure to describe the
location of each manhole and the type of material that needs to be removed.

The sediment level of the system should also be measured and recorded during the inspection
process. Recording the sediment level at each manhole is very i mportant in order get a history
of sediment that can be graphed over time (i.e. years) in order to estimate when the system
will need to be maintained next. It is also important to keep these record s to verify that the
inspection process was actually performed if anyone asks for your records in the future.

The sediment level in the underground detention system can be determined from the outside
of the system by opening up all the manholes and using a sediment pole to measure the
amount of sediment at each location. Force the stick to the bottom of the system an d then
remove it and measure the amount of sediment at that location. Again, do n ot go into the
system under any circumstances without proper ventilation equipment and training.

5. When to Clean the System

Any blockages should be safely removed as soon as practical so that the Stormwater detention
system will fill and drain properly before the next stormwater event.

The Dry Detention System should be completely cleaned whenever the sediment occupies
more than 10% to 15% of the originally designed system’s volume. The Wet Detention
System should be cleaned when the sediment occupies more than 30% or 1/3rd of the
originally designed system’s volume. NOTE: Check with your municipality in regards to

cleaning criteria, as the allowable sediment before cleaning may be more or less then
described above.

6. How to Clean the StormTrap

The system should be completely cleaned back to 100% of the originally designed storage
volume whenever the above sediment levels have been reached. Be sure to wait at least 3
days after a stormwater event to be sure that the system is completely drained (if it is a Dry
Detention System), and all of the sediments have settled to the bottom of the s ystem (if it is
a Wet Detention System).

Do not enter the System unless you are properly trained, equipped, and qualified to enter a
confined space as identified by local occupational safety and health regulations.

There are many maintenance companies that are in business to help you clean your
underground stormwater detention systems and water quality units. Please call your
StormTrap representative for referrals in your area.

A. Dry Detention System Cleaning

Maintenance is typically performed using a vacuum truck. Sediment should be flushed towards
a vacuum hose for thorough removal. For a Dry Detention System, remove the manhole cover
at the top of the system and lower a vacuum hose into one of the rows of the StormTrap
system. Open up the manhole at the opposite end of the StormTrap and use sewer jetting
equipment to force water in the same row from one end of the StormTrap row to the opposite
side. The rows of the StormTrap are completely open in one contiguous channel from one end
to the other for easy cleaning.

Place the vacuum hose and the sewer jetting equipment in the next row and repeat the
process until all of the rows have been cleaned.

When finished, replace all covers that were removed and dispose of the collected
material properly.

B. Wet Detention System Cleaning

If the system was designed to maintain a permanent pool of water, floatables and any oil
should be removed in a separate procedure prior to the removal of all sediment.

The floatable trash is removed first by using a bucket strainer to capture and remove any
floating debris.

The floatable oils are then removed off the top of the water by using the vacuum truck to
suck off any floatable fluids and liquids.

The next step is to use the vacuum truck to gently remove the clarified water above the
sediment layer.

The final step is to clean the sediment for each row as described above in the paragraph “A.
Dry Detention System Cleaning”. For smaller systems, the vacuum truck can remove all of
the sediment in the basin without using the sewer jetting equipment because of the smaller
space.

7. Inspection Reports

Proof of these inspections is the responsibility of the property owner. All inspection reports
and data should be kept on site or at a location where they will be accessible for years in the
future. Some municipalities require these inspection and cleaning reports to be forwarded to
the proper governmental permitting agency on an annual basis.

Refer to your local and national regulations for any addition al maintenance requirements and
schedules not contained herein. Inspections should be a part of your standard operati ng
procedure.

Figure 1. During inspection, measure the distance from finished grade to the top of the
sediment inside the system.

Sample inspection and maintenance log