HomeMy WebLinkAbout004 Storm Water Maintenance Plan
JOB NO. B14-008
MONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA
FEBRUARY 2022
406.586.0277
tdhengineering.com
234 East Babcock Street
Suite 3
Bozeman, MT 59715
CLIENT ENGINEER
Scott Hacker
Montana Crestview
4200 Expressway
Missoula, MT 59808
TD&H Engineering
234 East Babcock Street, Suite 3
Bozeman, MT 59715
ON-SITE STORM WATER MAINTENANCE PLAN
TROUT MEADOWS PHASE 3
BOZEMAN, MONTANA
Trout Meadows Phase 3 Storm Water Maintenance Plan
B14-008 1
TROUT MEADOWS PHASE 3
STORM WATER MAINTENANCE PLAN
PURPOSE AND INTRODUCTION
This maintenance plan identifies the recommended maintenance procedures necessary for the
proper function of the on-site storm water management system proposed at the Trout Meadows
Phase 3 apartment project in Bozeman, Montana. For the purpose of this plan, the on-site storm
water management system includes stormwater conveyance paths and pipes within the
properties, the subsurface retention chambers within the south parking lot, landscape area dry
wells, and the retention/detention pond (Pond 13) and overflow structure in the northwest corner
of the property.
The maintenance responsibility for the on-site stormwater management system belongs to the
landowner. The landowner may delegate routine inspection and maintenance responsibilities to
the on-site facility operations management team, or may hire a qualified professional entity or
individual to perform certain monitoring and maintenance tasks as necessary. A log shall be
kept for all required inspections and maintenance. These logs shall be made available to the
City of Bozeman Public Works Department for review as requested. A sample maintenance log
is included in the attached Appendix.
STORM WATER MANAGEMENT SYSTEM
The on-site storm water management system for the Trout Meadows Phase 3 lots includes curb
and gutter, curb inlets, drainage chases, trench drains, dry wells, stormwater ponds, and
subsurface infiltration galleries. These various components of storm water management
infrastructure are designed to collect, convey, clean, detain, and/or infiltrate storm water runoff
that is generated on the property before it leaves the site or enters local waterways.
Storm water systems require proper maintenance to prevent sediment clogging, overgrown
vegetation, erosion of detention ponds, obstruction of inlets, pipes, and structures, and
prolonged standing water. Such issues may result in downstream pollution, unpleasant odors,
unsightly areas, nuisance insects, or algae blooms, and must be mitigated. Scheduled
inspections, times of inspections, locations inspected, maintenance completed, corrective
actions taken, and any modifications or reconstruction performed shall be documented in the
maintenance logs to be readily available upon request. Disposal of accumulated sediment must
be in accordance with all applicable local, state and federal regulations.
Wetlands may be present within the boundaries of retention ponds, drainage ditches and
surrounding areas, and should be considered when planning maintenance activities. Wetland
permitting is generally not required for maintenance of constructed storm water management
features. However, maintenance of locations where pond outlet pipes or pond overflows
discharge to protected water bodies within wetland areas may require wetland or stream bank
permitting. If unsure of the regulatory status of wetland features observed at the site, consult the
local authorities prior to undertaking any activities that may cause disturbance.
Trout Meadows Phase 3 Storm Water Maintenance Plan
B14-008 2
STORM WATER MAINTENANCE PROCEDURES
The following maintenance procedures are intended to prolong the life of installed system
components and ensure their continued functionality:
General Storm Water System Maintenance –
1. Parking lot areas, curbs & gutters, drainage chases, and area drains should be cleared
of leaves and other debris once after primary leaf drop in the fall and once after snow
melt in early spring at a minimum. This will minimize the potential for debris to enter the
system which could lead to premature clogging of structures, reduced storage capacity,
and/or blockage of inlets.
2. Inspect the storm drain inlets, manholes, and cleanouts, for sediment build-up or
clogging and flush/clear as needed. Inspect for snow/ice buildup at least once weekly
during winter months and clear the inlet as needed. Do not pile snow over inlets.
3. Snow storage should be performed in designated areas during winter months and
should not be allowed to be piled in front of or over inlets. Piled snow around or over the
inlets could block early snowmelt run-off from entering the system, possibly causing
overflows and icy conditions.
4. Sanding of the parking lots and drive aisles should be done sparingly or avoided
completely. Sand or other sediment on the parking lot will likely be washed into
stormwater system components which can lead to buildup and reduced capacity or
blockages over time.
Subsurface Infiltration Gallery Maintenance –
The subsurface infiltration systems are equipped with inspection and maintenance ports for
monitoring and removal of accumulated sediments. The chambers should be inspected for
sediment buildup once every 6-months during the first year of operation, and once a year after
that. Use the general preventative measures described above to help reduce sediment build up
and clogging. Clean out sediment buildup as necessary following the attached manufacturer
recommended procedures.
Storm Water Pond Maintenance –
1. Routine Maintenance Activities (every 3 months):
a. Mow vegetation around each stormwater pond regularly throughout the
spring/summer months.
b. Designate a “no-mow” zone at the bottom of the ponds. This area will be trimmed
once a year and protected from regularly scheduled grass mowing. Excessive
mowing causes debris buildup and compaction of the soils in the bottom of the
pond, reducing the pond’s infiltration ability.
Trout Meadows Phase 3 Storm Water Maintenance Plan
B14-008 3
c. Remove trash, leaves, plant trimmings, grass clippings, pet waste and other
debris from the pond area.
d. Inspect pond inlets, outlets, and internal dry well grates for any obstructions that
would prevent stormwater from entering or leaving the pond and remove
obstructions as needed.
2. Annual Maintenance Activities (annually):
a. At the end of each fall, cut plants in the “no-mow” zone to a height of six inches
and rake and remove all clippings and leaves.
b. Re-establish vegetation on eroded or barren areas of the pond.
3. Long-Term Maintenance Activities (as observed/required):
a. Survey the pond elevations to determine the amount of sediment buildup, if any,
in the pond.
b. Excavate sediment and re-establish the pond to its initial design volume per the
construction plans if sediment build-up is found to be greater than six inches or if
the pond volume has decreased by more than ten percent.
c. Flush sediment from outlet structures/piping and from the outfall location if build-
up is observed. Remove sediment build-up from outlet structure or dry well
sumps if needed.
Drywell Maintenance –
1. The grate cover should be visually inspected on a weekly basis for debris or ice buildup.
All ice and debris (leaves, mud, etc.) should be removed to allow water to enter the
drywell.
2. The grate cover should be removed quarterly to inspect the drywell for sediment buildup.
If there is standing water inside the drywell due to sediment buildup, the drywell should
be vacuumed clean. Upon vacuuming, if water continues to pond in the drywell after
storm events for more than 48 hours, the soil surrounding the drywell may be
contaminated and should be examined by a professional familiar with drywell
construction.
3. The drywells should be vacuumed, at a minimum, every 3-5 years.
APPENDIX
City of Bozeman Stormwater Basin Maintenance Guide
Sample Maintenance & Inspection Log
R-Tank O&M Manual
FIGURE 5
Storm Water Facilities Inspection and Maintenance Log
Facility Name
Begin Date End Date
Date Location Facility Description Inspected
by:
Cause for
Inspection
Exceptions Noted Comments and
Actions Taken
Instructions: Record all inspections and maintenance for all storm water facilities on this form. Use additional log sheets and/or
attach extended comments or documentation as necessary. Save all completed logs in one place and have them readily available for
the City of Bozeman’s review upon request.
Location — Specify the exact location of the facility either by its name, facility ID or physical location.
Inspected by — Note all inspections and maintenance on this form, including the required independent annual inspection.
Cause for inspection — Note if the inspection is routine, pre-rainy-season, post-storm, annual, or in response to a noted
problem or complaint.
Exceptions noted — Note any condition that requires correction or indicates a need for maintenance.
Comments and actions taken — Describe any maintenance performed and need for follow-up.
FIGURE 1FIGURE 1
FIGURE 6
Operation
Your ACF R-Tank System has been designed to function in conjunction with the engineered drainage system on your
site, the existing municipal infrastructure, and/or the existing soils and geography of the receiving watershed. Unless
your site included certain unique and rare features, the operation of your R-Tank System will be driven by naturally
occurring systems and will function autonomously. However, upholding a proper schedule of Inspection & Maintenance
is critical to ensuring continued functionality and optimum performance of the system.
Inspection
Both the R-Tank and all stormwater pre-treatment features incorporated into your site must be inspected regularly.
Inspection frequency for your system must be determined based on the contributing drainage area, but should never
exceed one year between inspections (six months during the first year of operation).
Inspections may be required more frequently for pre-treatment systems. You should refer to the manufacturer
requirements for the proper inspection schedule.
With the right equipment your inspection and measurements can be accomplished from the surface without physically
entering any confined spaces. If your inspection does require confined space entry, you MUST follow all local/regional
requirements as well as OSHA standards.
R-Tank Systems may incorporate Inspection Ports, Maintenance Ports, and/or adjoining manholes. Each of these
features are easily accessed by removing the lid at the surface. With the cover removed, a visual inspection can be
performed to identify sediment deposits within the structure. Using a flashlight, ALL access points should be examined
to complete a thorough inspection.
Inspection Ports
Usually located centrally in the R-Tank System, these perforated columns are designed to give the user a base-line sediment depth across the system floor.
Maintenance Ports
Usually located near the inlet and outlet connections, you’ll likely find deeper deposits of heavier sediments when compared to the Inspection Ports.
Manholes
Most systems will include at least two manholes - one at the inlet and another at the outlet. There may be more than one location where stormwater enters the system, which would result in additional manholes to inspect.
Bear in mind that these manholes often include a sump below the invert of the pipe connecting to the R-Tank.
These sumps are designed to capture sediment before it reaches the R-Tank, and they should be kept clean to ensure they function properly. However, existence of sediment in the sump does NOT necessarily mean sediment
has accumulated in the R-Tank.
After inspecting the bottom of the structure, use a mirror on a pole (or some other device) to check for sediment
or debris in the pipe connecting to the R-Tank.
R-TANK OPERATION, INSPECTION& MAINTENANCE
TECHNICALSTORMWATER MANAGEMENT
For more information about our products, contact Inside Sales at 800.448.3636
or email at info@acfenv.com
If sediment or debris is observed in any of these structures, you should determine the depth of the
material. This is typically accomplished with a stadia rod, but you should determine the best way to
obtain the measurement.
All observations and measurements should be recorded on an Inspection Log kept on file. We’ve included a form you can use at the end of this guideline.
MaintenanceThe R-Tank System should be back-flushed once sediment accumulation has reached 6” or 15% of the
total system height. Use the chart below as a guideline to determine the point at which maintenance
is required on your system.
Before any maintenance is performed on your system, be sure to plug the outlet pipe to prevent contamination of the adjacent systems.
To back-flush the R-Tank, water is pumped into the system through the Maintenance Ports as rapidly
as possible. Water should be pumped into ALL Maintenance Ports. The turbulent action of the water
moving through the R-Tank will suspend sediments which may then be pumped out.
If your system includes an Outlet Structure, this will be the ideal location to pump contaminated water out of the system. However, removal of back-flush water may be accomplished through the
Maintenance Ports, as well.
For systems with large footprints that would require extensive volumes of water to properly flush the system, you should consider performing your maintenance within 24 hours of a rain event. Stormwater entering the system will aid in the suspension of sediments and reduce the volume of
water required to properly flush the system.
Once removed, sediment-laden water may be captured for disposal or pumped through a DirtbagTM (if permitted by the locality).
R-Tank Unit Height Max Sediment Dept
Mini 9.5” 1.5”
Single 17” 3”
Double 34” 5”
Triple 50” 6”
Quad 67” 6”
Pent 84” 6”
R-TANK OPERATION INSPECTION & MAINTENANCE
2831 Cardwell Road
Richmond, Virginia, 23234
800.448.3636
FAX 804.743.7779
acfenvironmental.com
Step-By-Step Inspection & Maintenance Routine
1) Inspection
a. Inspection Port
i. Remove Cap
ii. Use flashlight to detect sediment deposits
iii. If present, measure sediment depth with stadia rod
iv. Record results on Maintenance Log
v. Replace Cap
b. Maintenance Port/s
i. Remove Cap
ii. Use flashlight to detect sediment deposits
iii. If present, measure sediment depth with stadia rod
iv. Record results on Maintenance Log
v. Replace Cap
vi. Repeat for ALL Maintenance Ports
c. Adjacent Manholes
i. Remove Cover
ii. Use flashlight to detect sediment deposits
iii. If present, measure sediment depth with stadia rod, accounting for depth
of sump (if present)
iv. Inspect pipes connecting to R-Tank
v. Record results on Maintenance Log
vi. Replace Cover
vii. Repeat for ALL Manholes that connect to the R-Tank
2) Maintenance
a. Plug system outlet to prevent discharge of back-flush water
b. Determine best location to pump out back-flush water
c. Remove Cap from Maintenance Port
d. Pump water as rapidly as possible (without over-topping port) into system until at least
1”
of water covers system bottom
e. Replace Cap
f. Repeat at ALL Maintenance Ports
g. Pump out back-flush water to complete back-flushing
h. Vacuum all adjacent structures and any other structures or stormwater pre-treatment
systems that require attention
i. Sediment-laden water may be captured for disposal or pumped through a DirtbagTM.
j. Replace any remaining Caps or Covers
k. Record the back-flushing event in your Maintenance Log with any relevant specifics
R-Tank Maintenance LogCompany ResponsibleSite Name:___________________________________________ for Maintenance:__________________________________________________Location:_____________________________________________System Owner:______________________________________ Contact:__________________________________________________________________ Phone Number:__________________________________________________________For more information about our products, contact Inside Sales at 800.448.3636 or email at info@acfenv.com