HomeMy WebLinkAboutResolution No. 409-16 - SubEdgeDrainPolicyRESOLUTION
BE IT RESOLVED by the Common Council of the City of Rochester that the City adopt the
Subdrain and Edgedrain System Maintenance and Operations Policy that is attached.
PASSED AND ADOPTED BY THE COMMON COUNCIL OF THE CITY OF
ROCHESTER, MINNESOTA, THIS
ATTEST:
CITY CLERK
DAY OF , 2016.
PRESIDENT OF SAID COMMON COUNCIL
APPROVED THIS DAY OF , 2016.
MAYOR OF SAID CITY
(Seal of the City of
Rochester, Minnesota)
Res15Wdopt\SubEdgeDrainPolicy
Subdrain and Edgedrain System Maintenance and Operations Policy
City of Rochester Public Works 2016
Subdrain Operation and Maintenance Standard Operating Procedure
Table of Contents
Section
Topic
Page
1
Definitions
1
2
Purpose of Subdrain Operation Procedure
4
3
Routine Maintenance and Inspection Schedule
4
4
Problem Areas
6
5
Current Subdrain Distribution
6
6
List of Subdivisions and Streets with Subdrains
6
7
City Engineering Standards
7
8
Connection Permits
7
9
Background — Subdrain and Edgedrain
7
10
Benefits of Subdrain System
8
11
Backwater Flows from the Subdrain System
8
12
Subdrain Backups and System Capacity
10
13
GOPHERI Locates
11
14
Documentation
11
15
Actions for Property Owners
11
16
Appendices
12
APPENDIX A
List of Subdivisions and Streets with Subdrains
APPENDIX B
Subdrain PowerPoint Presentation to Council
APPENDIX C
Subdrain Letter to Property Owners
APPENDIX D
2002 North Park Letter to Property Owners
City of Rochester Subdrain and Edgedrain System Maintenance and Operations Policy - 2016
1. Definitions —The below definitions are to be used with the Subdrain and Edgedrain
System Maintenance and Operations Policy.
Atlas 14 - NOAA Atlas 14 contains the latest rainfall data for much of the United States, and
generally replaces the older data published in NWS Technical Paper 40 (TP-40). Atlas 14 is used
in Rochester for all City of Rochester Design Standards.
Backflow Preventer — A device to prevent backflow into a pipe, which could lead into a sump
pit or drainage system. Most sump pumps have backflow preventers built in to prevent the
backflow of water.
Calcite - or calcium carbonate, CaCO 3, is a naturally occurring mineral, found in a variety of
crystalline forms. Calcite is the main mineral creating limestone, waters in SE MN are naturally
high in Calcite. The build-up of flowstone or calcite has been found in deep subdrains.
City Engineer — The Director of Public Works.
Connection Permit — A permit from Public Works that indicates or shows where connections
into the public system exist.
Decorah Edge - The "Decorah Edge" is defined as the area in which the Decorah, Platteville, or
Glenwood formation is the first encountered bedrock according to the "Bedrock Geology:
Steele, Dodge, Olmsted and Winona Counties" data plate produced by the Minnesota
Geological Survey — University of Minnesota in 2004, as modified by field investigation or more
precise mapping; and having a depth to bedrock of less than twenty-five feet according to the
"Depth to Bedrock: Steele, Dodge, Olmsted and Winona Counties" data plate produced by the
Minnesota Geological Survey — University of Minnesota in 2004, as modified by field
investigation, reliable well logs, or more precise mapping; and for which there are contiguous
adjacent areas with the Cummingsville or higher formations as the first encountered bedrock.
Typically Decorah Edge areas can have springs, seeps, and clay soils.
Developer — Person, company, or corporation that develops land for real estate purposes.
Developer's Engineer —The engineer or consultant engineer firm or individual that prepared
the subdivisions plans and specifications for development.
Edgedrains - (4" or 6" (inch) perforated PVC) that is buried approximately 4 feet below grade
and located behind the curb. Services connections may be stubbed to this. Edgedrain
installation has replaced the deeper subdrains from 2002 till the present. Access can be thru a
cleanout or outlet into a catch basin, manhole, or outlet.
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City of Rochester Subdrain and Edgedrain System Maintenance and Operations Policy - 2016
Foundation Backfill — Material that is used to fill in along the foundation walls of a property. It
may consist of native soils or material brought into the site.
Footing Drain —The exterior foundation drainage system placed outside the foundation wall
near the wall footing. This usually consists of a perforated plastic pipe that is backfilled and
covered with gravel or special drain rock. The footing drain at a property might be connected
to the houses sump pit. The footing drain could be piped to daylight if grade is present, left
unconnected into a properties yard, or could be tied to the subdrain or edgedrain pipe. Any
blockages in the drain could prevent water from draining properly.
Foundation Drain —This is the underdrain system that is located on the inside of the footings of
the property, directly below the lower level floor. The foundation drain is typically connected
to the inside of the sump pit. Older properties may not have footing or foundation drains
present.
Gravity Drainage — Drainage that does not utilize a pump, or other device to aid in the flow of
water. Storm Sewer systems are designed to flow by gravity, typically at a specified pipe slope
dependent on size of the pipe and drainage area.
Groundwater — Water that collects or flows underground, typically within pore spaces of soils,
rocks, and earth.
Right -Of -Way (ROW) - a Right -Of -Way easement is a roadway or pathway for travel through or
along another's property. Road Right of Ways are platted and of a specified width, but vary
depending on type of area or development.
Sanitary Service Lateral — This is the sewer service for a property, it is typically 4" in width and
can be clay, PVC, and other types. Property owners are responsible for their service from their
house to the public sewer main (most cases this extends into the public street).
Saturated Soils — Soils that have pore spaces or voids that are completely filled with water and
can no longer accept or store water.
Seepage — Water moving thru porous material or a porous media. Seepage collections systems
are designed to drain and help capture from saturated soils.
Seeps — A flow or leak of liquid through porous material or holes. This could be through soil,
foundation walls, or other material.
Service Connection —Term used to describe where a service is connected to a public utility.
Sidewalk —That portion of the street between the curb line and the adjacent property line for
the use of pedestrians.
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City of Rochester Subdrain and Edgedrain System Maintenance and Operations Policy - 2016
Springs — Groundwater that leaves the ground at a rapid pace, much higher rate than a seep.
Storm Sewer System - Simply a drain or drain system that is designed to drain excess
precipitation and snowmelt from impervious surfaces such as paved streets, parking lots,
footpaths, sidewalks, and roofs. The storm sewer system is separate from the sanitary sewer
system.
Storm Water - water that originates during precipitation events and snow/ice melt. Storm
water can soak into the soil (infiltrate), be held on the surface and evaporate, or runoff and end
up in nearby streams, rivers, or other water bodies (surface water).
Street Opening — General term used to describe construction work that requires the street be
cut open in areas for repair or maintenance activities of underground utilities.
Subdrains - (4", 6", 8" (inch) perforated PVC) that is buried in the street right-of-way, drains
water from soils during construction, usually installed beneath other utilities. These may have
included a common service stub (thru gravity) in the same trench as sewer and water
connections. Subdrains were installed in Rochester as early as the 1960's until 2002. Access is
typically thru a manhole. Some older subdrains may be metal pipe material.
Subdrain Mineralization — Is the process of groundwater high in minerals that starts to settle
out in the pipe forming a hardened deposit and accumulates over time. If the mineralization is
left unchecked, it is possible to completely block the subdrain pipe.
Subdrain Service Lateral — The portion of the subdrain that extends from the Public Subdrain
usually located in the street and serves the property. All subdrain service laterals are privately
owned. Subdrain service laterals could be connected to subdrains or edgedrains. Many
developers provided subdrain services during the time of utility construction.
Sump Pit — Lowest point in the lower level of a house, typically is a lined pit, intended to act as
a water collection area.
Sump Pump — A mechanical device to pump water from the sump pit and out of the property.
Sump pumps are available in a variety of sizes, types, and configurations.
TP-40 — Technical Paper 40, was the previous hydrologic data used for Storm Even Designations.
Designs prior to 2010 meet TP-40 standards.
Other Definitions — Other definitions may be applicable to the Subdrain Policy not included
within the definitions section. The definitions listed above shall precede definitions from other
sources.
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City of Rochester Subdrain and Edgedrain System Maintenance and Operations Policy - 2016
2. Purpose of Subdrain and Edgedrain System Maintenance and Operations Policy
It is the policy of the City of Rochester to design, operate and maintain a Subdrain Management
System (hereinafter, the "Subdrain System") that complies with City standards and addresses
operational maintenance, as described below.
As of January 2016, the extensive subdrain system within Rochester's City Limits is comprised of
the following public and private components:
■ 208,000 Linear Feet of Perforated Tile
■ 500 Subdrain Manholes
■ 100's of Cleanouts for Edgedrain (not field verified)
The City intends to provide consistent, cost effective and efficient design, operation and
maintenance of the public Subdrain System to ensure it will address the following needs:
■ The intended design function.
■ Design, operation and maintenance costs vs. benefits (i.e., economics).
■ In-house staff vs. contractor availability/expertise to manage the System maintenance
work in consideration of other infrastructure maintenance needs.
It is the City's intent to inspect every subdrain manhole every year. It is the City's intent to
inspect approximately 20% of the subdrain pipes each year until data and trends are
established that direct a different inspection schedule. This inspection from 2016-2020 will be
performed by the City's Contractor.
These procedures, when implemented, should extend the service life of various components of
the Subdrain System and provide a cost effective maintenance approach.
While the City fully intends to meet the guidelines established in this Policy, there may be times
when this will not be feasible. The City may be prevented from meeting the guidelines
established herein when issues arise such as (but not limited to): budget constraints, competing
interests and priorities that favor solutions for one objective over another, equipment failure,
weather, and other emergencies. The City Engineer may, on a case by case basis, supersede
provisions established within this Policy. Deviations from the goals established in this Policy will
be documented.
The City will use this Policy to guide System design, operations and maintenance activities
performed by its employees/equipment, private contractors/equipment, or a party other than
the City.
3. Routine Maintenance and Inspection Schedule
Routine maintenance includes jetting of the lines to prevent the build-up of minerals and tree
roots. Additionally, routine televising and visual inspection of manholes and pipe will be
conducted to find potential issues. Since the first subdrains have been installed starting in the
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1960's a variety of maintenance methods have been employed, but no formal schedule has
been developed. The edgedrain systems are shallower systems which are less prone to mineral
build up, but can be more prone to tree roots, damage from other utilities, or blockage if a line
has a separation. Typically houses are not connected to edgedrain systems thru gravity, so the
risk for a backup is much less.
The following schedule is the anticipated annual schedule for all subdrain maintenance:
Subdrain mains and manholes — Visual Inspection and documentation once per year indicating
no ponding or pooling of water. To be performed in all subdivisions with subdrain systems.
Subdrain Outlets — Locations where the subdrains outlet or daylight should be inspected at a
minimum once per year.
Subdrain service laterals privately owned — No inspection or maintenance from the City on
privately owned service laterals.
Subdrain Jetting — Jetting of subdrain mains with known mineralization build up on at least an
annual basis. Routine jetting of subdrain mains should minimize the amount of mineral build-
up and maintain the conveyance capability of the subdrain pipe.
Edgedrain Inspections —There is currently no inspection system in place for edgedrains. There
is limited information available on edgedrain cleanouts and their locations. Edgedrains do not
have gravity connections from houses, so they pose less of a risk of backup. An inspection
procedure will be developed for reviewing edgedrains in 2016 and implemented in 2017.
Street Opening Repairs — Repairs to subdrains using open trench methods may occur when
jetting/rodding or other methods fail to repair or open the subdrain.
Scope of City's Responsibility - The City will maintain the components of the public System.
This includes subdrain and edge components such as manholes, cleanouts, and connection
points. Private property owners are responsible for the maintenance of their own Subdrain
Service to the Public Subdrain.
Schedule —The City's goal is to comprehensively inspect 100% of its subdrain manholes
each year.
Equipment —The equipment used to perform maintenance will depend upon the
equipment available and its effectiveness as determined by qualified staff. Equipment may
be City -owned, rented or contractor -provided.
Closed Circuit Television (CCTV) Inspection —The City's subdrain mains could be inspected
by CCTV camera under the following conditions:
• At the time of new construction, whether a City Project or a City -Owner contract for
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new development, to determine acceptability,
• Prior to a street reconstruction project to determine if replacement during
construction is warranted,
• In response to reports of System malfunction or failure, and
• Other situations as determined by the Manager of Infrastructure Maintenance.
City staff and the City's Contractor will utilize visual inspection and pole cameras to inspect
subdrain manholes.
4. Problem Areas
Routine inspections will be used to determine subdrain system conditions and maintenance
priorities. Infrastructure that receives a poor rating will be issued Work Orders (for projects
to be completed by City employees) and completed according to the schedule noted above.
If the City has insufficient capacity or capability to complete the maintenance project, then
Contracts or Purchase Orders will be issued for external contractor work. The schedule for
projects completed with external resources will depend on the complexity of the project,
available funding, public safety, and whether they must be approved through the Capital
Improvement Project budget process.
Additionally, City employees periodically receive reports from citizens and staff about
malfunctioning System elements. When these reports are received, City staff will make an
on -site inspection to determine whether:
■ The concern is a public or private issue,
■ The remedy can be managed through the Work Order system by in-house
staff thru the contractors hired via contract,
■ The project needs to be evaluated for inclusion in a future Capital
Improvement Project budget.
Based on periodic assessment, maintenance condition ratings and completion schedules
may be adjusted to account for changes in maintenance findings and workloads over time.
S. Current Subdrain and Edgedrain Distribution
As of January 2016, the City has mapped on its Geographic Information System (GIS) System,
138,969 feet (26.93 miles) of deep subdrain located in the approximate center of the street.
55,621 feet (12.12 miles) of edgedrain, located at a depth of about 3 - 4 feet below the surface.
39.05 miles and an estimated 3,968 services provided to homes. Updates to the GIS System
will be made as new subdrains and edgedrains are installed, and also as existing systems are
found and mapped. These numbers will be updated every January.
6. List of Subdivisions and Streets with Subdrains
Listing of Rochester Streets and Subdivision with subdrains see the Appendix sections. This list
will be updated annually.
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7. City Engineering Standards
City Engineering Standards 1005.13 indicates an edgedrain system must be installed on all
streets unless the consulting engineer requests an exception and provides evidence why a
subdrain / edgedrain is not needed. The Engineering Standard indicates the subdrain is to be a
minimum 6" in diameter, and perforated PVC pipe, with cleanouts, and no bends greater than
22.5 degrees. Deep subdrains are no longer installed, this change occurred in 2002.
City Engineering Standards require a subdrain or edgedrain system is installed with every
residential subdivision and every public street constructed. This has been included in the City
standards since 1988. Not every subdivision has subdrain or edgedrains. This is due to the
Developer and their Consultant choosing not to follow City Engineering Standards on installing
edgedrains or the Developer and Consultant indicating that an edgedrain will not be beneficial
to the Public.
City Ordinance 76.07 subd. 5 makes it illegal for a sump pump to be connected to the sanitary
sewer system. Clean ground water or storm water pumped into the sanitary sewer system and
downstream lift stations further adds to the cost of the treatment at the City's wastewater
treatment plant. The City and City Council has not created an extensive program to follow up
with residential or commercial properties that have clean water connections discharging to the
sanitary sewer system.
8. Connection Permits
The Department of Public Works may have permits on file that indicates or shows where
connections from private properties tie into the public system. Additionally, construction Plans
and connection permits may indicate if service stubs were provided to properties. Connection
Permits indicate if the property was connected to an existing subdrain service stub during the
Sewer and Water Connection process (when the house was constructed).
Connection Permits generally do not show disconnection or show if a private service is
functioning. The connection permit is a snapshot in time during construction. Connection
permits are field verified and GPS'd. Property owners may request a copy of the connection
permit for their property from Public Works.
9. Background — Subdrains and Edgedrains
The Subdrain System is not a storm sewer system that drains surface water collected in the
street. The subdrain is typically a 4 (four), 6 (six), or 8 (eight) inch perforated plastic or
corrugated metal pipe located within the street Right -Of -Way (ROW) either in the center of the
street (typically 8 ft +/- bury) or installed behind the curb (boulevard area) at a shallow depth
(typically 4 ft +/- bury). The purpose of the subdrain is to help drain sub surface soils of water
and ground water during the time of utility and street construction, provide for an edge
drainage system to protect subsurface water migration into the street / road section, and
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provide an outlet for connection of additional drainage systems.
The subdrain drains the soils and water after the initial street construction activity, which
extends the life and condition of the street. The subdrain can help prevent ground water from
discharging to the sanitary sewer system, can prevent ground water from discharging across
the sidewalk which can create icing conditions, and provides and outlet for property owners or
businesses to connect to. The subdrain and edgedrain is typically installed prior to the phase of
construction of houses in a residential development.
10. Benefits of Subdrains and Edgedrains:
Direct benefits to the City of Rochester and all of its Residents:
■ Aids in construction of utilities and streets, this can lower the cost for developer and
City projects
■ Increases the life of utilities (dries out sub surface soils)
■ Reduces major street repairs
■ Reduces street replacement
■ Prevents sidewalk hazards (ice and algae)
■ Prevents nuisance conditions from sump pumps (wet yards)
■ Prevents clean water from entering the sanitary sewer (which is sent to the Water
Reclamation Plant for Treatment)
■ In some cases prevents inflow and infiltration in aging sanitary sewer pipes.
Direct benefits to the house and property are listed below:
■ A house directly connected thru a gravity system can have the house drain water
thru gravity, therefore no sump pump is needed
■ Freezing of sump pump lines does not occur
■ Prevents ice from forming on the sidewalk and in street areas preventing nuisance
conditions from forming
■ Gravity is more reliable than electricity
■ Can provide an additional level of protection to a property
■ Allows properties to be built where high water ground water conditions and
saturated soils exist.
11. Backwater Flows from the Subdrain System.
If the storm sewer system becomes overwhelmed with water, the subdrain connected thru
gravity could become overwhelmed. This could lead to water entering into a property.
During the original street construction and planning by the Developer and the Developer's
Engineer, they might have extended service connections to the Subdrain from the subdrain in
the street, to the lot line of each building lot. Some subdivisions also have edgedrain that has
service connections stubbed to each lot (standard practice starting in the early 2000's). The
intent is to provide houses to have an outlet to discharge sub surface and ground water to.
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Homebuilders will install a foundation drain system around the exterior or perimeter of the
basement foundation and sometimes install a service lateral pipe form the home to the
subdrain in the street right-of-way. In some cases the foundation drain is also connected by the
homebuilder or plumber to the sump basket in the houses basement.
The decision on connecting a houses foundation drain to the subdrain in the street right-of-way
was made solely by the owner of the house or by the builder of the house. When the
homebuilder or plumber made the connection to the house they knew at the time whether this
connection was made by gravity (backflows could occur), whether a backflow preventer was
installed, or whether a mechanical pump (sump pump) was on-line. During the 1980's the City
did not require or prohibit a connection between the foundation drain and the subdrain system
in the street.
Some houses floor drains could be connected to the subdrain system (not allowed under the
current plumbing code). Houses could have external connections from their yard going into the
subdrain system (typically allowed as long as there is a connection permit for it).
The foundation drain for the house is installed by the homebuilder to collect surface water that
percolates into the less compacted soil that was backfilled around the foundation walls of your
home. The water collected by the foundation drain may drain away by gravity flow to the
subdrain in the street or it may flow into the sump pump basket of the house, to be pumped
out either into the subdrain or outside of the house into the lawn. When a sump pump
discharges to the outside of the house, this typically meets code. It is illegal to have the sump
pump discharge to the sanitary sewer system under City Ordinance 76.03 Supervision and
Control of Storm Sewers. If the house has a direct connection between the subdrain in the
street and foundation drain around the house, it is also usually connected to the sump pump
basket. Then the interior lower level of the house can be subject to backwater flows from the
subdrain system during high rainfall events, or if the subdrain simply becomes clogged.
Connection permits in some cases indicate that the homebuilder and their sewer and water
contractor secured a permit to make a connection to the subdrain system. The City records do
not indicate or provide evidence to show that the foundation drain or sump basket is directly
connected by gravity or by a mechanical system to the subdrain system. Because the City has
no record to show whether the houses foundation drain or sump pump is connected to the
subdrain system, there is no way to predict if a property is subject to backwater flows from the
subdrain system. The builder of the property may have the best source of information on how
the foundation drains were installed and if they were connected to the subdrain system.
If the houses foundation drain or sump pump basket is not connected by gravity to the subdrain
system in the street, or the edge drain, the house should not be subject to backwater or
backflows from the subdrain system. Property owners can hire a licensed plumber to televise
connections within the houses to determine if the foundation drains or the sump basket are
connected to the subdrain system. Property owners must install a backflow valve to ensure
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storm water / subdrain main water does not back up into their property.
12. Subdrain Backups and System Capacity
Most municipal / public storm sewers are designed to handle surface water flows that are
associated with a 10-year design storm. In some cases, the public storm sewers may be
designed to handle much higher storm events (a 25 or 50 year storm event). And in some older
areas of the City, storm sewers may not handle a 10-year event. New rainfall intensity data
(City standard to use since 2013) called Atlas 14 Data replaces the former TP 40 rainfall data for
rainfall intensity. The 10-year design storm is a storm with a rainfall intensity that would be
expected to occur 10 times in a 100-year period. It is common engineering practice to design
the storm sewers to convey storm water flows up to a 10-year storm and then use the street
(curb to curb) for storage of heavier rainfall events. It is not cost effective to upsize storm
sewers after they are installed in a street to handle a greater than 10-year storm event. It is
usually not cost-effective to design, construct, maintain, and replace storm sewers sized larger
than for 10-year storm events.
During heavy rains, soils can become saturated, the more likely that foundation drains around
homes begin to collect water and discharge it to the sump basket or to the subdrain system, or
both. The more it rains over a period of time, the less rain that can infiltrate into the already
saturated soils, causing more water to runoff of yards. This rate of runoff can be similar to
impervious surfaces such as roofs, driveways, streets. As rainfall continues, these events can
lead to the storm sewers reaching and exceeding their 10-year design conveyance capacity.
When a sewer reaches this capacity, it can surcharge, which results in water backing up in
storm sewers and any connections that leads into the storm sewers. A surcharged storm sewer
can cause manholes to become flooded, streets to flood with water, storm sewer drains are
unable to take additional water in, and in pressure events, the storm sewer manholes may
become dislodged from structures.
During surcharge events, the subdrain mains immediately upstream become full of water. This
causes the subdrains to not allow more water in them, and depending on the elevation of the
surcharge event, water can backup the subdrain. For subdrains that are connected by gravity
this will cause water to run back up the subdrain services, either causing water to saturate
footing drains and/or to backup inside the houses sump pump basket. Some subdrains are not
connected to storm sewers but discharge directly into drainage ways or ponds. If the outlets of
the drains become blocked with debris or sediment this may prevent the subdrain from
effectively draining.
Any house that is connected by gravity to the subdrain system could be subject to a backup.
The subdrain could become clogged by tree roots or mineralization in a short time. There is no
feasible way to fully protect each property that is connected to the subdrain by gravity. The
City is also unaware of connections to the subdrain at some properties such floor drains located
inside of a house.
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13. GOPHERI Locates
Public Subdrain mains and manholes are currently located thru the Minnesota GOPHERI Utility
Locate system by Public Works Utility Locaters. There are over 40 miles (208,000 linear feet) of
subdrain installed within the City with multiple connections from houses. This includes
subdrain and edge drain systems.
As new edgedrains are added to the City system, they will be mapped and included within the
City's GIS Database.
14. Documentation
The City will document its inspection and maintenance activities for the subdrain system. The
City will also document circumstances that limit its ability to comply with this Policy. A summary
of inspection and maintenance activities will be prepared for each calendar year. This summary
may be used to recommend future changes to this Policy. These records will be kept in
accordance with the City's records retention schedule.
15. Actions for Property Owners
All properties that are connected to the subdrain system (whether in the street or the edge
drain) need to take steps to protect their own property. The City thru this policy has attempted
to reduce the risk of failure of the subdrain system. Property Owner action includes either
disconnecting from the gravity system, installing a backflow preventer, or installing a sump
pump to their existing subdrain outlet (mechanical system). Each property owner needs to
make their own decision for disconnection from the subdrain system.
Homeowners and business owners are faced with a decision that needs to be evaluated in
terms of what is best for your property.
Some options to evaluate include the following:
1. Homeowners can have a plumber or licensed sewer and water contractor disconnect
the gravity flow foundation drain system located in the public Right -Of -Way. This would
mean that the house would need to be re -plumbed. The sump pump discharge water
would need to be directed outside to the properties lawn. By pumping or discharging
water onto the lawn, this can create saturated lawn conditions, icing on the sidewalk, or
if the discharge point is not away from the house, could cause the water to recycle back.
2. The homeowner may want to configure the gravity foundation drain system and sump
pump plumbing to eliminate the backflow risks. This still allows the property to a direct
connection of their sump pump discharge line to the subdrain system. The sump pump
has a backwater valve that is designed to prevent backflow from the subdrain. A sump
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City of Rochester Subdrain and Edgedrain System Maintenance and Operations Policy - 2016
pump discharge from the house to the subdrain system would exist through the
foundation wall at a higher elevation then the current foundation drain or sump pump
basket connection to the subdrain. The higher the elevation of the sump pump
discharge line provides additional protection from the surcharged conditions that can
occur in the subdrain system.
16. Appendices — See Appendix A, B, C, D, for Additional Information. Updates to this policy
will be in Appendix Sections for future years.
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2016 SUBDRAIN DISTRIBUTION LIST
Deep Subdrains Center of Street
Subdivision Name
Area
Year Installed
Pipe Type
Size
Depth
Length
(Feet)
Length
(Miles)
Number of
Manholes
Apple Ridge
SW
1986
Perforated PVC
6"
>8'
1,168
0.22
5
Apple Ridge II
SW
1984
Perforated PVC
6"
>8'
1,940
0.37
11
Baihly Estates and Baihly Meadows
SW
1991
Perforated PVC
6"
>8'
2,489
0.47
1 7
Baihly Woodland 5th Subdivision
SW
1986
Perforated PVC
6"
Unknown
871
0.16
5
Balloy's First and Jensen 2nd
SW
1998
Perforated PVC
8"
>8'
662
0.13
2
Diamond Ridge Area
NW
1992 - 2000
Perforated PVC
4" and 6"
>8'
14,955
2.83
48
Foxcroft Subdivisions
SW
1990 TO 1995
Perforated PVC
4" AND 6"
>8'
10,224
1.94
38
Glendale Hills
NE
1993
Perforated PVC
6"
>8'
3,223
0.61
11
Golf View Estates
NW
1993
Perforated PVC
6"
>8'
1,366
0.26
8
Hampton Rhodes and Klickpatrick Sub
NW
1993
Perforated PVC
4"
>8'
2,304
0.44
8
Lincolnshire Area
NW
1989 thru 2003
Perforated PVC
6"
>8'
11,000
2.08
36
Meadow Park Area
SE
1960's to 1980's
Perforated PVC, CSP,
CMP
4", 6", 8", 10"
>8'
44,219
8.37
100
North Park Subdivision
NW
1987 thru 2002
Perforated PVC
6"
>8'
37,410
7.09
124
Northern Valley
NE
1989
Perforated PVC
6"
>8'
2,049
0.39
6
Pine Ridge Estates Subdivision
SW
1991 AND 1992
Perforated PVC
6"
>8'
3,682
0.70
12
RIDGEVIEW MANOR 2ND
NW
2002
Perforated PVC
6"
>8'
950
0.18
5
RIDGEVIEW MANOR 4TH AND 5TH
NW
2005
Perforated PVC
1 6"
1 >8'
457
0.09
3
Totals
138,969
26.32
429
Edge Drains (Installed behind the Curb)
Subdivision Name
Area
Year Installed
Type
Size
Depth
Length
(Feet)
Length
(Miles)
Number of
Mapped
Cleanouts
2ND Street Phases (Downtown and
Uptown)
SW
2011, 2012, 2013
Perforated PVC
4", 6", 8"
< 4'
5,083
0.96
11
50TH AVE NW
NW
2009
Perforated PVC
4"
< 4'
6,174
1.17
50
55TH Street NW
NW
2001
Perforated PVC
4"
< 4'
7,314
1.39
0
Badger Hills Subdivision
NW
2004, 2005, and
2006
Perforated PVC
4"
< 4'
9,385
1.78
22
Century Hills 9th Subdivision
NE
2005
Perforated PVC
4"
< 4'
2,257
0.43
7
Hundred Acre Woods
SE
2005
Perforated PVC
4"
< 4'
5,443
1.03
14
Summit Pointe Subs
NW
2001, 2002, 2003,
2004
Perforated PVC
4" and 6"
< 4'
17,855
3.38
80
Weatherstone
NW
2005
Perforated PVC
6"
<4'
2,110
0.40
4
Total
55,621
10.53
188
DATABASE
TOTAL
194,590
36.85
617
5/16/2016
Subdrain Presentation
May 16, 2016 Committee of the Whole
• What are Subdrains and what are Edgedrains?
• The benefits of Subdrains and Edgedrains.
• Subdrain and Edgedrain Inventory
• Problems with Subdrains
• Maintenance Challenges
• Funding for maintenance
• Short Term Recommendations
• Long Term Recommendations
5/16/2016
Definitions Subdrain and Edgedrain
Subdrain — (4", 6", 8" (inch) perforated PVC pipe that is buried in the street
right-of-way, drains water from soils during construction, usually installed
deep beneath other utilities. These may have included installation of a
common private gravity service stub in the same trench as sewer and
water service connections. Subdrains were installed in Rochester from the
1980's until 2002. Access is typically thru a storm sewer system manhole.
Edgedrain - (4" or 6" (inch) perforated PVC pipe that is buried
approximately 4 feet below grade and located behind the curb. Private
services connections may be stubbed to this. Edgedrain installation has
replaced the deeper subdrains since 2002. Access can be thru a
cleanout or outlet into a storm sewer system catch basin or manhole.
Subdrain Plan and Profile
N ONE WWII; d a �
RECORD
Po W 8�wry M wY �' 9N vmrt
o- 7^��„�'�1 '+1hW1�Iw.EG]4"r� q.Po9 wW+M 41 r, ., iYa .. IN,. t+9.- ,ttv 9'
■ Subdrain located
in center of
street and
private service
laterals stubbed
to property line
■ Subdrain is
located 12 feet
below street,
beneath all
other utilities
2
5/16/2016
Edgedrain Plan and Profile
pp
M
OCKe 6 PYdYJi'K A
�............ ■
Edgedrain located between
the curb and sidewalk
Current City Standards
require all Streets have
Edgedrain installed
Houses can be connected to
edgedrain, but no
connections thru gravity
allowed
Edgedrain is shallow, located
down 3 — 4 feet and above
all over utilities
Access is thru cleanouts
Current Subdrain and Edgedrain Distribution
Subdrain: 138,969 feet (26.93 miles) of deep subdrain
located in the approximate center of the street.
Edgedrain: 55,621 feet (12.12 miles) of edgedrain, located at
a depth of about 3 - 4 feet below the surface under the street
curb.
Connections: 39.05 miles and an estimated 3,968 service
lateral connections to homes. Numbers are current as of
March 2016.
3
5/16/2016
Subdrain Distribution
Length
Length
Number of
Number of Services
Subdivision
Area
Year Installed Pipe Type
Size
Depth
(Feet)
(Miles)
Manholes
Provided
Apple Ridge I & II
SW
1984 Perforated PVC
6"
>8'
3,108
0.59
16
77
Baihly Estates and Baihly Meadows
SW
1991 Perforated PVC
6"
>8'
3,360
0.64
12
72
Balloy's First and Jensen 2nd
SW
1998 Perforated PVC
8"
>8'
662
0.13
2
12
Diamond Ridge Area
NW
1992-2000 Perforated PVC
4" and 6"
>8'
14,955
2.83
48
448
Eastwood Hills Subdivision
SE
1997-1998 Perforated PVC
6"
>8'
3,230
0.61
9
74
Foxcroft Subdivisions
SW
1990 TO 1995 Perforated PVC
4" AND 6"
>8'
10,224
1.94
38
174
Glendale Hills and Northern Valley
NE
1989 Perforated PVC
6"
>8'
5,272
1.00
11
134
Golf View Estates
NW
1993 Perforated PVC
6"
>8'
1,366
0.26
8
24
Hampton Rhodes and Klickpatrick Sub
NW
1993 Perforated PVC
4"
>8'
2,304
0.44
8
50
Lincolnshire Area
NW
1989 th ru 2003 Perforated PVC
6"
>8'
11,000
2.08
36
302
1960's to Perforated PVC,
Meadow Park Area
SE
1980's CSP, CM P
4", 6", 8", 10"
>8'
44,219
8.37
100
998
North Park Subdivision
NW
1987 th ru 2002 Perforated PVC
6"
>8'
37,410
7.09
124
905
Pine Ridge Estates Subdivision
SW
1991 AND 1992 Perforated PVC
6"
>8'
3,682
0.70
12
79
RIDGEVIEW MANOR 2ND
NW
2002 Perforated PVC
6"
>8'
950
0.18
5
22
RIDGEVIEW MANOR 4TH AND 5TH
NW
2005 Perforated PVC
6"
>8'
457
0.09
3
8
Totals
142,199
26.93
432
3,379
Edgedrain Distribution
Number of
Year
Length
Length
Mapped
Number of Services
Subdivision Name
Area
Installed
Type Size
Depth
(Feet)
(Miles)
Cleanouts
Provided
2ND Street Phases (Downtown
2011, 2012,
and Uptown)
SW
2013
Perforated PVC 4", 6", 8"
<4'
5,083
0.96
11
0
50TH AVE NW
NW
2009
Perforated PVC 4"
< 4'
6,174
1.17
50
0
55TH Street NW
NW
2001
Perforated PVC 4"
< 4'
7,314
1.39
0
0
2004, 2005,
Badger Hills Subdivision
NW
and 2006
Perforated PVC 4"
< 4'
9,385
1.78
22
134
Century Hills 9th Subdivision
NE
2005
Perforated PVC 4"
< 4'
2,257
0.43
7
23
Hundred Acre Woods
SE
2005
Perforated PVC 4"
< 4'
5,443
1.03
14
72
Southern Woods 1st
SW
2007
Perforated PVC 6"
<4'
1,307
0.25
4
12
southern Woods 4th
SW
2007
Perforated PVC 6"
< 4'
770
0.15
1
14
2001, 2002,
Summit Pointe Subs
NW
2003, 2004
Perforated PVC 4" and 6"
< 4'
17,855
3.38
80
256
Stonebrook and Sunnydale
SE
Perforated PVC 6"
< 4'
5,839
1.11
21
40
Weatherstone
NW
2005
Perforated PVC 6"
<4'
2,110
0.40
4
34
Wedgewood Creek
SW
1998
Perforated PVC 6"
< 4'
470
0.09
1
4
Total 64,007 12.12 215 589
M
5/16/2016
City Engineering Standards
■ Since 2002 City Engineering Standards require that a
edgedrain system is to be installed with all Public Streets,
unless the Engineer can show that a edgedrain system is not
needed for that area.
■ Engineering standards have been revised, all edgedrain is
now to be 6" perforated PVC pipe. Previous standard
allowed 4 inch.
■ Deep subdrains are no longer allowed / installed.
5
5/16/2016
Residential Construction
CKP Ea
�� wFFD-FOUNDATION
DRAIN
SUMP EASKET
SERMCE LATERAL__..
F,
m
5/16/2016
City Wide Distribution Map - South
■ Both edge drain and
subdrain systems
■ Meadow Park area has
subdrain installed starting
in the 1960's and is
corrugated steel pipe
■ Some houses have floor
drains connectioned to
subdrain system
■ 1000's of houses could be
connected
Private Benefit of Subdrains / Edgedrains
■ Prevents nuisance conditions from sump
pump discharges (wet yards & icy sidewalks)
■ Gravity foundation drains (sump pump not
needed)
■ Freezing of sump pump lines does not occur
■ Prevents ice from forming on the sidewalk
and in street areas
■ Gravity is more reliable than electricity
■ Can provide an additional level of protection
to a property against wet basements
■ Cheap to install on the front end of
construction, can be expensive to install
after the subdivision is built
7
5/16/2016
Public Benefit of Subdrains
■ Aids in Construction of Utilities and Streets
■ Prevents Clean Water from Entering Sanitary
Sewer
■ Increases the life of utilities (drying out soils,
specifically edgedrain)
■ Reduces major street repairs (Maine Street
Development does not have edgedrain)
■ Reduces street replacement
■ Prevents Sidewalk Hazards (ice and algae)
Rochester Geology
M.
5/16/2016
City Utility Connection Permits
TO, DEPARTMENT Of PUBLIC SERVICES -- ROCHESTER, MINNESOTA
RM UMXPW(;Nfl) MRIWIM MAKTS Ai'MuCA] [ON '(M A MAINE
RA ",rq
(0NNWrj()N sink] (XINIM KA
NMINNMIMION/ kulmA 1. 1 RELAIR A CONMCN .1
$17E & I Ym� OV m,&ff MAJ
slu I C.1
Moc 41w. S— fio Cl"o?.0,
Wy 5, MA" 1. 51'd.
00- 'P'mly)
q— )'0'
MmO 111.1 '7JN'
NA . .....
& A .... No , .... . .... .... . .
Addd- ......
IN!
....... .. . ..
Street / Utility Construction Plans
Indicate if stubs where left for future
houses
Connection Permits indicate if property
was connected to a subdrain during the
Sewer and Water Connection
Connection Permits do not show if
private subdrain service is functional or
has been disconnected
m Snapshot in time
M
5/16/2016
Residential Property Owners
■ Plumbers can TV individual subdrain
services for property owners and
determine if their service is properly
functioning.
■ Property Owners can disconnect their
subdrain service
■ Near Sump Basket
■ In yard of Property (usually buried down a
considerable distance below ground surface)
■ Other Options
■ Install multiple sump pits, pumps, beaver
systems inside of house instead of
disconnecting from subdrain
10
5/16/2016
2002 North Park Event and Mailing
■ Large Rainfall Event
■ Multiple houses experienced back ups through
their gravity subdrain service pipe
■ Subdrain connected to surcharged city storm
sewer
■ A 6" subdrain pipe has limited capacity
■ After event, some property owners decided that
the risk and cost due to water damage was still
worth being connected to gravity subdrain. They
did not install a sump pump or change their
plumbing connection. This was their private
decision.
Mineral Deposit Build Up in Subdrain
■ Water is naturally heavy in minerals (hard water) Southeast MN
■ Mineral deposits / formations develop fast under low oxygen
conditions
11
5/16/2016
Maintenance—
Jetting, Cutting, Removal
■ Mineralized
formations
broken up thru
high pressure
jetting and
removed from
manhole.
■ Labor intensive
process and
requires all
debris to be
recovered from
subdrains and
manholes.
Maintenance —Jetting, Cutting, Removal
■ Vacuum Truck
hopper filled with
mineral and grit.
■ Many 5 gallon
buckets full of
flowstone
retrieved.
■ Tree Roots
removed from
drains.
12
5/16/2016
Previous Subdrain Maintenance
■ Varying levels of maintenance over the past 30 years
■ Past maintenance included routine line jetting
■ Hazards associated with maintenance (traffic control, getting jetting tools stuck in the
subdrain, damage to subdrain pipes)
■ No formal maintenance plan in place
■ No Standard Operating Procedure
■ No set funding source
■ Subdrain is not considered part of the Storm Water System
■ Sewer crew has performed visual manhole reviews since 2013
■ Selected maintenance thru property owner notification of a problem
■ Located thru GOPHERI Call
Subdrain Operating Procedure
■ No prior formal written policy
■ Standard Operating Procedure Developed in 201E
■ Inspection Procedures for Manholes
■ Inspection Procedures for Pipe with inspection report
■ Frequency of cleaning
■ Mapping of subdrain system
■ Identification of Funding Needs by category
■ SOP to be presented to Council for Formal Adopt
■ 2017 Budget Line Item
■ Storm Water Utility as funding source
13
5/16/2016
2015 Unbudgeted Costs
■ 2015 1 (one) Street Opening by Contract $10K
■ 2015 10 subdivisions jetted, cleaned, debris removal through 1,000's of
feet of line, by contract at $80K
■ In -House Maintenance and Engineering Management $25K
■ Maintenance cost is high
■ Requires extraordinary maintenance schedule and needs, specialized
equipment and multiple operators
Claims and Backups
■ 1990 to 2006 —The City had recorded 0 claims resulting in payment
of damages
■ 2007 Flood Event — Multiple payments out of City Sewer Utility
Funds ....... 2007 No Fault Program"
■ The City's No Fault Sewer Back Up Reimbursement Program paid out
$70,079.20 for the 2007 subdrain backups.
■ 2015 to Present LMCIT Insurance Coverage paid $5K due to water
entering home during subdrain cleaning and work.
■ Cost of claims is low compared to risk
■ 4,000 possible services; historically have had very few, if any,
claims per year
14
5/16/2016
2015Subdrain Repair -Continued
■ Cost is high
■ Subdrain is usually deep
beneath other utilities
■ Street is closed for repair
■ Possible unintended
damage to other utilities
■ Confined space entry
■ Trench box work
■ Requires street
reconstruction
15
5/16/2016
Request for Professional Services 2016 - 2020
■ Request for Proposals was sent to 4 Contractors in March 2016
■ Proposed 5 Year Subdrain Maintenance contract (2016 - 2020)
■ Quotes received from two local contractors.
■ Low Bid Contractor is Rochester Plumbing/Roto Rooter
■ Storm Water Utility will cover the cost of the 2016 Subdrain
cleaning since there is currently no funding mechanism in place
for this.
■ How should subdrain maintenance be funded after 2016?
Condition Rating
■ Overall the Subdrain system has had minimal maintenance
performed
■ Each deep subdrain line has mineral deposit build up, this varies
for each area; the buildup ranges from 0% to 80% of the
diameter of the line being restricted.
■ Latest inspections show all subdrains are draining and that
currently there are no surcharged conditions in the manholes.
■ No formal review for condition of edgedrains has occurred.
16
5/16/2016
Next Steps for Council — Short Term
■ Mass Mailing to approximately 4,000 property owners
■ Infrastructure Division will review and assemble all connection permits or
aerial photos with GPS points
■ The letter will notify the Property Owner that they could be connected to
the Subdrain or Edgedrain and the potential damage to property risk that
poses
■ Letter to Commercial Properties where connections could be present
■ Council Adoption of a Subdrain Standard Operating Procedure
■ Discuss Funding Source(s)
Next Steps for Council — Long Term
■ Further Review of the Subdrain and Edgedrain System SOP
■ Further Review of the Subdrain and Edgedrain System
Maintenance Condition and Costs
■ Determine City's Role and Responsibility for Subdrains
■ Adopt a Financing Strategy for Subdrain Maintenance and
Replacement
■ Service Assured Program for Subdrain?
■ Subdrain Utility Fee for Owners Served by Subdrains?
■ Other?
17
June 6, 2016
Dear Property Owner
RE: Public Notification Letter Subdrain in Your Subdivision
Public Works Staff have reviewed and evaluated subdrains located throughout the City
of Rochester. During the review and evaluation period it was found that many
subdrains throughout Rochester are subject to mineral buildup in pipes, surcharging in
manholes and other issues despite maintenance activities. This letter is to inform you
as the property owner that your house, may be connected to these gravity subdrains
thru a service connection.
What is the subdrain system? The public subdrain is a perforated PVC pipe that is
buried in the street right-of-way and drains water from soils during construction. It is
typically installed beneath other utilities (usually over 8 feet deep). These may have
included a common service stub in the same trench as sanitary sewer and water services
to your house. During the original street construction, service connections might have
been extended from the street to your house. This occurred where wet soils and
saturated conditions were encountered. The purpose was to provide an outlet to
discharge sub surface and ground water by gravity without the need of a sump pump or
other drainage system installed for the house. Even if your house has a sump basket,
the basket may outlet to the subdrain service thru gravity if no pump is present. The
decision on connecting a house to the subdrain service located in the right-of-way was
made solely by the original owner of the house or by the builder of the house, not the
City.
If the public storm sewer system becomes overwhelmed with water, the subdrain
connected thru gravity can also become overwhelmed. Any house that is connected by
gravity to the public subdrain system could be subject to a backup. Additionally, the
subdrain could become clogged by tree roots or mineralization, putting those connected
at risk of a backup.
There is no feasible way to fully protect each property that is connected to the
subdrain by gravity.
The City will continue to maintain the components of the public system to the maximum
extent practicable. This includes subdrain maintenance and investigation of problem
areas, repairs, and replacements as necessary. Private property owners are responsible
for the maintenance of their own subdrain service to the Public Subdrain.
All properties that are connected to the subdrain system can determine if they want to
take additional steps to minimize their risk and provide additional protection. This
includes installing a backflow preventer or installing a sump pump to their existing
subdrain outlet. Each property owner needs to make their own determination and
decision for disconnection or continued connection with the public subdrain system.
I have provided this letter to you as the property or homeowner to provide notification
of the risks associated with gravity connections to the public subdrain system.
Additional information can be found on the City's web site at:
www.CltyofRochestersubdrain.com
Questions can be directed to my staff project managers: Mike Kraszewski (328-2431) or
Doug Nelson (328-2423).
Sincerely,
Richard W. Freese, P.E.
Director of Public Works
CC: Mayor and City Council
City Administration
City Attorney's Office
Public Works Department
DEPARTMENT OF PUBLIC WORKS
201 4th Street SE, Room 108
Rochester, MN 55904-3740
(507) 287-7800
FAX (607) 281-6216
North Park Subdivision Property Owner
Dear Sir or Madam;
The North Park area experienced several heavy rainfall events in
June of this year. In some cases the heavy rainfall totals
increased the amount of moisture in the soil to saturated levels.
We have been told that several homes in the North Park
Subdivision experienced wet basements or lower levels, not from
surface water flows or flooding, but rather from other
circumstances that I will discuss in this letter.
The City of Rochester Public Works Department has determined that
your house located in the North Park Subdivision may be subject
to backwater flow from the subdrain system installed in the
street infront of your property. This letter will describe what
the City has done to reduce the probability that you may
experience any future backwater flow problems. Because of the
possibility that your home maybe subject to backwater flows from
the subdrain system, you could experience varying levels of
inconvenience and property damage to furnishings and belongings
located in the lower level of your home.,
Options that you may want to consider to further alleviate the
probability that your property maybe subject to backwater flows
from the subdrain system are: also presented later in this letter.
What is a subdrain system? The subdrain is NOT a storm sewer
that drains surface water collected in the ,street. Subdrains are
6-inch diameter partially perforated plastic pipes buried in the
street right-of-way to help drain the subsurface soils of
groundwater at the time the utilities and streets are installed
prior to the time houses were built on your street. The subdrain
system is designed and constructed to be a gravity flow system;
ie, water that enters the pipe flows down gradient to a point of
discharge.The subdrain system drains the soils within the
utility trenches and under the street and that helps consolidate
the soil under the streets for a more stable street foundation.
In the long run the installation of the subdrain system in the
street increases the life of the street and thereby reduces the
frequency at which the street needs major repairs or replacement,
An E�jaa(Opportrjnihj Employer
September 20, 2002
the cost of which is borne: by the property owners, In most
cases, the subdrain system was constructed at a depth that is
deeper than your basement floor elevation.
may is my home subject to backwater flows from this subdrain
system? When designing and/or installing buried utility lines,
the developer's engineer or contractor may in some cases find
soils at depths of 5-15 feet that are "wet" due to subsurface
water flows. The developer may, to facilitate construction of the
utilities and streets, install a subdrain system to drain the
""wet''" soils encountered during the construction process. In
addition, the developer may install storm sewers to collect and
convey surface water drainage by gravity to a point of discharge.
The gravity discharge from the subdrain system is sometimes into
the storm sewer system. (Please refer to the last sheet of this
letter which contains two drawings intended to help illustrate
this narrative: explanation.) The storm sewer system and subdrain
system share a common point of discharge in the North Park
subdivision.
If the soils are "wet" in the lot areas adjacent to the street
right-of-way, the developer sometimes extends service connections
from the subdrain at to lot line of each building lot. This is
done to aid the homebuilder who would likely encounter similar
N%wet," soils while excavating basements in the same area. In
"wet" areas the homebuilder will install a foundation drain
system around the perimeter of your basement foundation and
sometimes may install a service lateral pipe from the home to the
subdrain in the street right-of-way. In some cases the
"foundation drain" is also connected by the homebuilder or
plumber to the "sump basket" in your basement.
The decision on whether or not to connect your home's foundation
drain to the subdrain in the street right-of-way was made solely
by the builder of your home. In making that connection the
homebuilder or plumber was required by the Plumbing Code to
protect the home from backwater flows from the subdrain. The
City did not require or prohibit a connection between the
foundation drain and the subdrain system in the street.
The foundation drain is installed by the homebuilder to collect
surface water that percolates into the less compacted soil that
was backfilled around the foundation walls of your home. The
water collected by the foundation drain may drain away by gravity
flow to the subdrain in the street or it may flow into your sump
pump basket to be pumped by your sump pump either into the
subdrain or outside your home onto the lawn. If your home has a
direct connection between the subdrain in the street and the
foundation drain around your home and if it is also connected to
your sump pump basket, then the interior lower level of your home
maybe subject to backwater flows, from the subdrain system during
very high rainfall events.
The City's records, in some cases, indicate that the homebuilder
,secured a permit to make a connection to the subdrain system, but
our records provide no evidence to show that either your
foundation drain or sump basket is directly connected by gravity
to the subdrain. Because the City has no records to show whether
your foundation drain or sump pump basket is connected by gravity
to the subdrain system, I cannot predict whether your home is
subject to backwater flows from the subdrain system. The builder
of your house would be the best source of information on how your
foundation drains were installed and if they were connected to
the subdrain system.
If your foundation dram or sump pump basket is not connectedby
gravity to the subdrain system in the street, then your home
should not be subject to backwater from the subdrain system.
What happened to make this an issue this summer? The storm
sewers in the North Park subdivision have been designed to handle
the surface water flows from the subdivision that are associated
with a 10-year design storm (a storm with rainfall intensity that
would be expected to occur 10 times in a 100-year period). It is
common engineering practice: to design the storm sewers to convey
storm water flows up to the 10-year storm and then utilize the
street for storage of heavier rainfall events. It is not cost-
effective to design, construct maintain and replace storm sewers
sized larger than necessary for the 10-year storm events.
The heavy rains, rainfall totals, and saturated soil conditions
this past June (June 21, 2002 is estimated to be a 25 year storm
event) caused a series of cumulative events to happen that raised
the City's awareness to these North Park subdrain problems.
First, the more it rains the more likely that the foundation
drains around many homes in your neighborhood begin to collect
water and discharges it, in some cases, to the subdrain system.
Second, the more it rains over a period of time the less rain
infiltrates into the already saturated soils in your yard causing
it to runoff at a rate and volume similar to the runoff from more
impervious surfaces such as, roofs, driveways and streets.
Third, as storm water runoff volumes increase, the greater the
likelihood that storm sewers will reach and exceed their 10-year
design conveyance capacity and the result is a surcharging of the
storm sewers. When the capacity is exceeded, the storm sewers
are "surcharged". A surcharged storm sewer may cause manholes to
become flooded and on occasion dislodge manhole covers thereby
allowing stormwater back onto the street surface. Some of you
may have noticed storm sewer manhole covers dislodged the morning
of June 21st along 44 th Avenue near 56 th and 57 th Streets.
The subdrain system constructed in your street in front of your
home drains by gravity into the storm sewer system at the
0 Page 4 Septembe- 20,,2002
manholes in the SSOO Block of 44th Avenue and in the 4400 Block of
56th Street. Once the storm sewers on 44th Avenue and 56th
Street
became surcharged the morning of June 21st, the subdrains
immediately upstream of these surcharged storm sewers also became
surcharged. With the subdrains surcharged, the water in the
subdrain system could not flow out of the 6-inch subdrain pipe.
Instead, the subdrain pipe became full and it continued to
surcharge as more water was added from the many private
,foundation drains and sump pumps connected to the subdrain
system, The more water that entered the subdrain system, the
higher the surcharge elevation became in the subdrain pipe.
Storm water eventually backed up into several homes along 56th
Street and 57 th Street. Some homes experienced several inches of
water in their lower levels or basements, some of which was
cloudy or muddy, sediment laden storm water that had surcharged
the subdrain system. other homeowners experienced several inches
of water in their lower levels or basements, some of which was
relatively clean water from there foundation drains that were
full of subsurface water and unable to discharge to the
surcharged subdrain system.
What has the City done since June 21st to reduce the risk of your
home being subject to backwater flows from the subdrain system?
1. City Public Works staff responded to several North Park
residents' calls related to basement and lower level back ups
after tale June 21, 2002 rain event. Working with several
impacted homeowners, the City conducted internal inspections of
the basement floor drains, sump baskets, and foundations drains.
The results of those several inspections formed the basis for the
Public Works Department's subsequent activities, including this
letter.
2. Upon investigation of the storm sewer surcharging problems,
City Public Works crews removed accumulated sediment from the
storm sewer discharge pipes and drainageways behind homes located
at 4434, 4438 and 4442 56th Street NW. They have also excavated
a wider and deeper drainageway from 44th Avenue east to the
culvert under 551,h Street. Storm sewer lines were checked for
blockages and sedimentation was removed, as necessary, in this
area. The accumulated sediment appears to be related to erosin
and sediment laden runoff from construction sites in the North
Park area,
3. Public Works Department engineers prepared design plans to
disconnect the subdrain system connections from the storm sewer
system and reroute the discharges from the: manhole location on
56th Street and the one on 44th Avenue. The City hired a
contractor to perform the work that was completed earlier this
month. The disconnection of the subdrain discharge from the
storm sewer system will reduce the risk of water in the subdrain
systems backing up into the private foundation drain systems of
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individual homeowners. It will also significantly reduce the
possibility that water from the storm sewer system can enter the:
subdrain system and back up into the private foundation drain
systems of individual homeowners.
4. Public Works Department staff have prepared a map identifying
homes that may be subject to backwater flow from the subdrain
system. This letter was sent all properties identified on that
map.
5. In July of this year the City Council imposed more stringent
erosions and sediment control requirements on the developer and
contractor constructing the North Park 11th Subdivision, This
should help reduce soil erosion from the construction site and
subsequent sedimentation of the downstream storm sewers and
drainageways.
6. The City retained a consultant to review data and photos taken
after the rain event of June 21, 2002 in an effort to determine
the reason for the flooding that occurred in the neighborhood
park located north of 55�h Street and west of 44" Avenue NW. The
consultant has made two significant findings. First, debris,
particularly corn stalks and mown hay from agricultural fields
west of 50th Avenue NW, plugged culverts leading into the white
Oaks storm water management ponds located west of the park.
Resultantly, some of the Stormwate:r from west of Soth Avenue
bypassed the ponds that were designed and constructed to handle
these flows and, instead, continued flowing along the Douglas
Trail until it found a path that allowed it to flow into the
drainageway southeast of the ponds. Second, the capacity of the
drainage way down stream of the White Oaks storm water management
ponds was exceeded forcing water over its banks. The drainageway
overtopped its banks and flooded the park for two reasons. The
first reason is the large water volume of the bypass flows and
second reason is that the north berm of the drainageway was found
too be lower than shown on the design drawings along a portion of
the berm. The City will be raising the height of the berm along
the drainageway this Fall. The construction of additional
stormwater ponds upstream and west of 50th Avenue NW is scheduled
for 2003 and will reduce the debris clogging problem from
floating agricultural plants and the resulting diversion of storm
water that bypasses the White Oaks ponds.
That can you do as a homeowner to eliminate the risk, that your
home may someday become subject to backwater flow from the
subdrain? The builder of your home, in good conscientious,
connected your homes' foundation drain to the City's subdrain
system. This was the builder's personal decision. You are now
faced with a similar personal decision that should be evaluated
in terms of what is best for you and at what level of risk do you
feel comfortable.
September 20, 2002
The presentation of the following options does not constitute an
endorsement or recommendations of any option.
1. You may conclude that because of the actions and improvements
undertaken by the City since June: 21", it is now less likely that
your home will be subject to backwater flow. Therefore you may
decide it unnecessary to make any changes to your private
foundation drain / sump basket / sump pump system.
2. You may determine that it is more likely that the electrical
power will go off' rendering your sump pump useless and so you
prefer to continue to let your foundation drain to drain by
gravity to the subdrain, just in case your sump pump fails or the
power goes off in a storm and you can not use your sump pump.
3. You may want to have your gravity flow foundation drain system
disconnected from the subdrain system located in the public
right-of-way. You could have your sump pump discharge replumbed
so that it pumps out, onto your lawn.
4. You may want to have the configuration of your gravity
foundation drain system and sump pump plumbing replumbed to
eliminate the backflow risks. This would still allow the
homeowner a direct connection of their sump pump discharge line
to the subdrain system. The sump pump has a backwater valve that
is designed to prevent backflow from the subdrain. In addition,
a sump pump discharge from your home to the subdrain system would
exit through the foundation wall at a higher elevation than your
current foundation drain or sump pump basket connection to the
subdrain. The higher elevation of the sump pump discharge line
provides additional protection from surcharged conditions that
may occur in the: subdrain system.
I have attempted in this lengthy letter to provide you with
information on why your home may have been subject to a risk of
backwater flow earlier this summer, what the City has done to
reduce that risk, and what additional steps you might choose to
take to further reduce or eliminate the risk to your home from
backwater flow from the subdrain system.
On a related note, during the Public Works staffs' inspections of
the basement plumbing in several North Park homes, we observed
direct connections of several sump pumps to the plumbing system
that drains to the sanitary sewer system. City Ordinance 76.07
Subd, 5 makes it illegal for a sump pump to be connected to the
sanitary sewer system. This Ordinance was in effect prior to the
construction of any home in the: North Park Subdivision.
Stormwater pumped into the sanitary sewer system greatly reduces
the capacity of the sanitary sewers and downstream lift stations
and further adds needlessly to the cost of treatment at the
City's wastewater treatment plant. If you have your sump pump
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directly connected to the sanitary sewer service lateral please
have it disconnected as soon as you can make arrangements.
The City will conduct a Neighborhood Meeting on Thursday, October
3, 2002 to further discuss this matter with you and your
neighbors. City staff will be availably to answer questions.
The meeting will be held at Calvary Evangelical Free Church,
located at the intersection of 551h Street and 25t" Avenue NW,
The meeting will begin at 7:00 PM.
Sincerely,
Richard W. Freese, P.E.
Director of Public Works
CC: Mayor and City Councilmembers
Doug Nelson
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