HomeMy WebLinkAboutRe: drainage problem Y ,
resourceful. naturally. BARB
engineering and environmental consultants
May 21, 2015
Ms. Kathy Pollock
950 North Shore Drive W.
Orono, MN 55364
Re: Drainage Problems at 950 North Shore Drive W., Orono, MN
Dear Ms. Pollock:
On Tuesday, March 31, 2015, I performed a site review of your property and the issues caused by drainage
from the neighboring parcel to your south (990 North Shore Drive).At your request I have prepared this
letter summarizing my observations and opinions about the drainage issues you have experienced since
that residence was built(uphill and immediately to the south of your property)..I have also included
recommendations for correcting or minimizing the associated problems.
Background
You have lived at 950 North Shore Drive since 1986. The neighboring residence at 990 North Shore Drive
(hereafter referred to as the 990 property)was built in 2013. Since the construction of that home and
driveway and the related yard grading, you have repeatedly experienced drainage problems on your
property during rainstorm events. In particular, significant quantities of water have flowed onto you
property causing (a) erosion and subsequent deposition of dirt and rock on your driveway and yard, and
(b)topsoil and woodchips to be washed from the garden on the north side of your property onto your
neighbor's property at 900 North Shore Drive.You have had discussions with the neighbor,the city, but
little has been done to correct the problems.As a result,you contacted Barr Engineering to review the
drainage issues, determine the cause of the problems,and recommend corrective actions.
Work Performed:
During and immediately after my site visit I performed the following activities:
• Observed your entire property
• Took numerous photos of your property and the 990 property
• Viewed the residence, landscaping, and drainage patterns on the 990 property(see Photos 1
through 5)
• Reviewed photos you have taken of your property during and immediately after storm events
occurring before and after the home on the 990 property was built
• Reviewed an eroded area along North Shore Drive near your north property boundary
• Reviewed aerial photos of your property and the neighboring properties to the south and north
before and after the residence on the 990 property was built
Barr Engineering Co. 4700 West 77th Street, Suite 200, Minneapolis, MN 55435 952.832.2600 www.barr.com
Ms.Kathy Pollock
May 21,2015
Page 2
• Reviewed available topographic information for 900, 950, and 990 North Shore Drive before and
after the residence on the 990 property was built
During this visit, I also listened to your description of your drainage problems since the residence on the
990 property was built. In particular,you described and showed me substantiating photographs of:
1. Channelized flows coursing from the 990 property through a forested portion east of your
house, running across your onsite sewage treatment drain-field area, eroding an area not far
from your east patio door, and flowing north across the lawn where your septic tanks and drain-
field pump station are located. Photo 6,which you provided to me, shows the channel of water
you described. Photo 7 documents conditions after the runoff subsided. To your recollection, in
the 29 years that you have lived at 950 North Shore Drive,you have never seen channelized
flows running through that area of your property, and the erosion was not present until the
residence on the 990 property was built.
2. Channelized flows coursing from the 990 property through another forested portion of your
property(to the west of your house), across your driveway, onto your lawn, and across your
garden along the north side.You provided me with Photos 8, 9, and 10, showing the channelized
flows in action and Photos 11 through 16, showing the aftermath of the channelized flows.In the
29 years that you have lived at 950 North Shore Drive,you do not recall seeing the magnitude of
channelized flows that now run through that area of your property(nor the ensuing damage)
prior to the residence on the 990 property being built.
3. Channelized flows coursing from the driveway on the 990 property onto the east gutter of North
Shore Drive,then down your driveway, across your yard, and into your garden area along the
north side.The arrows on Photo 17 show the drainage pattern of flows passing down the
driveway of the 990 property onto North Shore Drive and then down your driveway. Photo 9
shows the actual flow and Photos 11 through 14 show deposits from the 990 property(eroded
road base and stones) in your yard. Photos 15 and 16 show the deposition of material in the
garden on the north side of your property, as well as where woodchips were flushed from that
area.In the 29 years that you have lived at 950 North Shore Drive,you do not recall observing
the magnitude of channelized flows that now occur since the residence on the 990 property was
built.
4. A history of ongoing drainage problems relative to the way flows are managed on North Shore
Drive, and how the development of the 990 property has exacerbated those problems.In
particular,you described that in 1993 Hennepin County placed a bituminous bump feature at the
end of your driveway to keep flows from the then upgraded North Shore Drive from flowing
down your driveway. This bump caused other problems for cars entering or exiting your
driveway including cars bottoming-out, icing issues, and safe access when turning onto North
Shore Drive.As a result of those problems, Hennepin County removed this bump in 1995. In
1996, Hennepin County installed curb and gutter on North Shore Drive from the crest of the
roadway hill (south of your property)to the north along your property. The east roadway ditch
on your property was filled as part of the 1996 curb and gutter and roadway improvement
project.The fill that was needed to match into the increased roadway elevation essentially
removed the ditch and created a sloped shoulder that now largely drains into your yard rather
than draining where the ditch was.The increased runoff from the 990 property that flows onto
North Shore Drive,freely flows down your driveway and the road shoulder into your yard as
there is no ditch to capture or convey the flows to the north.The increased runoff volume and
flow velocity from the 990 property combined with the runoff from North Shore Drive has
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Ms.Kathy Pollock
May 21,2015
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caused washout-erosion and the deposition of rock and sediment on several occasions which
you have been forced to repair and clean-up at your own expense. Photo 18,which you
provided, clearly shows virtually no flow in the road easement(where a ditch was previously)and
substantial flow in your yard.
5. You have apprised the residents and owners of the 990 property of the damage runoff from their
property has caused to your property.They have replied by saying "the City of Orono permitted
the construction on the 990 property and as such they do not need to do anything to control or
redirect the runoff from the 990 property".
6. Flows on North Shore Drive exiting the road at a curb drain cutout channel near your north
property boundary(Photo 19).These flows are directed to a zone where rock was placed by the
City of Orono or the Hennepin County Highway Department, presumably for erosion control
(Photo 20).The soil under and around the rock in that area has eroded and the landscape near
your north property line has scoured. Photo 20 shows the erosion on both sides of the rock and
Photo 21 shows the erosion downstream of the rock area.
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Ms.Kathy Pollock
May 21,2015
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Observations and Conclusions
After observing your property and the 990 property(looking south from your property line) and reviewing
available topographic and aerial photographic information,we have come to the following conclusions:
1. Prior to the construction of the new home and driveway on the 990 property in 2013, much of the
runoff from that property drained onto your property; however,those flows were likely dispersed
sheet-flows, not the more concentrated, channelized flows that now occur.
2. Construction of the house and driveway on the 990 property in 2013 resulted in approximately
27,900 square feet (0.64 acres) of impervious surface (Figure 1).That amount of impervious cover,
combined with the lot grading and the conversion of forested woodland and tall-grass-meadow
vegetation areas (Figure 2) to a mowed lawn has: (a) significantly increased the volume, rate, and
flow velocity of runoff entering your yard from the south, and (b) converted what were once
largely sheet-flows running from the 990 property to concentrated, channelized flows at three
distinct locations on your property(the east side of your house, near the bump-out parking/turn-
around area on your driveway, and coming down your driveway from North Shore Drive).
3. You have removed much of the rock that was deposited in your front yard and you have
attempted to control the erosion in your backyard.
4. In our opinion, the damage to your yard and the deposition of rock and debris will be chronic and
worsen until the increased, concentrated flows from the 990 property are prevented from
entering your property.
5. In our opinion, the rock on the road ditch slope at the curb drain cutout channel along North
Shore Drive was not properly placed and is not functioning as a channel armoring/erosion-control
feature. Flows are not contained within the rock as they pass from the road, down the steep road
shoulder slope, and onto the roadway ditch near your north property line.The rock was mounded
and not dished to contain flows. Water is forced to flow along the outside edges of the rock,
carving an eroded channel on both sides. This causes the rock to drop into the scoured zones and
renders it useless as an erosion-control feature. Further,there appears to be no fabric or granular
filter beneath the rock. As a result, the rock is sinking into underlying soils.
Recommendations
To stop or minimize the problems described above, we recommend the following actions:
1. Have the owner of the 990 property place a bituminous, concrete or wood-timber curb along the
entire north side of their bituminous-paved and concrete-paved driveway.This will prevent water
from the roof, driveway and much of the yard from rapidly flowing onto your property.
2. Ask the County to place features on North Shore Drive to prevent flows from the 990 property
and North Shore Drive from running down your driveway.It is my understanding that the County
may be planning to construct a stormsewer with a catch basin in the road gutter between your
driveway and the 990 property driveway.Typically catch basins are designed to capture flows
from a 5-year to 10-year storm event. But in this case,I recommend designing in much more
catchbasin capacity for the following reasons:
• The velocity of flows and the resulting flow vector of flows from the 990 property may
create a condition where they could bi-pass the catchbasin and come down your
driveway.
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Ms.Kathy Pollock
May 21,2015
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• Certain types of catchbasins can collect leaves and debris which essentially plug the
catchbasin grates preventing flows from entering the stormsewer.
3. We do not recommend placing a gradual bituminous berm/speed bump at the end of your driveway
to prevent road flows from running down your driveway as the bump will likely cause other problems
that may be problematic including driver safety issues.
4. Remove the rock at the curb drain cutout on North Shore Drive(shown in Photo 20), re-grade the
terrain to be dished/swaled, and use new channel-armoring material to completely contain the runoff
from a 24-hour, 100-year, Atlas 14 storm event.The channel armoring material could be properly
designed riprap and filter material or turf-reinforcing material (TRM) such as Enka-Mat R45.
5. Ask the owner of the 990 property to re-grade their east yard area so that flows are directed to
the south, around their house.
6. Where runoff from the 990 property courses through the forested and lawn area on the east side
of your property(shown in Photo 7), grade a swale and armor it with TRM such as Enka-Mat 1060.
That swale should be designed with sufficient capacity to contain the peak flow rates from a 24-
hour, 100-year, Atlas 14 storm event.
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Please call me at 952-832-2809 with any questions you may have about this letter or our observations and
recommendations.
Sincerely,
Barr Engineering Co.
Steven M. Klein, PE, PH
Vice President
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