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MEN x7190 APPLIED ECOLOGICAL SERVICES, INC.
•� 21938 MUSHTOWN ROAD, PRIOR LAKE, MN 55372
L PHONE: (952)447-1919 FAX: (952)447-1920
■L, arIR email: info.mnCaappliedeco.com
NOMMLAId■ Bringing the science of ecology to all land use decisions
MEMORANDUM
TO: Mr. Bob Shiff(Temple Israel)
CC: Myra Giesener (Temple Israel)
FROM: Doug Mensing,Restoration Ecologist
DATE: July 9, 2008
RE: Camp Teko Drainageway Retrofit (AES 08-0529) —Conceptual Design
INTRODUCTION
On June 16,2008,Applied Ecological Services,Inc. (AES)was contacted regarding an erosion issue
at Camp Teko,located on the shore of Lake Minnetonka in Long Lake,Minnesota. On June 17,
2008,AES representatives (Doug Mensing,Restoration Ecologist and Chris Raebel,Contracting
Division Manager) met with a Camp Teko representative (John L.) to walk the project area, assess
the recent erosion damage,and explore opportunities to retrofit the drainageway to restore eroded
areas and reduce future erosion potential. On July 1,2008,you authorized AES to develop a quick,
conceptual,possibly hand-drawn sketch of stormwater management elements and restoration
techniques along the camp's drainageway,including filling in the blow-out area and providing some
interim rate/volume control techniques.
As stated in our July 8,2008 Disclaimer of Liability to you,AES's conceptual design is based on our
brief site review and conversations with you and other Camp Teko staff Therefore,AES offers no
guarantees that,if implemented, the ideas proposed will work wholly or in part, or for any period of
time. We do not guarantee that the solutions will protect property or safety.
RECOMMENDED PROJECTS
Our recommendations can be broken down into three main project areas. These projects are
described in priority order below and illustrated on the accompanying diagrams.
080529:070908 1 of 4 Camp Teko Drainageway Retrofit—Conceptual Design
Project 1—Upper Catchment Management
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A quick evaluation of topographic data suggests that the majority of the eroded drainageway's j
catchment (local watershed) collects in the large,grassed "bowl" on the site, as well as another
depressional area to the west,which consists of a smaller grassed depression and potentially a
forested wetland. Project 1 entails re-routing the large bowl runoff(which is already collected in a
drainage pipe) into the smaller grassed depression to the west. This can be done by digging a new
drainage path from the large bowl outlet pipe into the smaller grassed depression,lining it with filter
fabric,and overlaying it with small rip-rap (4"-6" diameter). The existing channel should be
abandoned (filled in) to prevent runoff from short-circuiting the depression. The smaller grassed j
depression should be excavated into a flat-bottomed basin (essentially a rain garden),with a cut of
0.5 to 1.5 feet deep (with the deeper cut on the northern and western edges of the depression). Cut
soil should be used to construct a berm (1 to 2 feet tall) along the southeastern edge of the basin to
retain runoff in the basin. The basin bottom should be,at a minimum,rototilled to provide greater
infiltration. Soil amendments such as sand and compost would also provide greater infiltration,
which will help reduce the time standing water sits in the basin. Optional perforated drain tile (like
the one already located in this area) could be installed to expedite drainage of the basin. Native seed,
plants,and erosion control blanket should be installed in the basin to stabilize soils and to expedite j
water removal. The constructed berm should be compacted, seeded with native plants,and covered
with erosion control blanket. A v-notch weir should be installed along the berm at the point where
water will leave the basin and flow into the existing drainageway. The weir can be constructed from
pressure-treated lumber (allowing for easy modifications later),and should be installed such that it is j
well keyed-in to the berm and ground beneath. The bottom of the v-notch should be approximately
0.5 feet above the bottom of the basin. Filter fabric,overlain with rip rap (>W' diameter), should be j
installed at the outlet so that water leaving the basin via the v-notch weir does not erode the
drainageway.
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It may be advantageous to raise slightly(0.5 to 1 foot) the pipe inlet located in the potential forested
wetland (downstream from the constructed basin/weir) so that this wooded area would pond more
water before it was able to flow into the pipe,under the footbridge,and into the well-defined
drainageway. Mounting a flexible plastic section to this pipe inlet and mounting it to a vertical post
would allow for variable water level control in this area.
Important Notes: Jurisdictional wetlands may exist in the area (e.g.,the potential forested wetland);
this can only be determined by a qualified wetland delineator/regulator. Placing fill in a wetland
requires a permit. Construction of a berm and placement of rip rap in a jurisdictional wetland would
be considered fill,but this project may fall within the"de mirnmis" exemption of the Minnesota
Wetland Conservation Act. This issue requires additional investigation,and it would be
advantageous to see if the Minnehaha Creek Watershed District is available to assist in this
determination and assessment of other permit requirements. Also, survey data from a previous
Camp Teko project identifies buried utility lines in the vicinity of this project. Gopher State One
Call (and potentially a private utility locator) should be contacted prior to any digging to mark any j
and all underground utilities prior to any excavation occurring. Regular inspections should be made
after the basin/berm/weir and flexible pipe inlet are installed to ensure that no new
erosion/sedimentation problems are occurring and that impoundment levels and drainage time are
performing acceptably.
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080529:070908 2 of 4 Camp Teko Drainageway Retrofit—Conceptual Design
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Project 2—Gravel Drive & East Slope Management
During our site reconnaissance,it appeared that a significant amount of runoff came down the
existing gravel drive located to the east of the drainageway. Digging shallow (2" to 4" deep)
trenches diagonally across this drive so that runoff from the drive is intercepted intermittently and
routed off to the west side of the drive will reduce erosion potential along the drive and downslope.
Runoff from these trenches should dissipate and infiltrate,and possibly some will sheet flow into the
drainageway. These diagonal trenches should be installed from near the top of the gravel drive all
the way to the log pavilion,with extreme care given to the already eroded/unstable areas near the
log pavilion.
It may be advantageous to also install a narrow rain garden or infiltration area between the
westernmost cabin and the log pavilion to manage runoff from the slope located just uphill. This
could be designed similar to the Project 1 basin, but soil amendments would be important given the
limited size, and the overflow would need to be designed such that overflow did not flood or
compromise the log pavilion foundation or cause additional erosion.
Important Notes: Regular inspections should be made after the diagonal trenches and/or narrow
rain garden are installed to ensure that no new erosion/sedimentation problems are occurring.
Project 3—Restore Eroded Gravel Drive
The eroded gravel drive (extending from the log pavilion to the boat dock) was created as a result of:
1. concentrated runoff from the upper gravel drive and associated areas,
2. concentrated runoff from the drainageway leaving the original channel,
3. steep slopes,
4. lack of stabilizing vegetation, and
5. saturated/unstable soils resulting from groundwater seepage in the area.
Before restoring the eroded gravel drive,all sources of concentrated runoff(including runoff from
the upslope portion of the drainageway) must first be re-routed into the original drainageway
alignment (currently a limestone swale with dense vegetation,located just west of the eroded gravel
drive). Any areas expected to receive significant runoff should be graded to create a well-defined
swale (as broad and flat-bottomed as space allows),lined with filter fabric, and overlaid with
moderate-sized rip rap (>_6" diameter).
Once all re-routing of concentrated runoff is accomplished, the eroded drive section should be lined
with filter fabric and backfilled with gravel and/or sand,as long as the material drains freely and
provides sufficient structural support for future uses in the area. The area should be compacted in
lifts (layer by layer) to minimize future settling,which could result in a future runoff/erosion
problem. Backfill should be slightly mounded (i.e.,higher than adjacent land) to prevent preferential
flow of runoff across this area,which could cause erosion. Any areas not required for driving
should be topdressed with 0.5 of topsoil,immediately seeded with cover crop and shade-tolerant,
deep-rooted native plants,and overlain with erosion control blanket.
Important Notes: The success of Project 3 is highly dependent on implementation of Projects 1 and
2; therefore,Project 3 should not be done first or by itself. Regular inspections should be made
after the eroded gravel drive is restored to ensure that no new erosion/sedimentation problems are
080529:070908 3 of 4 Camp Teko Drainageway Retrofit—Conceptual Design
occurring. Special attention should be given to the southwestern corner of the log pavilion,as the
erosion occurred very close to this corner of this structure.
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CLOSING
We hope that you find this Conceptual Design useful and that it provides Camp Teko with a cost-
effective solution to your drainageway erosion problems. Please feel free to contact me (612-202-
2252) if you have any questions.
Enclosures: Conceptual Design Plan and Details
AES Rain Garden Design Sheet(provides general information and plant lists for rain
gardens)
080529:070908 4 of 4 Camp Teko Drainageway Retrofit—Conceptual Design
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