03-09-2010 Council Work Session Packet

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�1" . ,, ;,�,�; ,. � _ �_.� ,r,,�, r��F:'�' �-s:: � � ,.. _,•�;,,,,� March 8, 2010 'p0�� '��' Hennepin Conservation District Board AiTN: Eilen 6. Sones 417 t�lorth 5`� Street, Suite 200 Minneapolis, MN 5540]-3206 Re: h1etropo!itan Landscape P.estoration Program and Clean Water Fund Grant Snorel;ne Restoration Demor,stration Project — Carmans Bay — Lake Minnetoilka Client Name: City of Orono 6onestroo File No.: 139-10000 Dear Ms. Efl?n Sones; The City of Orono is submitting the above referenced project to the Hennepin Conservation DistncJt Board for funding consideration for the Metropolitan Landscape Restoration Program and Ciear V`Jater Fund Grant. The projec� is located on Carmans Bay of Lake (�linnetonka (see attaLh� location). The drainage area to this site is approximately 0.50 acres. There is 350 linear f�et of shoreline that is experiencin_y substantial erosion. Poor soils, wave action, and shading of na;ivt piants by buckthorn have made this site susceptible, t� erosion. We estimate, based on a revieev of historic aerial photograph and sanitary sewer as-builts, that 1,800 squarc feet of shoreline have been lost and is currently exposing a sanitary sewer manhole. (5ee Attachment A, Photo A-1) Traditionally shorelines hav2 been stabilized along Lake Minnetoi�ka utilizing riprap and rock that extends from below the water, within tne littoral zone, up siope to above the Ordinary High Waker Level o`the Lake. (See Attachment A, Phota A-2) This approach to shoreline protection removes native vegetation and eiiminates che iiltering and !ittorai habitat that na�ive veaetation along shorelines provides. 1"he City proposes to compiete a project tnat demonstrates �Iternatives to just riprap. The project would involve the us� of a new appro�ch to shoreline stabilization cailed compost grouting of ro�_k along with native piantings. (See Attachment P., F�hoto A-3)This approach utilizes rc>ck for structural sup�art of the soil but involves t#ie use of compost in the gaps of the rock to allo�� for native plantinqs. We also propose the development of a 15 - 20 foot native buffer above the-_ rock. Typically yards around Lake Minnetonka are 0.5 acres. Thfs size lot can contribute 0.3 Ibs of phosahorus per year to the Lak�. lmprovements along the shor�line and buffering the la�eshore area� along this Lake wc�uld eliminate thi5 c.ontribution ot phosphorus frorn adjacent lawns. This projec` provides an excellent opportunity to demonstrate alternatives to riprap for shoreline s:abilization as well as native buffer� t:st�blishment, Project length is �SO line�r ft,et of shorelir.e and indudes the roilowing components: • Re-establishment of shoreiine ' ° � Buckthorn removal in a 40-foot area of buffc�r ;0.32 �3cres) "'�` "�''�'�` , iiP �� . p �. i i ¢� �:* s A � �� t � � . "' � G'jz,'��:� � - � ; ,�, n . �� �f -,. ;.. _. . .� y ,c� S e�n � d ; g+� r �^:. , . . .. � c` �'.'��x" �y ', s �. . _ _ . .. . . .. . .,...� , .,. ,. .. � � .. , .... _ . .. ._ . . . .. .. . .. . . ... . Yr .. _.