02-13-1996 Council Packet - Laserfiche WebLink

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Allan Blocks” Edgework Builders David Stockdale, President 8301 Audubon Road Chanhassen, MN 55317 November 15, 1994 ?e: Yorks Residence, Orono, MN. Dear Mr. Stockdale, Our in-house engineering staff has reviewed the proposed segmental retaining wall which is to replace an existing treated timber retaining wall. While it is true that no failure has occurred and your proposed walls do not substantially change the current wall geometry, this does not assure future success as this assumes a static condition and futi'.re conditions could change. Furthermore the construction of said wall(s) is on an overall slope and any design can address internal and external wall stability but not overall slope stability. For these reasons we suggest the following to insure that the replacement wall not exacerbate the current stable condition. 1. All walls should be geogrid reinforced to insure internal and external stability. 2. Geogrid reinforcement will necessarily require "benching" of the reinforced zone into the existing slope geometry. 3. To insure no future changes in the soil in the reinforced zone: a. use free draining material (limited to 5% fines) in backfill/reinforced zone and leveling pad. b. place drainage tile behind the base course of block and also at base of the reinforced zone where it meets the retained soil - all tile draining to daylight. c. backfill the top 6" (below top soil) with impermeable clay soil to prevent surface drainage into reinforced zone. d. grade to prevent surface ponding above walls. 4. Because of the slope at the toe of the wall(s) it is recommended that a minimum of 2 courses of block be buried or H'/7 embedment depth which ever is greater, course buried block for the top 2'wall is adequate. One Allan Block™ Retaining Walls Allan Block Corporation • 7400 Metro Boulevard, Suite 185 • Edina, MN 55439 • Phone 612/835-5309 • Fax 612/835-0013