Agenda - Parks and Recreation Commission - 06/09/2005 - Joint with CC

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Willow Control WJlloxvs may become a problem If xvillow's are groxving in proxknity to a trail, an aggressive mowing program should be established where they are mowed frequently within no less than 20 feet of the trails surface. An absolute minimum ,,f 15' feet of separation should be maintained xvith herbicide, betxveen any evidence of willoxv shoots and the trail surface. \',Tillows are identified in an area proposed for a trail la this case, the most cost effective strategy may be to mechanical remove the alluvial soils (with roots) t~o a depth of up to 36 inches by a significant width. This is often possible at large construction sites - with sand hauled back in place. If there is likelihood that viable willow roots remain, Biobarrier should bc installed at the time of trail construction. If there is loxv probability, black plastic may be a more economical solution. Case History of Effective Control '['here does not appear to be a great deal of history on the effectiveness of Biobarrier root control use (or other documented strategies) in association with bituminous trails. The City of Ramsey has however conducted several test areas to determine local effectiveness. Cottonwood Park (year 2000) This zone includes Biobarrier #1 installed as a 36" curtain on either side of the blacktop trail east of the bridge. Adjoining segments are also trenched, but instead of Biobarrier, they are backfflled with pea gravel. Savanna Trail (year 2002) This 160 feet of trail has 19 ½" of Biobamer #2 installed as a vertical curtain on both sides of the trail. 'l 'he other difference from the above installation is that 2,OD was used to 'kill' the Sandbar Willows prior t~o replacement of the bituminous surface instead of Glycol Phosphate [Round-up]. Lake Itasca Trail (year 2003) ~l'his site's willow control examination is likely to yield the most conclusive info~mafion. The test area consists of 180 feet of xvillow impacted trail divided into three sections. The first 60' foot portion (figure l.) xvill be the same Biobarrier #2 product applied horizontally under the trail's surface, after the removal ~f the blacktop and Class - 5. lit should be noted that both the manufacture and the vendor of this product recommend its use vertically as installed above, Apparendy, Biobarrier is intended to inhibit the growth of root tips; horizontal installation presumably could allow roots to grow parallel under the material, and as they become larger in diameter, 'lift' the trailversus breaching the surface which is the usual problem].