Loading...
CR 99-206 Approve Restoration & Trail Project Nine Mile Creek Headwaters CITY Or: ~ November 5,1999 HOPKINS Council Report 99-206 Approve Restoration and Trail Proj ect Nine Mile Creek Headwaters Proposed Action. Staff recommends adoption of the following motion: Move that Council approve a Nine Mile Creek Headwaters Restoration and Trail Project as proposed by the Nine Mile Creek Watershed District with joint funding at 50% each by the District and the City at a budget of $60,000. Overview. In late 1998 Nine Mile Creek Watershed District approached City staff with a Nine Mile Creek restoration project. As the Excelsior Boulevard reconstruction was well under way, it became apparent that Nine Mile Creek headwaters (located south of Excelsior Boulevard and between the Justus Lumber/Hopkins Auto Body site) was in need of maintenance. The District proposed a cleanup effort, tree trimming, creek bank stabilization and a possible nature trail to enhance the remaining vestiges of Nine Mile Creek (North Branch) headwaters. Staff, aware of the City's obligation to maintain the creek way, concurred and approved of District action to undertake field investigations and cost estimates. Council in the meantime has approved such a project in concept by placing this project in the 2000-2004 CIP. The District has submitted a plan that provides scope and a cost estimate for Council consideration and action. Primary Issues to Consider. . Proj ect location . City's obligations in creek maintenance . City's needs associated with headwaters area . Proj ect scope . Proj ect funding . Recommendation Supporting Information. . Location map . Barr Engineering Project Proposal ~~ James Gessele Engineering Superintendent Analysis. . Proj ect location The target area lies south of Excelsior Boulevard between Justus Lumber on the east and Hopkins Auto Body on the west. The area is a wooded strip along undeveloped 13th Avenue South right-of-way and is the last vestige of Nine Mile Creek's true headwaters to the north and west: a vast marshy low area before it became a City landfill and eventually Central Park. . City's obligation in creek maintenance As with other ponds, ditches or flood plain areas attendant to the creek and situated on City property, the City is held responsible for the maintenance ofthe creek to assure runoff water quality and the integrity of the waterway. Nine Mile Creek has historically been generous in assuming some share of maintenance costs. . City's needs associated with the headwaters area A large box culvert facility under Excelsior Boulevard on the 13th Avenue South alignment discharges into Nine Mile Creek and serves as the official headwaters of the creek's north fork. The structure is equipped with a trash guard device to trap debris and some sediments. The box culvert is in periodic need of maintenance to clean out the debris and to date the City has not been able to access it. This restoration project affords an appropriate opportunity to address that need. . Proj ect scope Barr Engineering, consultant to the Nine Mile Creek Watershed District, has prepared a project scope that is attached for Council review. In brief it lays out some background concerning the creek's original function and what has since evolved and the nature of creek bank vegetation then and now. It makes recommendations as to clearing of unwanted the restoration of desired vegetation. It also spells out the construction of an 8- foot wide wood chip trail connecting the Excelsior Boulevard trail with the Hennepin County Southwest Regional Trail. It calls for bank stabilization by installing a stone lining in the stream channel and regrading of banks where necessary, the latter to accommodate a natural ramping feature for City equipment to gain access for maintenance issues. Property owners on either side of this creek segment have been approached and are enthusiastic about the cleanup and restoration effort. Although current District regulations provide for a 50-foot setback requirement that precludes any buildings near the creek, the City will need to negotiate an easement with Justus Lumber for purposes of ramp access to the creek channel, the installation of the nature trail, and for long-term maintenance of vegetation. The understanding of this proposal is that the spraying of buckthorn and other invasive vegetative species is a responsibility of the City. . Project funding Trail construction, vegetative restoration, and stream channel stabilization are estimated to cost $58,000. The watershed district proposes that it and the City split the costs of such a project and that the City pay its share over a two-year period (2001 and 2002). The newly adopted CIP identifies the Storm Sewer Utility as the funding source for this project. . Recommendation Staff recommends approval of this restoration project and of the 50% funding apportionment plan with the watershed district at a budget not to exceed $60,000. ~ ~^'",U ~919.8 " o 911. : H adwater of Nin Mile Creek, R storation and Trail Project Fred RozumaIski June 28, 1999 Revised: November 4, 1999 , The headwaters of Nine Mile Creek once emanated from a large marsh. Nine Mile Ceek was likely a small winding channel that flowed through the lush vegetation and over the rich organic soils. To accommodate city growth, the wetlands were filled and the creek channelized. Today this straight channel accommodates a large volume of storm water runoff that drains from urban streets and buildings. Sudden surges of water during stonn events are eroding the banks of the channel, which are composed of the fragile peat soils of the original wetland. These banks should be stabilized as part of any creek restoration project. The vegetation along this reach of the creek has been drastically altered since iTS days as a marsh. Cottonwood and box elder trees now dominate where once a wet meadow existed. Box elder seedlings and invasive buckthorn currently choke the mid story, and invasive weed species cover the ground. A restoration of the original plant community is not possible, therefore revegetation goals of the area should be first. to cover open soil to prevent erosion, and second to establish a plant community that will survive under existing conditions and pCIpetuate without extensive maintenance. Two different approaches to plant community restoration are possible. The first would involve extensive eradication of the existing weed community and planting of potted woody and herbaceous plants. This would require considerable funds and a commitment to extensive maintenance. The second approach would be to eliminate some of the weedy invasive species, buckthorn and garlic mustard in particular. plant the resulting open soil with native herbaceous plants and tolerate some weeds. This would provide erosion control, make for an acceptable natural appearance and keep maintenance activities reasonable. A tree and topographic survey has been completed. Trees to be removed in the revegetation process include dead and diseased trees, female box eldcr and all buckthorn. These trees would be marked on site for removal. To provide a pedestrian connection between the County Road 3 trail and the Hennepin County Southwest Regional Trail Corridor, an 8 foot wide wood chip trail is proposed. A natural "bench" for this trail exists along the east side of the creek channel. Minor clearing and grading would be necessary for the trail construction however, disturbance would be minimal. Recommended Plant Community Restorstlon Process and Trsll Construction: 1. Remove all dead and diseased trees and all female box elder. 2. Brush understory of all buckthorn, honeysuckle shrubs and small box elder. Paint srumps with herbicide (Tordon). Pull small buck1:hom seedlings. 3. Treat invasive herbaceous plants (garlic mustard and reed canary grass, etc.) With Roundup herbicide. Repeat applications as necessary (at least once more) within five weeks. 4. Plant resulting open ground with live herbaceous plants such as: cardinal flower, culver's root, Pennsylvania sedge, wild columbine, zigzag goldenrod and heartleaf aster. These should be planted at approximately 1.5 feet on center. Approximately 9,000 square feet of planting will require 4,000 plants. 5. Site management. The primary restoration activity will be guiding the revegetation process through invasive plant control and encouragement of introduced native plants. This will require monthly herbicide treatments during the growing season and supplemental planting where necessary. It begins with a three year maintenance plan with monthly site visits (planting time through September) the first year, 5 site visits the second year and 3 site visits the third year. ' 6. Long-term maintenance should involve twice: per growing season spraying of buckthorn and other invasive species. This should be the responsibility oCtbe City of Hopkins. 7. Clearing and grading along the existing "bench" on the east side of the creek channel for the construction of an 8 foot wide pedestrian trail. Restoration would be with wood chips. Restoration Costs Tree removal Brush removal Weed eradication (site prep) Plantings Maintenance (f1J'St year) Maintenance (second year) Supplemental planting (second year) Maintenance (third year) Trail Construction Total Armoring tbe Stream Channel $4,000 $3,500 $1,500 $6,000 $2,500 $2,000 $2,000 $1,500 $5,000 $28,000 Erosion is occurring within the stream channel due to the force of water flowing through the channel and because of the loose peat soils that forms its bank. This process can be halted by the placement of rock within the channel. It is recommended that a stone lining be placed with the channel. Some regrading of the banks may be necessary in areas. An estimated cost for this channeJlbank stabilization is $30,000. 206613 ** TOTAL PAGE.03 ** -I ~ CD ~ Q. (J) -- ~ Cf)O ~JJ ~G> z- ZZ >~ ~~ :DlIJ __ _1:1 0(0 0-' ::rco ::To.. :::Jr-+ :::J COO> (I) (J)r-+ CJ) (J)O (J) :J , I , I \ , 1J , \1\) .., w ():) CD I 0 + ...... 0 ..... ex> 1+ :J II I\) ~ 0 - , I I I I -l- I I I I ...... /~ /; CO 0'1 0 + II I\) I - I , I l- I , , I I ~ ...... c.n CO ^ 1+ -....,J c.n ..... 0 0 :J + II I\) - I I I I J- -J- I I ...... , j CO ,^ }; ex> CO I If\) tV c.n 0 I II 0 c.n 0 , I- I I I I ~ I ~rr?~ ss ~/ A r '"'- i",-J ~ Invasive Shrub Dense MidstOrY Eroding Creek Channel Nine Mile Creek Existing Conditions , '^- \ ~ ..,. ((,,_r ......r - ,-I' .' ,-",.' r~~~c~ / ':/ ..... -:) ,J V' )' ~ J. '-. I ,J .-: --r- ~y'}~ ~ .... c. . '.> '( ~,' . ~ ~ . .' . \ ' '? "',~'~~ j ? ' ~ ~.-/l-S ( Herbaceous Weeds Managed Native Wildflowers Introduced' Stabilized Creek Channel Nine Mile Creek Trail and Planting Concept