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7A - Wonderland Creek Greenways Project through the Valmont City Park ~ ,~. City of Boulder Parks and Recreation ~ Parks Planning and Construction MEMORANDUM To: Members of the Parks and Recrearion Advisory Board From: Anne Noble, Interim Greenways Coordinator Subject: Item for Information/Discussion Wonderland Creek Greenways Project through the Valmont City Park Date: January 10, 2001 Purpose This information is being provided m response to issues raised at the December 18, 2000 Pazks and Recreation Advisory Boazd meedng regazding the Valmont City Pazk pro~ect This memorandum provides information regazding the following issues: Provision of a wildlife corridor Location of the path in relahonstup to the Wonderland Creek Channel Introduchon: The Wonderland Creek Greenways project is being undertaken by the Public Works Department ~ in conjunction with the Urban Drainage and Flood Control District. The proposed Wonderland Creek channel traverses the Valmont Ciry park site from the existing underpass at Valxnont Road southeast to the North Goose Creek Channel The pro~ect will provide flood and drainage improvements and alternative transportation connecrions across the pazk site Back r~ The Wonderland Creek Channel improvements and path connechon were approved by City Council m December 1991 as part of the Commumty and Envuonmental Assessment Process (CEAP) for the Valmont Road widening pro~ect. The Wonderland Creek conceptual design was brought before the Parks and Recreahon Advisory Boazd in February 1999, as well as a~omt meeUng of the Water Resources and Transportahon Advisory Boards m Mazch 1999 for review and comment. Three conceptual design alternahves were presented to the Boazds. All three conceptual designs proposed a small meandering trickle channel enhanced by riparian tree plantings and stands of riparian shrubs, wetland grasses and upland natural grass azeas. All three conceptual plan ophons show the proposed 10 foot ~tnde pedesinan/bicycle path followmg the east side of the channel from the Valmont underpass, ascending the side slopes of the channel to allow for appropriately graded trail connechons to Valmont Road and to the major park trail system, extending south to the exishng Goose Creek Path wluch connects to the Boulder Creek Path. The primary difference m the three altemahves presented was the amount of space designated for more natural ~~~y +.,, Wonderland Channel m Valmont City Park: Page 1 \ grass, cattail, and wetland planhngs. A combmahon of broad grassland/wetland development with some more parklike development was selected by staff, the Parks and Recreation Advisory ''1 Board, the Transportahon Advisory Boazd and the Water Resources Advisory Boazd. "r At the time the Wonderland Creek Channel conceptual design alternatives were presented to the boazds, the availability of both groundwater and surface water to support a natural landscape was not known. It was also uncleaz whether the landscape plan should be designed for wetland or upland conditions Staff originally planned to construct the channel in April 2000 and develop a landscape plan later once the availabihty of groundwater and surface water was better understood. The Wonderland Creek project was bid m Mazch 2000 with an anticipated wnshuchon completion by the fa112000. The proposed draznage channel and path cross a restrictroe easement for an underdram pipeline to the Cline Trout Farm The city was in the process of renegotiahng easements for the underdrain system throughout the pak site duting tlus hme. While the Chne Agreement was anhcipated to be fully executed eazly in June 2000, tlus did not happen unhl October 4, 2000. However, the contractor did proceed with the work in early June recognizing that he could not cross the Cline easements. When the contractor began excavahng m June, he encountered lugh ground water, which was luniting his abihty to construct the pro~ect. Vanous options of constructing the project, given the lugh groundwater levels and the Clmes concerns for maintaimng the quality and quanhty of groundwater they have received historically ,,,~ through their underdrazn system, were discussed. At this time, the contractor and city personnel concurred that it would be easiest for the contractor to construct this pro~ect during the winter when the groundwater was the lowest. Ken Cline also fek this was a better tune of yeaz for mmunizmg the impact on his operation As a result, the construction of the channel has been delayed. The Wonderland Creek channel conshuction is currently bemg rebid m con~unc6on with the Phase I Valmont City Pazk project, with an anticipated bid opening date of January 25, 2001. The Phase I Pazk project plans include a landscape plan for the pazk, as well as the Wonderland Creek Channel. Wlule additional mformarion regazding groundwater and surface water availabihty has not been fully determined, city staff proceeded with retaining a floodplain restoration specialist to develop a landscape plan for the Wonderland Creek Channel The proposed landscape plan provides sufficient flexibihty to accommodate a variety of water avazlability conditions. The landscape plan is also designed to honor the legal constraints associated with the Chne Trout Farm subdrazn system. The Wonderland Channel is anhcipated to be constructed during February and Mazch 2001. The landscape portion of the contract, including the grass seeding, will proceed m the fall of 2001, allowmg several months to observe the water conditions of the channel. The restoration specialist may ad~ust the specific locahon of plantings to respond to the observed water availability and to create a more self sustaimng landscape Wonderland Channel in Valmont City Pazk Page 2 ~ ..r / ~ Wildlife Comdor ~ The Pazks and Recreation Advisory Boazd has expressed an interest in providing a wildlife corridor on the Valmont Ciry Park site. The proposed Wonderland Creek Channel landscape plan (attached) utilizes a mixture of native wetland, riparian and upland vegeta6on. The plan proposes planting 23 deciduous trees, 516 deciduous shrubs, 14 evergreen shrubs, 96 wildflower plants, 416 nahve grass plants and vanous native seed and wildflower mixes. The proposed nparian corridor width varies from 10 feet at the bndge to 200 feet at the confluence with North Goose Creek, with an average natrve corridor width of about 40 to 50 feet In order to limit and direct access to the creek, the proposed plan includes two low water crossings, wluch will reduce the unpact on the habitat. The upland areas of the landscape contain native trees and shrubs that aze drought tolerant, once they have become established. A series of native shrub thickets will be planted throughout the length of the channel, interspersed with lazger nahve overstory tree plantings, to provide food and shelter for animals as well as visual interest. The channel cross sechon has been widened significantly at the south end to provide a lazger area for potential wetland forbs and grass stands. Several grass and wildflower mixes aze being proposed to allow flexibility with uncertain and fluctuahng water conditions, and to provide visual vatiation. A native mixed prairie grass seed will be broadcast along the channel, with specific azeas bemg over seeded wrth Western wheatgrass, a wetland mix and a tall grass mix. The width of the "natural" nparian comdor is limited by the following constraints: ~ • the availabihty of water to support the vegetation The avaxlabihty of water to support vegetarion is not lmown. The condition of the channel upstream of Valmont Road varies between a 30' to 40' wide flat ta11-grass covered channel with lazge and sma11 cat tazl stands to dense volunteer tree stands and shrubs. There is a moderately deep pond east of King's Ridge Road wtuch appeazs to be fed by groundwater and channel flows, however other portions of the channel downstream of this pond aze periodically dry Wlule the proposed Chne underdrain pipelme is not shown to be constructed withm Wonderland Channel (as is the exisring drain lme m North Goose Creek) the underdram will impact the amount of groundwater bemg uitercepted by the channel. A permanent imgahon system will be incorporated along the Wonderland Creek comdor in order to establish the nahve grassland and nparian vegetahon, as well as to provide minunal supplemental water when condihons require it. Tlus supplemental ungarion will also help develop a denser stand of vegetahon, wtuch will provide enhanced filtrat~on of sedunent and improve water quality. However, the intent of the landscape design is to develop native vegetarion to provide habrtat for wildlife, which is supported by naturally available water. the location and type of planhngs is limited by the Cline's Easement Agreement ,~- ,,,,, Wonderland Channel in Valmont City Pazk. Page 3 \ The Cline Agreement resh'icts the planting of any trees within 15 feet of the Clme pipeline and species of willow, cottonwood and elm can not be planted within 60 feet of the pipehne These ''",# limit lines aze shown on the attached landscape plan. `+" Path location The location of the proposed path is shown on the attached Wonderland Creek landscape plan The location of the path is limited at the following control pomts: the underpass and connection to Valmont Road The proposed path connects to the Wonderland Creek pattt system north of Valmont Road through an existing underpass that is currently buried. The proposed path must connect to the existing underpass The connec6on from Wonderland Creek path to Valmont Road has been designed to meet maYimum grade requirements. Therefore there is not much flexibility to change the location of the path at this mtersectron the proposed bridge at the south end of the site The future bike racing pattt crosses the Wonderland Creek mulh-use path, as well as the cross country ski trail at the south end of the site. A bndge is needed to provide grade sepazation of these paths In order to mimmize the length of the bridge, the Wonderland Creek path and cross country ski trail, which go under the bridge, must be as close as possible to the channel at this ~ location While the Wonderland Creek path ascends the east side slope of the channel, the distance between the centerline of the channel and path vanes between 20 and 70 feet except at the two conh~ol points described above (see attached) The path could be moved away from the creek between the underpass and the bridge and between the bndge and the connection to the North . Goose Creek path, with the location remaming the same at the control points Another option to increase potential native planting azea and habitat would be to e~ctend the native planhng azea east of the path at the proposed bridge. This could be accomplished without changing the tra~l location or the length of the proposed bridge If the path is realigned, the resulting grade of the path and the curve radmses will need to be checked for compliance with safety standards and the unpact to other pazk funcrions will need to be considered. The proposed path was located in relahonship to pazk elements identified in the approved Valmont City Pazk plans. The varied width of the channel natrve landscape azea was designed in response to an advisory recommendation of the Transportation Advisory Boazd. Given the uncertainty of available water, the width of nahve habitat that can be supported without a significant amount of supplemental water is not known. T'he increase in the riparian comdor width is also lunited by the restriction in the Cline Agreement wluch does not allow the planting of any trees within 15 feet of the Clme underdrain line. Wonderland Channel in Valmont City Pazk: Page 4 ~' .~. ~.. The bid opemng for the combined Valmont City Park Phase I and Wonderland Creek ~ Construction is scheduled for January 25, 2001 While the city has 45 days to awazd a contract, the Wonderland Creek construction needs to proceed as soon as possible in order to complete this work during the winter months when the impact on the temperature increase to the groundwater the Cline's receive is hmited and the amount of groundwater the contractor must work within is minimized Adjustments can be made to the path alignment and landscaping plan while the project is under construction in order to take advantage of new information. Attachments: Wonderland Creek Landscape Plan ~ ~ Wonderland Channel in Valmont City Pazk Page 5