a vision for renewal

the restoration project was conceived as part of a comprehensive plan to centralize and modernize court functions throughout polk county. with the goal of returning the courthouse to an aesthetic that closely mirrors its original elegance, while accommodating current operational requirements, the project involved extensive interior renovations. these upgrades included new masonry elevator shafts, modifications to existing ones, strategic floor removals and infills, and the implementation of innovative supports that harmonize with the historic walls.

tackling unique engineering challenges

renovating a structure originally built in 1906 presented several engineering challenges, particularly given the building’s robust construction methods and materials. the courthouse features multi-wythe masonry walls, sometimes several feet thick, and an original floor system designed by the columbian fireproofing company. this system, characterized by a combination of rolled steel bars suspended from steel beams with intricate stirrup connections, required a careful and innovative approach when introducing new openings and modifications.

2022足球世界杯小组赛赛程 ’s engineering team conducted a thorough analysis of the historic floor systems, developing creative solutions to meet the project’s rigorous demands:

• custom structural supports: to accommodate new elevator locations and modifications, engineers designed unique steel supports capable of bearing large wall loads while fitting within the tight spatial constraints of the historic structure.
• large lintel solutions: for the exceptionally wide historic masonry walls, specially designed large lintels were introduced to ensure structural integrity without compromising the building’s historic character.
• innovative access solutions: lightweight attic walkways were designed to provide necessary access for staff, demonstrating how modern engineering can coexist with century-old construction techniques.

these solutions exemplify how modern engineering principles can be integrated with historical construction practices, preserving the character of the original design while meeting contemporary needs.

preserving heritage for the future

the restoration of the polk county historic courthouse is much more than a renovation. it is a careful preservation of a vital piece of history. while opn architects led the overall design, ensuring that key architectural features such as restored plaster, refined woodwork, and the revival of original courtroom aesthetics were maintained, 2022足球世界杯小组赛赛程 ’s role was critical in ensuring that the building’s structural systems could support these historic elements safely and effectively.

the collaboration between opn architects and 2022足球世界杯小组赛赛程 has resulted in a building that not only serves the functional needs of today’s judicial and civic operations but also stands as a testament to the enduring value of historic preservation. by addressing the complex challenges posed by early 20th-century construction methods, the project paves the way for the courthouse to continue its legacy into the next century.

a collaborative achievement

the success of the polk county historic courthouse renovation highlights the importance of expert collaboration in heritage restoration projects. 2022足球世界杯小组赛赛程 ’s innovative structural solutions, developed in partnership with opn architects, have played a pivotal role in revitalizing a historic landmark while ensuring that it meets modern standards of safety and functionality. this project underscores snyder & associates’ commitment to excellence in structural engineering and their dedication to preserving the architectural heritage of our communities.

as the courthouse reopens its doors with a renewed blend of historical beauty and modern efficiency, it stands as a lasting symbol of justice, dignity, and progress for polk county.

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as a potential solution, the des moines county regional solid waste commission (swc) proposed a solution for the permanent leachate disposal at the west burlington sewer system. viewed as an option to lower taxpayer costs within the city of west burlington, both parties consented to the agreement, and plans for the project were launched.

managing dual client representation for leachate disposal solution

the snyder & associates team was hired to represent the city’s and the landfill’s needs throughout this project. when providing services for multiple parties, clear agreements and constant communication are vital to satisfactorily satisfy all needs. since the city leaders agreed to construct the project for the landfill, we helped both clients navigate the process to enter a chapter 28e agreement under the iowa code. this agreement allows cities to contract with other governmental units—in this case, the county landfill.

additionally, to ensure the partnership was protected in the future, we prepared a substantial industrial use agreement between our clients for monitoring and reporting the characteristics of the leachate. per this agreement, the landfill cannot exceed an average of 58,000 gallons of leachate disposal per day and has a maximum limit of 80 gallons per minute. the industrial use agreement also outlines specific parameters for contaminants such as cadmium, copper, lead, nickel, silver, btex, and benzene to ensure nothing harmful is conveyed to the west burlington treatment plant.

leachate conveyance route options & project construction

with agreements in place, our team began preparing preliminary studies for various pumping alternatives and piping routes to establish the most economical yet agreeable solution for the conveyance needs. alignment a offered a shorter route with fewer grade transitions but would require multiple permits to construct a utility within the state highway right-of-way. alignment b featured a longer route but avoided private property and easement acquisitions. despite the higher upfront construction cost, alignment b resulted in the cheaper option in the long run. the group unanimously selected alignment b, and the final designs were moved forward.

the force main will connect the landfill to west burlington’s wastewater distribution system for leachate disposal.

for this project, we started by constructing the lift station at the landfill. the station’s location was pre-determined as the site had a previously placed utility hole that allowed pumping and the necessary access to power. this lift station was constructed as a submerged wet well lift station typical for transmitting wastewater flows.

our team then transitioned the construction phase to installing piping sections, adding over 12,000 linear feet of 4-inch diameter, high-density polyethylene (hdpe) piping. this material was selected because it can be installed in longer sections than pvc. since the project pathway runs through the 世界杯足球比赛预选赛 right-of-way, most of the construction could be done via open-cut installation. however, the pipe intersects an active railroad at one location, and trenchless installation was applied to limit disruptions.

in a client request, we added pipe access cleanouts every 500 feet along the segments. while this is typically unorthodox for force main because of the pressure pipe, access was needed along this long expanse of pipe for special cleaning due to the nature of the waste.

this mutually beneficial waste management project reduced landfill expenses, and the lower costs ultimately trickle back to the taxpayers. the snyder & associates team was proud to bring the city and the county’s needs to the contractor to facilitate the construction of a project that minimized environmental impacts, avoided wastewater treatment plant operation interruptions, and mitigated the disturbance to nearby neighborhoods.

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the former bridge was damaged beyond any hope for repair.

the 3.75-mile-long trestle-to-trestle trail connects the inter-urban trail in des moines to the johnston trail system on the north side of interstate 35/80. in the spring of 2019, the trestle-to-trestle trail bridge over beaver creek was severely damaged by an ice dam and collapsed. the loss of this critical piece of infrastructure meant a major detour for trail users. through a multi-agency effort that included polk county conservation, the des moines metropolitan 2022世界杯32强预选赛 organization, the state of iowa, and city leaders from johnston and des moines, the snyder & associates team, along with our structural subsidiary, 2022足球世界杯小组赛赛程 , were able to create a replacement bridge that far surpassed the structural stability of its damaged predecessor.

rail bridge replaced with a modern structure

the former trail bridge was originally a 316’-long timber and steel railroad bridge that had been repurposed for trail use. when the ice dam caused its collapse, designers knew they needed to create a replacement that could withstand more significant threats from flooding and debris. the final design for the new bridge is a much more solid structure that incorporates modern aesthetics with practical design applications. at the same time, it honors the history of the former rail bridge with decorative corten steel design features integrated into the safety railing to resemble wooden trestles. this feature also mimics the styling used on several other area trail bridges, creating a cohesiveness to the mid-iowa trail network.

the nearly 320’-long replacement structure utilizes pretensioned, prestressed concrete beams instead of the trestle-style construction. this allowed for two large concrete and steel piers better suited to withstand the flooding forces and ice flow issues experienced along beaver creek. an observation “bump-out” near the middle of the span provides a place for trail users to stop and admire the surrounding creek and natural environment.

on both ends of the bridge are stone pillars built to resemble the welcome signs in nearby johnston. these predominantly limestone structures have a nameplate on one side with “beaver creek crossing” displayed. a structural steel “archway” at the bridge entrance provides a whimsical decorative feature.

distinctive aesthetic & customized lighting system sets this bridge apart

the customized lighting system makes the new bridge a destination stop for trail users.

the customized led lighting system incorporated into the design is unique to a structure of this type. it illuminates the bridge deck and approaching trail path and the bridge’s underside. the lighting system can be programmed to change colors in a near-unlimited pattern, sequence, or timeframe, creating a one-of-kind visual attraction for trail users and vehicle traffic on nearby interstate 80.

with this new trail bridge open and serving residents again, trail users no longer need to take an extensive detour to reach their destination. the solid construction and long-lasting materials ensure this structure will withstand whatever mother nature throws at it in the future. and thanks to its unique design and eye-catching lighting system, this bridge attracts people’s attention in the area and will for many years to come.

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the relatively flat grade of this trail section provides an easy ride for most bicyclists.

most trail 2022世界杯32强预选赛 in central iowa over the past two decades has centered around making connections. whether connecting small communities or social venues, providing alternative travel access between popular destinations has been a common factor. in development for the past seven years, the red rock prairie trail is adding perhaps one of the most critical links yet. this nearly 16-mile-long trail extension (connecting monroe, prairie city, and mitchellville) is part of the long-range goal of linking saylorville lake with lake red rock and the neal smith national wildlife refuge.

the red rock prairie trail will predominately run along a former rail corridor, eventually extending from lake red rock south of monroe to the mitchellville city limits. the snyder & associates team recently completed the design and plan preparations for approximately eight miles of this multi-use trail extending from red rock park in monroe to prairie city with a direct link to the entrance of the neal smith national wildlife refuge. the trail also provides access to prairie city’s garden square park in the center of town. two former railroad bridges required structural retrofitting to complete the alignment of the eight-mile, monroe to prairie city, trail section.

rail-trail funding drives project forward

this multi-use trail has a direct link to the entrance of the neal smith national wildlife refuge.

this new, hard-surface trail has been driven by relentless fund-raising efforts being led by jasper county conservation. this grant funding has included a “…$510,000 federal lands access program grant, a $263,711 federal recreational trails grant, a $240,000 transportation alternatives program grant, and a $116,839 state recreational trails grant.”

because the former railroad line used for the trail alignment was one of the first three rail lines across central iowa, the grant manager (iowa dot) required an additional level of historical and cultural studies to ensure the project did not adversely affect the original site. our design team worked closely with iowa-based wapsi valley archaeology to ensure the new trail would not damage any areas of historic significance.

by linking the two, major central iowa lakes via a multi-use trail, state and local agencies anticipate a marked increase in out-of-state (and in-state) recreational enthusiasts using this unique trail configuration to travel between these midwestern destination spots. our design team continues to work with jasper county conservation and other agencies to plan the remaining trail sections to wrap up this important trail connection.

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crews work on the rehabilitation efforts on the former railroad bridge over the iowa river.

while it’s been many years in the making and still has many miles remaining to construct, the river’s edge trail is ideally positioned to take advantage of the scenic beauty, diverse wildlife habitat, and sprawling wetlands in the heart of iowa. currently, two segments are open at either end of the trail. when completed, however, the approximately 37-mile-long trail will connect steamboat rock to marshalltown, passing through many communities in between. the snyder & associates team has been intimately involved in the extensive trail 2022世界杯32强预选赛 and bridge evaluation projects, working closely with hardin county officials on the northern leg of the trail.

following a former railroad corridor, the river’s edge trail (formerly iowa river trail) will ultimately connect seven cities and two counties to the iowa river greenbelt and the central iowa trail network. additionally, connections will be made to a handful of local trail networks, including the iowa river state water trail, gunderson trail in eldora, bates trail in union, and the pine lake state park trail east of eldora.

steamboat rock bridge over iowa river

our team initially began on this project in steamboat rock, working to design a 0.6-mile section of trail that starts at south 1^st street and heads west through a tree-lined corridor. the structural engineers from snyder & associates subsidiary, 2022足球世界杯小组赛赛程 , developed plans to rehabilitate a nearly 100-year-old railroad bridge over the iowa river. this 60’-long deck girder bridge was reinforced and retrofitted with a paved surface and decorative rails to accommodate bicyclists and pedestrians.

our team performed an air and slump test on the concrete as part of the construction observation process.

from the iowa river crossing, our team designed the trail alignment south to the community of eldora, crossing several rural roadways. at the 215^th street (t avenue) location, we incorporated a box culvert as a trail tunnel under the roadway, creating a safe passage for trail users. to date (2022), the entire trail from steamboat rock to eldora is paved. 2022世界杯32强预选赛 work and funding securement efforts will continue until the two trail sections meet around the marshall and hardin county lines.

世界杯足球比赛预选赛 support keeps trail development on track

like many multi-use trail projects, 世界杯足球比赛预选赛 buy-in and enthusiasm are critical to help keep them moving forward. the collaborative effort between marshall and hardin county officials, private groups that led fundraising efforts, and a design team dedicated to creating first-class amenities was the driving force that generated a level of enthusiasm that has not waned. with an estimated 223,000 people living within a half-hour drive of the new alignment, it’s anticipated that the river’s edge trail will provide ample opportunities to locals and visitors alike for recreation and exploration through america’s heartland.

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a rolling prairie trail system map shows the trail’s gently winding path through five rural communities.

when rail transportation in iowa peaked in the early 1900s, the state was home to more than 10,500 miles of track. as automobiles became the preferred mode of transportation, many short-line railroads that crisscrossed the state became less profitable and were ultimately acquired by larger companies or abandoned altogether. today, fewer than 4,000 miles of track remain operational throughout the state. advocates are working to convert many abandoned rail lines into multi-use trails, reinvigorating rural connections and providing recreation and tourism opportunities for residents and visitors.

the conservation board in butler county is diligently working to complete one such rails-to-trails project known as the rolling prairie trail. when complete, the rolling prairie trail will wind its way through five butler county communities and connect to trails in franklin county to the west and bremer county to the east. after receiving an iowa dot state recreational trails (srt) program grant and acquiring the land for the trail’s path, the butler county conservation board partnered with snyder & associates due to our firm’s extensive rail-trail development experience.

aging railroad crossings require structural retrofit

our team identified a previously unknown drainage structure on the trail route during an initial site visit. this discovery helped avoid a potential drainage issue before the project was awarded. from there, our seasoned trail professionals were able to quickly begin the process of designing the 5.45-mile stretch of the trail connecting the city of allison to neighboring bristow. the butler county conservation board had previously cleared and grubbed the trail path before the completion of the design. this enabled our team to begin their topographic survey and drainage analysis promptly, allowing 2022世界杯32强预选赛 and permitting to progress.

an in-ground drainage system manages stormwater and keeps the rolling prairie trail safe and accessible.

the trail alignment for the allison to bristow segment included five paved gravel road crossings and one crossing of local highway 14. additionally, multiple existing bridges and drainage structures required attention ranging from complete removal and replacement to reinforcement and retrofitting. our design team worked with butler county conservation to develop a plan for addressing each structure. the butler county conservation board updated and reinforced the existing bridge structures, and our team handled the 2022世界杯32强预选赛 and installation of in-ground stationary drainage systems. we also provided construction observation and administration services during the trail project’s excavation, grading, and paving portions.

to comply with the conditions of the srt grant, our team followed the dot’s federal aid policy guide and completed coordination with multiple agencies. they also ensured that each trail crossing was ada-compliant and included signage designed to alert drivers, bikers, and pedestrians of approaching intersections. removable bollards were added to the crossings to prevent motor vehicle access to the newly paved trail yet allow county vehicles to enter and exit for routine maintenance. the crossing on highway 14 includes all the same elements, with the addition of pavement markings indicating a crosswalk. fencing was added to one steep crossing to keep trail users safe.

rail-to-trail conversion provides unique recreation opportunities

today, the allison to bristow stretch of the rolling prairie trail provides users with access to wilder park and restaurants, campsites, and restroom facilities on each end. trail users experience a variety of landscapes and scenery along the trail, including native prairies, forested canopy, and updated historic railroad bridges. other trail segments provide access to wolter’s prairie preserve, heery woods state park, and multiple bicycle fix-it stations for unexpected breakdowns. the easy grade of this hard surface trail and the convenient amenities make it a popular destination for outdoor enthusiasts of all ages.

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beyond wetlands, creating new amenities in wanatee park

during the initial design stages, community leaders had the sole intention of creating new wetlands within the park. while conducting site inspections, our environmental team noticed a few additional improvements that would significantly benefit park amenities while also enhancing water quality within the local watershed. through discussions with linn county conservation officials, a new trail bridge and fishpond were approved in addition to the planned wetlands.

wetland creation & enhancements lead design efforts

in total, seven wetlands were constructed or rehabilitated to increase the park’s sustainability and improve the area’s water quality.

our project team focused on the wetlands portion of the project first. county officials already had specific areas in mind for potential wetland enhancement and creation. throughout these assessments, our team vetted the options, affirming their selections and providing new suggestions, as well. in total, seven sites were chosen for wetland improvements, with a net cut of 2,280 cubic yards achieved.

though all wetland sites required updates, there was a varying degree of work needed across the seven locations. some of the wetlands were enhancement projects where the area had once been deeper but had filled in with sediment over time. for these areas, the focus was excavating sediment and restoring hydrology to improve wetland functions and provide an environmental lift.

other wetlands were created from scratch based on the location of drainage features and tiles. agricultural tiling systems previously conveyed water from nearby fields into wanatee creek. a few of the newly constructed wetlands allowed tiles to flow openly within the wetlands, supplying hydrology and creating ideal wetland habitats. this was a great way to improve water quality as tiles that had previously outlet nutrients directly into the creek now drain into the wetlands and the nutrients are absorbed by plants rather than flowing downstream. several of these constructed wetlands included an agri drain water level control structure™ in the designs. these structures allow linn county conservation staff to draw down wetland water levels if necessary, for seeding or vegetation maintenance, such as treating invasive species.

consistent with the water and land legacy bond’s initial goal, these wetlands filter nutrients and provide floodplain storage benefits necessary to improve local water quality while enhancing wildlife habitat and the natural beauty of the surrounding landscape.

pedestrian trail bridge replaces high-maintenance culverts

the new bridge sits higher than its predecessor to avoid washout potential.

the next phase of this project focused on the construction of a 30-foot-long prefabricated steel truss pedestrian and maintenance bridge over wanatee creek. this bridge was designed to replace deteriorated twin corrugated metal pipe (cmp) culverts that were past their useful life. the culverts were covered by a soil and mulch mixture that would constantly be washed out and require replacement due to the low trail profile and the crossing’s location in the federal emergency management agency (fema) regulatory floodway.

a more permanent structure at a higher elevation was necessary. our team consulted with our structural subsidiary, shuck britson, to identify design solutions. it was determined that using a prefabricated structure with site-specific dimensions would be the best fit as these are well suited for similar span lengths and trail bridge loading. because this is a fairly simple design that requires no formwork or falsework, this option ended up being the most economical solution for the client, as well. the bridge was assembled off-site by the manufacturer and shipped to the park for placement. a crane was used to lift the approximately 20,000-pound bridge off the truck and position it on the newly designed and constructed abutments.

since this crossing is also the main access point for county maintenance vehicles, special consideration was taken during its design. to accommodate vehicle access across the bridge, the connecting trail had to be built at a different slope than the pre-existing crossing to allow for a wider trail radius. this also created an opportunity to perform 100 feet of stream restoration to stabilize the channel flowing under the new bridge.

stream restoration efforts improve aquatic habitat

during the new trail bridge design process, scour issues were apparent in the section of wanatee creek surrounding the crossing and the banks lacked stabilization as they had previously only been shielded by bits of broken concrete. despite all of this, the creek in this location was in decent shape, however, the aesthetics did not match the surrounding prairie or park objectives. to stabilize the streambanks and enhance aesthetics, flexamat® erosion mats were used to defend against streambank erosion and promote native vegetative growth.

since wanatee creek experiences high velocity flows, additional flexamat® was installed across the bottom of the channel to further protect against scour associated with the new bridge. the result was an extremely smooth streambank transition that is hard armored, easy to maintain, and much more aesthetically pleasing than the bits of broken concrete that previously lined the banks. after a summer’s worth of vegetation growth through the flexamat®, the project has shown a major improvement in water quality, stream function, stabilization, and in-stream wildlife habitat, all while successfully complementing the park.

after completing the construction of the bridge and stream improvements, linn county conservation staff observed orange-throated darters near the new bridge, which hadn’t been spotted in this area in some time. this freshwater fish species is on iowa’s endangered list and its arrival was seen as a significant success by county leaders and staff.

creation of recreational fishing pond draws anglers

the pond helps sustain the area’s high water quality and is stocked with bluegill, bass, crappie, and other local species.

the final piece of this project involved the construction of the first fishable pond owned by linn county. the pre-existing site for the pond consisted of a bermed-up area that was weedy, non-functional, and underutilized as a wanatee park attraction.

specific elements were incorporated into the pond’s design to promote water quality and meet project goals, including a sediment forebay, shallow slopes, an impermeable clay base layer, and seepage mitigation measures such as drainage diaphragms. these features, along with native plantings and a recently added prairie buffer, help filter pollutants off the adjacent highway and farm fields and protect the pond as water enters. with a healthy pond system established, our environmental team equipped the pond with various items to enhance fish habitat, including spawning beds, jetties, and assorted depth pools.

the pond also included an agri drain water level control structure™, a cmp riser outfall, and an emergency spillway. our experts determined this was the best fit for the area as it enables staff to control water depths and maintain fishing structures. these additions, along with shallow slopes near the interior perimeter, increase safety for recreational users. county crews are responsible for continual maintenance and routinely mow a trail around the pond for improved access. after construction was completed, the pond was filled and stocked with bluegill, bass, crappie, and other local fish species.

collaboration & communication leads to project success

the success of these projects involved significant collaboration between the snyder & associates project team and linn county conservation officials. our experts helped with the technical aspects while the client attended site visits, discussed site conditions, and helped determine where the various project features would be placed. between their vision and our expert designs, wanatee park continues to experience improved water quality and is viewed as a blueprint for future collaborative efforts.

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paving begins on the railroad highway trail.

now standing at more than 50% complete, the dream of a completely off-roadway, multi-use trail network spanning the entire country keeps taking steps to becoming reality. when completed, the great american rail trail will extend over 3,700 miles from washington d.c. to washington state. the success of this ambitious project has relied on countless local communities spearheading the construction of their trail sections. in western iowa, the most recent addition to this trail system includes the railroad highway trail just outside of council bluffs.

the trail route will run adjacent to the existing railroad highway and when completed, this 10-foot-wide, 15.7-mile-long, hard surface trail will connect council bluffs to the communities of underwood, weston, and neola. with significant trail 2022世界杯32强预选赛 , design, funding, and construction experience in iowa and throughout the midwest, the snyder & associates team was uniquely qualified to assist pottawattamie county leaders with their plans to connect these rural communities with the omaha/council bluffs area. when finished, the trail will not only fill a significant gap in the great american rail trail, but also provide a conduit for nearby residents to walk, run, or bike through an enjoyable mixture of urban and rural landscapes.

coordination & in-house bridge design keep the project moving

in the early 2022世界杯32强预选赛 stages, our team identified numerous parcels for easement acquisition along the preferred trail route. twenty-two of those parcels presented right-of-way conflicts that our team began to address with the appropriate entities to prepare the trail path. since this roadway was previously a state highway that had been jurisdictionally transferred from the iowa dot to pottawattamie county, extensive coordination with the county engineer’s office and the county gis department was crucial in determining what constituted the existing right-of-way line.

railroad highway trail’s current and planned segments.

additionally, the trail route crosses mosquito creek at two locations, creating a need for two bridges within one mile of each other. the structural engineers from snyder & associates subsidiary, 2022足球世界杯小组赛赛程 , were able to seamlessly step in to prepare detailed plans for each of the bridges and help pottawattamie county choose the best option. it was determined that prefabricated, truss-style bridges were appropriate to span the 152-foot and 192-foot crossings. to date, the bridges have been installed and a short 0.9-mile stretch of trail between them is currently being designed. once paved, this “bridge gap” will connect two paved segments for a total of 3.4 continuous miles of trail.

the southernmost segment of the trail from council bluffs to underwood is currently (2022) being designed. construction of this segment is slated for 2023 and 2024, followed by the final 6.3 miles of the trail from underwood to neola.

throughout this project, the snyder & associates team has served as the lead 2022世界杯32强预选赛 and design firm, providing preliminary survey, boundary survey, and construction staking, along with our design services for trail alignment, profile design, as well as detailing for the extension and replacement of several box culvert locations along the route.

trail funding sources for the final stretch

the keys to success on projects of this magnitude are the identification and utilization of numerous trail funding sources. our team is uniquely qualified to help find the resources to get the job done. this project has been funded by a diverse collection of grants and donations, including the omaha-council bluffs metropolitan area 2022世界杯32强预选赛 agency transportation alternatives program (mapa tap), the iowa west foundation, iowa dot’s state recreational trail fund, pottawattamie county, and the pottawattamie county trails association.

seeing the full picture

multi-use trails have been gaining in popularity for decades by bringing benefits to the communities they pass through and the nearby businesses. they can increase the quality of life for residents in a community by providing space for healthy recreation and safe multimodal transportation. businesses benefit from the increased traffic and awareness of their goods and services. many rural communities in iowa and throughout the midwest have recognized the immense benefits trails have brought to similar communities and have made plans to invest in links to their existing networks.

once completed the railroad highway trail will join a growing network of hard-surface trails across iowa, including the well-known high trestle trail spanning story, boone, and dallas counties, the raccoon river valley trail in dallas county, and the t-bone trail connecting audubon and neighboring cass county. 

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expansion project ties trail to local network

this before image shows the bill riley trail location where the great western trail extension will connect.

beginning on the southern edge of water works park near downtown des moines, the great western trail meanders through both urban and rural landscapes as it winds its way south to the community of martensdale. this nearly 19-mile-long route, however, was lacking a critical connection to the des moines local trail network. our team worked with multiple organizations to create a trail link that filled this gap.

in consultation with polk county conservation and the city of des moines, our team designed a one-mile-long, hard-packed, gravel trail extension to connect the paved portion of the great western trail to the bill riley trail to the east. running parallel to george flagg parkway to southwest 30^th street, this trail section mainly follows a former railroad right-of-way through a heavily wooded area.

the chosen route for the trail required a modification to a levee. working in conjunction with the u.s. army corps of engineers (usace), our project team applied for the necessary levee modification — a section 408 review request — through the city of des moines. this included the development of a flood contingency plan and detailed drawings of the levee modifications.

since the trail is owned and managed by polk county conservation, but a portion of the property is owned by the city of des moines, a 28e agreement was also necessary between the two entities to govern the roles and responsibilities regarding the trail construction and future maintenance. our team coordinated with both jurisdictions to establish this agreement.

during the construction phase of the trail extension project, our team reviewed shop drawings, tracked quantities, provided weekly progress reports, submitted partial payment applications, and processed necessary change orders. we also ensured the trail was built in compliance with the plans, specifications, and recommended acceptance upon completion.

trail realignment creates opening for commercial development

construction begins on the great western trail realignment project.

establishing trail alignments in coordination with private development efforts also requires careful 2022世界杯32强预选赛 and frequent reevaluations. when knapp properties was focused on developing a privately-owned parcel of land to the south of the highway 5 bypass, an at-grade trail crossing was proposed to provide access to the new development. our team was called upon to recommend a trail realignment alternative that avoided crossing the trail, while also providing the developer with complete access to their property.

our designers proposed moving a 1,600-foot-long-existing section of the great western trail to the west to run adjacent to the existing highway 5 on-ramp and veteran’s parkway. this proposed realignment also replaced a deteriorating section of the trail that was going to need replacement in the future. this necessary realignment provided a solution that kept trail users safe and allowed the developer to quickly move forward with their plan.

trail reconstruction benefits from cares act funding

our 2022世界杯32强预选赛 and design work also focuses on reconstruction efforts that keep trail systems operating smoothly. because several sections of the great western trail are over 20 years old, deterioration levels had led to people not using parts of the trail where it winds through warren county. fortunately, the coronavirus aid, relief, and economic security act, also known as the cares act, included a provision to provide funding for the state recreational trail program in iowa.

with funds available for repairs, renovations, and some expansion, our team partnered with warren county conservation to determine those areas most in need of repaving. our team is helping county leaders stretch their share of the funding to make as many repairs as possible. this project, currently underway, could ultimately result in the reconstruction of several miles of trail in the area south of cumming.

as societal and commercial needs continue to change around us, trail expansions and realignments are sure to follow suit. these unique challenges inspire our designers, planners, and engineers — energizing them to develop creative solutions that help keep active trail networks moving forward.

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the banks of fourmile creek are undergoing stabilization efforts utilizing rip-rap and vegetation.

the fourmile creek watershed in central iowa consists of nearly 80,000 acres of urban and agricultural communities. it’s also home to over 80,000 residents. as this population has grown over many decades, this expansive watershed has become increasingly prone to regular flood events.

these reoccurring floods have impacted numerous residents, resulting in frequent evacuations and the costly destruction of property. extensive efforts have been taken by several government agencies to minimize flooding and enhance the overall water quality in the watershed. a seasoned team of engineers and environmental scientists from snyder & associates has been at the forefront of these efforts since 2006. through a multitude of projects, our team has made a significant difference in the health and safety of this critical water system.

updating fourmile creek modeling & assessments

initially, snyder & associates was commissioned to study the fourmile creek watershed to establish an accurate floodplain model to update the significantly outdated federal emergency management agency (fema) maps. our team of environmental scientists and engineers used hydrologic and hydraulic flood models, along with stream assessments, to evaluate the impact of flooding on future development and the impact that development may have on the watershed.

hydrologic methods from previous studies only accounted for current land use while grouping the entire watershed into one basin. our team completed a comprehensive review of both existing and future land use plans to predict potential conditions in hydrologic models. each of these models divided the 118-square mile watershed into individual sectors to provide a more accurate analysis.

peak flow rates developed through modeling were used to predict fourmile creek’s response to flood events of varying magnitude and duration. a profile of the watershed patterns was established to create flood maps utilizing lidar data and arcgis software. these maps provide valuable information by increasing awareness of the likelihood of flooding and ultimately, reducing the devastating impacts floods can produce.

streambank stabilization increases watershed resilience

stream flooding in fourmile creek tributary a prior to stream stabilization improvements.

in addition to extreme flooding issues, fourmile creek has a long history of erosion and poor water quality. many factors, such as above-normal precipitation and runoff volumes, impervious surfaces, and agricultural practices within the watershed contribute to the stream’s degradation and erosion. specifically, two tributaries of the creek located in ankeny — northeast tributary a and southeast tributary b — experienced extensive stream degradation and bank erosion after the 2008 floods and placed many properties and infrastructure at risk.

to address these individual tributaries, our team assessed over 7,400-feet of the stream before proposing improvements that would not only mitigate flooding but also complement the stream’s natural protection, as well. this assessment, along with our intimate knowledge of the watershed, led to sustainable design solutions.

homeowner input, technical assessments, and an evaluation of alternatives were utilized to prepare conceptual designs for both tributaries using an integrated stream restoration approach. this approach provided cost-effective and aesthetic creek restoration through the combination of several techniques including vegetated buffers, toe protection, graded floodplain benches, and weirs. combined, approximately 6,500-linear-feet of the stream was successfully stabilized at the conclusion of both projects.

fourmile creek watershed management authority & stormwater management plan

while the rehabilitation of the two tributaries drastically improved the creek’s overall water quality, additional efforts were necessary to continue mitigating flooding, erosion, nutrient loading, and bacteria issues. to address these problems, local communities created the fourmile creek watershed management authority (fcwma) in 2012. this group focuses on collaborative work to address both flooding issues and water quality. snyder & associates was commissioned to study the region with the intent of improving the understanding of the watershed and preparing a stormwater management plan.

our experts knew that appropriate mitigation had to account for a powerful, meandering alluvial stream that transports significant sediment load. in some cases, extreme events caused substantial channel changes due to high flow, debris jams, erosion, and sediment deposition. toe rock protection integrated with bendway weirs, floodplain benches, and native vegetation buffers were incorporated into the design. additional measures included establishing permanent easements and expanding polk county’s adjacent conservation area which helped diversify stream habitat and increased wildlife access to the water.

this management plan also addresses overall maintenance goals and responsibilities, budgetary costs, and phasing for the full development of the comprehensive system. additionally, potential regulatory tools, grants, and funding opportunities were outlined and adopted by all jurisdictions involved.

fourmile creek greenway master plan

natural vegetation was incorporated during restoration to enhance wildlife ecosystems.

a series of eight watershed goals aimed at reducing flooding and improving water quality were included in the plan to provide guidance. each goal was assigned subgoals and tasks to help track milestones and develop a schedule. the adoption of a greenway system, or master plan, was one of the eight primary goals of the fcwma. this specific goal outlines practices, such as native vegetation re-establishment, stream restoration, and wetland enhancements. the greenway master plan addresses these improvements, as well as potential recreation and education opportunities along approximately 10-miles of the creek.

stakeholder input and thoughtful consideration of multiple elements are essential when 2022世界杯32强预选赛 and implementing a greenway system. during a 世界杯足球比赛预选赛 open house, our team gathered community input for the future of fourmile creek, which helped shape the plan’s objectives.

greenway master plan objectives:

• flood management and water quality
• native habitat protection and management
• define greenway
• make connections
• 世界杯足球比赛预选赛 access and service
• education
• economic development
• implementable steps

the greenway master plan provides a path to transform the current, developed landscape to a more natural state. to start, it’s necessary to move at-risk human life, property, and infrastructure away from the floodplain. in place of the developed landscape, work commenced establishing oxbow wetland connections, construction of a stormwater wetland, and prairie restoration. once completed, this corridor will provide many community benefits including recreation, alternative transportation, improved water quality, habitat conservation, and flood control.

stormwater wetland reduces nutrient overloads & flooding

as the greenway plan expanded, partners of the watershed project saw an opportunity to be proactive in developing a solution to protect the environmentally sensitive fourmile creek. this resulted in a stormwater wetland which once again brought our team on board to provide environmental and stormwater design services.

positioned adjacent to the popular gay lea wilson trail, the stormwater wetland provides a natural means to remove pollutants from stormwater and reduce overall flow rates. as stormwater is captured within the wetland, pollutants are removed naturally through reduced water velocity and increased settling, uptake, and filtering by vegetation.

volume control is a particularly important benefit as there are downstream portions of fourmile creek that have been restored and stabilized, but there are other locations that continue to suffer from severe bank erosion. managing the channel protection volume in the wetland improves overall stabilization efforts to reduce sediment transport.

the stormwater wetland helps to treat and slow down 23 acres of stormwater runoff from an adjacent suburban landscape before entering fourmile creek. improvements like this help to reduce sediment and pollutant loading into the des moines river further downstream, protecting it for years to come.

fourmile creek restoration gives new life to natural areas

for over 15 years, snyder & associates has helped shape implementation efforts across the fourmile creek watershed through both agricultural and urban areas. today, work on the fourmile creek watershed continues with stabilization improvements and 世界杯足球比赛预选赛 education outreach that teach residents how to better take care of our watersheds. the snyder & associates team stands ready to continue providing guidance for this beneficial and forward-looking endeavor.

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