Category Archives: Project Report

South Waterfront Greenway Nearing Completion

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Relatively fresh off of working in construction management, one of my first big design assignments was the civil engineering work for the South Waterfront Greenway Central District – a combination park and active transportation corridor through Portland’s South Waterfront area. Our team spent the better part of 2007 through 2009 designing a gentler, more natural riverbank and stormwater infrastructure to support the Greenway.

Then, at the end of 2009, with the design process nearly complete, my family and I decided to move to Haiti to work on water and sanitation projects. This decision led to an incredibly unique adventure in engineering, world view and community.

After a life defining two year journey we returned home and I was fortunate enough to be re offered my old job at KPFF. It was the same position, the same desk and – surprisingly – some of the same projects. During one of my first days back in the office I was greeted by a smiling PM who warmly shook my hand saying, “It’s so great to have you back. You can help us finish South Waterfront!”

Indeed, I had assumed that the 90% complete plan set that I had left two years previous had in the those years become an actual park. I imagined bikers happily zipping along the river. I imagined families picnicking. I even imagined juvenile salmon resting on their journey up the Willamette. None of these existed. What did exist was a much different project – the result of two years of agency reviews and an economy that had forgotten the bold development of 2006.

So with that as prologue, I am excited to report that this past week I participated in the final walk through for the actual, constructed South Waterfront Greenway! The project is a stunning addition to Portland’s collection of waterfront trails and parks. The following is a highlight of some of the primary functions and features of the newly constructed park.

Pathways and Parklets

South Waterfront Greenway
Facing north up the Greenway. Note the lawn terraces on the slope and the separated pathways.

As originally envisioned, the Central District project would set the vision for a greenway trail that would run throughout the South Waterfront area. The completed corridor would include: separated bike and pedestrian paths for increased modal safety; parklets and overlooks where people could stop and enjoy the riverfront setting; and a notable focus on environmental stewardship and habitat restoration.

South Waterfront Bike Symbol
Brass bicycle (above) and pedestrian (below) symbols were cast into the trail at nodes along the corridor to direct traffic.

South Waterfront Greenway Ped Symbol

South Waterfront Greenway Trails
A view south from the top slope of the project. Note that though the geese began their journey on the asphalt bike path (above), they were able to correctly interpret the pathway symbols and soon moved to the concrete pedestrian path (below).

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Riverbanks and Low Water Habitat

As mentioned, the vision for the Greenway included an intentional focus on habitat restoration. The riverbank within the project – once stabilized by concrete rubble and demolition debris – has been cleaned up and flattened to create low water habitat for migratory fish.

South Waterfront Greenway Low Water Habitat
A view of the “cove” created to provide low water habitat. Much of my own work on the project is now underwater here. Note that the flatter banks have already begun recruiting beneficial woody debris.

South Waterfront Greenway Woody Debris

River Overlooks

The newly restored riverbank can be viewed from several overlooks. The overlooks vary in size and style and add to the sense that the Greenway is a destination and not just a transportation corridor.

South Waterfront Greenway Small Overlook
A small overlook where pedestrians can stop and admire the Willamette.
South Waterfront Greenway Large Overlook
A larger overlook near a node between the trails.

Stormwater Management

Runoff from the trails and adjacent features is treated and managed through a gravel swale that runs between the bike and pedestrian paths. Flow in these swales ultimately collects in one of several catch basins, which discharge to “level spreaders” that redistribute the flow along the riverbank.

South Waterfront Greenway Swale
A catch basin in the central water quality swale. Note the ponded water surrounding the grate. By forcing the water to pond, sediment is allowed to settle out of the runoff before it crosses to the river.
South Waterfront Greenway Level Spreader
Stormwater from the swale is piped to one of several level spreaders, where it fills the gravel trench shown and redistributes along the riverbank.

Site Furnishings and Artwork

Like the neighborhood that it supports, the Greenway has an obvious upscale character. The site is dotted with multiple, unique styles of benches and there is a riverbank stabilization themed art piece that was specifically commissioned for the site.

South Waterfront Greenway Benches
Multiple bench types provide ample opportunity to sit and enjoy a close up view of the Willamette River.
South Waterfront Greenway Concrete Bench
The use of wood decking is a common and unique theme throughout the project.
South Waterfront Greenway Artwork
Artist Buster Simpson designed this riverbank stabilization themed art piece specifically for the project. Root wads – which are often used to create bank roughness – are supported by jack type objects that were inspired by a barbed structure that has been historically used in coastal bank applications.

As you can see, the only thing missing from these pictures are the walkers, bikers and park enthusiasts who will undoubtedly discover this great new place once construction and the winter weather pass.

If you enjoyed this article, you may also be interested in the following past posts. Thanks for reading!

Detailing Vegetated Riverbanks

The Engineer and the Fisherman

LID at Metro’s Gleason Boat Ramp

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Roadway Construction at PDX

If you flew in or out of Portland International Airport (PDX) this summer you probably noticed that there has been quite a bit of street construction underway near the terminal building. Here’s what’s been happening.

PDX Pavement Rehabilitation

The Port of Portland,  KPFF and Kerr Contractors are nearing the end of a project to preserve and rehabilitate the pavement leading to and from PDX’s arrival and departure gates. Because of the overlap between the peak construction season and the peak travel season, this has been a high profile project for everyone involved. As an engineer at KPFF, I have had the opportunity to work on the planning, development and implementation efforts over the past year and a half.

Our team’s work began with building a 40 year life cycle cost analysis to compare the construction and maintenance costs associated with three options to extend the pavements service life: rehabilitation with an asphalt concrete inlay, reconstruction with asphalt concrete pavement and reconstruction with portland cement concrete pavement. Following selection of a preferred combination of work, we developed plans and specifications detailing the project, and we will continue to provide support until construction is completed in early October.

The following photos are from recent site visits and cover the major components of the work.

Lower Bus Lanes

PDX-LOR

Each day about 540 bus trips are made shuttling people from the PDX economy lots, to the terminal building and back again. The buses making these trips are big, double rear axle vehicles and they all follow the same route. Understandably, the asphalt pavement along this route had lived a difficult life. The buses’ weight combined with starting and stopping forces had lead to severe rutting in the pavement – so much so that it had begun shoving the adjacent curb and sidewalk.

Based on our life cycle cost analysis and existing pavement conditions, the team determined reconstruction with portland cement concrete pavement to be the best rehabilitation option in the bus lanes. The resulting roadway provides a more rigid platform for heavy bus loading, which should result in a more durable pavement structure.

Lower Passenger Lanes

PDX-LIR

Near the bus lanes is a separate roadway dedicated to carrying the thousands of passenger cars that visit the arrival gates each day. These lanes carry a high volume of traffic, but it is not heavy traffic, so pavement distress was limited to wear and minor cracking in the top surface.

Under typical conditions, asphalt concrete pavement fails from the top down. Loading creates small cracks in the top surface and these cracks gradually work their way down through the pavement. If the cracks reach the bottom of the pavement section, the pavement fails and must be replaced. However, if those responsible recognize that this cracking has begun, the corrective work can be limited to removing and replacing the top surface to the crack depth, resulting in a significant savings of both time and money.

During predesign work, the project geotechnical engineer determined that with proper top surface maintenance, the pavement section in this area will essentially never fail under passenger car loading. Such a design is called a “perpetual pavement.” As such, our life cycle cost analysis showed there to be a significant savings in using an asphalt concrete inlay here. The completed work involved removing and replacing approximately 2 inches of the existing pavement.

Upper Passenger Lanes

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Traffic to and from the airport’s departure gates is carried on an elevated roadway that is split into two sections. The section furthest from the terminal building is used by taxis and other commercial traffic and exists entirely on a concrete bridge structure. This section was not included in the project and remains unchanged. The section nearest the building is used by all other passenger car departure traffic and is built partly on that same bridge and partly on the roof of the lower baggage claim area. Because it is constructed on top of an occupied space, the original construction of this roadway included a waterproofing membrane on top of the building, overlain by a layer of asphalt concrete pavement. The existing pavement and membrane were both at the end of their expected service lives and had begun to show signs of distress.

This past week, the contractor finished removing this existing pavement and waterproofing membrane and began preparing the surface to receive a new spray applied membrane. Spray applied waterproofing membranes are relatively new in the US and, in the right applications, offer superior performance in almost every respect when compared to more traditional products. After the new membrane is placed, the road will receive a layer of pavement. The completed roadway will look much the same as the original, but will have a renewed service life.

Pedestrian Signing

One of the project’s smallest but most visible changes involved removing the miniature stop signs that used to guard the airport’s raised crosswalks. These signs have long created a headache for both drivers and maintenance personnel. The new crosswalk delineation includes cross hatch striping and overhead “Stop for Pedestrians” signs.

So, it has been a busy summer at PDX. Pavement preservation work can create a temporary inconvenience from time to time, but streets are expensive and proper maintenance is a critical part of protecting our infrastructure investments. Hopefully this post has given you some insight into the work and the engineering behind this particular preservation project.

KPFF’s Stormwater Cinema

Over the past few weeks, I have presented some concepts, design guidance and project examples around the topic of low impact development (LID). This post will wrap up the topic, at least for now.

As you may know – or should by now at least strongly suspect – my employer, KPFF Consulting Engineers, has a long history of designing LID projects. KPFF’s history with LID in Portland mirrors the city’s own experience, starting with our design of the bioswales in the OMSI parking lot, Portland’s first large scale LID project. This legacy carries through to today with our work on the green street retrofit of SE Division Street, which will be completed this summer and has been billed by the city as America’s first green main street. Through our project work, KPFF has worked closely with the city to stay on the leading edge as standards have evolved, to the point of helping to develop some of the tools and guidance that are now required elements of stormwater design in Portland.

Last year, in order to celebrate this history and to take stormwater design to the streets, KPFF launched the Stormwater Cinema series. This group of short films has highlighted a few of our more unique stormwater projects along with some of the design considerations that went into those projects. Having featured one of these shorts – The Stormwater Toolbox – in a previous post, I thought this might be a good opportunity to share the other parts of the series.

Under One Umbrella

Though many had faith in the idea, no one was quite sure how successful Stormwater Cinema would ultimately be, but Under One Umbrella – the series’ first release – passed even the highest expectations. Highlighting a unique stormwater art installation, this clip went about as viral as any stormwater engineering content could ever be expected to.

A Garden to Play In

The series’ second video focuses on Tabor Commons, a project that brought together neighborhood residents, local designers and community building organizations. Engineers at KPFF have donated many hours to this effort over the years, both in the office and on the site.

Stay tuned to KPFF’s Vimeo channel so that you won’t miss the next great installment of the Stormwater Cinema series!

LID at Metro’s Gleason Boat Ramp

Gleason-Ramp

Last week I introduced some design ideas for Low Impact Development (LID). One of these ideas is what I am calling LID layering – a decentralized approach in which the designer incorporates multiple layers of LID elements throughout the drainage path. The land side component of Metro’s M. James Gleason Boat Ramp site is a good example of this technique. While nothing more than a big parking lot, design features throughout the project combine to create a system that treats and infiltrates stormwater runoff onsite in all but the biggest storms.

Completed in 2013, Gleason is the result of a master planning effort that reaches back to 1999. Oregon’s most used boat launch provides urban access to the Columbia River for users of all types, and conveniently hosts extensive parking for both trailered and non-trailered vehicles, restrooms and a river patrol office. Master planning and design was completed by KPFF Consulting Engineers with landscape architecture by Mayer Reed and plumbing and mechanical design by MFIA. Engineering features of the site include a debris deflection wall and both traditional and bio-engineered slope stabilization measures.

Gleason-Trees

The tree canopy is the first possible point of contact between falling rain and the Gleason site. The site’s main purpose is providing parking for people using the river and admittedly landscaping was a secondary consideration in the design process, but there are trees and over the coming years they will grow to cover portions of the parking lot. The truth is, though, that most of the rain at Gleason will land on pavement.

Gleason-Pavers

Pavement type is Gleason’s second LID layer. While heavy loads, high levels of use and cost considerations dictated that most of the site be paved in asphalt, permeable pavers were used on the single car parking spaces, which will see much less traffic. Rain on these areas directly infiltrates, reducing the amount and delaying the concentration of runoff from paved areas. The change in material also adds a nice aesthetic. As with canopy cover, permeable pavement is a small piece of the storm drain system, but the cumulative impact of small measures early in the drainage path can be as important as larger downstream measures when developing a layered LID system.

Gleason-Flat-Pvmt

Perhaps the most significant piece of the drainage approach at Gleason is the fact that, except in isolated areas, all of the pavement is sloped to sheet flow to stormwater facilities. This avoids concentrating flows – both at the surface and in piped systems – and led to more flexibility in designing the site’s stormwater planters. This is not to mention the fact that a flat, smooth parking lot with few or no drainage structures makes a better driving surface in both wet and dry conditions than one littered with dips, valleys, warps and catch basins.

Gleason-Curbs

Flush curbs were used on most parts of the Gleason site, providing both edge restraint for the pavement and walls for the adjacent stormwater planters. As opposed to collecting water in catch basins, shedding it from the surface into the planters delays flow concentration and allows the system to be much shallower. Wheels stops were added where the curb line also needed to serve as protection for parking vehicles, and slotted curbs where planters run adjacent to traffic lanes.

Gleason-Swales

At this point, it is worth noting an often overlooked LID layer. As stormwater flows across paved surfaces, it picks up a large amount of the sediment that cars track onto the pavement. Much of this sediment can be quickly filtered out by directing water through a short conveyance swale or across a small filter strip before it enters a larger stormwater facility, resulting in better water quality and less maintenance. These features were incorporated into Gleason’s design where possible, but – as can be the case – space and geometry constraints precluded their use in some instances.

Gleason-Planter

Runoff entering Gleason’s stormwater planters infiltrates fairly quickly, thanks to the site’s well drained, sandy soils. Because of this, it was possible to over design some planters by basing the planter depth on what the surrounding curb walls could support and not on what was required to meet the minimum standards. Designing to the “maximum extent feasible” like this is a core LID principle. In many cases it is possible to exceed minimum requirements without adding cost to the project. Where planter bottom elevations varied, steel weirs were installed to ensure that different levels filled together.

Gleason-Overflow

Some larger storms will exceed Gleason’s onsite stormwater management capacity. In these cases, water will overflow through raised catch basin structures and outfall into the river. Each planter also has an overland overflow route to the river that would be used if its basin were to clog. This route could also be used in extreme storms, but most of the site is below the flood plain and could be underwater in those cases.

Gleason’s storm drainage system is a good example of using LID on a pavement and vehicle centric project and counters the view of LID as a “greener” design option that only works on heavily landscaped or naturalized projects. In truth, while they work better in some cases than in others, LID concepts can and should be used on every project. These concepts don’t as much represent a new group of options, as they signify a shift in what is considered best practice in stormwater engineering design.

While there is a significant environmental benefit from this shift, there are economic and functional benefits, too. LID measures saved Metro money on the Gleason project by reducing the amount of pipe and number of drainage structures that needed to be installed. These same measures resulted in a simple grading and storm drain design that makes the site more friendly to drivers.

With simultaneous benefits to the function, economics and sustainability of civil design projects, it is clear that LID is worth the focus and advocacy it is currently being given.