Over the past 30 years, the City of Portland, Oregon, USA, has emerged as a national leader in green stormwater infrastructure (GSI). The initial impetus for implementing sustainable stormwater infrastructure in Portland stemmed from concerns about flooding and water quality in the city’s two major rivers, the Columbia and the Willamette. Heavy rainfall often led to combined sewer overflows, significantly polluting these waterways. A partial solution was the construction of “The Big Pipe” project, a large-scale stormwater containment system designed to filter and regulate overflow. However, Portland has taken a more comprehensive and long-term approach by integrating sustainable stormwater management into urban planning. Over the past three decades, the city has successfully implemented GSI to mitigate these challenges. Low-impact development strategies, such as bioswales, green streets, and permeable surfaces, have been widely adopted in streetscapes, pathways, and parking areas, enhancing both environmental resilience and urban livability. This perspective highlights the history of the implementation of Portland’s GSI programs, current design and performance standards, and challenges and lessons learned throughout Portland’s recent history. Innovative approaches to managing runoff have not only improved stormwater control but also enhanced green spaces and contributed to the city’s overall climate resilience while addressing economic well-being and social equity. Portland’s success is a result of strong policy support, effective integration of green and gray infrastructure, and active community involvement. As climate change intensifies, cities need holistic, adaptive, and community-centered approaches to urban stormwater management. Portland’s experience offers valuable insights for cities seeking to expand their GSI amid growing concerns about climate resilience, equity, and aging infrastructure.

The authors would like to make the following corrections to the published paper [1]:(1)In the abstract, the word “overly” should be replaced by word “overlay” in the following sentence: [...]

I intend to submit a full paper and present this work. Abstract: Ethics is a critical topic that is often overlooked in engineering education. To improve understanding of the many ethical issues students may face as practicing engineers, we developed ethics modules in four civil engineering classes at the University of Portland (UP). These ethics modules ranged from traditional writing assignments to interactive class discussion. As a result, students receive ethics instruction at least one time per year throughout their four years at UP. Survey results indicate students thought their understanding of the ASCE Code of Ethics improved, and the ethics modules were helpful for their professional career. Student comments and survey results also indicated the interactive class discussion was more impactful than the writing assignments because they were able to learn about more than one ethical situation. The results of the survey will help improve the ethics modules, and continue our efforts to integrate ethics into the Civil Engineering Program at UP.

Stormwater runoff from large roads is a major source of pollutants to receiving waters, and reduction of these pollutants is important for sustainable water resources and transportation networks. Porous pavements have been shown to substantially reduce many of these pollutants, but studies are lacking on arterial roads. We sampled typical stormwater pollutants in runoff from sections of an arterial road 9–16 years after installation of three pavement types: control with conventional asphalt, porous asphalt overly, and full-depth porous asphalt. Both types of porous pavements substantially reduced most of the stormwater pollutants measured. Total suspended solids, turbidity, total lead, total copper, and 6PPD-quinone were all reduced by >75%. Total nitrogen, ammonia, total phosphorus, biochemical oxygen demand, total and dissolved copper, total mercury, total zinc, total polycyclic aromatic hydrocarbons, and di-2-ethylhexyl phthalate were all reduced by >50%. Reductions were lower or absent for nitrate, orthophosphate, E. coli, dissolved lead, and dissolved zinc. Most reductions were statistically significant. Many pollutants exceeded applicable water quality standards in the control samples but met them with both types of porous pavement. This study demonstrates that porous overlays and full-depth porous asphalt can provide substantial reductions of several priority stormwater pollutants on arterial roads for many years after installation. Porous pavements have the potential to substantially enhance water quality of urban waterways and provide ecological benefits on urban thoroughfares.

Bioretention systems use plants and soil media to treat pollutants in stormwater. Biochar can be an effective amendment to bioretention soil media for removing pollutants due to its adsorption properties. This study evaluates biochar as an amendment to bioretention soil media for the removal of contaminants in stormwater. Columns with varying ratios of biochar to bioretention soil media (0%, 25%, and 50% biochar) were tested to evaluate the removal efficiencies of copper, zinc, phosphorus, nitrogen, and microplastics from stormwater. Five trials were conducted with stormwater collected from parking lot runoff. Results show that the addition of biochar in bioretention systems improves the removal efficiency of zinc (average of 79% in columns with 50% biochar compared to 54% in columns without biochar) and copper (average of 73% in columns with 50% biochar compared to 25% in columns without biochar). Stormwater effluent from the biochar-amended columns also had significantly lower turbidity (21 NTU) than that of the control columns (58 NTU). Consistent leaching of nitrogen and phosphorus species was evident in the control as well as the biochar-amended columns, with average removal efficiencies of -1,114% for total nitrogen and -703% for total phosphorus. Microplastics were effectively removed by all columns, regardless of biochar amendment, with an average removal of 86%. This study indicates that biochar has the potential to reduce metal concentrations in stormwater when used as an amendment to bioretention systems but has a limited impact on nutrients and microplastics.

Stormwater runoff from large roads is a major source of pollutants to receiving waters. Porous pavements have been shown to substantially reduce many of these pollutants, but studies are lacking on arterial roads. We sampled typical stormwater pollutants in runoff from sections of an arterial road 9-16 years after installation of three pavement types: control with conventional asphalt, porous asphalt overly, and full-depth porous asphalt. Both types of porous pavements substantially reduced most of the stormwater pollutants measured. Total suspended solids, turbidity, total lead, total copper, and 6PPD-quinone were all reduced by >75%. Total nitrogen, ammonia, total phosphorus, biochemical oxygen demand, total and dissolved copper, total mercury, total zinc, total polycyclic aromatic hydrocarbons, and di-2-ethylhexyl phthalate were all reduced by >50%. Reductions were lower or absent for nitrate, orthophosphate, E. coli, dissolved lead, and dissolved zinc. Most reductions were statistically significant. Many pollutants exceeded applicable water quality standards in the control samples but met them with both types of porous pavement. This study demonstrates that porous overlays and full-depth porous asphalt can provide substantial reductions of several priority stormwater pollutants on arterial roads for many years after installation.

Permeable pavements can be an effective stormwater mitigation technique, but there are concerns that polluted stormwater may contaminate groundwater as stormwater infiltrates through the soil beneath the pavement. This research evaluates the pollutant removal capabilities of pervious pavements using pervious cement concrete (PC) and porous asphalt concrete (PA) cylinders. Stormwater collected from an outfall was used to perform three tests. The influent and effluent were analyzed for metals, semi-volatile organic compounds (SVOCs), phosphorus, and turbidity. Average percent removal for metals were 37–63% except for zinc, which had an average export of 21% for pervious cement concrete and 52% for porous asphalt concrete. Only 10 of the SVOCs tested had an influent concentration above detection levels. Complete removal (below detection levels) was observed for benzo(a)anthracene, benzo(a)pyrene, chrysene, and indeno(1,2,3-cd) pyrene. Average removals for benzo(b)fluoranthene, benzo(g,h,i)perlyne, fluoranthene, phenanthrene, pyrene, and bis(2-ethylhexyl)phthalate were 63–96%. No significant removal was observed for total phosphorus and reactive phosphate. All contaminant concentrations were below drinking water limits except lead, which would likely be removed in the soil layer below the pavement. This study indicates permeable pavements can effectively remove stormwater contaminants and protect groundwater as a drinking water source.

Stormwater is considered a pathway of microplastics to surface water systems, but the magnitude of microplastic pollution in stormwater and the efficacy of existing stormwater treatment methods are unknown. One potential solution for minimizing microplastics in surface waters is leveraging green infrastructure, such as green roofs, bioswales, and bioretention cells, which can be optimized for the removal of conventional and emerging contaminants. The goals of this study were to (1) establish baseline types and quantities of anthropogenic microparticles, including microplastics, found in stormwater, and (2) evaluate bioretention as a possible solution for reducing microplastics in stormwater. To understand baseline conditions, samples were taken from five different catch basins in north Portland, Oregon, during four storm events and analyzed to quantify and characterize microparticles between 106 & mu;m and 5 mm. A baseline concentration of 4.5 & PLUSMN;2.2 (range 1.1-9.7) particles/L was found, with no observed differences in concentrations between sampling locations or storm events. Most identified microparticles were fibers (66%), and approximately 47% of the particles were cotton, followed by polyester/blend (33%) and nylon (9%). Microparticle concentrations were correlated with the concentration of total suspended solids and the number of pieces of litter collected during a litter survey. To determine the efficiency of bioretention systems for microplastic removal, laboratory bioretention columns were constructed and filled with three different geomedia (a City of Portland, Oregon, standard mix, a proprietary mix, and layered sand and compost). A total of nine columns (three replicates of each geomedia) were tested with stormwater collected from a catch basin in Portland that was spiked with synthetic microplastics (106-5,000 & mu;m). A removal efficiency of 99.8% was observed across all bioretention columns, regardless of the media type. Results indicate green stormwater infrastructure, such as bioretention, may be an effective tool for reducing observed microplastic transport from urban runoff to receiving water bodies.

ABSTRACT Green roofs have become increasingly common in urban areas to slow and reduce stormwater runoff from buildings. However, phosphorus has been found to leach from green roofs. Water treatment residuals (WTRs), a waste product in the water treatment process, may help reduce leaching of phosphorus from green roofs. This study evaluated a green roof retrofit that consisted of a WTR filter at the green roof drain to reduce phosphorus in runoff. Samples of rainfall, runoff from a green roof, and runoff from a regular roof were collected every time it rained and analyzed for total phosphorus (TP), phosphate (PO43−), copper (Cu) and zinc (Zn). Samples were taken January–March 2020 and September 2020–March 2021. Phosphate and TP concentrations were significantly lower (p<0.05) with the retrofit during the winter (Jan–March 2020 and 2021) but not during the fall (Sept–December 2020). The change in WTR efficacy may be due to the WTRs drying out during the summer months, although it appears the WTRs are effective once they have been resaturated during the fall wetting period. This study shows that the WTR retrofit may reduce phosphorus leaching as long as the WTRs do not dry out. The WTRs should be replaced each fall in regions that experience dry summer months to maximize efficacy.

Rivers are a major pathway for the transport of plastics into the ocean. Plastic pollution capture devices offer one way to reduce the accumulation of plastic in the environment. This paper provides a framework for selecting a device to reduce plastic pollution in freshwater, synthesizing information of forty prevailing plastic pollution capture devices. We distinguish three major components of plastic pollution technology (booms, receptacles, and watercraft vehicles) and collect details on each technology including its features, limitations, efficiency, reported costs, and maintenance requirements. A framework is developed to aid in device selection by water and waste managers, which highlights the need for a watershed assessment, an understanding of site conditions, the attainment of community buy-in, and a long-term maintenance plan. While plastic pollution capture devices can help reduce the flux of plastic waste from freshwater, management of plastic waste at the source is also needed to ultimately clean our oceans and waterways.

Bioretention systems are commonly used to treat and detain stormwater runoff and help mitigate many negative effects of urbanization. The goal of this project is to assess the pollution reduction effectiveness of lined bioretention facilities that have been in use and functioning for four to eight years. Lined bioretention facilities are installed with an impermeable liner below the facility to prevent exfiltration of stormwater into the surrounding soil. Grab samples were taken from seven facilities in Portland, Oregon, over a two-year period to measure the quality of stormwater flowing into and out of the facilities. Results showed decreased concentrations of total suspended solids (TSS; 94%), ammonia (85%), total copper (59%), total zinc (80%), and dissolved zinc (41%). However, the facilities were found to increase levels of nitrate (2,070%) and orthophosphate (141%) in the outflow. Based on this study, effective TSS removal by bioretention facilities does not necessarily equate to equally effective treatment of other pollutants (especially orthophosphate and nitrate). Additional research is necessary to determine the significance of the observed increase in nutrients, understand the underlying mechanisms, and test possible design modifications to improve nitrate and orthophosphate removal. (C) 2021 American Society of Civil Engineers.

The trend of using larger boats for wake surfing in river systems has caused concern for dock stability, bank erosion, safety of other boaters, and natural resource conservation. This study evaluates the wave energy due to boat traffic in the Newberg Pool of the Willamette River using budget conscious equipment and involving community stakeholders. Low-cost motion activated game cameras were used to record videos of waves when boats passed. The video processing was completed using image analysis in the computational tool Matlab. For each image a high-contrast point of reference was used for the tracking, often tape on a dock piling. As the wave or dock moved, the reference point in the image was tracked in Matlab using the maximum or minimum grayscale pixel in a specific part of the image. This calculation allowed the research team to approximate the change in vertical direction in pixels. A computational analysis tool was used at 4 sites, 2 in wake surfing zones, 1 in a wake zone, and 1 in a no wake zone, to quantify wave height and period. A total of 8567 videos were collected from the four sites, and 1227 were analyzed. For the wake surfing zone, the average and maximum wave heights were 0.026 m and 0.149 m, respectively, and average and maximum wave energies were 0.905 W/m and 19.2 W/m, respectively. In the wake zone, the average and maximum wave heights were 0.031 m and 0.137 m, respectively, and average and maximum wave energies were 1.405 W/m and 5.74 W/m, respectively. The average wave energy was higher in the wake zone, however, the maximum wave height and the number of boat-caused waves recorded were higher (2984 in the wake surfing zone compared to 1117 in the wake zone) in the wake surfing zone. Cameras were attached to dock pilings which may have resulted in lower values due to the dampening of the dock. Wake surfing was also observed in wake zones, where it is not allowed. This study indicates that the large boats used for wake surfing create larger waves that can potentially cause damage to property along the river and natural resources. The processes and procedures used within this research would not have been possible without citizen involvement. The citizens partaking in the research allowed for their property to be used as a heavily monitored site or a self-monitored site. The self-monitored sites were a useful tool in collecting more data.

Green stormwater infrastructure (GSI) has become increasingly common to mitigate urban stormwater runoff. However, there is limited research on the impact of age and type of GSI. This study evaluated nutrient and metals concentrations in the soil water of five different GSI systems located at the University of Portland in Portland, Oregon. The GSI systems included a bioretention curb extension (part of Portland’s Green Street project), a bioretention basin, a bioretention planter, an infiltration basin, and a bioswale ranging in age from 2 to 11 years. Samples were taken from each system during rain events over a 10-month period and analyzed for copper (Cu), zinc (Zn), phosphate (PO43−), and total phosphorus (TP). Copper and zinc concentrations were found to be impacted by GSI age, with lower concentrations in older systems. The same trend was not found with PO43− and TP, where almost all GSI systems had soil water concentrations much higher than average stormwater concentrations. Age likely played a role in phosphorus soil water concentrations, but other factors such as sources had a stronger influence. Phosphorus is likely coming from the compost in the soil mix in addition to other sources in runoff. This study shows that GSI systems can be effective for copper and zinc, but changes to the soil mix design are needed to reduce high levels of PO43− and TP in soil water.

In traditional introduction to environmental engineering classes, students commonly do book problems and never see applications to real problems such as lack of access to clean water in developing countries or algal blooms. This leaves a disconnect between what they learn in class and what they see in the news. To improve the connection between equations learned in class and real-world problems, two class activities were developed: 1) Access to Clean Drinking Water and 2) Low Oxygen Levels in the Santiam River. During both activities, students had to determine what information they needed, find that information on the internet, evaluate conditions, and determine solutions. Students completed the majority of the assignment in class, summarized results in a technical memorandum written outside of class, and reported their results at the beginning of the next class period. Students were then asked to evaluate how well the activities improved their ability to: 1. Identify and evaluate sources of information 2. Connect life experiences with course content 3. Identify real world engineering opportunities and constraints 4. Identify links between course knowledge and real world systems Students were asked to evaluate whether or not they agreed with each of the above statements on a Likert scale, where a score of 1 was “not at all” and a score of 5 was “to a great extent.” Results indicate the majority of students believed the activities helped them identify real world engineering opportunities and constraints (4.57) and identify links between course knowledge and real world systems (4.64). Although not as strong of a response, students also thought the activities helped them identify and evaluate sources of information (3.61) and connect life experiences with course content (3.91). These results indicate that the two class activities helped students make the connection between what they learn in class and real-world problems.

This study investigated the effectiveness of metal and nutrient removal from stormwater in bioretention systems amended with agricultural byproducts. Both batch and column studies were conducted to evaluate three amendments: hazelnut shells, pecan shells, and spent grain from the brewing process. Batch studies using buffered synthetic water containing copper and zinc evaluated adsorptive properties of the three amendments. Of the three amendments, hazelnut shells had the highest sorption coefficient based on Kd ranges of 19,200-106,000 L/kg and 8,610-18,900 L/kg for zinc and copper, respectively. Both pecan shells and spent grain had significantly lower Kd values for zinc (2,160-6,030 L/kg and 1,702-55,932 L/kg for pecan shells and spent grain, respectively) and copper (1,090-1,760 L/kg and 1,270-2,030 L/kg for pecan shells and spent grain, respectively). However, the spent grain contained zinc that potentially could add to zinc concentrations in the stormwater. Column studies using stormwater collected from an industrial site evaluated metal and nutrient removal from stormwater. Six columns were packed with 90% bioretention soil mix and 10% hazelnut shells, pecan shells, or spent grain, and two columns were packed with 100% bioretention soil mix as a control. Five tests were conducted with stormwater collected from a nearby industrial site. Influent and effluent samples were analyzed for copper, zinc, nitrate, ammonia, total nitrogen, phosphate, and total phosphorus. The columns with pecan shells had the highest removal, with 53% removal of copper and 87% removal of zinc. Removal in the columns with hazelnut shells and spent grain was 47% and 19% for copper and 83% and 65% for zinc, respectively. All columns exported nutrients. Although hazelnut shells had the highest sorption coefficient, the pecan shells removed more metals from the stormwater. This study indicates both hazelnut and pecan shells improve metals removal potential of bioretention systems.

This study investigated whether amending the bioretention soil mix with biochar improves the reduction of copper, zinc, nitrate, ammonia, and phosphate from stormwater. Four vegetated test planters were setup for this experiment: one control with the bioretention soil mix, one control with the components of the bioretention soil mix (compost and loamy sand) in layers, one with biochar mixed with the bioretention soil mix, and one with layers of compost, biochar, and loamy sand. Five tests were conducted with stormwater collected from a nearby industrial site, and influent and effluent were analyzed for copper, zinc, total nitrogen, nitrate, ammonia, total phosphorus, and phosphate. The results show that copper and zinc removal was inconsistent in the mixed and layered setups. Removal varied significantly between tests and did not appear to be impacted by biochar. Nutrient removal was also inconsistent, with varying removal rates between tests for the control and biochar planters. Layering of bioretention soil components appeared to slightly improve removal during some of the tests, but differences were not statistically significant over all 5 tests. This study showed that removal of stormwater contaminants in bioretention systems did not significantly improve with the addition of biochar.

This paper describes a laboratory experiment that was designed to improve engineering education in fluids and hydrology courses. The laboratory module is part of a broader effort to enhance the undergraduate engineering laboratory curriculum to incorporate modern pedagogical methods and to improve a defined set of student outcomes. The experimental module design is based on a theoretical framework for hydrology and tied to specific student outcomes. The new laboratory module uses a low-cost tank that has been modified to create a hydrology apparatus. Students are first asked to design their own experiment using available materials. They then conduct their experiment and plot hydrographs to evaluate the impact of soil type, land use, and so on on peak flow and time to peak. To assess the effectiveness of the new laboratory module, three methods were used: a student survey, course observation, and pretest and posttest. Results of the pretest and posttest indicate conceptual understanding improved as a result of the laboratory module, with average gains of 0.39. The students also completed a survey that included more traditional laboratory modules in the class. All assessment methods demonstrate the value of the new, more engaging laboratory module for engineering education to enhance professional skills in students.

Currently, nutrients are not removed by standard wastewater treatment processes. Constructed wetlands placed after conventional wastewater treatment may be one way to remove nutrients before wastewater flows to receiving waters. To evaluate the effectiveness of constructed wetlands on nutrient removal, 5 constructed wetlands with varying amounts of sandy loam, compost, and shredded bark were tested. The same three plant species were planted in each wetland. Treated wastewater was placed in each planter and samples were taken after 2, 3, 4, 5, and 7 days. On average, total phosphorus increased by 289%, phosphate increased by 130%, total nitrogen decreased by 70%, nitrate increased by 23%, and ammonia decreased by 83%. The only nutrient impacted by residence time was ammonia where a peak residence time was achieved after 2–4 days. Soil mixture impacted total phosphorus, total nitrogen, and ammonia; the planters with 20% or less compost retained more nutrients than the planters with 30–40% compost. Leach test data suggests that the increase in total phosphorus and phosphate were caused by leaching of organic material present in the compost. Results show that constructed wetlands effectively remove nitrogen, but do not effectively remove phosphorus with the soil mixtures tested in this study.