This project was designed by ALBA Consulting. ALBA Consulting is an academic exercise
comprised of four members of an undergraduate capstone class in engineering at Portland
State University during winter and spring terms, 2018. ALBA Consulting strives to be a steward
of sustainable solutions by engineering effective future assets for the communities we serve.
The group sorted itself into professional roles, including: a Project Manager, an Assistant
Project Manager, a Scribe, and a Quality Control Technician. Furthermore, each member also
had a technical role providing supplemental content generated in AutoCAD, GIS, and Excel.
The following design report consists of preliminary facility designs and an alternative analysis
for the TriMet Southwest Barbur Boulevard Stormwater Capstone Project. Over the course of
six months, ALBA consulting prepared a construction cost estimates, a construction schedule, a
drawing set, calculations, and site hydrographs in addition to other deliverables for this project.
This capstone project was developed from the ongoing Southwest Corridor Light Rail Transit
(SWC) Project, which is presently underway at TriMet. The purpose of the SWC Project is to
connect downtown Portland, Tigard, and Tualatin with public transportation, thus providing a
more convenient way for people to commute within the area while also reducing the number of
personal vehicles on the roads. This project is currently in the preliminary design phase, and
many aspects of the project have not been finalized, therefore, this report will focus on only one
aspect of the overall project: the light rail line alignment option. The chosen alignment option
runs along Barbur Boulevard, with a focus on a one-mile-long segment, south of downtown
Portland. This particular alignment option was chosen for the purpose of addressing the issues
of stormwater drainage from Barbur Boulevard and Interstate 5 into Stephens Creek. Currently,
stormwater that flows into Stephens Creek has a high level of pollutants from the highways.
This compromises the quality of the stream and increases erosion and toxic sediment levels
in the creek. The objective of ALBA Consulting’s portion of the project is to provide TriMet with
stormwater designs and analyses for the Barbur Boulevard alignment option. This information
can be used to assist TriMet with their design of the alignment along Barbur Boulevard, with
the goal of treating and detaining stormwater onsite to meet the criteria of predevelopment
discharge levels. Treating stormwater onsite reduces the load on the conveyance pipes and
helps recharge the groundwater system. The stormwater from the chosen section of the
boulevard will then be discharged at the approved outfall for Stephens Creek. By treating the
stormwater from the possible expansion on the boulevard, improvements in the water quality at
Stephens Creek are expected.
ALBA Consulting focused on the preliminary design of planters and ponds for this project.
Planters and ponds were chosen because of their low maintenance costs, ability to improve
greenspace, and effectiveness at managing stormwater. The recommendation is planters are
placed along the length of Barbur Boulevard to meet pollution reduction requirements. Since
planters alone will not meet detention requirements (due to low soil infiltration rates in the
surrounding area), ponds were chosen as the preferred facility to meet detention requirements.
Therefore, the preliminary design of one planter and one pond was conducted. The locations
of potential planters along the length of the boulevard were identified, as well as two additional
pond locations. Due to elevation and space constraints along the new road development, no
location large enough to install one pond to detain all the stormwater from this section was
found on the boulevard itself. As a result, the design of one pond was selected to treat water
from approximately one-third of the road section in the southeastern end of the area. Additional
ponds or other detention facilities will be needed to meet the total detention requirements for
the stormwater from this section of Barbur Boulevard as well. The planter that was designed
using a presumptive approach calculator online showed that the planter was able to meet
pollution reductions requirements. Based on this information, it is assumed that planters
placed along the length of the boulevard will be adequate to meet the total pollution reduction
requirements of the road section considered.
The information provided in this report is intended to be used as a preliminary design for
stormwater detention and treatment along Barbur Boulevard if this alignment option is chosen.
All designs were based on preliminary site assessments from previous geotechnical reports of
the surrounding area as well as a hydrograph based on estimated values for the Portland area
as found from the Stormwater Management Manual (SWMM, 2016). Further analysis of the site
should be conducted in order to ensure that all facilities are sized appropriately.
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