There’s something very different about the train platforms of the Interstate 205 segment of TriMet’s I-205/Portland Mall Light Rail extension project which starts construction Thursday.

By using a unique product called the Silva Cell in the construction of the light rail platforms along the West side of I-205 and the North side of Holgate, TriMet will begin supporting green infrastructure in the city of Portland and surrounding areas in a way no major American city has yet, TriMet officials said.

The Silva Cell is a modular, underground bio-retention system that utilizes the proven capacity of soils for storm water management and healthy tree growth to bring green infrastructure to man-made environments.

The large quantities of healthy soil housed within the Silva Cell serves two important functions: growing large trees and treating rainwater onsite.

The integration of green utilities like soil, trees and water into urban areas dramatically enhances their design sustainability and helps alleviate some of the most pressing ecological challenges, including poor air quality, rising temperatures, and flooding and pollution from daily rainfall.

The soil volumes provided by the Silva Cell are typically unavailable in urban areas, causing most street trees to die within 5-7 years of planting. Trees provide a simple and ecological way to reduce the flooding that can be caused by even small rainfall amounts.

TriMet ordered a total of 290 Silva Cells and is planning to divide them between 2-3 trees along each of several station platforms, working out to about 18 Silva Cells per tree.