Performance of a Hydraulically Linked and Physically Decoupled Stormwater Control Measure (SCM) System with Potentially Heterogeneous Native Soil

Min-Cheng Tu,Robert Traver

doi:10.3390/w11071472

Abstract

This study shows that a physically decoupled but hydraulically linked design focusing on surface infiltration components (i.e., excluding underdrain and infiltration bed systems) can be the preferred way to have a low-cost and robust stormwater control measure (SCM) system. The SCM under investigation in Philadelphia, PA, is a green infrastructure (GI) and has a mirrored design of two sets of hydraulically linked planters. Each planter has an overflow pipe connected to an underground infiltration bed. The system showed excellent overall performance as no overflow/bypass entering the combined sewer. A large variation of saturated hydraulic conductivity was found for the planter soil, and the planter with lower saturated hydraulic conductivity created surface runoff that overflows to the next planter in line. Due to the linked design, the unexpected deviation of performance of a single planter did not affect overall system performance. The infiltration bed showed great variation in water drawdown rate at different water depth, which could be caused by the possible high heterogeneity of the native soil. The study argued that overflow systems, which handled only about 18% of runoff in this study, can be replaced by slightly larger surface area for lower building cost, lower maintenance cost, and more reliable performance.

Highlights

Mitigation of stormwater issues caused by urbanization continues to be a priority [1] to protect the quality of our waters
Using data from a green infrastructure (GI) system in Philadelphia, the current study provides an analysis that shows, using a hydraulically linked design and focusing on the surface infiltration is the preferred approach to have a low-cost and robust stormwater control measure (SCM) system that is more likely to sustain the designed performance in the field
A custom-designed and lab-tested orifice insert is installed on the overflow riser pipe to facilitate measurement of the flow rate to the infiltration bed based on water depth above the insert (Figure 3)

Summary

Introduction

Mitigation of stormwater issues caused by urbanization continues to be a priority [1] to protect the quality of our waters. Many of the literature studies [13,15,20,21] considered SCM systems as perfect models, i.e., SCM systems with the same design will always work the same way in the field This is hardly true in the field as unexpected construction error, unknown material randomness, unknown complexity of the native soil, and required maintenance to sustain SCM performance must be considered. Using data from a green infrastructure (GI) system in Philadelphia, the current study provides an analysis that shows, using a hydraulically linked design and focusing on the surface infiltration (i.e., excluding underdrain systems) is the preferred approach to have a low-cost and robust SCM system that is more likely to sustain the designed performance in the field

Site Description and Data Collection

Green infrastructure sidewalk planters under investigation and Traver

Summary

Findings

Discussion

Conclusions