Proper Sizing of Infiltration Trenches Using Closed-Form Analytical Equations
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Proper Sizing of Infiltration Trenches Using Closed-Form Analytical Equations Jun Wang 1,2 & Yiping Guo 1 Received: 10 February 2020 / Accepted: 30 July 2020 / Published online: 15 August 2020 # Springer Nature B.V. 2020
Abstract
Infiltration trenches in urban areas are mainly used for the purposes of water balance maintenance and water quality improvement. To ensure that a high enough fraction of runoff from a contributing catchment is infiltrated, trenches are usually sized to provide enough storage capacity so that runoff from a design storm of certain depth can be temporarily stored and infiltrated. Since it is difficult to quantify the actual long-term average runoff reduction ratio provided by individual trenches, their exact long-term average performances are often unknown. In this study, the closed-form analytical equations derived and verified previously for the estimation of the long-term average trench performance are applied in the practical design analysis of infiltration trenches following the detailed design guidelines of Atlanta, Georgia and New Durham, New Hampshire, U.S.. The results demonstrate that the conventional design storm-based design procedure cannot always ensure uniform trench performances because of different site soil and infiltration conditions. Use of the analytical equations (also known as the analytical stormwater models) can facilitate more accurate and consistent design of infiltration trenches because the effects of soil type, trench footprint dimensions, drain time and infiltration conditions on trench performance are all taken into consideration. The analytical equations are recommended as a convenient tool for the proper sizing of infiltration trenches so that a uniform long-term average performance can be achieved for all individual cases. Keywords Analytical stormwater model . Runoff control . Side infiltration . Water quality volume . Stormwater management
* Yiping Guo [email protected] Jun Wang [email protected]
1
Department of Civil Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada
2
CIMA Canada Inc. (CIMA+), Mississauga, Ontario L4V 1W5, Canada
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Wang J. and Guo Y.
1 Introduction Urban stormwater best management practices (BMPs) are used to capture and treat runoff from urban areas (USEPA 2011). For the sizing and operation of BMPs, the idea of designing facilities so that they can properly control or treat the first flush of runoff from an urban area was originally introduced in the 1970s (Sartor and Boyd 1972). To reduce pollutants carried by first flushes, many jurisdictions often require that runoff from the contributing catchment equaling a specific Water Quality Control Volume (WQCV) can be processed by a BMP within a prescribed length of time (Burack et al. 2008; Chang et al. 1990; Guo and Urbonas 2002 and Park et al. 2013; WEF and ASCE 1998). To measure the performance of BMPs, runoff reduction ratio is defined as the ratio between the annual runoff volume captured by a BMP and the total annual runoff generated from its contributing c
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