Dissertation
Modifications on the existing design parameters to improve the performance of infiltration treatment BMPs in cold climates
Washington State University
Doctor of Philosophy (PhD), Washington State University
08/2008
DOI:
https://doi.org/10.7273/000006135
Abstract
Many newly developed areas rely on infiltration treatment best management practices (BMPs) for managing excess stormwater runoff volumes. Semi-arid, cold climates pose unique challenges to designers of infiltration treatment BMPs. This study addresses two of the cold climate challenges and proposes modified design parameters to improve the performance of infiltration treatment facilities in these regions. The proposed modifications account for both: 1) reduced soil infiltration caused by frozen soils, and 2) increased runoff volumes during snowmelt and rain-on-snow events. To study the impacts of frozen conditions on the conductivity of soils, a laboratoryscale experiment was carried out on frozen soil columns collected from two BMPs sites located in the cities of Spokane and Richland, Washington. Hydraulic conductivity measurements were conducted on 16 frozen soil columns using a developed air permeameter flow test. The time allowed for soil-water redistribution prior to freezing was varied among the soil columns (t = 2, 4, 8, and 24 hr) to investigate its significance on the reduction of conductivity of frozen soils. Results showed that conductivity of frozen soils depends greatly on the time available for soil-water redistribution prior to freezing. Based on the results of this experiment, two regression equations were proposed to assist in the selection of appropriate hydraulic conductivity reduction factors for loam and sandy loam soils when designing infiltration treatment facilities subject to freezing conditions. Increases in runoff volumes caused by snowmelt and rain-on-snow events were investigated by the assessment of the initial abstraction ratio Ia/S in the SCS curve number (SCS-CN) equation. This was accomplished by designing, constructing and testing a 1.22 m wide x 2.44 m long rainfall simulator system to mimic design storm rainfall distributions on snow covering an impervious plot. By comparing calculated versus measured runoff hydrographs obtained from 19 rain-on-snow simulated under different snow conditions (snow depths and densities) and plot slopes, an alternative methodology for assigning Ia/S ratios during rain-on-snow events was developed. These new design parameters will result in more effective BMP designs in terms of runoff treatment. Nevertheless, the final designs will ultimately require larger and more costly stormwater facilities.
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Details
- Title
- Modifications on the existing design parameters to improve the performance of infiltration treatment BMPs in cold climates
- Creators
- Zain Mohammed Al-Houri
- Contributors
- Michael E. Barber (Chair)Muhunthan Balasingam (Committee Member)Marc Beutel (Committee Member)Jeffrey L. Ullman (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 159
- Identifiers
- 99901055118101842
- Language
- English
- Resource Type
- Dissertation