Laboratory study of infiltration into two frozen engineered (sandy) soils recommended for bioretention

Abstract

Infiltration of water into two frozen engineered soils of different gradation was studied in laboratory soil columns 1.2 m long and 0.1 m in diameter. Prior to testing, the soil moisture was adjusted to two levels, described by the gravimetric water content of 5% or 10%, and soils were compacted to about 80-90% of the maximum dry density and refrigerated to temperatures ranging from À8 to À2°C. Water with temperatures 8-9°C was thereafter fed on the top of columns at a constant head, and the times of water breakthrough in the column and reaching a steady percolation rate, as well as the percolation rate, were recorded. The soil water content was a critical factor affecting the thawing process; during freezing, soil moisture was converted into ice, which blocked pores, and its melting required high amounts of energy supplied by infiltrating water. Hence, the thawing of soils with higher initial water content was much slower than in lower moisture soils, and water breakthrough and the attainment of steady percolation required much longer times in higher moisture soils. Heat transfer between infiltrating water, soil ice, and frozen soil particles was well described by the energy budget equations, which constitute a parsimonious model of the observed processes. The finer grained soil and more compacted soil columns exhibited reduced porosity and required longer times for soil thawing. Practical implications of study results for design of bioretention facilities (BFs) in cold climate include the use of coarse engineered soils and fitting bioretention facilities with a drain facilitating soil drainage before the onset of freezing weather.

Adapting Bioretention Construction Details to Local Practices in Finland

“…Laboratory experiments tend to use multiple soil layers and materials [14,32] and often lack vegetation, while field experiments are based on simplified construction layers with vegetation, but layers in general and in cold climates. Construction details for cold climate focus on limitations of nutrient removal [23], dimensioning [24], material specifications [12,25,26], and the functioning of coarse [12,24,26,27] and fine grained growing media [28,29]. The aim of this summary was to provide the necessary knowledge for practical implementation, and to stress the balance between water, soil, and vegetation.…”

Infiltration into frozen soil: From core‐scale dynamics to hillslope‐scale connectivity

“…The scaling difficulties lie partly in the presence of environmental factors, for example, wind-driven snow redistribution, land-use-driven accumulation, and soil insulation, which may affect melt, thaw, and thereby the infiltration process itself (Hayashi, 2013). They can also be attributed to the design of laboratory studies, in which the use of repacked (as opposed to intact) soil columns and a focus on ponded water conditions are typical (Hansson et al, 2004;Lilbaek & Pomeroy, 2010;McCauley et al, 2002;Moghadas, Gustafsson, Viklander, Marsalek, & Viklander, 2016;Watanabe et al, 2012). With the notable exception of the study of Watanabe and Kugisaki (2017), who conducted one-dimensional column experiments with macroporous soils, these typical laboratory studies cannot be easily scaled to understand field conditions where macropore flow and nonponded infiltration may dominate (Ishikawa, Zhang, Kadota, & Ohata, 2006;Stähli, Jansson, & Lundin, 1996).…”

Infiltration Response of Adsorbent Amended Filters for Stormwater Management under Freezing/Thawing Conditions

“…This variable was monitored with the help of an actuator that triggered in contact with water. The infiltration rate was measured at 24 h after breakthrough was observed, which is near steady percolation observed by [24]. Therefore, the second variable for evaluating the infiltration response was the decrease in infiltration rate of the partially frozen media with regard to the previously measured K 2 • C .…”

“…In order to avoid phase changes due to infiltrating water, [8,22] used an air permeameter to measure infiltration in a frozen sand sample, and the influence of freezing prior to drainage on the infiltration of two typical soils for bio-filtration. Column experiments were performed to examine the effect of the initial soil moisture content prior to freezing and soil temperature on the hydraulic conductivity of a soil used in infiltration based swales, and to study soil thawing processes in two engineered soils designed for bio-filters [23,24]. However, there is a lack of information about unfrozen water content for these stormwater solutions subjected to freezing temperatures.…”

“…Two variables, which are of interest for designing infiltration based systems for stormwater control, were measured to evaluate the infiltration response under freezing/thawing conditions. The first variable was the time it took to observe water breakthrough at the outlet, which has been used by other authors to estimate the travel time required for ponding water to infiltrate into and through the depth of the column media [23,24]. This variable was monitored with the help of an actuator that triggered in contact with water.…”