Changes

Another important element of infiltration practice design in the context of fine textured soils relates to the attraction of soil surfaces to water, which are strong in fine textured clays and silty clays and weaker in coarse textured sands or sandy loams.  This attraction, referred to as the matric potential, allows water to move up from the groundwater table into the soils.  In fine textured soils, this distance can be in excess of one meter.  Therefore if the base of the infiltration practice is only one meter above the seasonally high groundwater table, a direct connection between the practice and groundwater may form, bypassing the treatment properties of the soils.  It is recommended, therefore that the groundwater table be 1.5 m or lower when practices are installed on fine textured soils.           

Another important element of infiltration practice design in the context of fine textured soils relates to the attraction of soil surfaces to water, which are strong in fine textured clays and silty clays and weaker in coarse textured sands or sandy loams.  This attraction, referred to as the matric potential, allows water to move up from the groundwater table into the soils.  In fine textured soils, this distance can be in excess of one meter.  Therefore if the base of the infiltration practice is only one meter above the seasonally high groundwater table, a direct connection between the practice and groundwater may form, bypassing the treatment properties of the soils.  It is recommended, therefore that the groundwater table be 1.5 m or lower when practices are installed on fine textured soils.           

===Performance studies on fine textured soils===

==Performance studies on fine textured soils==

A number of field studies of LID practices have been conducted in southern Ontario on fine textured soils.  Several of these studies have yielded data that allow for calculation of the facility wide infiltration rate during natural rain events of varying sizes.  These are summarized in Figure xx.  Infiltration rates on silty clay, clayey silt and sandy silt textured soils had a median value of 3.3 mm/h and a range between 0.3 and 17.8 mm/h.  Permeable pavements had lower values in part due to compaction of the subsoils to accommodate traffic loading.

A number of field studies of LID practices have been conducted in southern Ontario on fine textured soils.  Several of these studies have yielded data that allow for calculation of the facility wide infiltration rate during natural rain events of varying sizes.  These are summarized in Figure xx.  Infiltration rates on silty clay, clayey silt and sandy silt textured soils had a median value of 3.3 mm/h and a range between 0.3 and 17.8 mm/h.  Permeable pavements had lower values in part due to compaction of the subsoils to accommodate traffic loading.