Stormwater runoff captured by an
infiltration best management practice (BMP) must infiltrate into the underlying
soil within 48 hours. Properly designing an infiltration BMP therefore depends
on obtaining accurate information on soil infiltration rates. Getting the soil
infiltration rate wrong at a site can lead to increased cost and likely failure
of the BMP.
Unfortunately, soils vary greatly
in their infiltration properties, even within a specific soil type over very
short distances. Ideally, soil infiltration rates are determined in the field using an
infiltrometer, permeameter, or other appropriate method. More often, borings
are utilized to identify soil type and an infiltration rate is associated with that soil type.
The Minnesota Stormwater Manual
contains a new page discussing the collection and
interpretation of soil borings for infiltration BMPs. The manual includes the
following caution:
Objectives for collecting soil
borings for stormwater infiltration practices differ from objectives for
collecting borings for structural engineering purposes. Identification of low
permeability or restrictive layers in soil are critical to proper design and
construction of infiltration practices.
The new manual page discusses
important considerations for collecting and interpreting soil borings, number
to collect, what to do when sample recovery is low, how to identify a confining
layer, and more. The page includes sample boring logs, summary tables, images,
references, and links to additional information. If you use soil borings in the
design and construction of stormwater infiltration BMPs, the new manual page
should be valuable to you.
No comments:
Post a Comment