Split-spoons samples are 1-3/8 inch diameter cylindrical columns of soil obtained using a split-spoon sampler.These samples are usually auger cuttings from the top 5 feet, or taken from an excavation test pit or trench.
Larger samples can be collected in 5- gallon buckets. These can be a small grab sample that fits into a zip-lock bag. There are generally three types of disturbed samples that can be collected during an investigation. These types of samples can be used for classification tests such as the grain size analysis which is described in greater detail below. A disturbed sample does not retain the in-situ structure of the soil.There are two categories of soil samples, disturbed and undisturbed. Iowa State University - University Extensionġ For information on blow counts, link here or link here for table illustrating blow counts.ĭisturbed versus undisturbed soil samples May not be able to collect enough information to determine if infiltration is possible due to depth and limited soil information collected. The sample can also be collected within a liner inside the probe. The probe cuts a core sample smaller than the diameter of the probe body. Soil probes are a basic form of soil sampling, used to collect shallow or surface samples by pushing a T-shaped probe into the ground. Summary of drilling methods to collect soil samples for infiltration basins.
Finding unexpected soil conditions during construction can result in time delays and costs associated with modifying the design. Knowing existing conditions as a result of proper soil investigation allows the design team to develop an accurate design and cost estimate prior to bidding or construction. Soil borings provide the greatest amount of data. Of these six types of soil sample collection methods, soil borings are highly recommended.
Recommended number of soil borings, pits or permeameter tests for bioretention design. The recommended number of borings is shown in the folowing table.
DISTURBED UNDISTURBED SOIL SAMPLES MANUAL
The Minnesota Stormwater Manual recommends that soil borings or pits be dug to verify soil types and infiltration capacity characteristics and to determine the depth to groundwater and bedrock. Section 16.10 of the Construction Stormwater general permit states “Permittees must provide at least one soil boring, test pit or infiltrometer test in the location of the infiltration practice for determining infiltration rates”. Soils determine how quickly stormwater will infiltrate, affect plant growth, and affect the fate and transport of pollutants. Knowing the soils in the area of a proposed infiltration best management practice (BMP) helps determine the suitability and design of the BMP. If soil borings or soil pits are utilized, it is Highly recommended a certified soil scientist or geotechnical engineer interpret the borings. Caution: The MPCA Highly recommends field determination of soil infiltration rates.