HomeMy WebLinkAboutC&H Geotech 8-21-20 Engineering and Surveying Inc.
1091 Stoneridge Drive - Bozeman, Montana - Phone(406)5874115 - Fax(406)587-9768
www.chengineers.com - E-Mail: info@chengineers.com
July 28, 2020
Mountain High Homes, Inc.
Attn: Dan L. Barnes
E-mail: dan@mountainhighhomes.net
Re: Geotechnical Recommendations — Lot 1, Block 5, Southbridge Subdivision Phase
IA; Bozeman, MT(200793)
Dear Dan,
Per your request, C&H Engineering has provided the following recommendations regarding
subgrade improvements for the multi-family residential structures to be constructed on the above
referenced property in Bozeman, Montana. The scope of services was to provide
recommendations regarding subgrade improvements for the proposed structures foundations
based on the subsurface conditions observed in exploratory test pits excavated on the subject
property.
On October 17, 2018 a site visit was made to review the excavation of test holes across the
subject property. The test holes revealed that the typical soil profile consists of an organic soil
layer to depths of approximately 0.9 to 1.8 feet below ground surface (bgs), followed by a soft
and compressible lean clay to depths of approximately 2.5 to 4.1 feet bgs, after which "pit-run"
gravel is present. Groundwater was encountered at depths of 4.2 to 5.2 feet bgs and evidence of
seasonally high groundwater was observed starting at a depth of approximately 2.5 feet bgs.
It is recommended that the excavation for the foundation elements continue down to the native
"pit-run" gravel and structural fill be used to achieve the desired bottom of footing elevation.
Structural fill is recommended to consist of 3-inch minus "pit-run" gravel. The structural fill
shall be placed in a maximum of 12-inch thick lifts and be compacted to a minimum of 97
percent of its maximum dry density, as determined by ASTM D698.
It should be noted that if a foundation perimeter drain is installed around the foundation, it must
be connected to a sump pump that discharges to a location on the subject property and not be
allowed to discharge into the public right-of-way. This can typically be accomplished by
installing a retention pond and/or dry well that the sump pump can discharge into. Please note
that our scope of work does not include a design of the retention pond or dry well and the
homeowner and/or contractor are solely responsible for the construction, sizing and performance
of any retention pond or dry well that the sump pump will discharge to.
Foundation footings may be dimensioned for an allowable bearing capacity of 2,500 pounds per
square foot. It is recommended that typical strip footings have a minimum width of 16 inches,
Civil/Structural Engineering and Surveying
provided the allowable bearing capacity is not exceeded. If you have any questions or comments,
please contact the undersigned
Sincerely
Michael J. Welch, P.E. ,,
G:\c&h\20\ A*-
W+riihary GeolecbtRcal Recommendations-1927 Ryun Sun Way(200090).doc