HomeMy WebLinkAbout219 Haggerty Lane - Geotechnical Addendum #1 - April 2026Civil • Geotechnical • Water Resources • Land Surveying • Construction Services
Corporate Office
32 Discovery Dr.
Bozeman, MT 59718
Ph: (406) 582-0221
www.alliedengineering.com
SAM UEI: LYARYWD1YSZ1 CAGE: IGHU7
April 16, 2026
Haggerty Infill LLC
c/o: Jackson Bruff
402 E. Main Street, Suite 3
Bozeman, MT 59715
Email: jsbruff@gmail.com
RE: Addendum #1 to the Geotechnical Report for 219 Haggerty Lane dated January 2026
Bozeman, Montana
Dear Mr. Bruff:
As requested, this letter is Addendum #1 to the Updated Geotechnical Report issued for 219
Haggerty Lane in January of 2026. This addendum is intended to address the possibility of
reducing the thickness of the geogrid-reinforced section of structural fill originally
recommended under the buildings from 3.0 feet to 2.0 feet.
Based on our analysis, modifying the present 3.0-foot geogrid-reinforced section with three
layers of grid to a 2.0-foot geogrid-reinforced section with two layers of grid results in an
approximate 36 percent increase in estimated settlements. However, the total settlement is
still estimated to remain under one inch (industry standard) with minimal differential
settlement. Therefore, we believe it is acceptable to reduce the thickness of the geogrid-
reinforced section under foundations from 3.0 to 2.0 feet and reduce the number of layers of
grid from three to two. Please note that our analysis assumes continuous, 2.0-foot-wide strip
footings buried 4.0 feet deep, with an applied bearing pressure of 2,000 pounds per square
foot. Groundwater was assumed to be at 7.0 feet.
The 2.0-foot geogrid-reinforced section should be installed the same manner as the originally
proposed 3.0-foot geogrid-reinforced section. The 2.0-foot section simply eliminates one of
the layers of geogrid and one foot of structural fill. All structural fill under foundations should
be compacted to 98 percent of its Standard Proctor density.
The subgrade should be proof-rolled to an unyielding condition prior to the placement of fabric,
geogrid, and structural fill. Any wet/soft spots identified in the subgrade will need to be
removed and replaced with compacted structural fill. We ask that we be allowed to view the
subgrade soils at the time of construction such that we can modify our recommendations if
needed.
In summary, reducing the geogrid-reinforced section of structural fill under foundations from
3.0 to 2.0 feet should not pose an issue from a geotechnical perspective, assuming the other
recommendations found in our 2026 report are followed.
Addendum #1 to the Geotechnical Report for 219 Haggerty Lane dated January 2026
Bozeman, Montana
Proj. # 22-097.01
4/16/2026
Bozeman Office: 32 Discovery Drive. Bozeman, Montana 59718. ● Ph: (406) 582-0221 ● Fax: (406) 582-5770 Page 2
We appreciate the opportunity to perform these services. Please call if you have any questions.
Sincerely,
Allied Engineering Services, Inc.
____________________________________ ____________________________________
Craig Madson, PE Jessi Ellingsen, EI
President/Geotechnical Engineer Geotechnical Engineer
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