GEOTECHNIC REVIEW FOUNDATION UNDERPINNING - PROPOSED SILO KEVIN M. MARTIN, P.E.,.
KMM GEOTECHNICAL CONSUL'TAN'T, LLC'
7 Marshall Rodd c Y 1 1 4: !t 3
Hamp5tead, NH 0384'x`
603-489-5556 (p)/ 603-489-5558 (0/781-718-4084(m)
kevi n m a rt i n peOa o l.co m
MEMORANDUM
TO: Robert P Dandreo
Dandreo Brothers ,
106 Oakville Street ,,;
Lynn, MA 01905 CNL
FROM: Kevin M. Martin, P.E.
Geotechnical Engineer
DATE: May 11, 2018
RE: GEOTECHNICAL REVIEW
FOUNDATION UNDERPINNING
JACQUELINES GOURMET BAKERY
PROPOSED SILO FOUNDATION
SALEM,MASSACHUSETTS
This memorandum serves to address foundation underpinning at the referenced project. The contents
of this review are subject to the attached Limitations.
BACKGROUND
The site includes an existing commercial food processing facility. The project includes new exterior
silos. The area in question is located adjacent to the building and existing silos. There is an
approximate =13 ft wide strip of land between the building and associated access drive. The strip
of land (which the new silo is to be located) is ramped up about =3 ft to the building. Further
complicating the project are an existing water line and nearby drain line that parallel the building.
The water line also laterals below the proposed pad to connect with the building. We understand that
the water line can be re-located but the lateral can not be re-located.
It is intended to support the silo on a new reinforced concrete pad foundation. The new foundation
will be impacted by loading,subgrade conditions,grading,the existing building foundation and the
intersecting utilities. Given the site constraints, a mat foundation that extends below grade to
develop proper base and lateral support has been designed by BAI. Such a foundation will
undermine the existing foundation (which is shallow). The adjacent silo foundations may also
become undermined during construction. These should require further review as they become
Jacqueline's Bakery May 11,2018
Salem, Massachusetts Page 2 of 3
exposed and verified. The existing foundation will need be underpinned for temporary and
permanent support. Sequential concrete pit underpinning has been selected in this regard. Concrete
pit underpinning involves localized undermining(z 3-4 ft wide)of the footing with approach pits that
are filled with consolidated concrete to lower the BOF. The BOF will need to be lowered about =4
ft to accommodate the proposed construction.
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SUBGRADE CONDITIONS
Apparent Rock Fill was encountered to depths of 9-10 ft below grade. It is difficult to distinguish
rock fill (especially large boulders, cobbles, etc) from small diameter test bores. Nonetheless,
apparent rock fill with embedded sand was vacuumed,sampled and penetrated to z 10 ft. It would
appear that the rock fill may have been generated on-site with bedrock excavation but there is no
verification in this regard. Further review of the subgrade should be completed during construction.
Groundwater was not encountered and should not impact the underpinning.
Jacqueline's Bakery May 11, 2018
Salem, Massachusetts Page 3 of 3
ENGINEERING EVALUATION
Given necessary protection of the existing building, it is intended to underpin the foundation prior
to the new silo foundation construction. Concrete pit underpinning will be employed to transfer
foundation load to proper subgrade and provide necessary shoring. Concrete pit underpinning is a
staggered undermining with subsequent concrete pitting of the existing foundation to transfer the
foundation to proper depth. We have provided the attached Sketches, Profiles & Technical
Specifications for Concrete Pit Underpinning.
We trust the contents of this report are responsive to your needs at this time. Should you have any
questions or require additional assistance,please do not hesitate to contact our office.
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TECHNICAL SPECIFICATIONS
CONCRETE PIT UNDERPINNING
JACQUELINE'S BAKERY
SALEM, MASSACHUSETTS
PURPOSE: Concrete pit underpinning is to be used to shore and protect the existing foundation
prior to new constriction.
• The underpinning pits shall be no greater than z3 ft wide. The underpinning pits should
extend to the inside face of the existing foundation. The pits should also extend no less than
z 5 inches beyond the front edge of the footing.
• Approach pits shall be used for each underpinning. The approach pits shall be no greater
than z 5 ft wide. The approach pits shall be shored per OSHA Regulations. Trench boxes
may be used for the approach pits by others.
• This design is for the existing building foundation. Critical attention shall be given at the
column footings to mitigate extended exposure (no more than 40%). The adjacent silo
foundations shall also be reviewed during construction and shored, underpinned and/or
protected accordingly.
• The underpinning pits shall be hand excavated below the foundation. Jack hammers or other
power tools may be used to facilitate the excavation.
• The bottom of the existing footings shall be cleaned or all loose soil, rock and debris to
provide a clean,rough surface.
• The bottom and side limits of the underpinning pits shall be manually hand trimmed.
Shoring shall be used within the pits as necessary to maintain safe and stable conditions.
Rock Fill is expected to be present below BOF. KMM shall be notified if differing subgrade
conditions.
• The underpinning should be completed in a sequential manner. No more than '/s(third)of
the continuous foundation shall be undermined at one time. The attached Sketch shows a
proposed staggered layout for the pits. The lateral extent of the underpinning shall be
dictated by the proposed excavations. Excavations slopes no steeper than 2H:1 V shall be
excavated below the existing BOF.
• The bearing subgrade shall ultimately be dry, stable, free of frost and compact throughout
construction. Soils which become weakened or disturbed shall be rendered unsuitable for
structural bearing support. Field conditions shall dictate the use of a protective base.
• Set forms then place and consolidate concrete (minimum 4 ksi high early strength) at a
maximum 5 inch slump. Leave a z 3-4 inch space(gap)between the top of the underpinning
pit and the bottom of the existing footing. Allow concrete to set for at least 36 hours(or until
3 ksi strength). Refer to the attached Detail.
• Force dry-pak between the footing and underpinning pit. Dry-Pak shall consist of a 1:1 mix
of Type I/H Portland Cement and concrete sand damped with enough water to hydrate. The
amount of water should be enough to allow the mix to retain the shape of a 4 inch ball. The
dry-pak shall be rammed with a wood post (2x4) and 10 pound sledge hammer to provide
tight contact. A low shrink grout may also be used in lieu of Portland Cement.
• Allow the Dry-Pak to set for no less than 24 hours.
• Excavate additional pits as the underpinning continues.
• KMM should be scheduled to review the pits and subgrade conditions to observe compliance
with these Specifications.
• Survey control of the existing foundations shall be monitored during construction.
Movement greater than '/4 inch shall be reported to the Engineers.
END OF SECTION
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LIMITATIONS
Explorations
1. The analyses,recommendations and designs submitted in this report are based in part upon the data
obtained from preliminary subsurface explorations. The nature and extent of variations between
these explorations may not become evident until construction. If variations then appear evident,it
will be necessary to re-evaluate the recommendations of this report.
2. The generalized soil profile described in the text is intended to convey trends in subsurface
conditions. The boundaries between strata are approximate and idealized and have been developed
by interpretation of widely spaced explorations and samples; actual soil transitions are probably
more gradual. For specific information,refer to the individual test pit and/or boring logs.
3. Water level readings have been made in the test pits and/or test borings under conditions stated on
the logs. These data have been reviewed and interpretations have been made in the text of this
report. However,it must be noted that fluctuations in the level of the groundwater may occur due
to variations in rainfall, temperature, and other factors differing from the time the measurements
were made.
Review
4. It is recommended that this firm be given the opportunity to review final design drawings and
specifications to evaluate the appropriate implementation of the recommendations provided herein.
5. In the event that any changes in the nature,design,or location of the proposed areas are planned,the
conclusions and recommendations contained in this report shall not be considered valid unless the
changes are reviewed and conclusions of the report modified or verified in writing by KMM
Geotechnical Consultants,LLC.
Construction
6. It is recommended that this firm be retained to provide geotechnical engineering services during the
earthwork phases of the work. This is to observe compliance with the design concepts,
specifications, and recommendations and to allow design changes in the event that subsurface
conditions differ from those anticipated prior to the start of construction.
Use of Report
7. This report has been prepared for the exclusive use of Dandreo Brothers in accordance with
generally accepted soil and foundation engineering practices. No other warranty, expressed or
implied,is made.
8. This report has been prepared for this project by KMM Geotechnical Consultants,LLC. This report
was completed for preliminary design purposes and may be limited in its scope to complete an
accurate bid. Contractors wishing a copy of the report may secure it with the understanding that its
scope is limited to preliminary geotechnical design considerations only.
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