AdditionalSoilBoringInfo_5-6-15.pdf

1301 N 3 rd

St. Superior WI 54880 715-392-7114 1800-373-2562 F 715-392-7163 www.twinportstesting.com

May 6, 2015 TPT Project 13M6259

Kurt Straus, PE

Structural Integrity, Inc.

7702 Terrace Avenue

Middleton, WI 53562

Re: Addendum No. 1 to Geotechnical Evaluation Report

Forest Lodge Boathouse

Cable, Wisconsin

Dear Mr. Straus:

Project

We understand that Structural Integrity, Inc. is working on designs for foundation repairs to the existing

Forest Lodge Boathouse. Twin Ports Testing, Inc. (TPT) previously completed a subsurface investigation at this site and issued results in a Geotechnical Evaluation Report (TPT Project #13M6259) dated March

8, 2013. This report included recommendations for the use of timber piles and helical piles for foundation support at the site.

Our initial report for this project was prepared for AMI Consulting Engineers, PA (AMI). It is our understanding that AMI is no longer involved with this project and designs are being prepared by

Structural Integrity, Inc. Since issuing the initial report, we have been asked to provide additional recommendations regarding the allowable bearing capacity of soils at the site.

The existing boathouse is supported on wooden cribbing which has experienced deterioration and settlement throughout its life. For this project, we understand that new concrete footings are proposed to be constructed on the lake bottom for support of the boathouse. Wooden timbers and ballast stone will be used to construct new crib walls above the footings with an expected height between five and seven feet. Prior to construction, the existing boathouse will be temporarily supported, a temporary cofferdam will be installed and dewatered, and all existing foundations will be removed.

Bearing Capacity, Settlement, and Foundation Design

Based upon the encountered soils at the site, it appears that spread footings are a feasible option for this project. In our opinion, a net allowable bearing stress (with a minimum factor of safety of at least

2.5) of 1,500 psf may be used to design shallow foundations placed directly on native sand soils.

Existing crib walls beneath the boathouse have existed for many years. The majority of soil settlement due to increased vertical stresses within soil beneath foundations has likely already occurred at this site.

We expect that the removal of existing crib walls and the construction of new foundations and crib walls will result in a negligible net increase in vertical stress beneath foundations. Since no increase (or only a very small increase) in vertical stress is expected to occur, we anticipate that additional settlement beneath spread footings will be negligible.

We recommend that new foundations be designed to resist lateral loads caused by ice. We were not provided with anticipated ice loads for this project. For spread footings cast directly on native soils or compacted fill over native soils, we recommend using a frictional coefficient between concrete and soil equal to 0.43.

Site Preparation

For construction of new foundations at this site we anticipate that all existing foundations will be completely removed. We expect that a temporary cofferdam will be constructed for this project and construction will occur in dewatered conditions. About two feet of soft bottom sediments were encountered at this site prior to reaching higher quality sand soils. We recommend removing all soft bottom sediments or soils containing organics encountered within the footprint and influence area (1H:1V out from the outside edge of footings) and replacing with compacted engineered fill or crushed stone to reach design elevations.

General

Please see our original report 13M6259 for items not addressed by this addendum. If you have any questions concerning the recommendations presented, or if we may be of further service on this project, please call us at 715.392.7114.

Respectfully submitted, Twin Ports Testing, Inc.

Martin L. Halvorson, EIT Geotechnical Engineer

I hereby certify that this plan, specification, or report was prepared by me or under my direct supervision and that I am a duly Licensed Professional Engineer under the laws of the State of Wisconsin.

Michael A. Haapala, PE Principal Engineer