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HomeMy WebLinkAboutLA21-000076, 1720 Bohns Pt Rd, VAR, Exhibit B Engineering Report        April 25, 2022 Christian Harker 1720 Bohns Point Road Wayzata, MN 55391 Submitted by email: christianharker@yahoo.com Re: Retaining Wall Evaluation Project Location: 1720 Bohns Point Road, Wayzata, Minnesota Criterium File No.: 22-6174 Dear Mr. Harker: At your request, a visual inspection of the retaining wall at the above property has been completed. The report that follows has been prepared based on that inspection. This inspection was performed by Paul Schimnowski, PE. My work includes the following: 1. Visual observations during a site visit on April 20, 2022. 2. Observe factors influencing the performance of the structure. 3. Provide a written report containing the following: a. Scope of services. b. Observations, site characteristics, and data deemed pertinent by me. c. Discussion of structural factors influencing the performance of this wall. d. Conclusions and any recommendations for further investigation and remedial or preventative measures. e. You asked me to pay special attention to the forward movement of the wall, horizontal gaps in the face of the wall, deteriorated block at the top of the wall, and erosion at the base of the wall SUMMARY In my professional opinion, the overall structural condition of this concrete masonry unit (CMU) retaining wall is considered to be poor when compared to others of similar age and construction type. The wall is failing and is reaching the end of its expected useful life. Due to its deteriorated condition, options for repairs to re-establish structural stability of the wall are limited and may not be cost-effective in extending the life of the wall. Replacement should be anticipated in the next few years. SPECIFIC ITEMS NOTED & ASSOCIATED RECOMMENDATIONS: 1. The top of the wall is displaced outward by about 2 to 3 inches near the center and north sections of the wall. 2. Horizontal gaps have developed at the wall face due to wall displacement and settlement. 3. Some of the cap units, block, and mortar are deteriorated due to freeze-thaw damage. 4. The cores of some of the blocks are exposed. This will allow water to infiltrate and further deteriorate the block. 5. Structurally significant erosion has occurred at the base of the wall which has exposed the footing. For a wall of this type, the bottom of the footing should be at least 42-inches below 1720 Bohns Point Road, Wayzata, Minnesota April 25, 2022 Page | 2    grade. In order to establish proper frost protection of the footings and structural stability of the wall, several feet of fill will need to be added at the front of the wall, and/or the wall will need to be underpinned with helical piers or a similar method. 6. The footing of the wall has been exposed and undermined from wildlife burrowing activity. See Item 5 above for recommended repairs. 7. Refer to the attached photos for additional notes and observations. OPTIONS FOR REPLACEMENT 1. For this location, a rock/boulder wall similar to the newer wall at the north end of the failing wall could be considered. Alternatively, a segmental block (i.e. Versa-Lok, Anchor) retaining wall could be designed and installed. These types of walls do not require frost-depth footings. They are constructed on aggregate leveling pads 1 to 2 feet below grade.   Figure 1: Existing, nearby stone retaining wall 2. Replacing the wall with a similar CMU wall would require construction of a concrete footing at least 42-inches below grade. The front-to-back width of the footing could exceed 6-feet. Generally, these types of walls will disturb more area than rock or segmental block walls discussed in Item 1 above. DESCRIPTION OF TERMS Terms used in this report to describe the condition of observable components and systems are listed and defined below. It should be noted that a term applied to an overall system does not preclude that a part or a section of the system or component may be in different condition: Excellent- Component or system is in “as new” condition, requiring no rehabilitation, and should perform in full accordance with expected performance. Good- Component or system is sound and performing its function. Although it may show signs of normal wear and tear, some minor rehabilitation work may be required. Fair- Component or system falls into one or more of the following categories: a) Evidence of previous repairs not in compliance with commonly accepted standards, b) Workmanship not in compliance with commonly accepted standards, c) Component or system is obsolete, d) Component or system approaching end of expected performance. Repair or replacement is required to prevent further deterioration or to prolong expected life. Poor- Component or system has either failed or cannot be relied upon to continue performing its original function as a result of having exceeded its expected performance, excessive 1720 Bohns Point Road, Wayzata, Minnesota April 25, 2022 Page | 3    deferred maintenance, or state of disrepair. Present condition could contribute or cause the deterioration of other adjoining elements or systems. Repair or replacement is required. SCOPE OF SERVICES and LIMITATIONS The report is not to be considered a guarantee of condition and no warranty is implied. Our observations are non-destructive, and limited to those portions of the site/wall that could be visually examined without excavation, removing surface finishes, disassembling equipment, or removing finishes, furnishings and equipment. Our scope of services did not include an exhaustive technical investigation. No material sampling, analytic tests, precise measurements or engineering calculations were performed. This includes but is not limited to: compaction testing, soil sampling, global stability calculations. We did not determine whether the wall and its operation or use conform to any city codes, or regulations, or restrictions that may be enforced within the jurisdiction. As Professional Engineers, it is our responsibility to evaluate available evidence relevant to the purpose of this inspection. We are not, however, responsible for conditions that could not be seen or were not within the scope of our service at the time of the inspection. DESCRIPTION OF WALL/SITE: This wall is a single tier, concrete masonry unit (CMU) retaining wall approximately 100-feet in length with a maximum exposed height of about 7.5-feet. The wall is located on the eastern shore of Bohns Point. DOCUMENT/INFORMATION REVIEW No documents were provided. CONCLUSION In summary, I consider the structural condition of this retaining wall to be poor when compared to others of similar age and construction type. The wall is reaching the end of its expected useful life. Replacement should be anticipated in the next few years. This professional opinion is based on the information that you provided (verbal, photos, documentation) and my non-destructive observations at the site. Keep in mind that without invasive investigation, such as described above in scope of service, not everything about the condition of the existing retaining wall can be known. Further, improper water control, flood events, or extensive soil saturation can quickly change the condition of a retaining wall. Opinions and recommendations in this report are limited to the scope of work. This report has been prepared in strict confidence with you as our client. Reliance upon our report by other parties is strictly prohibited. If you choose to share our report, you agree to indemnify, defend and hold harmless the Engineer from any third-party action. No reproduction or re-use is permitted without express written consent. Further, we will not release this report to anyone without your permission. If additional documentation or information is made available for review, I reserve the right to amend or add to the opinions and observations presented in this report. 1720 Bohns Point Road, Wayzata, Minnesota April 25, 2022 Page | 4    Please call with any additional questions you may have. Thank you for the opportunity to be of assistance to you. Sincerely, Paul Schimnowski, P.E. MN #40126   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 Minnesota. Paul Schimnowski, P.E.  Date: April 25, 2022 License #: 40126 (MN) Location 1720 Bohns Point Road, Wayzata, MN Photos Taken by: Paul D Schimnowski, P.E. Inspection Date: April 20, 2022 1 View along top of wall. Outward displacement noted. 2 View along top of wall. Outward displacement and deteriorated block noted. 3 View along front of wall. Outward displacement noted. 4 View along front of wall. Outward displacement at top of wall noted. 5 View along wall. Outward displacement and deteriorated CMU noted. 6 Measurement photo of wall displacement at corner. Location 1720 Bohns Point Road, Wayzata, MN Photos Taken by: Paul D Schimnowski, P.E. Inspection Date: April 20, 2022 7 Deteriorated block at top of wall.8 Horizontal gaps at wall due to outward wall displacement. 9 Erosion and undermining at front of wall.10 Erosion and undermining at front of wall. 11 Undermined footing at front of wall.12 Undermined footing at front of wall.