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AGENDA RECOMMENDATION |
Planning Commission 6.B.
City Council Regular Meeting
- Meeting Date:
- 08/11/2025
Agenda Item:
Resolution approving a Conditional Use Permit to allow the installation of a retaining wall in an area having a slope equal to or in excess of 17.6 percent. The subject property is described as Lot 3, Block 1, Mayan Way Subdivision Phase 3 (208 Mayan Way); by request of Larry Krmpotich.
Recommendation/Action(s):
At the July 23, 2025, meeting, the Planning Commission recommended approval of the conditional use permit to allow the installation of the retaining wall.
Summary:
Larry Krmpotich, owner of 208 Mayan Way, is requesting a conditional use permit to allow the installation of a retaining wall in an area containing slopes equal to or exceeding 17.6 percent. The subject property is legally described as Lot 3, Block 1, Mayan Way Subdivision Phase 3.
Pursuant to Mankato City Code, Chapter 10, Article X, Division 2, Section 10-1499, a conditional use permit is required for all cut, fill, and development activities proposed on slopes that meet or exceed a 17.6 percent grade. The Code also stipulates that improvements in such areas must be designed and signed by a registered engineer.
Existing conditions on the site include an established retaining wall on the easterly portion of the property, landscaping blocks in the rear yard, and two drain tile lines that direct water from the principal structure to a ravine area located on-site. The applicant has indicated that this sloped ravine area is subject to erosion, and that the proposed improvements are intended to mitigate ongoing concerns related to site stability.
The applicant submitted engineered plans showing the construction of a new retaining wall to be located in the rear yard, within the environmentally sensitive slope area. The plans delineate the “top of slope,” and the proposed retaining wall will extend into this regulated area, thereby necessitating the conditional use permit.
The proposed retaining wall spans nearly the full width of the property, extending from west to east and connecting to the existing wall located on the east side of the parcel. The engineering plans include corrected property line data, labeled as “Corrected Property Line Locations.” Staff recommends that, prior to commencement of any work, the property lines be verified and staked by a licensed surveyor. As with fences, retaining walls may be placed up to the property line but not on or over it. In the event that temporary or permanent encroachment onto an adjacent parcel is necessary to complete the work, staff recommend that the applicant obtain written authorization from the adjoining property owner prior to any construction activity.
The proposed wall will be constructed of 4-foot by 2-foot by 2-foot dry stack “County Rib” blocks, with wall heights varying based on the existing topography. The submitted plans include structural details for both a standard and low wall condition, as well as a 15-foot surcharge zone on the southerly side of the wall to accommodate construction and long-term loading. The plan set also calls for limited regrading of the existing yard area at a slope of 3/8 inch per foot, directing surface runoff toward the new wall.
The retaining system includes the installation of “geogrid SRW-7” reinforcement. According to manufacturer specifications, geogrid SRW-7 is a high-strength, uni-directional woven polyester reinforcement that is resistant to chemical and biological degradation, making it well-suited for structural applications such as retaining walls, embankments, and steep slopes. The product is designed to enhance stress transfer and prevent structural failure of the wall over time.
Drainage improvements are also proposed. The site plan includes the installation of a drain tile system running parallel to the retaining wall, as well as 4-inch PVC outlets through the wall. Three existing drain tile lines in the backyard will be reconstructed and tied into the new system behind the retaining wall. Staff recommend a condition requiring that all drainage from the subject site be directed to an outlet at the base of the ravine or an established watercourse. This condition is intended to minimize the risk of erosion that could result from outlets discharging mid-slope.
The property is mapped in the City’s environmentally sensitive area inventory as “Woodlands.” The applicant has indicated that the removal of one tree is necessary to facilitate the installation of the new retaining wall. The City Forester has reviewed the request and determined that tree removal is appropriate, and that additional plantings in the area are not recommended due to the placement of the new structure and associated grading limitations.
Erosion and sediment control measures are identified in the plans, including the installation of a silt fence along the ravine and slope area. Staff recommends the condition that a pre-construction meeting be held on-site with the property owner, contractor, and City staff after the installation of Best Management Practices (BMPs) but prior to any further ground disturbance. Additionally, the applicant will be required to obtain a building permit prior to commencement of construction activities.
Pursuant to Mankato City Code, Chapter 10, Article X, Division 2, Section 10-1499, a conditional use permit is required for all cut, fill, and development activities proposed on slopes that meet or exceed a 17.6 percent grade. The Code also stipulates that improvements in such areas must be designed and signed by a registered engineer.
Existing conditions on the site include an established retaining wall on the easterly portion of the property, landscaping blocks in the rear yard, and two drain tile lines that direct water from the principal structure to a ravine area located on-site. The applicant has indicated that this sloped ravine area is subject to erosion, and that the proposed improvements are intended to mitigate ongoing concerns related to site stability.
The applicant submitted engineered plans showing the construction of a new retaining wall to be located in the rear yard, within the environmentally sensitive slope area. The plans delineate the “top of slope,” and the proposed retaining wall will extend into this regulated area, thereby necessitating the conditional use permit.
The proposed retaining wall spans nearly the full width of the property, extending from west to east and connecting to the existing wall located on the east side of the parcel. The engineering plans include corrected property line data, labeled as “Corrected Property Line Locations.” Staff recommends that, prior to commencement of any work, the property lines be verified and staked by a licensed surveyor. As with fences, retaining walls may be placed up to the property line but not on or over it. In the event that temporary or permanent encroachment onto an adjacent parcel is necessary to complete the work, staff recommend that the applicant obtain written authorization from the adjoining property owner prior to any construction activity.
The proposed wall will be constructed of 4-foot by 2-foot by 2-foot dry stack “County Rib” blocks, with wall heights varying based on the existing topography. The submitted plans include structural details for both a standard and low wall condition, as well as a 15-foot surcharge zone on the southerly side of the wall to accommodate construction and long-term loading. The plan set also calls for limited regrading of the existing yard area at a slope of 3/8 inch per foot, directing surface runoff toward the new wall.
The retaining system includes the installation of “geogrid SRW-7” reinforcement. According to manufacturer specifications, geogrid SRW-7 is a high-strength, uni-directional woven polyester reinforcement that is resistant to chemical and biological degradation, making it well-suited for structural applications such as retaining walls, embankments, and steep slopes. The product is designed to enhance stress transfer and prevent structural failure of the wall over time.
Drainage improvements are also proposed. The site plan includes the installation of a drain tile system running parallel to the retaining wall, as well as 4-inch PVC outlets through the wall. Three existing drain tile lines in the backyard will be reconstructed and tied into the new system behind the retaining wall. Staff recommend a condition requiring that all drainage from the subject site be directed to an outlet at the base of the ravine or an established watercourse. This condition is intended to minimize the risk of erosion that could result from outlets discharging mid-slope.
The property is mapped in the City’s environmentally sensitive area inventory as “Woodlands.” The applicant has indicated that the removal of one tree is necessary to facilitate the installation of the new retaining wall. The City Forester has reviewed the request and determined that tree removal is appropriate, and that additional plantings in the area are not recommended due to the placement of the new structure and associated grading limitations.
Erosion and sediment control measures are identified in the plans, including the installation of a silt fence along the ravine and slope area. Staff recommends the condition that a pre-construction meeting be held on-site with the property owner, contractor, and City staff after the installation of Best Management Practices (BMPs) but prior to any further ground disturbance. Additionally, the applicant will be required to obtain a building permit prior to commencement of construction activities.