CY46-24

Request of Andrew Manske for a conditional use permit to allow for cut, fill and development activities on a slope equal to or in excess of seventeen-point six (17.6) percent for ravine stabilization. The subject property is described as Lot 5, Block 1, Ironwood Oaks subdivision (80 Telemark Drive).

The anticipated date of final City Council action is December 9, 2024. 
 

The applicant and property owner is Andrew Manske. 

The applicant is seeking a conditional use permit to allow cut, fill and development activities on a slope equal to or in excess of 17.6%. 

The subject property is located at 80 Telemark Drive and is legally described as Lot 5, Block 1, Ironwood Oaks subdivision.

The subject property is the location of an existing single-family residential home. 

The subject property is zoned T, Transition. 

The property contains bluffs/ravines as defined by Mankato City Code. 

The property is served by public utilities. 

Mankato City Code section 10.82 subd. 10 pertaining to Environmentally Sensitive Areas, Slopes, can be found at this link: 

https://library.municode.com/mn/mankato/codes/code_of_ordinances?nodeId=CH10LAUSZO_PTIXSTGEAP_S10.82SPPRAPSPPECOUS
 

The Site Plan and Traffic Advisory Committee reviewed the item at their November 5, 2024 meeting and provided the following comments: 

1. Applicant shall be aware that signed, engineered drawings will be required for construction to be permitted, and a building permit will need to be applied for the proposed work. A staging plan for the project will be required during application of permit.
2. Applicant shall be aware that a condition will be put in place to fix all drainage issues on the property. New drainage plans that include pool drainage shall be provided, and this will need to demonstrate that it does not cause additional issues and shall be part of the plans as signed off by an engineer licensed to do with in the State of Minnesota.
3. Applicant shall conduct a neighborhood meeting a minimum of 10 days prior to the start of the construction project unless emergency repairs are needed. The purpose of this meeting is to provide neighborhood with sufficient information about project in an effort to have a smooth construction process.
4. Any emergency repairs, tree removal prior to official approval, etc. will first need to be evaluated by the City’s designated engineer and the owner, or owner’s representative.
5. Applicant shall be aware that improvements should reestablish the minimum setbacks, which include all structures and surfaces at least 10’ from the bluff line. This includes, but is not limited to, the sport court and pool areas.
6. Applicant shall pay the neighborhood notification fee in the online portal prior to the hearing, if this has not already been done. 

 
 

Andrew Manske is requesting a conditional use permit to allow for cut, fill and development activities on a slope equal to or in excess of seventeen-point six (17.6) percent for ravine stabilization. The subject property is located at 80 Telemark Drive and is legally described as Lot 5, Block 1, Ironwood Oaks subdivision.

Mankato City Code section 10.82 Subd. 10, Environmentally Sensitive Areas, Slopes, states that, "All cut, fill, and development activities on a slope equal to or in excess of seventeen point six (17.6) percent may be permitted only as a conditional use. In addition to the submittal requirements for a conditional use permit application, a plan shall be submitted at a scale required in Section 10.90, Subdivision 6, and the plan shall include two (2) foot topographic contour intervals depicting existing and proposed topography. The plan shall be signed by a registered surveyor or engineer in the State of Minnesota."

The existing residential house located at 80 Telemark Drive has a bluff/ravine area in the rear yard. In July 2024, due to excess rain events, slope failures occurred in the bluff/ravine area of the subject property. According to the engineering report provided, the area had seen excessive rain (10+ inches of rain) prior to the slope failure. The house and property, including a pool area, driveway, and sport court are located at the top of a ravine that extends down approximately 40 feet in elevation to the southwest to a flat area. The slope failure extends adjacent to the property down into the ravine to the southwest.

According to the preliminary engineering report, based on the topographic map, prior to slope failure, the ravine slope had an inclination of approximately 30 to 40 degrees. A creek exists to the southwest of the property at the bottom of ravine area. Per the topographic map, the creek channel is approximately 100 feet southwest from the toe of the ravine slope adjacent to the house. The creek channel is incised approximately 8 to 10 feet. Maps also show a peninsula/ bluff extending to the south of the house before dropping off into the ravine area.

The applicant has obtained preliminary engineering outlining options for ravine stabilization in the area. The options provided in the report are: 

1. Regrade the slope to an inclination suitable for the soils present at the site. Preliminarily, based on the soils observed, a stable inclination could be approximately 20 to 30 degrees (approximately 3H:1V to 2H:1V). This option would likely require clearing of most of the trees. Regraded slope extents may be controlled by property boundaries and permits required for construction and may require removal of the sport court and pool areas. Regraded soils should be keyed into the toe of the slope to reduce the potential for sliding.
2. A pattern of grouted soil nail anchors and a high-strength wire mesh (Teccomesh or similar product) facing installed in the slope. For this option, some slope clearing will be required, but large trees could potentially stay in place. This option allows for the site to freely drain and will allow for plant growth through the wire mesh on the slope. A fabric can also be installed below the wire mesh to control the fine-grained soils and allow for seeding and plant growth as well. A shotcrete facing could also be used instead of the wire mesh system. If shotcrete is used, additional clearing and drainage will be required.
3. A soldier pile and lagging wall with tieback anchors installed along the top of the slope adjacent to the yard, pool and sport court. Soldier piles would generally be installed to a depth below the creek bottom elevation to reduce the potential for undercutting and to provide lateral support. Tieback anchors would be installed in rows near the top of the wall to stabilize the soils in the upper slope and provide support for the yard, pool and sport court. The soil below the wall could be left in place but would be subject to future erosion.

A recommended condition is included herein that when the final corrective action path/method is selected, construction plans shall be prepared and signed by an engineer licensed to do work in the state of Minnesota that identifies the construction details and methods of the correction. The plans shall be submitted with a building permit request, and are subject to review and approval by the City's engineering department. A condition is also recommended that the proposed final design shall return the area to the most natural state possible, as approved by the City's engineering department.  

The Braun engineering report states that for any of the slope repair options, the recommendation is that the homeowner review water runoff from the property down the ravine slope to reduce the potential for excessive runoff over and down these oversteepened slopes. If drainpipes are used, the pipes should extend to at least the toe of the ravine slope to reduce water runoff onto the slope. A recommended condition is included herein that addresses this engineering recommendation. 

The Braun engineering report goes on to state that for each of the slope repair options, access may be difficult for construction equipment. A recommended condition is included that with the submission of the construction plans, a construction staging plan is provided that demonstrates how the construction equipment will access the site and how any potential material storage will be handled for the project. A recommended condition is also included that once the final scope of work is developed and the repair method established, a minimum of 10 days prior to work beginning, the applicant conducts an informal meeting with the neighbors to inform them that the project will be occurring. Staff will provide the applicant with the list of names and addresses that were used for the required conditional use for assisting with this condition. 

The provided Braun report states, "additionally, the yard, pool and sport court will likely be affected by slope repair construction activities." A recommended condition is included herein that states that upon the completion of a project, all attempts shall be made to reestablish the minimum 10' bluff setbacks for code compliance for the sport court which was recently constructed. The pool is in an existing condition that was constructed in 2014 prior to the current property ownership. The recommendation related to the pool area is that all reasonable attempts shall be made to reestablish the previously approved pool setback location on the bluff. Ideally, the project will reestablish all minimum setbacks. However, if a licensed engineer determines that it is not feasible for the noted setbacks to be reestablished, the City's engineer department will analyze the engineering documentation for reasonableness and approval. 

The Braun report makes reference to property boundaries. The information that has been provided indicates that all work will be contained wholly upon the subject property. A recommended condition is included that prior to any work occurring, the official property boundary be established to ensure that there are no encroachments onto adjacent properties. If, through the preparation of the engineered construction plans, encroachments are recommended, the property owner will be required to work with the adjacent property owner(s) and secure appropriate permissions for any desired encroachment prior to work occurring and being permitted.

The subject property is included within the plat of Irownwood Oaks, which was approved in 1984 while the property was located in Mankato Township. The plat identifies a 20' drainage easement on the southern boundary of the subject parcel. A recommended condition is included herein that the referenced drainage easement be maintained and that further changes or modifications to the existing 20' drainage way and easement area are prohibited. 

A site visit was conducted with staff, the applicant and the applicant's construction professional on October 14, 2024. At the time of the inspection, the bluff was noted to be stable and additional failure was not actively occurring. In the event the stability of the bluff changes prior to the final approval, or the building permit being issued, a recommended condition is included herein that recommends that emergency repairs, including tree removal prior to official preparation and approval of the construction plans, will require evaluation by an engineer hired by the applicant, the city's designated engineer and the owner or owner's representative. 

In addition to the bluffs on the site, the subject property contains areas identified as, "Environmentally Sensitive Areas, Woodlands" in Mankato City Code section 10.82 Subd. 12. Several of the existing trees located in the slope failure area were damaged when the slope failure occurred, and additional trees may need to be removed when the engineered plans are prepared for complete correction. Mankato City Code provides that removal of trees or other vegetation from woodlands where such action is necessary to protect public health, protect property from damage or to restore public order is an activity that is not subject to further limitation of the woodland section of the Code. As noted above, modifications to the property are necessary in order to protect the property from additional damage and to restore conformity on the subject site. A recommended condition is included herein that, in conjunction with the project, the applicant shall work with the City Forester to evaluate reasonable options for replanting trees and natural wooded vegetation where determined reasonable and feasible, and the applicant will be required to provide a landscaping plan incorporating the subject plantings and the plantings shall be installed in conjunction with the project. The landscaping plan shall incorporate restoration of the natural, wooded ravine to the greatest extent feasible, based on the final, approved engineering solution. 

Staff submits the following findings with respect to the Conditional Use Permit request: 

1. The proposed use, an existing residential dwelling, is not proposed to change. The fill, cut and development activities within the slope area equal to or in excess of seventeen point six (17.6%) percent is considered a conditional use permit in Mankato City Code section 10.82 Subd. 10. 
2. The request is in keeping with the comprehensive planning policies of the City as the underlying land use plan identifies this parcel as "Low Density Residential", which is in keeping with this request that is not seeking any changes to the current use of the property.  
3. The proposal does not interfere with or diminish the use of property in the immediate vicinity.  
4. The primary structure will continue to be served by public facilities and services, and no utility service provider changes are proposed with this proposal. 
5. The proposal does not cause undue traffic congestion as no changes are proposed to the public street system. 
6. There are no known historical or architectural resources on the site. 
7. The site contains bluffs and woodlands as natural or environmental features on the site. With the recommended conditions, it is intended that impacts to these areas will be corrected and minimized. 
8. It will not cause a negative cumulative effect and effect on the City as a whole. 
9. To the extent known, the development, when considered with the recommended conditions, conforms with all other applicable regulations of the district, and other applicable ordinances. 
10. The proposal will not jeopardize the public's health, safety, or general welfare.

Staff recommends approval of the requested conditional use permit with the following conditions: 

1. The existing drain pipes, new piping, and drainage routes that were found in the sloped area shall be adjusted according to recommendations contained in the Braun engineering report. New drainage plans, prepared and signed by an engineer licensed to do work in the state of Minnesota, shall include pool drainage, and should demonstrate that additional issues are not caused by the placement of the drainage. 
2. The applicant shall submit engineered drawings, signed by an engineer licensed to do work in the State of Minnesota, for the proposed construction and bluff repair. The final design shall return the area to the most natural state possible. The plans will be subject to the review and approval of the City's engineering department. The applicant shall submit for a building permit for the subject work, and work may not commence until the building permit is in place.
3. With the submission of the construction plans, a construction staging plan shall be provided that demonstrates how the construction equipment will access the site and any potential material storage will be handled for the project.
4. The applicant shall conduct an informal neighborhood meeting a minimum of 10 days prior to work beginning. 
5. All attempts to reestablish the minimum setbacks for the sport court, which include a setback of least 10’ from the bluff line and reestablishment of the approved pool setback shall be made. If an engineer licensed to do work in the State of Minnesota determines that achieving the 10' setback is not possible, coordination and approval with the City's engineering department shall occur and verification that the bluff will be secure in the proposed manner will be required. 
6. Prior to work beginning, the official property boundaries be clearly marked to ensure that encroachments onto adjacent properties do not occur. 
7. The existing 20' drainage easement, as shown on the plat of record, shall be maintained and unaltered. 
8. Work, including tree removal or any additional bluff activity, shall not begin until a building permit is in place, and the final engineering plans have been reviewed and approved. In the event of an emergency situation where the slope conditions change prior to the construction plans being completed and approved, temporary shoring and stabilization measures shall be evaluated and approved by an engineer hired by the applicant, the city's designated engineer and the owner or owner's representative. 
9. The applicant shall work with the City Forester to determine what reasonable tree replanting and natural woodland vegetation efforts can be undertaken on the subject project in conjunction with the slope correction project. The applicant shall provide a landscaping plan incorporating the subject plantings (trees and vegetation) and the plantings shall be installed in conjunction with the project. The landscaping plan shall incorporate restoration of the natural, wooded ravine to the greatest extent feasible, based on the final, approved engineering solution. The landscaping plan shall be submitted to the City Forester and the City engineering department for final review and approval.