In any SG district, the following performance standards shall be observed:
(A) Permit required. No sand and gravel operations shall occur except under the terms of an approved sand and gravel conditional use permit with a planned unit development agreement for phased reclamation and proposed end uses of the land. After issuance of the permits, the applicant shall be subject to an annual excavation permit issued by the City Council.
(B) Fencing. A minimum six-foot high chain link type fence meeting Minnesota Department of Transportation standards for right-of-way fencing shall be constructed at the property lines at required fence setback lines along all property lines by the operator to control access to any excavation from adjacent developed residential property.
(C) Hours of operation. Hours of operation for excavation, processing and truck hauling, which may be amended by the City Council in the conditions attached to the conditional use permit, shall be as follows:
(1) Areas less than 3,600 feet to residential areas. The maximum hours of operations for excavation, processing, except concrete and asphalt processing, and truck hauling equipment in a sand and gravel district where these activities are located closer than 3,600 feet to the city’s, or an adjacent city’s, developed or zoned residential property which existed prior to the effective date of this chapter and zoning map amendment, shall be 6:30 a.m. to 5:30 p.m., Monday through Friday, unless otherwise stipulated in the approved conditional use permit based upon noise and air pollution control mitigation measures.
(2) Areas more than 3,600 feet from residential areas. The maximum hours of operation for excavation, processing, except concrete and asphalt processing, and truck hauling equipment in a sand and gravel district where these activities are located farther than 3,600 feet to the city’s, or an adjacent city’s developed or zoned residential property which existed prior to the date of this chapter or map amendment, shall be 6:00 a.m. to 6:00 p.m., Monday through Saturday, unless otherwise stipulated in the approved conditional use permit based upon noise and air pollution control mitigation measures.
(3) Processing and mixing extended hours. The maximum hours of operation for concrete and asphalt processing and associated truck hauling equipment, not excavation or crushing, in a sand and gravel district wherein the processing equipment is located in a centralized location and within an enclosed processing building shall be 5:00 a.m. to 10:00 p.m., Monday through Saturday, unless otherwise stipulated in the approved conditional use permit based upon noise and air pollution control mitigation measures.
(D) Soil and water conservation and watershed review and recommendations. As a part of the original application for a conditional use permit, and annually with the application for an excavation permit, the applicant shall submit grading plans and phased rehabilitation plans to the Dakota County Soil and Water Conservation Service and to the Vermillion River Watershed Management Organization for review and recommendations. The recommendations on the phased rehabilitation grading, soil and water retention plans shall be reviewed annually by the City Council and may be included as a condition of the conditional use permit or the annual excavation permit.
(E) Setback and slopes to adjacent uses or zones.
(1) Berm heights and setbacks from property or zoning district boundaries are as set in Appendix D.
(2) Adjacent to residential developed or zoned areas, excavation, mining and stockpiling shall not be conducted closer than 300 feet to any city or adjacent city’s residential or multiple-dwelling structure, residential or multiple-dwelling structure, residential zoning boundary, or proposed residential structure “pad,” existing on the approval date of the sand and gravel conditional use permit.
(3) Adjacent to non-residentially developed or zoned areas, excavation, temporary crushing, interior concrete and asphalt production, sedimentation ponds and stockpiling without berming and vegetative buffering shall not be conducted closer than 300 feet to the boundary of an adjoining property line except to reduce the elevation thereof in conforming to the adjoining property, as stipulated in the conditional use permit. Exceptions:
(a) In the last 18 months of operation, after filing and acceptance by the City Council of a written notice of intent to complete operations, the operator may complete excavation and reclamation operations to within 100 feet from any nonresidential property line. For a maximum of 36 months after the acceptance of the notice of intent, the operator may stockpile and process on the site, if not prohibited by other sections of this code.
(b) In the annual excavation permit, the operator may request approval to complete temporary excavation and temporary crushing to within 100 feet from any property line. This activity may occur for up to one year. The maximum height of any excavation, temporary crushing equipment or temporary stock piles located less than 1,000 feet from the property line shall be a minimum of eight feet below the average height of the adjacent berms within the 100-foot mandatory setback.
(4) (a) During excavation operations, the slope to the bottom of the pit from the required setback line shall be no greater than two feet horizontal to one foot vertical. All unprotected or untreated soil banks, or pit bottoms of excavation areas not excavated to a ground water depth, shall be left with a slope no steeper than 10%, except as specifically stipulated in the conditional use permit or annual permit.
(b) Greater slope may be permitted if it is in conformity to the immediately surrounding area. When excavation is completed on a section of the pit, all excavated areas shall be completely graded and seeded in conformity to the surrounding natural topography and in accordance with the city’s comprehensive guide plan and the end use plan for the site. The grades shall provide for sufficient drainage so that both natural and storm water leaves the property at the original or natural drainage points shown on the plan, except where otherwise designated by the City Engineer.
(F) Slopes to water bodies. All groundwater or stormwater storage areas resulting from excavation shall be rehabilitated as follows:
(1) Any stormwater pond constructed for interim or final end uses shall have a minimum 100- foot natural plant material shore land buffer zone setback constructed by the applicant as part of the reclamation of the site.
(2) Stormwater ponds shall have shallow water slopes of 10:1 to 20:1 in areas with less than three feet of water depth.
(3) In manmade groundwater lakes, the bottom contour shall be gradually sloping from the shoreline to the deepest portion of the water body at a maximum slope of six feet horizontal to one foot vertical (6:1) for at least 100 feet from the proposed shoreline toward the center of the water body. Beyond 100 feet in horizontal distance, the slope of the bottom contours may be steeper than 3:1 or as stipulated in the sand and gravel mining conditional use permit.
(4) Shoreline slopes ascending from any water body shall not exceed one foot vertical to six feet horizontal, except as stipulated in the conditional use permit or excavation permit.
(G) Setback and slopes along streets. Sand and gravel excavation, shall not be conducted closer than 100 feet to the right-of-way line of any existing or platted street, road or highway except:
(1) Excavation may be conducted within the limits in order to reduce the elevation thereof in conforming to a street grade established by the City Engineer, as stipulated in the conditional use permit for the operation.
(2) In the last 18 months of operation, after City Council acceptance of a written notice of intent to complete operations, the operator may complete reclamation grading operations within the 100-foot required setback to any right-of-way property line. The final graded slope to the bottom of the pit from the road right-of-way line shall be no greater than three feet horizontal to one foot vertical.
(H) Setbacks of access roads. The mining setback area required may, in part, be used for a central, paved access road as stipulated in the conditional use permit.
(I) Visual screening.
(1) The minimum required setback area, as set out in Appendix D, along all exterior property lines shall be bermed, landscaped and planted in accordance with the terms and conditions of the sand and gravel conditional use permit. Within the required setback area, the 100 feet adjacent to the property line shall be bermed, the “primary berm,” to a height of 16 feet, with a maximum 2:1 slope and landscaped with a seeded fiber mulched turf and coniferous tree seedlings to a density of 800 seedlings per acre. All areas within the required setback shall be landscaped with a seeded turf within 15 days of excavation.
(2) Processing plants and towers from crushing, concrete and asphalt plants shall be located at the lowest or base elevation on the site. The height of the plant and towers, and the base elevation shall be stipulated in the conditional use permit. Plant and towers shall be screened with secondary stockpile berms not to exceed 40 feet in height.
(J) Weed control. Weeds and other unsightly or noxious vegetation shall be controlled as necessary to preserve the appearance of the landscaped area. Existing trees and topsoil along existing public rights- of-way shall be preserved, maintained and supplemented for the depth of the setback or as stipulated in the conditional use permit or excavation permit.
(K) Location of driveway access. All means of driveway access to a sand and gravel operation from any street shall be so located and designed as to avoid the routing of vehicles from the property over streets that primarily serve abutting residential development.
(L) Paving access roads.
(1) All access roads from a sand and gravel operation to any public roadway shall be paved with asphalt or concrete for a distance of at least 300 feet to the intersection with a public roadway to minimize dust conditions. During the annual excavation permit review, the City Council may require additional paving length, up to 600 feet on any access road, if dust and truck tracking are identified as a problem by the city. All unpaved access roads shall be treated with a dust retardant on a regular basis as stipulated in the annual excavation permit.
(2) Soil tracking from truck hauling onto public roads from the access road may also be reduced through improvements required as part of the annual excavation permit. These improvements may include, but are not limited to:
(a) Extension of the pavement length or width on the access road.
(b) Installation of a wash facility and wash rack.
(M) Dust control standards. All internal roads and access roads within the sand and gravel operations shall be treated to minimize dust conditions as stipulated in the conditional use permit or excavation permit. All processing equipment shall be contained within a fully enclosed building unless otherwise stipulated in the conditional use permit and meeting Minnesota Pollution Control Agency requirements. All processing equipment not enclosed in buildings shall be surrounded by berms at least 30 feet in height. All stockpiles higher in elevation than the permanent berms along property lines shall have permanent sprinkling/wetting equipment to reduce wind erosion from the stock pile.
(N) Noise.
(1) The maximum noise level at the perimeter of the site shall be within the limit set by the Minnesota Pollution Control Agency and U.S. Environmental Protection Agency. In no case shall the noise level exceed 50 decibels measured at 3,600 feet from the noise making equipment shall be located in enclosed buildings unless otherwise stipulated in the conditional use permit and meeting Minnesota Pollution Control Agency requirements. All processing equipment not enclosed in buildings shall be surrounded by berms at least 30 feet in height. All screens, hoppers and conveyors belts shall be nonmetallic.
(2) Noise levels at specific setbacks shall not exceed the following:
(a) Centralized crushers:
1. Eighty-eight dBa at 100 feet; and
2. Fifty dBa at 2,000 feet.
(b) Pit face crushers:
1. Eighty-three dBa at 100 feet; and
2. Fifty dBa at 1,000 feet.
(c) Front end loaders:
1. Eighty-one dBa at 100 feet; and
2. Fifty dBa at 1,000 feet.
(d) All other machinery:
1. Eighty dBa at 100 feet; and
2. Fifty dBa at 1,000 feet.
(O) Water pollution. Operators shall comply with all applicable Minnesota DNR and Pollution Control Agency regulations and U.S. Corp of Engineers and Environmental Protection Agency regulations for the protection of water quality. No waste products or process residue, including untreated waste wash water, shall be deposited in any lake, stream or natural drainage system, except that lakes and ponds wholly contained within the excavation site may be utilized. All human waste materials shall utilize city central sewer disposal or sealed septic tanks with monthly septic tank pumpings.
(P) Wastewater. Operators shall dispose of all wastewater used on the site in a manner which will not adversely affect adjoining property and shall use silting ponds or other means of disposing of the suspended solids in the waste water as stipulated in the conditional use permit or excavation permit and approved by the City Engineer.
(Q) Removal of buildings. Within a period of 18 months after filing a letter of intent to complete operations or within six months after determination by the Council that the site has been abandoned by the sand and gravel operation, all buildings, structures and plants incidental to the operation shall be dismantled and removed by and at the expense of the sand and gravel producer last operating the building, structure or plant, or the owner of the property, unless the structure or use is compatible with the anticipated ultimate use of the property. All buildings, structures or plants not removed as required by this section may be removed by the city with the costs for the removal charged to the producer last operating on the property or the owner of the property.
(R) Topsoil.
(1) Stripping of topsoil from either A or B soil horizons shall be done only as used in the excavation and mining operations, that is area-wide stripping without vegetative replanting shall not be allowed. Graded or backfilled areas (or banks in the case of excavations made to a water producing depth) shall be covered with topsoil to a minimum depth of four inches as part of the reclamation process. The topsoil shall be capable of supporting the growth of vegetation. The operator shall guarantee that either:
(a) All A horizon topsoil scraped from the site shall be retained at the site and used as surface soil in permanent berms or used for the restoration of the site; or
(b) A performance bond or other guarantee stipulating that the operator will replace all topsoil, to a depth of four inches, needed for reclamation of the site is filed with the original conditional use permit.
(2) Other soil retention methods may be stipulated in the conditional use permit or excavation permit.
(S) Landscaping.
(1) Upon replacement of the topsoil, trees, shrubs, legumes, grasses or other ground cover, similar to Minnesota Department of Transportation Mix #800, shall be planted upon the areas in order to avoid erosion. The restoration shall be on a continuing basis as excavation is completed. Berm, stockpiles, drainage channels and setback areas shall be seeded within 15 days after the completion of final grading. All culvert inverts and outlets shall be sodded within 15 days after completion of final grading.
(2) The applicant shall be responsible for final grading and reseeding of all reclaimed land, including public parks land. Seeding dates shall be between April 15 and August 15. Additional seeding dates may be approved in the annual excavation permit. On slopes greater than 6%, seeded soils shall be mulched with a fiber or straw hydro-mulch and tacking agent. On slopes less than 6%, a disk anchored straw mulch may be used. Soil erosion fences, bales, dikes or combinations thereof shall be used at the base of slopes greater than 12%. Staked fiber blanket or staked sod shall be installed on all slopes greater than 2:1.
(‘81 Code, § A1-48) (Ord. 291, passed 4-21-83; Am. Ord. 472, passed 1-25-90)