(A) Requirement. A minimum of six inches of topsoil must be provided in all green space areas of the project. Topsoil shall meet one of the topsoil standards described in § 153.62(B) below. When available on-site, topsoil shall be managed to protect and/or restore soil permeability to non-compacted soil conditions following construction.
(B) Topsoil standards.
(1) Carver County topsoil standard.
Table 2. Carver County Topsoil Standard.
Requirement | Range | Test Method |
Requirement | Range | Test Method |
Material passing the ¾ in [19 mm] | 100% | ASTM D 422 |
Material passing No 4 in [4.75 mm] | 85% | - |
Clay | 5% - 33% | ASTM D 422 |
Silt | 5% - 35% | ASTM D 422 |
Sand | 30% - 75% | ASTM D 422 |
Organic matter | 2.5% - 15% | ASTM D 2974 |
pH | 6.1 - 8.0 | ASTM G 51 |
Compaction | - 1,400 kilopascals (kPa) / 200 pounds per square inch (psi) in the upper 12 inches of soil, or - bulk density of less than 1.4 grams per cubic centimeter (g/cm3) in the upper 12 inches of soil | Field test |
(2) Match existing soils. For linear reconstruction projects and sites that have not been previously graded, a site-specific topsoil standard can be developed using one of the methods described below:
(a) Soil survey data. A site-specific topsoil standard can be developed using information on physical soil properties from the Natural Resource Conservation Service’s Web Soil Survey for Carver County. The proposed site-specific standard must be submitted prior to permit approval;
(b) Onsite testing. A site-specific topsoil standard may be developed using onsite sampling results. Sample results and the proposed site-specific standard must be submitted prior to permit approval.
1. Non-linear projects. One sample shall be collected of the top 12 inches of soil from each soil map unit within the disturbed area of the project. Alternatively, a minimum of two samples can be collected per five acres disturbed, from locations that characterize the site overall or from which topsoil will be stripped and stockpiled. Samples shall be collected and analyzed for percent clay, percent sand, percent silt, organic matter content, and pH. A site-specific standard shall then be developed using a weighted average of the samples collected on site.
2. Linear projects. One composite sample shall be collected in select areas where grading and topsoil replacement are proposed, or at a density of approximately one sample per mile. Each composite sample will be comprised of eight individual samples collected of the top 12 inches of soil. Samples shall be collected and analyzed for percent clay, percent sand, percent silt, organic matter content, and pH. A site-specific standard shall then be developed using a weighted average of the samples collected on site.
(3) Site-specific standard. Clay, sand silt standards. To develop a site-specific topsoil standard for clay, sand, and silt:
(a) Calculate the weighted average for each parameter.
(b) Round to the nearest whole number.
(c) When the rounded average matches the lower end of the standard range, subtract 3% from the low end of the CCWMO standard range to establish the lower end of the site-specific standard.
(d) When the rounded average matches the upper end of the standard range, add 3% to the high end of the CCWMO standard range to establish the upper end of the site-specific standard.
(e) When the rounded average falls below the CCWMO standard range, subtract 3% from the rounded average and use that value as the lower end of the site-specific standard.
(f) When the rounded average falls above the CCWMO standard range, add 3% from the rounded average and use that value as the high end of the site-specific standard.
(g) If the weighted average falls within the CCWMO standard range, use the CCWMO standard range.
(h) Organic matter, pH, and compaction standards. All site-specific topsoil standards shall include the ranges described in the Carver County Topsoil Standard for organic matter, pH, and compaction. The ranges for organic matter, pH and compaction may not be changed for the site-specific topsoil standard.
(4) Non-linear sites that were mass-graded before 2016 are not eligible to create a site-specific topsoil standard. For these sites, if topsoil does not meet the Carver County Topsoil Standard, two inches of compost must be added to the soil and tilled to a depth of six inches. No further amendment will be required.
(C) Topsoil replacement methods.
(1) (a) Stockpile existing material and re-spread. When available, on-site topsoil shall be stripped and stockpiled for later reapplication. Stockpiled topsoil shall meet the standard selected for the project. If stockpiled material does not meet the selected standard for the project, the material shall be amended to meet the selected standard or topsoil meeting the selected standard shall be imported to the site.
(b) Stockpile testing. The stockpile shall be tested prior to re-spreading. Sample results must be submitted to county staff a minimum of two business days prior to re-spreading. Topsoil test results are valid for one year.
(2) Import material and spread. If topsoil is not available on-site due to previous construction activity and existing material cannot be amended to meet the Carver County Topsoil Standard, topsoil meeting the standard shall be imported to the site.
(D) Submittal requirements. A topsoil management plan shall be submitted as part of the application for erosion and sediment control permits and shall include information on the topsoil management strategies to be utilized to maintain soil permeability at or above required standards. Required components of the topsoil management plan are outlined in § 153.43(I).
(Ord. 83-2016, passed 9-20-16; Am. Ord. 99-2022, passed 6-28-22)