A. 
Models. All computations of runoff volumes and peak flow rates used in the development of erosion control and stormwater management plans in accordance with this chapter shall be based on United States Department of Agriculture, Natural Resources Conservation Service (NRCS) methodology. Models such as SLAMM, P8 or other Designated City Representative approved models may be used to evaluate the efficiency of the design in reducing total suspended solids to meet this chapter. Models such as RECARGA or other Designated City Representative approved models may be used to evaluate the efficiency of the design in meeting the infiltration requirements of this chapter.
B. 
Rainfall depths. To determine compliance with this chapter, the following design storm rainfall depths shall be used:
Design Storm
1-year
24-hour
2-year
24-hour
10-year
24-hour
25-year
24-hour
100-year
24-hour
Rainfall depth
2.3 inches
2.7 inches
4.1 inches
4.7 inches
5.8 inches
C. 
Runoff curve numbers. All computations of predevelopment conditions as specified in this chapter shall use those NRCS runoff curve numbers assigned for a "good" hydrologic condition for each land cover type. For lands where the predevelopment land use was cropland, the following NRCS curve number values shall be used as maximums:
Soil Hydrologic Group
A
B
C
D
NRCS Runoff Curve Number
33
58
72
78
Note: Soil hydrologic groups are available from the Designed City Representative and can be found on the county GIS system.
D. 
Average annual rainfalls. All modeling involving average annual rainfall or runoff volumes shall use rainfall data from the Minneapolis area between March 13 and November 4, 1959, as the typical annual rainfall pattern for Amery.
E. 
Rainfall distribution. All peak flow calculations shall use Type II rainfall distribution patterns, as defined in NRCS methodologies.
F. 
Other methods. All velocity and peak flow computations for open channels and storm sewer pipe flows shall be based on Manning's Formula. Flow routing, culvert design, weir and orifice flow and other related hydraulic computations used to design stormwater management facilities shall be based on standard applicable engineering formulas. Any design data or methodology proposed to be used for hydrologic or hydraulic computations other than those prescribed in this chapter shall be approved by the Designated City Representative. Revisions or updates to the rainfall depths and distribution prescribed above may be allowed upon approval by the applicable regulatory agencies and the Designated City Representative.
A. 
The design, installation and maintenance of all BMPs used to meet the requirements of this chapter shall comply with the technical standards identified, developed or disseminated by the Wisconsin Department of Natural Resources under Subchapter V of Ch. NR 151, Wis. Adm. Code, or otherwise approved by the Designated City Representative.
B. 
Where BMP standards have not been identified or developed under Subsection A above, the Designated City Representative may approve the use of other available standards.
The Designated City Representative may adopt technical guidelines for consistent administration of the provisions of this chapter.
The construction or installation of all BMPs shall comply with all applicable manufacturer and industry standards and specifications, including but not limited to those published by ASTM and the USDA Natural Resources Conservation Service (NRCS).
All soil profile evaluations and forms submitted for review by the Designated City Representative under the provisions of this chapter shall be completed in accordance with Ch. SPS 385, Wis. Adm. Code, and any applicable standards under § 367-31 above. Where there are no specific standards for the number, location or depth of soil profile evaluations for a proposed BMP, the Designated City Representative shall determine the minimum requirements based on the design of the BMP and the likely variability of the on-site soils.
Copies of all technical references made in this article shall be available for review and distribution through the Designated City Representative by means of written request. Fees may be charged for hard copies of these items.
The technical references in this article are made a part of this chapter and shall be updated periodically in order to keep current with field experiences, research, technological advances and the development of related technical standards by other agencies and units of government. Any future revisions of the documents incorporated herein are also made part of this chapter unless otherwise acted upon by the Designated City Representative.