Fiscal Note
No appropriation required.
Title
Amending Section 37.09(3)(e)1 of the Madison General Ordinances to establish soil infiltration design standards.
Body
DRAFTER’S ANALYSIS: Under the City’s existing ordinances, certain types of land development are required to get a stormwater management permit. As a condition of such permits, the applicant must submit a stormwater management plan documenting the system(s) and measures proposed to control stormwater runoff from the site. Consistent with State law, the City has established stormwater management performance standards, including requirements relating to infiltration of stormwater when 20,000 square feet or more of new impervious area is created. Infiltration refers to any precipitation that does not leave the site as runoff. Under this ordinance, technical standards for infiltration are being added to the City’s standards applicable to all developments where infiltration is required, which change would require the infiltration design to utilize the best on-site soils for this purpose.
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The Common Council of the City of Madison do hereby ordain as follows:
1. Paragraph 1 entitled “All Developments” of Subdivision (e) entitled “Infiltration” of Subsection (3) entitled “Stormwater Management Performance Standards” of Section 37.09 entitled “Stormwater Management Plan Requirements” of the Madison General Ordinances is amended as follows:
“1. All Developments. Developments within the City of Madison, regardless of development type, shall be required to infiltrate sufficient runoff volume so that the post-development infiltration volume shall be at least ninety percent (90%) of the pre-development infiltration volume, based on an average annual rainfall, regardless of area necessary for this requirement. Should the applicant prove to not be able to meet the infiltration requirement without dedicating more than two percent (2%) of the site area for this purpose, they may optionally choose to meet the secondary recharge standard. In accordance with Wisconsin DNR Post Construction Technical Standard 1002 (Site evaluation for stormwater infiltration), upon completion of site investigation (borings/pits) the infiltration system shall be designed to utilize the on-site soils having the highest design infiltration rate to meet their requirements for stormwater infiltration.”