06-08-1998 Council Packet - Laserfiche WebLink

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r #2339 - James Render June 4,1998 Page 2 Stormwater Management Policies Staff and the City Engineers met with representatives of the MCWD and applicant’s sur\'eyor on June 2 to review and discuss stormwater management policies related to small subdivisions. This meeting was called by staff due to perceived inconsistencies in how the City and MCWD are dealing • with drainage for the current handftil of 2-lot and 3-lot subdivisions. MCWD's Rule B has not been revised as anticipated and may not be revised for some time, if at all. Rule B currently exempts certain categories of development from providing stormwater runoff quality treatment facilities. One of the exempt categories is "Residential developments where the total site area is less than tv\'o acres and contains four or fewer living units". Under this rule, the Render and Waade plats are exempt, but the Van Moorlehem and Haglund plats are not. The City in 1993 amended its Comprehensive Plan by adding language to the "Natural Resource Management General Policies" (Item 13, Page 3-21) stating that "National Urban Runoff Program rNURP) standards will be applied to the design of new stormwater ponds." No thresholds of development were adopted for exemption, hence it can be argued that NURP ponds are required for even the smallest developments. However, NURP ponds require s much larger land area than simple rate control ponds, in part due to the need for a 10:1 perimeter bench mainly for safety purposes, since Walker Model NURP ponds are always full of water. The standard Walker Model NURP pond design was developed to be most efficient for large contributing watersheds (say 20-40 acres or larger) and is relatively inefficient for small drainage areas in the 1-5 acre range. This begs the question of whether NURP ponds should be required for small subdivisions with small watershed areas. It can be shown that for small watersheds, rate control ponds coupled with grassy swales or vegetative buffers may accomplish the same degree of phosphorus removal as a NURP pond, which is the primary end goal of our stormwater quality management regulations. While the Render proposal is feasible and can be approved, the proposed NURP pond with a 1.2 acre contributing watershed may in fact be 'overkill' and it may be more appropriate to allow some alternative stomiwater management methods. Staff anticipates that applicants surveyor may propose such an alternative for this plat. Existing House/Garage To Be Removed Applicant has concluded that the house on Lot 1 and garage on Lot 2 will be removed from the site, negating the need for a Special Lot Combination Agreement. A condition of final plat approval has been added requiring that these structures be removed within 90 days, and stipulating that no building permits will be issued for the subdivision until these buildings have been removed.