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� j�� Apnl 20, 2007 �� Michelle Grimes 1741 Stanbridge Roseville, Minnesota 55113 RE: Variance Rain Garden requirement Dear Ms. Grimes: � We have had an opportunity to review your building permit and determine the size and a proposed location for the rain garden required as a result of your impervious area variance. From the information you provided the additional hard surface is 530 square feet more than what is allowed by code. I have enclosed a copy of "Rain Gardens: A how-to-manual for homeowners" this resource will help you in the construction of your rain garden. It was originally written for Wisconsin, but the information applies in Minnesota. Here is some background for the design of your rain garden: • Page 9, Table 1: we do not have soils information on your site, as a result I assumed that your soil was clayey, so to determine the size of a 6 inch deep rain garden we multiplied 530 sf by 0.32 to get 170 s£ Your rain garden should be at least 170 sf in area. • Page 9 also discusses a simple soils test. I recommend that you conduct this test to better assist with sizing of this garden. Simply dig a hole and fill it with water, if the water disappears within 24 hours, the rain garden will be successful in your yard. • If you have silty or sandy soils, the size of this garden can be reduced. Page 9 also has some guidance on how to determine if the type of soil. A silty soil rain garden for your yard would need to be 133 sf, a sandy soil one would need to be 80 sf. I have assumed clayey because I have no other information. • As we discussed last Monday, some of your perennials will do well in a rain garden, if you have any question about the plant suitability here is a website that you can use to look up plants: htt�//www.pca. state.mn.us/publications/manuals/stormwaterplants.html. • See page 11-15 for construction information for the rain garden. Be very careful to not compact the soils by driving heavy machinery on the bottom of the garden. If you havf incerely, V` ra Bloc City Engincc� Phone: 651-792-7042 deb.bloom(a�ci.roseville.mn.us CC: Bryan Lloyd Dean Findell me. 2660 Civic Center Drive ❖ Roseville, Minnesota 55113 6�1-792-ROSE ❖ TDD 651-792-7399 �:• wwwcisoseville.mn.us Recycled paper - 30% post-consumer content