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Mr. Boryczka Page 4 The plan does not meet MPCA REQUIREMENTS because the plan does not include pretreatment. 6. MPCA has a Major Design Elements section for guidance on preparing vegetation and landscape management plans and an Operations and Maintenance (O & M) section for guidance preparing an O & M plan. MPCA highly recommends that deep rooted plants such as prairie grass be used, because they increase the infiltration capacity of the underlying soils. However, infiltration facilities can be covered with permeable topsoil and planted with grass to match the surrounding landscape. If regular grass is installed, the underlying soils will not receive the increased infiltration capacity provided by deep rooted plants and the City's O & M costs may be higher. A vegetation plan, landscape management plan or O & M plan was not available during our review. TEI understands that a landscape plan is required as a condition for final plat approval. TEI believes the City of Roseville should carefully consider the type of vegetation to be installed and who will maintain the vegetation in the Bioretention facility, which is to be on private property in a city easement. The Plan shows that sand, salt and debris from the street will be deposited on top of the facility by stormwater that will flow down the proposed concrete spillway. If grass is installed, the street debris will create maintenance problems for the home owners because it will be going onto their yard. The city should consider this impact during their review. 7. The MPCA has other recommendations for infiltration practices that the plan may not meet including: a. Impervious area construction should be completed and pervious areas established with dense and healthy vegetation prior to introduction of stormwater into an infiltration facility. b. Infiltration facilities should be designed to handle the smaller, more frequent rainfall events. Stormwater associated with the larger rainfall events should bypass these facilities (off-line configuration where water quality volume is diverted (flow splitting) to the infiltration facilities). The plan has no bypass; all stormwater enters the facility. 8. MPCA states that minimum setback requirements are REQUIRED by the Minnesota Department of Health (MDH) for the design and location of infiltration practices. The plan does not meet MDH REQUIREMENTS because it has the infiltration practice within 10 feet of a property line and it may be too close to other facilities. T:\Projects\Gary Boryczka\]tr to Gary 8-27-07.doc Engineering and Environmental Solutions