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May 2, 2014 Attachment C RE: Sherren- Dellwood Neighborhood Drainage Improvements Dear Resident As you are aware, during extreme rain events, Flooding occurs on your street, as well as in several backyards. City staff has completed an analysis of the storm sewer system to better understand the xi sting drainage and l ocalized Flooding issues. We have also identified improvements to alleviate some of these Flooding cone ems. There are three areas of improvements to be inapt emente d this constmetion season as a part of the street improvement project on Dellwood Street: Undereround storaae Pipes trader Dellwood Street: North of Sherven Street, three 150 foot long rows of 60 -inch diameter pipe will be constmeted under the pavement. Storm water will be retained in this system until the storm sewer pipe drains to a level where it can ace ept more water. The pipes will then drain back into the storm sewer (similar to draining a bath tub.) The pipes will also be perforated, to allow for infiltration into the ground. The cul-de-sac will be modified to allow for an emergency high water overflow to the north. Holding back water will delay the storm water from reaching the system, making the system better able to convey the storm water over a longer period of time and reduce the depth of the street Flooding. Storm sewer extension south of Sherren Street: South of Sherven Street, a single row about 100 feet long af48-inch diameter perforated pipe will be onstmete d trader the pavement. Dtis will provide additional underground storage, as well as provide an outlet to a new 12 -inch diameter pipe that will be extended into the backyard at 2246 Dellwood. A catch basin c onstmeted in the backyard will provide an outlet for stormwater that drains the backyards between Merrill and Dellwood north of Sandhurst. Storm sewer replacement behind 2263/2271 Dellwood. and 1290 Dellwood: There is an existing storm sewer pipe along the back property lines of these properties. Dtis will be replaced with 48 -inch diameter p erforated pipe, to increase pipe storage capacity, as well as allowing for infiltration. An added benefit for infiltration in this area is it will allow the ground above the pipe to eeept water, even during peri ods o f snow, or if idets bee one clogged. The ground above the pipe will be graded to ensure positive drainage to the catch basins, and the final outlet to the north will be cleaned and graded to ensure water can overflow if needed. Please contact me at kristine.ei etas ci.roseville.mn.us or 651-792-7048 if you have any questions or would like to schedde a meeting to discuss the improvements. Sincerely, �// y4r Krisfine Giga, RE. Civil Engineer CC: Marc Cdver, City Engineer 2660 Civic Center Drive fi Roseville, Minnesota 55113 651 -792 -ROSE el TDD 651-792-7399 e, v ..ci.roseville.mn.us