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I I I Council Meeting Minutes April 25, 1989 Page 6 Public Hearing, continued Larson said he has viewed the other storm sewer at the end of 15th Street and sympathizes with Mr. Kalkes' decision not to install the storm sewer on his property. A larger storm sewer outfall is located between 1501 and 1503--14th Avenue NW. Existing is a 18 inch corrugated metal storm sewer which i5 undersized and causes serious flooding. The proposed storm sewer will be lined with large stone rip rap. to dissipate energy and mitigate the scour hole. The installation of curbing should greatly reduce the amount of soil erosion from the road edges. Bav'r Engi tleeri ng had researched methods for cl eani ng stormwater di c;charQes from sma 11 areas. A 22 1/2 foot long by 10 f00t wi de u~derground grit chamber would cost $10,000, and would have the best removal rate for settleable solids. This chamber would increase the storm sewer cost by about 15%. A grit chamber in this location would be difficult and costly to clean because the bottom would be about 4 feet below lake level and be difficult to dewater. Special equipment would be needed to vacuum the heavy grit from the tank. Grit sumps could be added to existing catch basins for less cost than the grit chamber. However, to operate properly, these sumps nlUst be cl e<lned at 1 east once a month. Staff feels thi s method would spend a significant amount of effort on a very small area of drainage. Grassed swales used instead of a pipe would be moderately effective in the removal of pollutants, if vegetation is maintained. Because of the short length of the swale from the pipe to the lake, there is questionable effectiveness. Street sweeping captures high percentage of the sand deposited during the winter. Proper feels the combinat'jon of street sweeping, installat'ioll of cuy'bing, and adding rip \'a.p to thE! end of the pipe to prevent the scour hole from developing, wculd be the best alternatives in this small drainage area. Council received a petition signed by 8 of the 17 residents of 15th Terrace who support a 32 foot wide street. Jim Kalkes, 1673--14th Avenue Nl4, is pleased with the drainage option Proper suggested and his assistance in the matter. Mr. Ka 1 kes suggested that Ms. Schuessler's property shaul d be watched closely to prevent drainage onto her property. Public Hearing Long Lake A~'ea Street/ Storm Sewer Improvemen Report 89-118 Resolution 89-62 7:45-9:05 p.m.