06-24-2003 Council Agenda - Laserfiche WebLink

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MEMO To: From: Subject: Date: Little Canada City Council Joel Hanson, City Administrator Lee Elfering, City Engineer Inman Addition / Thoroughfare Plan Proj. No. 821450 June 17, 2003 R. Green Co mpany As you are aware Mr. Inman is proposing to extend Allen Avenue to the east to create new residential lots within his property. As part of the development he will be extending sanitary sewer, storm sewer, and watermain to provide utility services to these new lots. This street and utility extension project will be the first improvements within this undeveloped area since the completion of the thoroughfare study in 2000. This study looked at the entire area south of Leeward Way between Greenbriar Street and Arcade Street and the most effective means of providing for streets and utilities through the area. The attached exhibits, 1 through 3, show the proposed layout for the watermain, sanitary sewer, and storm sewer as laid out in the study. Mr. Inman is proposing to extend sanitary sewer and water service from the existing utilities in Greenbriar Street. This will provide adequate service for the lots being developed and either follows the layouts within the study or would not have an adverse affect on the remaining area left undeveloped. We would comment that the sanitary sewer at the east manhole is only 8.42 feet deep. Ideally the sanitary sewer should have a miminum depth of 10 -feet to provide more flexibility in the style of home; however, the 8.42 feet will have sufficient depth to serve several house layouts and can be allowed from an engineering standpoint. The proposed watermain within the Inman Addition follows the recommended watermain alignment within the study and would accommodate future extension. The storm sewer system being proposed f for the Inman Addition is a single catchbasin at the east end of the cul-de -sac. All storm water from the street is directed to this catchbasin and then discharged to the north into the existing storm sewer system in Leeward Way. The Leeward Way system then discharges into an existing drainage swale to the west of the Leeward Way cul -de -sac and then runs to the north through a swale along the back lot lines of the homes along Leeward Way. While this layout will provide storm sewer service for the extension of Allen Avenue, it is not the layout proposed in the thoroughfare study and does not accommodate any treatment of the storm water prior to discharge from the site. The storm sewer layout proposed in the study, as shown in Exhibit 1, collects storm water from the entire undeveloped area and takes it to the south to the intersection of Labore Road and Arcade Street. A storm water pond would be created as part of this system near lots 10 and 11 for treatment and rate control of the storm water prior to discharge from the site. While the proposed storm sewer system does not follow the system laid out in the thoroughfare study, the storm sewer system could be easily modified when the remainder of the area develops. The storm water could then be directed to the south as laid out in the thoroughfare plan. It is our understanding that the Watershed has indicated that no storm water treatment would be needed for the proposed development due to its small size. However, when the storm sewer is redirected to the south we believe it should be included in the pond sizing calculations. C: \Documents and Settings\melabba \Local Settings \Temporary Internet Files \OLK3 \Inman Addition Memo.doc