Agenda - Public Works Committee - 10/21/2008

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CASE #2 DISCUSSION ON STORM SEWER IMPROVEMENTS WITHIN ALPACA EST A TES FOR RAMSEY COMMONS By: Tim Himmer, Assistant City Engineer Background: The Ramsey Commons project was approved at City Council on May 13,2008. The project is located at the northwest comer of Armstrong Boulevard and Riverdale Drive. It consists of a 7,800 square foot multi-tenant building, which includes a drive through for a US Bank. The parcel description is Lot l, Block 1 ALP ACA ESTATES and is subject to the City's stormwater management requirements for developments. The property owner/developer also owns the property directly to the west, which is described as Lot 7, Block 1 ALPACA ESTATES 4TH ADDITON. There is an existing regional storm basin at the west end of Riverdale Drive that was created for the benefit of ALPACA ESTATES 4TH ADDITON. As part of the site plan application the property owner decided to split the regional ponding capacity equally between the two parcels that they own, therefore requiring some on-site stormwater rate and quality control for each lot. The idea was to develop Lot l, Block 1 with a reduced on-site ponding requirement, and then duplicate the process for Lot 7, Block 1 when a proposal came forward in the future. The applicant would construct the reduced on-site ponding required as part of the initial development, including a discharge pipe down to the regional basin approximately lOOO' to the west. There is existing storm sewer in Riverdale Drive approximately 600' to the west but it is undersized to accommodate any additional flow, therefore a separate pipe would be required to carry the discharge from their proposed on-site pond to the regional basin. The applicant's initial design was to discharge water directly from their on-site pond into the Riverdale Drive right-of-way and allow it to flow down the street to the existing storm sewer causing additional ponding concerns on the roadway. Observations: The case brought before Council at the time of approval outlined a process that the City was willing to undertake to construct the storm sewer to accommodate the applicant's properties, as well as future development along Riverdale Drive within ALPACA ESTATES 4TH ADDITION. The applicant was going to construct a temporary basin on Lot 7, Block 1 4TH ADDITION to retain all the runoff from both their sites until such time that the City installs a trunk storm sewer line along Riverdale Drive to the regional basin. It was anticipated that this could be done in conjunction with the Armstrong Boulevard improvements planned for 2009. It was also noted that the installation of sewer and water may be warranted if the storm sewer project was advanced. The applicant would pay their stormwater . management fees for both lots and deposit the estimated cost of the improvement in escrow as a funding mechanism to justify the project. The City's obligation would be to pay for the cost of oversizing the pipe, and the installation of other features necessary to serve the larger drainage area. These additional City costs would be recouped through future stormwater management fees from the undeveloped benefiting parcels, and quarterly stormwater utility charges. It is estimated that the total project cost for this storm sewer trunk is $70,000, and the City oversizing cost is approximately $25,000. The property owner is now stating that they believe this project should be a City endeavor, and they should only be required to pay their pro rata share of the infrastructure improvement. Staff has told the applicant that we would not advance a project without designated funding, and that at this time they are the only party asking forthis improvement. 9