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Regular Planning Commission Meeting Minutes – Wednesday, June 4, 2014 Page 8 Ponds 352 Mr. Culver advised that any stormwater management mitigation was based on best 353 management practices (BMP’s); and in this case indicated an infiltration basis, not simply 354 traditional ponds that would retain water over a long period of time, but in fact designed to 355 accept water and drain it, with what didn’t drain, going into pipes underneath the pond to 356 overflow to the two on the west. On the east side basins, Mr. Culver noted that the catch 357 basins that drain overflow into the existing stormwater system would flow north into the 358 overall systems. Mr. Culver assured the public and Commission that the mechanisms 359 were designed from that drainage perspective. 360 While not having committee the entire drainage report to memory, Mr. Culver advised 361 that City staff and Watershed District staff were tasked with review of drainage reports as 362 well as oversight and their provided requirements to be met as a project and/or 363 development was permitted by both those jurisdictions, including a Maintenance 364 Agreement signed by the developer with the Watershed District. 365 For the purposes of a public road, Mr. Culver stated that staff would like all the water to 366 drain into one of those facilities; and had a blanket agreement with the Watershed District 367 that would include any future homeowners association in lieu of the developer for that 368 agreement to address other basins accepting private water. Mr. Culver noted that there 369 were already a number of such agreements across the City – both large and small – with 370 those property owners having to install similar stormwater devices to deal with the 371 requirements of the City and Watershed District. Mr. Culver advised that the City 372 maintained an inventory of all of those private best management practices, and will be 373 tasked with monitoring and inspecting them, as well as a recurring permit for those 374 private BMP’s for recertification as well. 375 At the request of Mr. Cheney, Mr. Culver advised that, at this time, there was no 376 proscribed mandatory inspection schedule to ensure maintenance is being met, but 377 advised that staff’s goal was to have recertification or inspections occur on a minimum 378 five year basis. 379 Mr. Cheney suggested that the inspections would most likely be complaint-based, with 380 Mr. Culver admitting that essentially that could also occur, but assured all that staff was 381 attempting to be more proactive than reactive; and as more private BMP’s came on line, 382 there would be added staff to work with Watershed Districts to maintain recertification 383 and inspection routines. 384 Mr. Cheney questioned if in fact the intent of the ponds was to slow drainage versus 385 holding it, with Mr. Culver stating that the ponds captured a significant amount of water 386 during big events; and held some while some overflowed. However, Mr. Culver reiterated 387 that it was difficult to predict future events and design for those events; even though the 388 basins were designed with permeable materials (e.g. engineered soil). Mr. Culver noted 389 that the effective depth of the device is often more than observed, based on engineered 390 soil to allow water to flow into it and ultimately down to further soil layers and/or drain tile. 391 At the request of Mr. Cheney, Mr. Culver confirmed that if the soils were clay, typically 392 clay tile would be installed underneath for draining. 393 At the request of Mr. Cheney, Mr. Culver confirmed that City and Watershed District staff 394 dictated the technical aspects of ponds, not the developer; and any lack of maintenance 395 by a property owner or homeowner association requiring the City to access and perform 396 that maintenance would in turn be charged back to the property owner based on the 397 signed maintenance agreements. 398 At the request of Member Murphy, Mr. Culver addressed current traffic counts versus 399 projected additional traffic from the addition of three homes, which he opined would be 400 negligent based on his experience with traffic patterns during peak hours. Under typical 401 PM peak hours, Mr. Culver estimated an additional 3 – 4 cars for this class of street, 402 based on a range of 200-300 vehicle trips daily and considering density and an average 403 of ten trips per day for each single-family home. Mr. Culver noted that there may be some 404