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Planning Commission MeetingPage of 12 ? Public Comment Mr. S. Ramalingam, 2182 Acorn Road Mr. Ramalingam reviewed various elevations, gradients, and his calculations with the proposed grading plan and stormwater basins; and potential impacts to Mr. Irv Crosss property on the east ? side. Mr. Ramalingam further addressed the flow moving from this site to the 8” drain into Acorn Road infrastructure, and questioned if it would be able to accommodate that additional flow, seeking further evaluation by the City Engineer as to how many inches per hour it could accommodate. Mr. Ramalingam asked staff to further evaluate the high water level on the western basin and surrounding area and height differences. Mr. Ramalingam noted that, once all the trees were removed as proposed, there would be no longer any transpiration from the property, opining that 3040% of the propertys drainage today ?? was handled by those mature trees, and questioned how that would impact neighboring properties. Member Murphy suggested the questions raised by Mr. Ramalingam would be most likely addressed by the citys engineering staff. ? Member Bull noted that engineered soils in the ponds should address that based on their understanding. Mr. Ramalingam opined that engineers were addressing low, not high water levels; and groundwater was an unknown in the equation. However, Mr. Ramalingam further opined that the grading plan indicated the basins would be higher than Mr. Crosss property and the water had to ? go somewhere and based on his calculations, it was currently going to the Cross property. Mr. Ramalingam further addressed the 32’ width of Acorn Road with no parking, while this private street, while short will have parking on both sides; and sought a guarantee that emergency vehicles would be able to access properties or turn around. Janet Romanowski, 2195 Acorn Road In listening to tonights conversation, Ms. Romanowski noted there still appeared to be problems ? with drainage, then homeowners association and tree removal, as well as the private road and ? parking and emergency vehicle access. Ms. Romanowski suggested that Mr. Mueller keep his existing beautiful home and build one additional home on the extra lot, similar to that done by others in that neighborhood. Engineer Chuck Plowe Regarding concerns raised during public comment about the level of groundwater in basins, Mr. Plowe reported that soil boring information indicated to engineers designing them, that their design should be 3’ or more below water basins for infiltration and for the drain tiles to function properly. Mr. Plowe noted that all of these designs would require review and approval by the City Engineer as well as engineers with the Watershed District. Regarding those levels, Mr. Plowe advised that they were typical for down water streams, with water infiltrating and percolating onto adjacent properties with tight soils, thus the reason for drain tiles without the advantage of sandy soils, negating the need for the drain tile system. Mr. Plowe clarified that engineered soil materials would be installed above those drain tiles with the intent to make the water drain down into that system. In response to Mr. Ramalingams questions related to the ponds, and whether they would be dry ? before the next rainfall event begins, Mr. Plowe responded that typically they would be as the soil media and drain tile draws that water level down over a 4872 hour period; but again noted the City ? Engineer and Watershed District engineers would also review and ultimately approve the stormwater management plan. Specific to groundwater levels, Member Murphy sought clarification that in order for this design as proposed to pass muster, it needed to be at least 3’ less than the number needed; with Engineer Plowe responding affirmatively. Specific to the removal of trees and impacts to the soil evaporation rate, Member Murphy asked Mr. Plowe if that was a common consideration in site drainage plans. Mr. Plowe advised that it was, and in developing the whole design, both existing condition calculations and redesigned or proposed calculations were taken into consideration, including taking into account added impervious surfaces and how much additional runoff would occur and not be infiltrated; providing the overall system design. At the request of Member Murphy, Mr. Plowe stated that removal of trees for grading and other file:///R:/CommDev/PLANNING_AND_ZONING/PLANNING_COMMISSION/Minutes/...4/11/2016