11-13-2018 Council Meeting Packet

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Ms. Katie Larsen October 4th, 2018 Page 2 S:\Community Development\Projects\Planning Cases\Watermark\1st Addition PUD Final Plan-Final Plat\Staff Reports\20181113 CC (FP)\a1 20181004 Engineering Review - Watermark 1st Addition FP.DOCX 1. Open space buffer signs MUST be surveyed and locations shall be shown with final grading as-built. The applicant shall note, grading as-built must be approved prior to release of any building permits. 2. The applicant shall label bench for Pond 100 3. The applicant shall show silt fence around entire perimeter of ponds (until street & utility construction is complete). 4. SWPPP Plan to be reviewed by the City’s Environmental Coordinator and not included here within. 5. The applicant shall install an outlet control structure at the temporary pond prior to outletting to Lake 20.  Stormwater Management The stormwater management for the Watermark 1st Addition development includes a storm sewer conveyance system to Pond 100, Pond 200, and Pond 300 for treatment and storage, with an eventual outlet to Lake 20. Comments: 1. The applicant shall provide storm sewer calculations for all of proposed piped systems. 2. The applicant shall clarify NWL for Pond 100. Detail OCS 100A shows Pond NWL at 901 and orifice at 900.2, plan shows NWL at 900.2. Additionally, show location of OCS100A on Storm Sewer plan. 3. The applicant shall provide profile and detail for OCS between Pond 20 & Lake 20. OCS is shown on the Storm Sewer Sheet Index, but not on a detailed plan sheet. 4. The applicant shall label bench for Pond 300. 5. The applicant shall note that CB’s installed adjacent to ped ramps shall allow enough space for ADA curb transitions. 6. The applicant shall limit storm sewer crossings underneath sidewalk when feasible. 7. The applicant shall add a CB on Crane Drive, approx. Sta. 0+50, 20’ LT. 8. The applicant shall add a CB on Cass Drive, approx. Sta. 0+50, 15’ LT. 9. The applicant shall provide narrative regarding re-use system, connections to City supply (if necessary), specific areas watered by re-use system, irrigation used for wetland buffer establishment (if applicable), and why the irrigation area appears to be slightly greater than what was analyzed for the feasibility report. Option 2 from that report included the berm, townhomes, and park. This plan includes additional area from streetscaping. 10. The applicant shall address how the taller native grasses shall be watered by the irrigation system. 11. Based on the watering schedule on Sheet P13, The average rate of the system is higher than the rate proposed in the feasibility report. This will increase the storage volume by 2 MG and change the water level drop to 5 ft versus 4 ft as discussed previously. Since the system is proposed to be expanded in the future, this water level drop will only further increase. The applicant shall provide further analysis and explanation into the storage volumes and watering area for this irrigation line. 12. The applicant shall provide further detail on the pump station shown on sheet P12. It is likely that this source will need disinfection. Does the current pump station include a plan for a filter system or disinfection? 13. Fountain shop drawings were reviewed and approved by Public Works Superintendent.  Water Supply As part of the City’s Comprehensive Plan, 16-inch diameter trunk watermain would be extended north/south, extending from a stub at 21st Avenue, along Street A and north along Street O. A 12-inch watermain loop would serve the townhome area on the southeast side of the development, and 8- inch watermain would serve the remaining lots. 1-inch Type K copper services would be extended to each lot. Comments: