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HomeMy WebLinkAbout21063AmbientAirEngineeringComments_06242021MEMORANDUM ------------------------------------------------------------------------------------------------------------ TO: Danielle Garber, Planner II FROM: Cody Flammond, Engineer II RE: Ambient Air Solutions Site Plan APPLICATION No. 21063 DATE: April 13, 2021 ----------------------------------------------------------------------------------------------------------- ENGINEERING COMMENTS: These comments are provided in reference to the February 24, 2021 Application 21063 submittal. The following comments must be addressed prior to Site Plan approval. Lighting 1.SP Civil & Utility Plan: The applicant must show the light poles, conduit routes, and pull/splice boxes on the general civil and utility plan sheets. Pole locations must be coordinated with other site utilities. Ten feet of clearance is recommended at pole locations. See lighting, conduit underground electric called out on updated Sheet C3.0. Water and Wastewater 1.SP Utility Plan: The applicant must include water and sewer pipe schedule and materials on plan sheet. The applicant must include the existing service depth to verify building can connect with minimum 2% slope. See updated plan sheet C3.0. The sewer service is called out as SDR 26 PVC and the water service is Type K copper. The sewer main in Prince Lane has approximately 10 feet of cover, so the service will have no problem meeting the 5-foot depth of cover requirement. It should be noted that the publicly-available as-builts for Nelson Meadows do not specify whether deep service or regular service was installed to the property, nor the elevation of the end of the service stub. It was verified with Morrison Maierle that standard service was installed and the elevation of the top of service pipe is 4,587.86’ according to information provided by Morrison Maierle. 2.SP Utility Plan: The applicant must show the water meter size and location on the plan sheet. The mechanical engineer sized the water meter size at 3/4”. See updated sheet C3.0. 3.38.410.070. and DSSP.V.A: Prior to a determination of adequacy, the applicant must provide an estimate of the average and max day demands of domestic water usage for the proposed site development. The estimates must be certified by a professional engineer. Jesses mechanical engineer is working on this. 4. The applicant must verify the minimum bury depth is maintained for the water and sewer services where they pass beneath the stormwater retention facilities. The applicant must install a trench plug in the water and sewer service trenches between the stormwater retention facilities and the water and sewer mains. Given the 10’ depth of cover over the existing sanitary main in Prince Lane, the sanitary sewer service is deep and 7.9 feet of cover is maintained where it crosses the side slope Retention Pond #3. Where the water service crosses Retention Pond #1 there is a short 10-foot section of service that has less than 6.5 feet of cover with 4.9 feet being the least amount of cover in that section. We are proposing to cover that section with a 2” thick piece of rigid foam insulation. See updated sheet C3.0. Regarding the trench plug, see attached deviation request. Stormwater 1.BMC 38.410.080: Storm water facilities may not encroach into the twenty‐foot utility easement unless written approval is obtained from all impacted utilities. The applicant must provide documentation of this approval prior to site plan approval. We have received approval from Northwestern, Charter, and MT Opticom regarding the encroachment of the pond into the utility easement. The utilities maintain approximately 9 feet of separation from the top of the proposed pond. See included email correspondence with utility companies allowing the encroachment. 2.SP Grading & Drainage Plan: The applicant must show the drainage chases and/or underground piping for roof drainage conveyance. The applicant must provide the invert elevations for all roof drains that terminate at the ponds. The roof downspouts all discharge on the ground surface and flow over landscaped areas or the parking lot to retention ponds around the site. There is no underground conveyance system for roof drains on this project. 3.SP Grading & Drainage Plan: The applicant must provide invert elevations and details for the retention facilities including the 4’x4’ infiltration pits. A trash rack and separation fabric are recommended for sedimentation control. The 4’x4’ infiltration pit has been changed to a vertical 36” HDPE pipe that provides a hydraulic connection from the surface of the retention pond to the underlying native gravel layer. The site contains a 9-foot layer of silty clay under the existing topsoil. The low point in each pond will be excavated to native gravels and then the 36” HPDE pipe will be placed vertically resting on the native gravel layer and then backfilled with free draining material. The area around the pipe will be backfilled with the silty clay. The pipe will be cut about 6” short of finished grade and covered with a piece of filter fabric. Then the landscaper will put down the final 6” of topsoil over the pipe and seed it. The top soil is well draining and will allow water to percolate into the vertical pipe filled with free draining material. The design will require no maintenance because the free draining material in the vertical pipe is separated from the landscaping top soil by the filter fabric. The design will provide a maintenance-free hydraulic connection for the retention ponds to drain given their location within the 9-foot layer of native silty clay. See updated sheet C4.0 and detail 3/C5.1. 4.DSSP II.B Storm Drainage Plan: The design grades west of the proposed building (4600’ contour) indicate water is flowing toward the building (4599.75 @ curb FL). The applicant must correct the grading in this location and ensure water flows away from the building to proposed retention facilities. This was originally due to an AutoCAD 3D labeling style error. The contour label has been updated. Dry Utilities 1.SP Utility Plan: The applicant must show the routes of proposed telephone, cable, and fiber optic utilities that will serve the building and include any necessary easements. The typical power, communication and gas service trench is shown on Sheet C3.0. This shows a new transformer in the southeast portion of the site located within the existing easement along Nelson Road. The electric, gas and communication lines that extend from said existing easement to the southeast corner of the building are not required to be in an easement. Details 1.SP Civil Details: The applicant must provide details for the drive approach and sidewalks. See updated detail sheet 7/C5.0 and 9/C5.0. Water Rights 1.BMC 38.410.130: The City acknowledges that the applicant has contacted Griffin Nielsen for a determination of cash‐in‐lieu of water rights for this site. The applicant must pay the cash‐in‐lieu of water rights fee prior to Site Plan approval. See attached CILWR calculation. RECOMMENDED CONDITIONS OF APPROVAL 1. City of Bozeman Resolution 5076, Policy 1 ‐ The applicant must provide and file with the County Clerk and Recorder's office executed Waivers of Right to Protest Creation of Special Improvement Districts (SID’s) on City standard form for the following: a. Street improvements to Prince Lane between Nelson Road and Frontage Road including lighting, signalization, paving, curb/gutter, sidewalk, and storm drainage. b. Street improvements to Nelson Road between Frontage Road and Prince Lane including lighting, signalization, paving, curb/gutter, sidewalk, and storm drainage. c. Street improvements to Frontage Road between Nelson Road and East Valley Center Spur/Prince Lane including lighting, signalization, paving, curb/gutter, sidewalk, and storm drainage. d. Intersection improvements at Prince Lane and Nelson Road including lighting, signalization/channelization, paving, curb/gutter, sidewalk, and storm drainage. e. Intersection improvements at Prince Lane and Royal Wolf Way including lighting, signalization/channelization, paving, curb/gutter, sidewalk, and storm drainage. f. Intersection improvements at Prince Lane and Frontage Road Avenue including lighting, signalization/channelization, paving, curb/gutter, sidewalk, and storm drainage. g. Intersection improvements at Royal Wolf Way and Nelson Road including lighting, signalization/channelization, paving, curb/gutter, sidewalk, and storm drainage. h. Intersection improvements to Nelson Road and Frontage Road including lighting, signalization/channelization, paving, curb/gutter, sidewalk, and storm drainage. i. Intersection improvements to East Valley Center Spur and Frontage Road including lighting, signalization/channelization, paving, curb/gutter, sidewalk, and storm drainage. The document filed must specify that in the event an SID is not utilized for the completion of these improvements, the developer agrees to participate in an alternate financing method for the completion of said improvements on a fair share, proportionate basis as determined by square footage of property, taxable valuation of the property, traffic contribution from the development, or a combination thereof. The applicant must provide a copy of the filed SID waiver prior to site plan approval. See draft SID waiver included in this resubmittal.