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HomeMy WebLinkAbout036.01 - Appenidx Z - SurfaceWaterDescriptionMemomemo N:\6916\004 - Turnrow Preliminary Plat\04 Design\Letters and Memos\SurfaceWaterDescription_202407\SurfaceWaterDescription_202407.docx Page 1 TO:City of Bozeman FROM:Morrison-Maierle Inc. DATE:July 31, 2024 JOB NO.:6916.004 RE:Turnrow Subdivision – Surface Water Description CC: Urgent For Review Please Comment Please Reply For Your Use The purpose of this memo is to address surface water per Bozeman Municipal Code Section 38.220.060.A.1. Mapping The subject property proposed for subdivision contains two surface water features. These include Cattail Creek and an unnamed tributary to Buster Gulch. A third artificial surface water feature (irrigation ditch) is located an adjacent property to the east and will be impacted as a result of construction activities for the new configuration of the Davis Lane and East Valley Center Road intersection. All three waterways are shown and labeled on the Preliminary Plat drawings that are included as attachments to the project submittal within the drawings folder. Additionally, the water features are also shown on exhibits provided within the Flood Hazard Analysis, which was included in the submittal file as Attachment M. Description Cattail Creek is a natural waterway that runs year-round and has a defined channel and banks. Prior to entering the site, the stream conveys water to the north within a meandering channel located east of the existing Davis Lane roadway. Cattail Creek is currently conveyed onto the property via an existing 36” culvert beneath Davis Lane at the northeast portion of the property. It then runs via meandering channel along the northeast corner of the property where it is conveyed into the Montana Department of Transportation’s (MDT) right-of-way (ROW) for East Valley Center Road. Once in MDT ROW, it is channelized and runs northwest and beneath an existing access approach to Valley Center Road via an existing 60” culvert. After this access Turnrow Subdivision – Surface Water Description N:\6916\004 - Turnrow Preliminary Plat\04 Design\Letters and Memos\SurfaceWaterDescription_202407\SurfaceWaterDescription_202407.docx Page 2 approach culvert, the creek continues northwest within MDT’s ROW prior to being conveyed beneath Valley Center via two 60” diameter culverts. The Unnamed Tributary to Buster Gulch was classified by the Montana Department of Natural Resources and Conservation as a stream-ditch, and flows water year-round. This feature operates as a source of water for irrigation. The waterway enters the property via a 24” diameter culvert at the south boundary and is conveyed within the property through a defined channel to the western boundary. Once at the western boundary of the property, the water is conveyed north and meanders, straddling the common boundary with adjacent properties in the Valley Center Subdivision. Finally, this water enters MDT’s ROW for East Valley Road and is conveyed beneath it via an existing 48” RCP culvert. The nearby ditch which is present on an adjacent property to the east (Geocode #06-0904-26-2- 03-01-0000) will be impacted as a result of construction activities for the new configuration of the Davis Lane and East Valley Center Road intersection. This artificial water system feature is located on the parcel and runs north (parallel to and east of Cattail Creek). Construction of buildings, sewer facilities, water mains, and streets are generally proposed outside of the 50-foot watercourse setbacks for the facilities, with the exception of direct crossings required for streets and transportation pathways. Additionally, a stormwater treatment system for Davis Lane (including storm mains to this system) is located within the Zone 2 setback for Cattail Creek, as that is a permissible location. The City of Bozeman’s Planning and Engineering departments have provided findings that will allow the construction of a multi-use path within portions of the Zone 2 setback. Water Body Alteration Alterations to small portions of Cattail Creek and the adjacent irrigation ditch are necessary to accommodate the widening of Davis Lane to a 3-lane section and the reconfiguration of the intersection of East Valley Center Road and Davis Lane. New culverts are also proposed within Cattail Creek to accommodate Quicksilver Road and the shared use path parallel to East Valley Center Road. Turnrow Subdivision – Surface Water Description N:\6916\004 - Turnrow Preliminary Plat\04 Design\Letters and Memos\SurfaceWaterDescription_202407\SurfaceWaterDescription_202407.docx Page 3 Pursuant to the flood hazard analysis performed on the site (Appendix M), we have proposed to upsize the existing 36” culvert to a 60” culvert for Cattail Creek beneath Davis Lane. Along with upsizing the existing culvert, we are proposing to alter the alignment of the culvert crossing to better convey water to the existing channel pathways and minimize disruption and downstream erosion of the existing channel. As a result of fish crossing concerns, the design incorporates an embedded culvert configuration and fish resting structure. To allow for construction of the required multimodal pathway adjacent to East Valley Center Lane, a new 60” culvert is proposed where the path crosses Cattail Creek. This crossing was performed as perpendicular to the stream as practicable to minimize the impact. Another 60” culvert is planned at the crossing of Quicksilver Road. This culvert at the road crossing includes a fish resting structure near its midpoint due to its length. Culverts are proposed to be embedded for the multimodal pathway and the crossing at Quicksilver Road in order to function more naturally for aquatic organisms per guidance from the Montana Fish, Wildlife, and Parks. The existing irrigation ditch located on the adjacent parcel will be impacted as a result of expanding the width of the road section for Davis Lane. This will include replacing the existing 30” culvert with a new 30” culvert and extending the length of the culvert beyond the proposed daylight slopes. To minimize disruption of the ditch within the adjacent property, the upstream invert location shall be modified to intercept at the channel slightly south of the current location. Separately, a small extension to the south end of a downstream culvert for this facility which crosses East Valley Center shall also be required. This is required to accommodate the installation of the shared use path on the southwest corner of that intersection. There are no alterations to the Unnamed Tributary to Buster Gulch planned for Phase 1 of the subdivision. Any future alterations will be described during the entitlement for subsequent phases. Wetlands Existing wetlands will be impacted with the Phase 1 construction proposed for this subdivision. Wetlands were delineated in accordance with standards listed in division 38.610 of the Bozeman municipal code. The proposed impacts are necessary for construction of the required items listed above, including street connections to East Valley Center Road and Davis Lane, and the Turnrow Subdivision – Surface Water Description N:\6916\004 - Turnrow Preliminary Plat\04 Design\Letters and Memos\SurfaceWaterDescription_202407\SurfaceWaterDescription_202407.docx Page 4 installation of the shared use path along East Valley Center Road. Draft exhibits for expected impacts to wetlands have been included as attachments to the project submittal folder. Permits Wetland and watercourse impacts shall be permitted via submission of Joint Application for Proposed Work in Montana’s Streams, Wetlands, Floodplains, and other Water Bodies. This application is currently being drafted for submission to the US Army Corps of Engineers, Gallatin Conservation District, and Montana Department of Environmental Quality, pending final design and known impacts. Respective permits include 404, 310, and 318. These permits will be applied for during infrastructure drawing review and final permits shall be provided to the City prior to construction. References Turnrow Subdivision – Phase 1 – Flood Hazard Evaluation Report. March 2024 Revision. Morrison-Maierle. Davis Lane 115-ac Property, Gallatin County, Montana. Wetland Delineation. Morrison-Maierle. November 9, 2023. Turnrow Subdivision, Aquatic Resource Analysis Response Feb 2024. Morrison-Maierle.