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HomeMy WebLinkAboutNarrativeAdditionalPPSupplementals_05162021Preliminary Plat Supplements Annie Subdivision Phase 4 (2305 Durston Road) City of Bozeman, MT May 2021 Russell Hosner LLC 7003 Jackson Creek Road Bozeman, Montana 59715 109 E. MAIN STREET, BOZEMAN, MT 59715 I OFFICE 406.728.4611 I EMAIL wgm@wgmgroup.com CONTENTS 1.0 SURFACE WATER ............................................................................ 2 2.0 FLOODPLAIN .................................................................................... 2 3.0 GROUNDWATER .............................................................................. 3 4.0 GEOLOGY, SOILS, AND SLOPE ...................................................... 4 5.0 VEGETATION .................................................................................... 4 6.0 WILDLIFE .......................................................................................... 5 7.0 HISTORICAL FEATURES ................................................................. 5 8.0 AGRICULTURE ................................................................................. 5 9.0 AGRICULTURE WATER USER FACILITIES .................................... 6 10.0 WATER AND SEWER ..................................................................... 6 11.0 STORMWATER MANAGEMENT .................................................... 8 12.0 STREETS, ROADS AND ALLEYS .................................................. 9 13.0 UTILITIES ........................................................................................ 9 14.0 EDUCATIONAL FACILITIES ......................................................... 11 15.0 LAND USE ..................................................................................... 11 16.0 PARKS AND RECREATION FACILITIES ..................................... 11 17.0 NEIGHBORHOOD CENTER PLANS ............................................. 12 18.0 LIGHTING PLAN ........................................................................... 12 19.0 AFFORDABLE HOUSING ............................................................. 12 20.0 MISCELLANEOUS ........................................................................ 13 2 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application 1. SURFACE WATER An existing stream runs near the east boundary of the subject property. It is our understanding that this stream is the West Fork of Catron Creek. The approximate location of this stream is shown on the preliminary plat documents. This stream will be protected from development with a 50-foot wide watercourse setback as shown on the preliminary plat. The stream is fed by two concrete culverts extending under Durston Road. A wetland delineation along this watercourse was completed as part of the project. The wetland boundary is shown on the preliminary plat. The 50-foot watercourse setback extends from the west edge of the surveyed wetlands. The Phase 3C plat (J-482) shows a 35-foot wide setback from the stream. The Phase 3C plat also shows a 100-foot floodplain line located inside of the 35-foot wide setback. Per email correspondence with the City, additional evaluation of the floodplain is not required with this project. Alteration to the stream or stream corridor will not occur with the project. The entire 50-foot watercourse setback area will be encompassed by the proposed Open Space lot. Landscaping details specific to the watercourse setback and open space have been provided as part of the landscape plan drawings. It is also notable that the adjacent site plan to the east (Arcadia Gardens dated 1995) labels this stream an “irrigation ditch” flowing from east to west paralleling Durston Road, then north adjacent to the project site. 2. FLOODPLAIN Per email correspondence with the City of Bozeman, a flood hazard evaluation for the project is not required. There is no regulated floodplain associated with the stream on the east side of the site. The Phase 3C plat identifies a 100-year floodplain, the west extents of which are located inside the 35-foot wide stream setback. Phase 4 will utilize a 50-foot watercourse setback which provides additional clearance from this floodplain shown on the Phase 3C plat. The Open Space lot will include the 3 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application entirety of the 50-foot watercourse setback. Therefore, there will be no construction within or near the floodplain shown on the Phase 3C plat. 3. GROUNDWATER In March 2021 a geotechnical site evaluation was completed by Allied Engineering. During this site evaluation, seven (7) test pits were excavated and groundwater monitoring wells were installed within all of the test pits. Groundwater monitoring of the wells has been conducted approximately weekly and this data has been provided with the preliminary plat application. Per the data, the majority of the test pits have remained dry (i.e. no groundwater encountered) except on the northeast side of the site (MW- 7) where groundwater appears to be located near the bottom of the test pit. The geotechnical summary notes that there are no issues due to deep groundwater. The test pit locations map shows the locations of the test pits and corresponding monitor wells. The ground surface elevation near MW-7 is approximately 4 feet higher in elevation than the stream bottom. The well casing sticks up about 1.17 feet above the ground surface. Therefore, the measured depth to groundwater in MW-7 is about 7.2 feet, which is about 3.2 feet lower than the adjacent stream bottom elevation. These elevations indicate that the stream is “losing” and groundwater may become lower moving further away from the stream. Stormwater infrastructure including the detention pond located in the Open Space lot, near MW-7, was designed while considering the potential for high groundwater. The proposed bottom of the stormwater detention pond is located about 2 to 3 feet below the existing ground surface. The adjacent stream bottom is deeper, about 4 feet below the ground surface. Therefore, the detention pond will not become inundated by stream water, and has adequate separation between the pond bottom and shallow groundwater. It is notable that the Gallatin Valley had a relatively dry winter/spring and therefore groundwater elevations and fluctuations this year may not be indicative of potential “high” groundwater during a wet year. That said, based on the elevation of the adjacent stream (shown on the site groundwater cross section), the understanding that the stream is “losing”, and the fact that the existing home had a full basement, it appears as though groundwater does not come close to the ground surface even during wetter years. It is understood that basements will not be allowed with future development. However, 4 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application crawl spaces appear acceptable based on the data, and the geotechnical engineer’s comments that crawl spaces are acceptable due to relatively deep groundwater. Crawl spaces are proposed to be allowed for the development, with the understanding that minimum structure elevations may be required to be listed on the final plat, along with recommendations for lot-specific geotechnical investigations prior to development of individual lots. The well log for the on-site well does not list a static water level. Groundwater was measured in the two existing wells on May 12, 2021. The results are as follows: · Existing Well Near the House (S of house) o Groundwater measured at 17.1 feet below the ground surface · Existing Irrigation Well (SE side of lot) o Groundwater measured at 13.0 feet below the ground surface This data supports the “losing” stream designation, and indicates that groundwater is significantly lower within the central part of the lot as compared to the east portion of the lot adjacent to the stream. 4. GEOLOGY, SOILS, AND SLOPE A geotechnical investigation was completed by Allied Engineering for the property. The geotechnical summary report has been provided with this application. The report summarizes the on-site soils, which are typical of the Gallatin Valley. The report provides recommendations for the design road section (3” asphalt, 6” base course, 15” sub-base course, Mirafi RS580i geosynthetic, compacted subgrade). The report also notes there are no geotechnical issues due to shallow gravels and deep groundwater. The report also notes that crawl spaces will be ok due to deeper groundwater. This observation is in line with groundwater monitoring data for the site. Groundwater monitoring wells were installed within the test pits as part of the geotechnical field work. There are no unusual soil features at the site. The site slopes mildly to the north. NRCS soils information has been provided with this application. This includes an NRCS soils map. Cuts and fills of three or more feet are not anticipated. The road will be designed to minimize cuts and fills and attempt to match the natural ground surface to the extent practical. Natural vegetative buffers will be used during construction to protect the site against erosion and stormwater discharge, per the future SWPPP. 5 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application 5. VEGETATION A wetland evaluation was completed for the stream corridor as part of this project. The evaluation was completed by Sarah Howell, a wetland biologist with WGM Group. Results of the evaluation have been provided with the application. Weeds at the site were also mapped as part of the project, per the weed map included in the wetland report. The Noxious Weed Management and Revegetation Plan submitted to Gallatin County was approved for the project. The site includes multiple rows of mature trees including rows along the north property line, and two rows of trees east of the existing home. Consideration was given to keeping some of these trees through construction. However, due to potential conflicts with construction access, staging, etc., these trees are planned to be removed as part of the project. If, during vertical construction, trees can be salvaged, the developer may request approval from the City. However, at this time salvaging trees is not anticipated. The existing trees along the stream on the east side of the site, and along Durston on the south side of the site, are planned to remain, as they will not be impacted by construction. 6. WILDLIFE A waiver for wildlife was granted by the City during the Pre-Application review for the project. 7. HISTORICAL FEATURES A waiver for historical features was granted by the City during the Pre-Application review for the project. 8. AGRICULTURE A waiver for agriculture was granted by the City during the Pre-Application review for the project. 6 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application 9. AGRICULTURE WATER USER FACILITIES There are no active agricultural water user facilities located within this proposed development. 10. WATER AND SEWER As Constructed drawings for Annie Subdivision Phase 1 dated March, 2002 and for Phase 3A & 3C dated May 2007 were reviewed as part of the water and sewer design. These as-builts provide information regarding the infrastructure adjacent to the project site. An existing 48-inch diameter sanitary sewer manhole (MH#12) marks the dead-end at Rogers Way with a bury depth of 6.17 feet and invert in elevation of 4755.62. A 48-inch diameter manhole (MH#14) with 9.56-foot bury depth marks the dead-end on Daffodil. An existing 8-inch diameter plug and 2-inch diameter blow off assembly, with thrust blocking, marks the dead-end water main at Rogers Way with a bury depth of approximately 7 feet. The Daffodil dead-end consists of an 8-inch diameter plug with thrust blocking buried at 6.5-foot minimum cover. Water Supply Water for domestic use and fire protection will be provided by connections to the City of Bozeman water system. Existing water mains currently dead-end at both the west side of the site (Daffodil Street) and north side (Roger’s Way) and will be extended and connected (looped) as part of the project. The dead end along Roger’s Way includes a blow-off hydrant as shown on the image below. Please see the Water Design Report for additional information. 7 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application Figure 1 - Hydrant on Roger's Way (north of project site) The existing domestic well (located just south of the house) is planned to be properly abandoned. The existing irrigation well located near the southeast part of the site is planned to remain, within the open space lot, and used for irrigation of the open space lot and the Durston boulevard. The attached email correspondence provides City estimated increase in annual municipal water demand attributable to the development. This will be offset by the owner through transfer of water rights into City ownership appurtenant to the development. We anticipate that the unit cost for cash-in- lieu of water rights may be updated based on the current established cost. Sanitary Sewer Sanitary sewer service will be provided via connection to the City of Bozeman’s existing sanitary sewer collection system. Existing sewer mains dead-end at both the west side of the site (Daffodil Street) and the north side (Roger’s Way) and will be extended into the development to serve the new lots. As builts for Annie Subdivision Phase 3C and Phase 1 show existing sewer manholes at each of the dead-ends. It is assumed that these manholes exist, buried by debris and dirt, located outside of the pavement (as shown on the as-builts), although the exact locations of these manholes have not been verified to this point. Please see the Sewer Design Report for additional information. 8 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application The project is pursuing an exemption from MDEQ for water and sewer review. The project is pursuing an MDEQ Municipal Facilities Exclusion (MFE). This form has been provided with the application. This form was previously sent to the City of Bozeman specific to the project via email. 11. STORMWATER MANAGEMENT Currently, stormwater runoff from the site enters the existing adjacent City roads (Daffodil and Roger’s Way) or directly enters the existing stream on the east side of the site. With the proposed development, additional impervious area will be created, contributing additional stormwater runoff, and therefore requiring adequate stormwater management. Stormwater is planned to be managed on-site within the Phase 4 development area. Two drainage basins are proposed, one which drains to the west and the other to the northeast. Two basins are utilized due to a high-point in the proposed road profile located which separates the basins. Creation of one drainage basin which drained the entire site to the northeast was desired, but straight grading the new road from the Daffodil Street connection to the Roger’s Way connection resulted in a road grade lower than City standards. Stormwater design and details are provided in the Stormwater Design Report. The proposed stormwater design includes a detention pond located on the Open Space lot which handles stormwater from the east (larger) drainage basin. Stormwater gets to this pond via curb flow and an underground pipe located within a stormwater drainage easement between Lots 9 and 10. This drainage easement is shown offset to the property line (5 feet on to Lot 9 and 15 feet on to Lot 10). For the west (smaller) basin, a low-impact stormwater design is proposed using cobble infiltration galleries adjacent to the lots. Initial planning evaluated the possibility of utilizing the existing Annie Subdivision stormwater pond located north of the subject property between Roger’s Way and Annie St. However, since this existing pond appears to not be sized to accommodate stormwater from the subject property (per the original design report), and due to conflicts/uncertainties with the existing stormwater infrastructure (i.e. a shed built over the piping as noted in comments on the Pre-Application), it was determined that connection to the existing Annie Subdivision stormwater infrastructure is impractical for the project. Therefore, on-site management of stormwater is utilized. 9 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application 12. STREETS, ROADS AND ALLEYS Per email correspondence from the City (included with this application), a traffic impact study is not required for the development based on estimated trip generation. The estimated trip generation for the development is as follows: Land Use Size ITE Land Use Code Average Daily Traffic (ADT) AM Peak-Hour Trips PM Peak-Hour Trips Entering Exiting Entering Exiting Townhomes 16 210 151 3 9 10 6 Single Family Home 1 210 9 0 1 1 0 Apartments 8 220 59 1 3 2 2 Figure 2 - Trip Generation from Proposed Development The project involves the continuation and connection of Daffodil Street and Roger’s Way through the site. The design road horizontal alignment is based on 1) the adjacent “mirrored” roadways to the north (Roger’s Way on the south side of Annie Sub. Ph. 3B) and to the west (Daffodil Street on the south end of Harvest Creek Ph. 1). It is notable that per the Findings of Fact for Annie Subdivision Phase 3C: “If and when Lot 1 is further divided, access will be available from Daffodil St. and Roger’s Way.” Findings of Fact for Annie Subdivision Phase 3 also note: “Provisions shall be made for the future extension of Daffodil Street to the east to end in a cul-de-sac or continue north to link with Rogers Way upon approval by the Director of Public Service, City Engineering, and Water/Sewer Superintendent”. Road maintenance for all streets is proposed to be provided by the City of Bozeman after the improvements have been accepted by the City. Erosion and siltation control will be included during construction by using the appropriate best management practices as outlined in the “Montana Sediment and Erosion Control Manual” (May 1993) prepared by the MDEQ Water Quality Bureau. As required by City Pre-Application comments, the project intends to construct a Rapid Rectangular Flashing Beacon (RRFB) at the intersection of N 27th and Durston Road. Coordination with a local RRFB installer has been conducted. The preliminary design involves the installation of two (2) solar activated RRFBs (solar only, no electrical). The Eastbound unit would be mounted on the existing luminaire pole and the Westbound unit would be installed on a new 2.5-inch telespar sign post with 10 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application concrete anchor. These units would be single direction signs, made by Tapco, the same as recently installed units on 11th Ave near Bozeman High School. We anticipate additional plans, and coordination with the City of Bozeman prior to acceptance of the design and construction. The existing approaches along Durston Road are proposed to be abandoned as part of the project. This will likely involve some traffic control along Durston and the temporary closure or one lane (westbound traffic could be redirected into the center turn lane). Bicycle and pedestrian routes will connect with existing adjacent routes. 13. UTILITIES Standard 10-foot front yard utility easements have been provided across the lots, per comments received on the Pre-Application. The adjacent Phase 3C development (to the west) provides 15-foot wide front utility easements. The Phase 4 easements could be made 15-feet wide to match Phase 3C, but have been left at 10 feet, since it appears that the existing underground dry utilities adjacent to the site, as mapped during the survey, are within a 10 foot corridor, and therefore could be extended through the proposed Phase 4 utility easement. A 15-foot wide utility easement has been provided along Durston Road, on the south side of the project site, to match the adjacent 15-foot wide easement per Phase 3C. There are no proposed utility road crossings associated with the project. A Northwestern Energy construction application has been submitted for the project and on-going meetings and correspondence with Northwestern Energy have occurred. Existing northwestern utilities will be properly abandoned with the development. Northwestern Energy has noted via email correspondence that the subject property has existing utilities within the adjacent developed subdivision, and an extension of the utilities should be available. The development will meet Northwestern Energy’s requirements including those provided via comment on the Pre-Application. Century Link (Lumen) has responded that service can be provided to the site. Irrigation is intended to be provided to the open space via the existing well which is located near the southeast corner of the lot, within the open space lot. Per conversations with the well driller, and Northwestern Energy, this well provides adequate water, and can be used for the irrigation supply. 11 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application 14. EDUCATIONAL FACILITIES The Director of Facilities for the Bozeman Public Schools has been contacted as part of the project. Via email correspondence, the Director has indicated that given the nature of the project, the enrollment impacts will not be substantial. The Director has been contacted to provide additional input. 15. LAND USE Annie Subdivision Phase 4 is a 20-lot subdivision located on approximately 3.24 acres. The subdivision includes 16 townhome lots, 2 multi-family lots, 1 single-family lot, and an open space lot. The proposed preliminary plat shows the land uses. The Open Space lot is intended to be a connection/continuation of the open space lot located northeast of the subject property, which is part of the existing Annie Subdivision. Although the pedestrian trail is located east of the open space, on the adjacent parcel, this linear open space acts as a semi-natural undeveloped corridor adjacent to the stream. 16. PARKS AND RECREATION FACILITIES No parkland is proposed for the project. The development has requested cash-in-lieu of parkland. Cash-in-lieu of parkland is proposed for the development. Calculations have been provided as follows: · Gross Lot Area = 3.24 Acres o Road Right of Way Area = 0.52 Acres o Net Lot Area = 2.72 Acres · Estimated Dwelling Units = 25 o Dwelling Units/Acre = 9.2 (12/Acre Max) · Required Dedication = 0.03 Acres/Dwelling Unit o Total Req. Dedication = 25 x 0.03 = 0.75 Acres = 32,670 Square Feet (SF) · Proposed Park Lot Size = 0 SF · Remainder Required Parkland = 32,670 SF · City Approved Land Value per Square Foot = $1.72 o Required CIL of Parkland = 32,670 SF x $1.72 = $56,192.4 12 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application An open space lot is included on the east side of the site, as shown on the site layout. This open space lot includes the entirety of the 50-foot watercourse setback. The west side of the open space lot extends past (west of) the watercourse setback. We understand that watercourse setbacks are unacceptable for parkland dedication unless approved by the review authority per Section 38.420.020. This open space lot continues/connects the existing open space lot located north of the subject property within Annie Subdivision Phase 3A. Maintenance of this open space will be by the HOA. The open space area is currently undeveloped grassland with scattered trees next to the creek. There is no sign of pedestrian use through the open space. Access to this open space is proposed to be from Durston. The existing trail east of the site (the Westside Trail) is located east of the creek and east of the subject property, within Lots 1 and 2 of Block 14 of Annie Subdivision Phase 1. Per the Arcadia Gardens Site Plan as-builts dated July 1995, the trail (“bike path”) is located within a 20-foot utility easement on the site. 17. NEIGHBORHOOD CENTER PLANS A waiver for neighborhood center plans was granted by the City during the Pre-Application review for the project. 18. LIGHTING PLAN New lighting is not proposed for the development. An evaluation of the existing street lights along Durston Road was performed as part of the project. Details for the existing lights were from the City of Bozeman’s GIS website along with direct coordination with the City. Manufacturer and series were provided by the City (Cree, XSP series). The analysis used less luminous LED as a conservative assumption. The IES file used was for LEDs that are typically used to replace 250W HPS, although the Durston luminaries were originally installed with 400W HPS. The evaluation showed that additional lighting along Durston is not required. 13 Annie Subdivision Phase 4 Narrative for Preliminary Plat Application 19. AFFORDABLE HOUSING An Affordable Housing Plan Application has not been provided with this submittal. 20. MISCELLANEOUS  The development will have no adverse impact to access to public lands (i.e. the open space and trail east of the project site). Pedestrian access will be maintained via Durston Road.  Per correspondence with the Deputy Chief/Fire Marshall, additional fire hydrants would not be required with the development. There is an existing fire hydrant located just west of the project site, on the north side of Daffodil (hydrant #2145) and another hydrant located northeast of the site (hydrant #1449) along Roger’s Way. There is also a hydrant located in the yard east of the project site, between the trail and parking lot (hydrant #1015). Multiple fire hydrants are also located along Durston Road adjacent to the project site. If the buildings are over four-stories, fire sprinklers and stand pipes would be required.  A fire hydrant flow test was recently conducted adjacent to the project site, specific to the development, as summarized in the Water Design Report.  Dedicating a shared access easement between Lot 10 and Lot 11 was considered. This shared access easement would theoretically allow for one single access for both lots to use, which could provide additional room for future development or parking. However, this shared access easement is not shown on the plat currently with the understanding that a shared access easement could be provided in the future, if desired.  Per discussions with the City Operations Manager and Finance Department, the project site contributed to the original Durston Road SID since it was within City limits at the time the SID was put in place. In 2011, the property owner paid the remaining balance. The payback only applies to properties within the County at the time of SID creation.  Demolition permits have been submitted to the City for both the barn and the existing home. The Owner is working with the City Buildings Department to fulfill all requirements regarding demolition. It is notable that the previous owner demo’d the existing barn  Information regarding the planned Rapid Rectangular Flashing Beacon (RRFB) at the Durston Road and N 27th intersection is provided in this narrative in the Streets, Roads and Alleys section.