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Home My WebLink About21430 Eng. Saccocia 407C PP MMI Narrative MMI – NARRATIVE ------------------------------------------------------------------------------------------------------------ MEMORANDUM TO: Project Applicant FROM: Karl Johnson, Engine – er I – - R -- E - : --------------- A -- p - p -- l - i - c - a -- t - i - o -- n -- # -- 2 -- 1 -- 4 -- 3 - 0 ---- S -- o -- c - c - o -- c - i - a --- M -- i - n -- o -- r -- S - u -- b --- 4 - 0 -- 7 -- C -- P -- P ----- R -- e - v -- i - s - i - o -- n --- 0 - 0 --- DATE: December 27, 2021 ENGINERING REQUIRED CODE CORRECTIONS: The following comments pertain to areas of the project that do not currently meet code and must be addressed prior to Preliminary Plat adequacy. Grading and Drainage 1. BMC 40.04.700.A.4 - Stormwater management plans and comprehensive drainage plans shall: a. Prevent any off-site direct discharge of untreated stormwater and non-stormwater from development or redevelopment improvements. i. It appears a majority of Basin 1 will drain offsite. Provide sufficient detail to insure drainage will reach the proposed destination. The current stormwater treatment plan for the Saccoccia Minor Sub. 407C is for Lot 2A1 to utilize the existing Lowe’s PUD pond. This is with the addition of a pre-treatment forebay design that was submitted with the HOME-2 Site plan application / infrastructure review (COB#: 19394 and ENGINF - 1305). Lot 2A2 will not use the existing Lowe’s PUD Pond, but instead will store and treat stormwater on-site (Lot 2A2). Anything dealing with Basin 1 is being addressed with the HOME-2 Site plan application / infrastructure review (COB#: 19394 and ENGINF - 1305). b. Implement accepted BMPs to minimize impact of a development on existing offsite infrastructure and stormwater facilities. i. The applicant has described the use of a pretreatment forebay for the existing wet detention basin. The proposed pretreatment forebay does not meet the following recommendations for pretreatment forebays in the Montana Post-Construction Storm Water BMP Design Guidance Manual. a. A barrier separating the pretreatment forebay and wetpool cell should be constructed to contain the forebay opposite of the inlet. b. A concrete bottom is recommended to facilitate sediment removal during maintenance. c. Provide a way to monitor sediment accumulation. The pre-treatment forebay design was submitted with the HOME-2 Site plan application / infrastructure review (COB#: 19394 and ENGINF - 1305). Lot 2A2 will not use the existing Lowe’s PUD Pond, but instead will store and treat stormwater on-site (Lot 2A2). c. Comply with section II of the city Design Standards, and chapter 38, article 23. i. The applicant has described utilizing the existing Lowe’s detention pond to comply with this section. The applicant has adequately demonstrated the subject property can be adequately served by the Lowes detention pond as designed. The stormwater design report for the Lowe’s PUD describes “the hydraulic capacity of the pond for stormwater runoff functions is the top 1.5 feet of the pond.” The water surface elevation is currently above the pond outlet as observed 12-24-2021 (a time of little to no runoff due to winter conditions). The existing condition of the pond does not allow for any storage of runoff from the subject property as proposed and therefore utilizing this pond in its current condition would not satisfy the requirements of Section II of the city Design Standards. The applicant must provide a means of stormwater storage on site or provide maintenance or modification to the existing Lowe’s PUD pond to provide adequate storage for the subject property. The current stormwater treatment plan for the Saccoccia Minor Sub. 407C is for Lot 2A1 to utilize the existing Lowe’s PUD pond. This is with the addition of a pre-treatment forebay design that was submitted with the HOME-2 Site plan / infrastructure review (COB#: 19394 and ENGINF - 1305). Lot 2A2 will not use the existing Lowe’s PUD Pond, but instead will store and treat stormwater on-site (Lot 2A2). See the Stormwater Design Report for Lot 2A2 in the Documents folder for details. ENGINEERING CODE PROVISIONS: The following comments pertain to areas of the project that do not currently meet code and must be addressed prior to Final Plat. Easements 1. BMC 38.410.060 - All Easements indicated below must be provided on city standard easements templates. Drafts must be prepared for review and approval by the city. Signed hard copies of the easements must be submitted to the city and recorded easement numbers must be shown on the final plat. The applicant may contact the reviewing engineer to receive standard templates. a. The applicant must provide the proposed ten foot utility easement (power, gas, communication, etc.) along the developments property frontage with Baxter Lane and Sacco Drive. A 10’ PUE has been granted on the Preliminary Plat. See the attached Plat located in the Plans folder for details b. The applicant must provide the proposed drainage easement for the prosed storm sewer crossing multiple lots. There is no longer stormwater crossing multiple lots. Lot 2A2 will treat and store stormwater on-site. See the Stormwater Design Report for Lot 2A2 in the Documents folder for details. c. The applicant must provide the proposed pedestrian access (trail corridor) easement. This easement must be 25’ in width and provide a connection between public access points. The 25’ pedestrian access easement is included on the preliminary plat. See the preliminary plat in the Drawings folder for details. d. The applicant must provide a public access easement over the existing mutual access easement along the western border of Lot 1A and Lot 2A2. This easement must extend along the western border of Lot 1A and at least 25 feet into proposed Lot 2A2 to meet lot access requirements. There are existing public access easements on the western border of the project. This issue was resolved back in early 2022. See the email document (Email Exchange - Western Boundary Easements.pdf) located in the Documents folder for details. e. The division of Lot 2A into Lot 2A1 and 2A2 will create the proposed sewer service to lot 2A1 to cross lot lines. The applicant must provide a sewer service easement on Lot 2A2. This shall be a private easement. A recorded copy of the easement must be submitted and the recorded easement number shall be recorded on the Final Plat. There are existing sewer easements and an existing 8” main stubbed into Lot 2A1. See the preliminary plat in the Drawings folder for details. There are (2) existing easements to provide sewer to Lot 2A1 – see Doc. No. 2518681 (in Documents folder -Easement Doc 2518681.pdf) and an existing 30’ easement that was created with Minor Subdivision 407. Therefore, there is no need for a sewer service easement across Lot 2A2 for lot 2A1. ENGINEERING RECOMMENDED CONDITIONS OF APPROVAL: The following comments must be addressed prior to Final Plat 1. The subject property is located within the N 19th and Baxter Intersection Payback. The payback must be paid prior to Final Plat approval. The subject property did participate in the original cost of the construction N 19th and Baxter Intersection improvements. ENGINEERING ADVISORY COMMENTS: The following comments must be addressed with future applications 1. DSSP Plans and Specification Review Policy – Plans, specifications, and submittals for public infrastructure improvements (watermain) must be submitted to the City Engineering Department (engsubmittals@bozeman.net) for infrastructure review. 2. DSSP Fire Service Line Standard – Plans for all fire service lines must be submitted to the City Engineering Department (engsubmittals@bozeman.net) for review. 3. DSSP V.A.7.a - All connections to an existing water main will begin with a new valve. 4. DSSP V.B.12 - Access Roads: A 12'-wide all-weather gravel access road, with turn-arounds if needed, shall be constructed to provide access to all sanitary sewer manholes and water main valves not located within a paved public or private street or parking lot. A temporary access road shall be constructed if water main valves are to be located outside of the proposed parking lot. 5. The provided geotechnical report suggests corrosivity concerns. The applicant shall specify corrosion protection or provide an analysis based on the DIPRA Design Decision Model showing protection is not needed prior to infrastructure approval. Acknowledged. N:\2927\012 - Minor Sub 407C PreApp\04 Design\Platting\PRE-Plat\21430 Eng. Saccocia 407C PP R00.pdf V1 MMI Narrative 091522.docx