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Home My WebLink AboutBLD2021-00602 - 05 Stormwater SWMP Review Comments 1-28-2022 Stormwater Review for Quilcene Bus Barn Page 1 of 3 Date: 1/28/2022 To: David Wayne Johnson, DCD From: John Fleming PE, JCPW Project: Quilcene School District #48 Bus Barn Stormwater Project: (BLD2021-00602, Assessor Parcel # 937200301, JCPW Project # 91021602) Subject: JCPW Stormwater Site Plan Review and Comments APPLICATION REVIEW A. Stormwater Management Unified Development Code Requirement(s): The Jefferson County Unified Development Code, Sections 18.30.060, Grading and excavation standards and 18.30.070, Stormwater Management Standards both set standards for erosion and sedimentation control and stormwater management. The code adopts the requirements set forth by the most current version of the Washington State Department of Ecology, Stormwater Management Manual for Western Washington (SWMMWW). The most current version is the 2019 SWMMWW. JCPW Findings: Jefferson County Department of Community Development (DCD) has requested that the Public Works Department review a Plan set, a stormwater pollution prevention plan, and a Storm Drainage Report prepared for the Quilcene School District #48 by Jaime Saez PE of Saez Consulting Engineers Inc., in Bainbridge Island, WA. The most recent Plan was received 1/25/2022. The Drainage Report was stamped received by DCD 10/12/2021. The relevant portions of the plan set included seven (7) civil sheets: cover sheet and notes, site prep and TESC, grading and drainage, utilities, and three (3) detail sheets. stormwater pollution prevention plan. The Drainage Report referenced other documents that included a topographical survey, a geotechnical report prepared by Chris Heathman PE of Mud Bay Geotechnical Services LLC in Olympia, WA, and a septic design with additional soil information prepared by Nathan Cleaver Septic Design in Poulsbo, WA. The geotechnical report had 2 addenda, with the most current dated 1/23/2022. The 4.64 acres site has approximately 1.6 acres of existing impervious graveled hard surface, and 1,970 square feet of building roof area. The redevelopment proposal calls replacing the buildings with a new 4,880 square feet (0.11 acres) bus barn, 29,344 square feet (0.67 acres) of pollution generating impervious surface (PGIS), and 1,908 square feet (0.04 acres) of non-pollution generating surfaces. This is a large project, and is subject to meeting all nine (9) Minimum Requirements (MR) of the 2019 SWMMWW. Stormwater Review for Quilcene Bus Barn Page 2 of 3 The site conditions were characterized by the septic design with six (6) soil test pits, free of ground water to 62 inches. Geotechnical Engineering Design Report characterizes the site with 6 soil test pits free of ground water to 72 inches, 2 small pilot infiltration tests performed within the upper 31 to 33 inches of soil, near the elevation of proposed bioretention stormwater facility. The report recommended a maximum allowable infiltration rate for design purposes of 4.25 inches per hour and apply a factor of safety of 2. Based upon soil evaluations on adjacent properties, the geotechnical addendum estimated the water table to be greater than 10 feet below ground surface. The existing terrain is already level, with minimal grading proposed. The Plan proposes to meet requirements of the 2019 SWMMWW by implementing a stormwater pollution prevention plan during construction, and a permanent stormwater system consisting of - BMP T5.13 Post-Construction Soil Quality and Depth in the landscaped areas; - BMP T7.30 for a Bioretention cell for up to 38,768 square feet (0.89 acres) of pollution generating impervious surface (PGIS) from the Bus Barn property and the bus loading zone in the Jefferson County right of way for East Rose Street, designed using 4.25 inches per hour infiltration rate of soil under the bioretention soil media; - BMP T7.20 Infiltration Trench receiving overflow from the Bioretention cell, designed using 4.25 inches per hour infiltration rate and a factor of safety of 2. The project includes clearing, grading and/or excavation that results in the disturbance of more than 1 acre. Per the application it appears as though discharge of stormwater to waters of the State (as defined by WA State Department of Ecology) may occur. JCPW Recommendations: 1. The proponent shall install the stormwater management facilities and implement the Best Management Practices (BMP’s) consisting of BMP T5.13 Post-Construction Soil Quality and Depth in the landscaped areas; BMP T7.30 for a Bioretention cell for up to 38,768 square feet (0.89 acres) of pollution generating impervious surface (PGIS) from the Bus Barn property and the bus loading zone in the Jefferson County right of way for East Rose Street; BMP T7.20 Infiltration Trench receiving overflow from the Bioretention cell. Construction shall conform with: 7 sheet Civil Plans last revised 1/25/2022, SWPPP and Storm Drainage Report both received by DCD 10/12/2021, all prepared by Jaime Saez PE, Saez Consulting Engineers of Bainbridge Island; Geotechnical Engineering Design Report dated 7/31/2021 and addendum dated 1/23/2022 prepared by Chris Heathman PE, of Mud Bay Geotechnical Services LLC in Olympia, WA. 2. Sites with greater than 1 acre of disturbance trigger the requirement to have a developer provided Certified Erosion and Sediment Control Lead (CESCL) inspector and site log book, as per Element #12 Manage the Project, of Minimum Requirement #2 Construction Stormwater Pollution Prevention. The CESCL inspector must be identified by the time of start of construction, and must be present on-site or on call at all times. 3. The proponent should verify with WA State Department of Ecology as to whether they are required to apply for an NPDES Construction Stormwater General Permit (CSWGP). 4. Prior to commencing land disturbing activity, the proponent shall notify Jefferson County Public Works (JCPW) and arrange a Preconstruction Meeting. 5. Before any construction begins on-site, erosion control facilities shall first be installed. Stormwater Review for Quilcene Bus Barn Page 3 of 3 6. In accordance with the Jefferson County Unified Development Code, Section 18.30.080 (1) (f): Clearing, grading, and construction of roads, bridges, utilities, and stormwater management facilities shall be inspected by JCPW. In order to enable the department to conduct inspections in a timely manner, the applicant shall notify the department in a timely manner regarding the project construction schedule. Typical Inspections: • Installation of temporary erosion and sediment control measures; (Required) • Clearing (and Grading) and road subgrade preparation; • Placing roadway gravel base; • Placing roadway crushed surfacing top course; • Placing improved roadway surface (chip seal or asphalt concrete); • Construction of stormwater management facilities; (Required) -Bioretention Cell (Rain Garden) excavation bottom before placing Bioretention Soil Mix; (Required) -Infiltration Gallery trench bottom before placing perforated pipes; (Required) • Final plat review. • (Additional inspections may be deemed necessary as project progresses.) 7. After construction is complete and prior to final DCD project approval, the proponent shall submit a letter to the Public Works Department, from the Engineer of Record (EOR), certifying that the stormwater management facilities have been constructed per the approved plans & specifications. It is the responsibility of the proponent to schedule inspections with the E.O.R., his designee &/or qualified inspection firm(s), approved by the E.O.R., to provide for said final certification. 8. To meet MR#9 Operation & Maintenance, and ensure that the approved stormwater management facilities are appropriately maintained for the life of the project, prior to final project approval, the proponent shall enter into a Stormwater Management Facility Maintenance Agreement with Jefferson County. The Public Works Department will send a copy of the Agreement to the proponent which has been signed by the Public Works Director. The proponent shall sign the Agreement before a notary, file it with the Jefferson County Auditor, and provide Public Works with a copy of the recorded document. County Auditor 2022 recording fees are $203.50 for the first page and $1 for each additional page. B. Public Works Department Fees Requirement: Unified Development Code Requirement(s): The Jefferson County Unified Development Code Chapter 18.30.080(1)(u) authorizes the Public Works Department to assess fees in accordance with the Jefferson County Fee Schedule Ordinance for development review activities including application and plan review, inspections, meetings, hearings, and final review. • Prior to DCD project approval, the proponent shall pay all costs related to the Department’s application review, plan review, inspections, and preparation of the Stormwater Management Facility Maintenance Agreement. In accordance with the Jefferson County Public Works Department Fee Schedule, the Department’s hourly development review fee is $95 for 2022. In the event that approval for the proposal is denied by Jefferson County or the proposal is not completed, the proponent shall still be responsible for paying the Department’s fee.