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TIR-4354
Renton Fire Station #16 Technical Information Report July 1, 2025 The information contained in this report was prepared by and under the direct supervision of the undersigned: Owner: Renton Regional Fire Authority 18002 108th Ave SE Renton, WA 98055 Contact: Daniel Alexander Prepared for: Marc Servizi, P.E. LPD Engineering, PLLC 1932 1st Ave, Suite 500 Seattle, WA 98101 (206) 725-1211 Renton Regional Fire Authority 18002 108th Ave SE Renton, WA 98055 Contact: Daniel Alexander Surface Water Enginering jfarah 09/18/2025 DEVELOPMENT ENGINEERING HHuynh 09/23/2025 LPD Engineering, PLLC Page 30 Renton Fire Station #16 Technical Information Report, July 1, 2025 RENTON FIRE STATION #16 TECHNICAL INFORMATION REPORT TABLE OF CONTENTS Section 1 – Project Overview .................................................................................................................................. 1 Section 2 – Conditions and Requirements Summary ........................................................................................ 3 Section 3 – Offsite Analysis ...................................................................................................................................... 5 Section 4 – Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and Design ............................................................................................................................................................................. 8 Section 5 – Conveyance Systems Analysis and Design ................................................................................... 13 Section 6 – Special Reports and Studies .............................................................................................................. 13 Section 7 – Other Permits ...................................................................................................................................... 14 Section 8 – CSWPPP Analysis and Design ......................................................................................................... 14 Section 9 – Bond Quantities, Facility Summaries, and Declaration of Covenant .................................. 15 Section 10 – Operations and Maintenance Manual .......................................................................................... 15 FIGURES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: Downstream Drainage Map 1 Figure 4: Downstream Drainage Map 2 Figure 5: Soils Map Figure 6: Proposed Conditions Figure 7: Proposed Modeled Conditions Figure 8: Existing Drainage Figure 9: Conveyance Tributary Areas APPENDICES Appendix A – Design Drawings Appendix B – Design Calculations and Supporting Information Appendix C – Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Appendix D – Operations and Maintenance Manual Appendix E – Facility Summaries, Declaration of Drainage Covenant, and Bond Quantities Worksheet Appendix F – Special Reports and Studies – Geotechnical Report Appendix G – Drainage Observation Report LPD Engineering, PLLC Page 1 Renton Fire Station #16 Technical Information Report, July 1, 2025 RENTON FIRE STATION #16 REPLACEMENT TECHNICAL INFORMATION REPORT JULY 1, 2025 SECTION 1 – PROJECT OVERVIEW This Technical Information Report (TIR) is for the replacement of the Renton Fire Station #16 for the Renton Regional Fire Authority, located at 15815 SE 128th St in Renton, Washington. Refer to Figure 1 – TIR Worksheet for basic site information. The proposed project site is comprised of four parcels (parcel numbers: 3664500008, 3664500330, 3664500009, and 3664500007). The project site is bounded by SE 128th St to the north, a neighboring church property to the east, single family residential properties to the west and south, and 158th Ave SE along the southwestern side. The project site can be accessed from SE 128th St in the north and from 158th Ave SE in the southwest corner. The site is located in Section 14, Township 23 North, Range 5 East, Willamette Principal Meridian. Refer to Figure 2 – Vicinity Map. The project site is currently developed with single-family structures and gravel driveways. The project proposes to demolish the existing on-site structures and redevelop the site with a new Fire Station building in the north, maintenance building, driveway and parking areas. The project also proposes improvements to the adjacent right of ways along SE 128th St and 158th Ave SE. The storm drainage design will be in accordance with the requirements of the 2022 Surface Water Design Manual amendment (RSWDM) and 2021 King County Surface Water Design Manual (KCSWDM) as adopted by the City of Renton, as well as, additional stormwater requirements in the City of Renton Code and the City’s Standard Details. Existing Conditions and Hydrology The project site parcel is approximately 3.38 acres (147,314 SF). According to City of Renton critical areas mapping, there are no designated sensitive areas on the existing site. The current zoning classification for all of the subject parcels is R-4 Residential and located within the City of Renton. GeoEngineers, Inc. completed a Geotechnical Report, dated March 25, 2025. Their field study included 10 exploration borings across the site ranging between 10.5 to 50.5 feet below the ground surface. The explorations typically encountered existing fill soils, generally consisting of soft/loose to medium dense sandy silt/silty sand with variable organic and gravel content ranging between 2 to 7.5 feet below the ground surface. Below the fill soils weathered glacial till soils, which consisted of medium dense to dense silty sand, were observed between 4 to 9 feet below the ground surface. Very dense unweathered glacial till soils, consisting of very dense silty sand with variable gravel content, beginning at a depth ranging from about 5 to 10 feet below the ground surface and extending to the depths explored were observed below the layer of weathered glacial till. LPD Engineering, PLLC Page 2 Renton Fire Station #16 Technical Information Report, July 1, 2025 Based upon GeoEngineers evaluation, the on-site soils are not suitable for infiltration. Per Section 5.0: “Design of infiltration facilities will be constrained at the site because of the relatively high percentage of fines and low permeability of the native glacial soils. We anticipate the native glacial soils will have a very slow infiltration rate (permeability on the order of 10 -5 to 10 -6 centimeters per second or typical infiltration rates less than 0.1 inches per hour). Furthermore, we anticipate a seasonally perched groundwater will be present above the weathered glacial till and/or relatively unweathered glacial till soils. Depending on the design configuration, below-grade infiltration facilities are likely not feasible due to seasonally perched groundwater and the hydraulic restrictive layers encountered at the site.”. The full Geotechnical Report is attached in Appendix F. Topographically, the site slopes down from the southwest to the northeast from a high elevation of approximately 548-feet at the southwest corner of the westernmost parcel (3664500009). The lowest point on the multiple parcel property sits at approximately 529-feet at the northeast corner of the easternmost parcel (3664500330) adjacent to SE 128th Street. The project site has two threshold discharge areas that discharge to separate drainage basins. Threshold Discharge Area 1 (TDA 1) includes the majority of the stormwater from the site, flows norther-easterly to discharge to May Creek drainage basin. Threshold Discharge Area 2 (TDA 2) includes a small area on the southwestern most parcel, and flows southerly, and discharges to the Lower Cedar River drainage basin. Refer to the Offsite Analysis section of this report for further information. Proposed Site Improvements and Hydrology The proposed project improvements will include a Fire Station building and maintenance building with a central driveway connecting access to both buildings, and 158th Ave SE and SE 128th St. There will be three parking areas, one located in the northeast corner, one located south of the fire station building and one located south of the maintenance building. Refer to Figure 6 – Proposed Conditions. Per coordination with the City of Renton, improvements will be made to the frontage along SE 128th St to support two proposed driveways, a sidewalk and street trees. Frontage on 158th Ave SE will be improved to support the southwest driveway access and frontage improvements. The project will also include a 905 feet 8-inch diameter public sewer mainline extension in 158th Ave SE from the site to existing 8-inch diameter public sewer mainline in SE 132nd PL. Sewer stubs will be provided for each residence. The utility installation will remove and replace the existing roadway pavement with in kind material per City of Renton Standards as well as grind and overlay the existing pavement to full extents of the west lane. The project proposes 81,305 SF (1.87 acres) total of new plus replaced impervious surface. In order to preserve the drainage patterns of the existing site, the post-developed grading of the project site has been designed to maintain the existing threshold discharge areas, to the extent feasible. TDA 1 is comprised of 4.24 acres located within the project site and adjacent right-of-way along SE 128th St, with 79,469 SF (1.82 acres) of new plus replaced impervious surface. Refer to Figure 6 – Proposed Conditions, for a visual representation of the proposed project areas. Stormwater runoff from TDA 1 will be collected in a series of catch basins and trench drains and routed via pipe conveyance systems to one of three detention facilities: an SC-740 StormTech Chamber system LPD Engineering, PLLC Page 3 Renton Fire Station #16 Technical Information Report, July 1, 2025 located in the north portion of the site and two detention vaults located in the eastern area of the site. The three systems will each have a flow control structure to attenuate flows. Pollution generating surfaces will be routed to a Modular Wetland System for water quality treatment downstream of all three detention facilities at the northeast corner of the site. The detained and treated discharge will discharge to the existing ditch near the northeast corner of the site at SE 128th St. TDA 2 is comprised of 0.14 acres of onsite pervious surface and right-of-way improvements on the east side of 158th Ave SE, with 1,835 SF (0.04 acres) of new plus replaced impervious surface. Refer to Figure 6 – Proposed Conditions, for a visual representation of the proposed project areas. Stormwater runoff from TDA 2 will be collected in a culvert in the right-of-way on the east side of 158th Ave SE. The stormwater will continue to follow the existing downstream pathway. Refer to Section 4 – Flow Control and Water Quality Analysis and Design for further information on the storm drainage design. SECTION 2 – CONDITIONS AND REQUIREMENTS SUMMARY Per Figure 1.1.2.A, Flow Chart for Determining Type of Drainage Review Required of the RSWDM, the project is subject to a Full Drainage Review because it results in greater than 2,000 square feet (SF) of new plus replaced impervious surface, is not defined as a large project or single-family residential project and results in less than 50 acres of new impervious surface. Per Table 1.1.2.A, Requirements Applied Under Each Drainage Review Type, the TIR addresses Core Requirements (CR) 1 through 9 and Special Requirements (SR) 1 through 6 of the 2022 RSWDM. Additionally, per the RSWDM Chapter 1, the project is not considered a redevelopment project as the existing impervious coverage is less than 35%. This section addresses the requirements set forth by the 2022 Renton SWDM, Core and Special Requirements listed in Chapter 1. Core Requirements Core Requirement 1 – Discharge at Natural Location (1.2.1): The proposed conditions will maintain the existing discharge locations. As mentioned previously, the site is divided into two threshold discharge area, TDA 1 and TDA 2. Flow control detention facilities and BMPs will be implemented, thus attenuating discharge from the project area and creating no adverse impacts on the downstream system. Refer to the Offsite Analysis section of this report for a description of the existing discharge points from the site. Core Requirement 2 – Off-site Analysis (1.2.2): A Level 1 Downstream Analysis is in Section 3, Task 4. Core Requirement 3 – Flow Control (1.2.3): The proposed project improvements are greater than 5,000 SF of new plus replaced impervious surface. Per the City of Renton Flow Control Application Map, the project site is located within Flow Control Duration Standard area. Therefore, the flow duration of predeveloped rates for forested (historical) site conditions over the range of flows extending from 50% of 2-year up to the full 50- year flow AND matches peaks for the 2- and 10-year return periods. Per the RSWDM, flow control facilities must mitigate the runoff from the target surfaces which include new and replaced impervious surfaces that are not fully dispersed and new pervious surfaces that are not fully dispersed. LPD Engineering, PLLC Page 4 Renton Fire Station #16 Technical Information Report, July 1, 2025 The proposed project improvements in TDA 2 result in less than 0.15 cfs increase in 100-year peak flows, so flow control is not required nor provided in TDA 2. For further information regarding the flow control design, refer to Section 4 of this report. Core Requirement 4 – Conveyance System (1.2.4): Refer to Section 5 of this report for conveyance analysis. Core Requirement 5 – Erosion and Sedimentation Control (1.2.5): A Temporary Erosion and Sediment Control (TESC) plan has been included with the plan set. The TESC plan will be considered the minimum for anticipated site conditions. The Contractor will be responsible for implementing all TESC measures and upgrading as necessary. The TESC facilities will be in place prior to any demolition, clearing, grubbing or construction. Core Requirement 6 – Maintenance and Operations (1.2.6): The Operations and Maintenance Manual for the project is in Appendix D. Core Requirement 7 – Financial Guarantees and Liability (1.2.7): Financial guarantees and liability are not anticipated to be required since the Owner is a public agency. Core Requirement 8 – Water Quality (1.2.8): The proposed project improvements in TDA 1 result in more than 5,000 SF of new plus replaced pollution-generating impervious surface (PGIS), and therefore water quality treatment is required. As Fire Stations are considered a commercial land use, Enhanced Basic Water Quality Treatment is required. For further information regarding the water quality design requirements, refer to Section 4 of this report. The proposed project improvements in TDA 2 result in less than 5,000 SF of new plus replaced pollution-generating impervious surface (PGIS) AND less than ¾ acre of new pollution-generating pervious surface. Per the RSWDM Exemptions from Core Requirement #8, this area meets Exemption 1 Surface Area and therefore water quality treatment for TDA 2 is not be required. Core Requirement 9 – On-Site BMPs (1.2.9): The proposed improvements result in more than 2,000 SF of new plus replaced impervious surfaces, therefore an evaluation of BMP feasibility for all target surfaces is required. Per section 1.2.9.2 of the RSWDM, this project area will be subject to Large Lot BMP Requirements since the project site is larger than 22,000 SF. Refer to the On-Site BMPs evaluation within Section 4 of this report. Special Requirements Special Requirement 1 – Other Adopted Area-Specific Requirements (1.3.1): The City of Renton Surface Water Design Manual is one of several adopted regulations in the City of Renton that apply requirements for controlling drainage on an area-specific basis. Other adopted area-specific regulations include requirements that have a more direct bearing on the drainage design of a proposed project. These regulations include the following: • Master Drainage Plans (MDPs) – The project is not within an area covered by an approved Master Drainage Plan. Project is not a Master Planned Development, a Planned Unit Development, a subdivision that will have more than 100 lots, a commercial development that will construct more than 50 acres of impervious surface, and will not LPD Engineering, PLLC Page 5 Renton Fire Station #16 Technical Information Report, July 1, 2025 clear more than 500 acres within a drainage sub-basin. Therefore, a Master Drainage Plan is not required. • Basin Plans (BPs) – The Watershed Management Committee Lower Cedar River Basin and Nonpoint Pollution Action Plan, adopted 1997, was reviewed to determine if there are regulations applicable to this site. There are no additional water quality requirements listed by the report. • Salmon Conservation Plans (SCPs) – The project is not within an area governed by SCPs. • Lake Management Plans (LMPs) – The project is not within an area governed by an LMP. • Hazard Mitigation Plan – The proposed project is not within an area with a Hazard Mitigation Plan. • Shared Facility Drainage Plans (SFDPs) – The proposed project is not within an area with an SFDP. Special Requirement 2 – Flood Hazard Area Delineation (1.3.2): According to King County iMap, the project does not contain nor is it adjacent to a Flood Hazard Area. Special Requirement 3 – Flood Protection Facilities (1.3.3): The project does not have existing flood protection facilities, nor does it propose new flood protection facilities. Special Requirement 4 – Source Control (1.3.4): The applicable water quality source controls are evaluated based on RSWDM Section 1.3.4. The proposed conditions, kitchen facilities will involve activity A-8 listed within the 2022 King County Stormwater Pollution Prevention Manual (KCSPPM) that will require the use of source control measures. Activity A-8 includes storage of solid and food wastes (including cooking grease). Therefore, a grease interceptor will be required as a source control measure. Vehicle washing will be completed within the bays of the building, which drain to the sewer. Special Requirement 5 – Oil Control (1.3.5): Per the Definitions Section of the RSWDM, the project will not be considered a high-use site nor is it an existing high-use site. The expected average daily traffic count is expected to be less than 100 vehicles per day, which is far less than 100 vehicles per 1,000 square feet of gross building area (2400 vehicles per day). It is not subject to petroleum storage or transfer in excess of 1,500 gallons per year and it will maintain of a fleet of 14 vehicles that are over 10 tons net weight, which is less than threshold of 25. Therefore, oil control is not required. Special Requirement 6 – Aquifer Protection Area (1.3.6): The project is not located within an aquifer protection area. SECTION 3 – OFFSITE ANALYSIS The following is the Level 1 downstream analysis for the proposed project. Task 1 – Study Area Definition and Maps The downstream analysis was completed using the Site Survey, King County iMap, City of Renton GIS Mapping, an onsite investigation on May 8th, 2024 and the Geotechnical Report dated August 5th 2022. The detailed topographic information for the project area is shown in the design drawings. Refer to Figure 3 – Downstream Drainage Map 1 and Figure 4 – Downstream Drainage Map 2. LPD Engineering, PLLC Page 6 Renton Fire Station #16 Technical Information Report, July 1, 2025 Task 2 – Resource Review Basin Summary According to the site survey and GIS mapping, the project is situated within two threshold discharge areas to two drainage basins. The majority of the site is tributary to the May Creek drainage basin. A small portion of the southwestern area of the site is tributary to the Cedar River drainage basin. May Creek and the Cedar River both ultimately discharge to Lake Washington at approximately 4 miles downstream. Floodway Map The site is not located within a Floodway or Floodplain per the Washington State Department of Ecology Flood Maps and King County iMap. Sensitive Areas The following is a summary of SAO sensitive areas located within the project area or within the downstream drainage course from the project area. The King County iMap application was used to examine the SAOs. SAO Erosion Hazard – The project site and downstream areas are not located within an erosion hazard area. SAO Seismic Hazard – The project site and downstream areas are not located within a seismic hazard area. SAO Landslide Hazard – There are no landslide hazard areas located within or downstream of the project site. SAO Coal Mine – There are no coal mines located within or downstream of the project site. SAO Stream –There are no unclassified stream or any waterbodies through the project site. SAO Wetland – There is a Type 1 wetland located approximately 0.31 miles downstream of the project site and a Type 2 wetland located approximately 0.5 miles downstream of the project site. Groundwater Contamination – The project site is located in an area susceptible to groundwater contamination. It is not anticipated that this project will impact groundwater contamination. Sole Source Aquifer – The project site and downstream areas are not located within a sole source aquifer area. Critical Aquifer Recharge Area – The project site downstream areas are not considered a Critical Aquifer Recharge Area. Channel Migration Hazard – The project site and downstream areas are not located within a channel migration hazard zone. Soils Survey Refer to Section 1 of this report and Figure 5 - Soils Map for soils information. Wetlands Inventory According to City of Renton Mapping, there are no wetlands located within or directly adjacent to the project area. LPD Engineering, PLLC Page 7 Renton Fire Station #16 Technical Information Report, July 1, 2025 Section 303d List of Polluted Waters As mentioned previously, the majority of the project area is tributary to May Creek. According to the Washington State Department of Ecology’s Clean Water Act Section 303d list of polluted waters approximately 3 miles downstream of the site, a section of May Creek is listed as a Category 5 Waterbody due to temperature. It is not anticipated that this project will impact the temperature of May Creek. Landslide and Erosion According to City of Renton Mapping there are no landscape or erosion hazard zones located within or downstream of the project area. Task 3 – Field Inspection A field inspection and Level 1 Downstream analysis was conducted by LPD on May 7, 2024 to verify the on-site conditions, downstream drainage paths, and upstream basins. The weather during the site investigation was clear and sunny, with a temperature of approximately 65 degrees Fahrenheit. Task 4 – Drainage System Description and Problem Descriptions Below is a description of each TDA to a distance of approximately one-quarter mile downstream. TDA 1 The stormwater runoff from the site sheet flows towards the northern eastern corner where it discharges from the site into an existing open ditch system. Refer to Figure 3 – Downstream Drainage Map 1. From here the downstream path is as follows: 1. Stormwater is conveyed east along SE 128th St via an open ditch line for approximately 68-feet before entering a 12-inch concrete pipe system. 2. Stormwater is conveyed east via the 12-inch concrete pipe system for approximately 129-feet before entering a catch basin where the system transitions to 18-inch diameter concrete. 3. The stormwater is conveyed east along SE 128th St via the 18-inch concrete piped system for approximately 1840-feet, passing the ¼-mile mark downstream of the project site. 4. The stormwater enters an 18-inch plastic pipe system and is conveyed south for approximately 14 feet before the system becomes 24-inch diameter plastic pipe. 5. The stormwater is conveyed east via the 24-inch plastic pipe system for approximately 44-feet before reaching a catch basin. 6. The stormwater exits the catch basin and is conveyed east for approximately 35-feet via a 24- inch diameter concrete pipe before entering another catch basin. 7. The stormwater exits the catch basin and is conveyed southeast conveyed via a 24-inch diameter corrugated polyethylene pipe for approximately 41-feet before flowing into a 6-foot bioretention swale maintained by King County. 8. The stormwater discharges from the bioretention swale into a stream approximately 0.31 miles from the site. 9. The stream flows north along 164th Ave SE, through a series of open ditch lines and driveway culverts before crossing 164th Ave SE. The stormwater eventually discharges to May Creek approximately 1 mile from the site. May Creek outlets to Lake Washington. TDA 2 LPD Engineering, PLLC Page 8 Renton Fire Station #16 Technical Information Report, July 1, 2025 A small portion of stormwater runoff from the southern area of the site sheet flows towards 158th Ave SE and enters into the existing ditch line system along the east side of 158th Ave SE. Refer to Figure 4 – Downstream Drainage Map 2. From here the downstream path is as follows: 1. Stormwater flows south along 158th Ave SE conveyed through a series of open ditch line and culverts for approximately 460 feet before reaching a shared driveway and entering a 12-inch diameter concrete piped system. 2. Stormwater continues south along 158th Ave SE conveyed via the 12-inch diameter concrete pipe system for approximately 332 feet before reaching the intersection of 158th Ave SE and NE 2nd Pl. 3. Stormwater is conveyed south across NE 2nd Pl via a 12-inch diameter polyethylene pipe system for approximately 43 feet before reaching an open ditch channel. 4. Stormwater continues to flow south along 158th Ave SE through the open ditch channel for approximately 46 feet before reaching a 12-inch diameter corrugated metal pipe (CMP). 5. Stormwater is conveyed approximately 70 feet via the 12-inch diameter corrugated metal pipe system before transitioning to a 12-inch diameter polyethylene system. 6. The stormwater continues to be conveyed south via the 12-inch diameter polyethylene pipe system for approximately 336 feet before reaching a catch basin and transitioning to a 16-inch diameter ductile iron pipe. 7. Stormwater is conveyed along 158th Ave SE via the 16-inch diameter ductile iron pipe for approximately 9 feet before entering an open ditch system. 8. Stormwater flows through the open ditch system for approximately 24-feet, passing the ¼-mile mark downstream of the project site before entering a 12-inch concrete driveway culvert. 9. From here the stormwater continues via piped and open ditch systems until approximately 1 mile from the site where it discharges at a discharge point and flows into the Cedar River. The Cedar River ultimately discharges to Lake Washington. Task 5 – Mitigation of Existing or Potential Problems During the desk investigation and field investigation May 7th, 2024 there were no signs of erosion or overtopping of the downstream drainage system. At this time, the existing downstream drainage course appears to have adequate capacity to convey the proposed mitigated flows from the project. SECTION 4 – FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Exiting Hydrology Please refer to Section 1 – Project Overview and Section 3 – Offsite Analysis of this report for a description of the existing hydrology. Developed Site Hydrology Please refer to Section 1 – Project Overview and the Flow Control System Section of this report for the full description of the proposed site hydrology. Performance Standards Please refer to Section 2 - Conditions and Requirements Summary, and the On-Site BMPs, Flow Control System, and Water Quality sections of this report for a description of the required standards applicable to this report. LPD Engineering, PLLC Page 9 Renton Fire Station #16 Technical Information Report, July 1, 2025 On-Site BMPs Per Core Requirement #9, the project improvements result in more than 2,000 SF of new plus replaced impervious surfaces, therefore an evaluation of BMP feasibility for all target surfaces is required. Per section 1.2.9.2 of the RSWDM, the project improvements will be subject to Large Lot BMP Requirements since the project site is larger than 22,000 SF. Due to the fill and glacial till found on the project site, there is no suitable stormwater infiltration receptor for infiltration BMPs. For these reasons, the LID performance standard cannot be achieved. Below is an evaluation of BMP feasibility for the site and frontage improvements. The Geotechnical report (See Appendix F) states that typical infiltration rates will be less than 0.1 inches per hour), and a seasonally perched groundwater will be present above the weathered glacial till. BMP Evaluation per Appendix C of the RSWDM: 1. Full Dispersion: Full Dispersion is infeasible, per section C.2.1.1, for all surfaces due to a lack of native vegetation and space. 2. Full Infiltration of Roof Runoff: As mentioned previously in the Existing Conditions Section of this Report, per the geotechnical evaluation by Geoengineers, the site soils are not suitable for infiltration. 3. Since the target impervious surfaces could not be mitigated by Requirements 1 and 2 above, the following has been reviewed and implemented where feasible: • Full Infiltration: Full infiltration of runoff from target surfaces is not feasible. As stated above: the on-site soils are not suitable for infiltration. • Limited Infiltration: As stated above: the on-site soils are not suitable for infiltration. Therefore, limited infiltration is considered infeasible. • Bioretention: Per Section C.2.6, a bioretention facilities without underdrains are considered infeasible, per Criteria #20 a vertical separation of 3 feet to the impervious layer cannot be achieved below the bioretention for areas that meet or exceed 5000 SF of PGIS. As stated above: the on-site soils are not suitable for infiltration. Per Section C.2.6.1.5 underdrains are not permitted by the City of Renton to meet Core Requirement #9. • Permeable Pavement: Per section C.2.7 Criteria #24, the use of permeable is in-feasible because as mentioned previously in the Existing Conditions Section of this report, the geotechnical evaluation indicated that the infiltration rate is less than 0.3 inches per hour. Additionally, as mentioned previously in the Existing Conditions Section of this report, there is anticipated to be seasonally perched ground water present at the site above the impermeable dense to very dense glacial soils. 4. Basic Dispersion: is not feasible to be used as BMP per Section C.2.4 of the RSWDM due to the limited vegetative flow path downstream of the target surfaces. Flow Control System TDA 1 is required to meet the Flow Control Duration Standard Matching Forested Site Conditions, for which the project developed discharge durations shall not exceed predeveloped durations for the range of predeveloped discharge rates from 50% of the 2-year peak flow up to the full 50-year peak flow. Developed peak discharge rates shall not exceed predeveloped peak discharge rates for the 2-year and 10-year return periods. Per the RSWDM forested site conditions as the predeveloped condition. Per the RSWDM, flow control facilities must mitigate the runoff from the target surfaces which include new and replaced impervious surfaces that are not fully dispersed and new pervious surfaces that are not fully dispersed. LPD Engineering, PLLC Page 10 Renton Fire Station #16 Technical Information Report, July 1, 2025 TDA 2 Per the Flow Control Duration Standard Areas Exception 3, “The facility requirement in Flow Control Duration Standard Matching Forested Site Conditions Areas is waived for any threshold discharge area in which there is no more than a 0.15-cfs difference (when modeled using 15 minute time steps) in the sum of developed 100-year peak flows for those target surfaces subject to this requirement and the sum of forested (historical) site conditions 100-year peak flows (modeled using same time step unit (e.g., 15 minute) used to calculate the developed flow) for the same surface areas.”. The proposed project improvements in TDA 2 result in a difference of 0.06 cfs, which is less than 0.15 cfs. Therefore, the proposed improvements in TDA 2 meet the criteria for Exception 3 and flow control is not required. See Appendix B for the WHMM report for the comparison of the 100-year peak flows in TDA 2. Refer to Figure 6 – Proposed Conditions for the delineation between the threshold discharge areas. Per RSWDM Chapter 1 the definition of new pervious surface includes the conversion of a native vegetated surface or other nonnative pervious surface to non-native pervious surface (e.g. conversion of forest or meadow to pasture land, grass land, cultivated land, lawn, landscaping, bare soils, etc.), or any alteration of existing non-native pervious surface that significantly increases surface and storm water runoff (e.g., conversion of pasture land, grass land, or cultivated land to lawn, landscaping, or bare soil; or alteration of soil characteristics). The existing site includes areas of landscape and lawn. The proposed landscape improvements will also include landscape and lawn areas. Some existing areas can be described as native vegetation that proposed improvements convert to lawn areas, but not all. For existing lawn areas that are also lawn in the proposed condition, there will be no modification of runoff characteristics from the pervious areas and these areas are not included as target surface areas. New pervious surfaces that are existing native vegetation converted to lawn are tabulated as target surfaces in Figure 7 – Proposed Modeled Conditions. Per RSWDM Chapter 1 definition, replaced impervious surface “does not include the removal of pavement material through grinding or other surface modification unless the entire layer of PCC or AC is removed”. Therefore, the areas of proposed grind and overlay improvements included in both frontages for TDA 1 on SE 128th St, for TDA 2 on 158th Ave SE and for the offsite improvements along 158th Ave SE are not included as replaced impervious surface. Additionally, per the RSWDM Chapter 1 definition for replaced impervious surface excludes impervious surface removed for the sole purpose of installing utilities. Therefore, the offsite improvements for the proposed sewer and water connections along 158th Ave SE are not counted as replaced impervious surface. As shown in Figure 6 – Proposed Conditions, the total new and replaced impervious area for TDA 1 is 79,469 SF (1.82 acres). As discussed in the On-site BMPs Section above, full dispersion for these surfaces is infeasible. Due to the site elevations, some areas of impervious surface were unable to be routed to detention. These areas include the northeastern area of the right-of-way frontage improvements on SE 128th St and northeastern driveway access, which total 3,678 SF (0.084 acres) of target surface area. In lieu of mitigating these areas 4,013 SF (0.092 acres) of the existing roadway along SE 128th will be collected and routed to the proposed detention system as compensatory area, shown in Figure 7 – Proposed Modeled Conditions. Per Section 1.2.3.2.G of the 2022 RSWDM, below is a description and evaluation of the mitigation trade for this project: LPD Engineering, PLLC Page 11 Renton Fire Station #16 Technical Information Report, July 1, 2025 1. The existing developed non-target surface area (i.e., an area of existing impervious surface and/or nonnative pervious surface) must have runoff discharge characteristics (i.e. peak flow and volume) equivalent to those of the target surface area for which mitigation is being traded and must not be currently mitigated to the same flow control performance requirement as the target surface area. Evaluation: To match runoff discharge characteristics of the target surface area being traded, a non-target surface area of similar land cover, (e.g. pavement), was selected that was not currently mitigated to the same flow control performance requirement as the target surface area. 2. Runoff from both the target surface area being traded and the flow control facility must converge prior to discharge of the runoff from the target surface area being traded onto private property without an easement or through any area subject to erosion Evaluation: Runoff combines in the public ditch, so neither condition is applicable. 3. The net effect in terms of flow control at the point of convergence downstream must be the same with or without the mitigation trade Evaluation: Discharge from the Mitigated Site, TDA 1, plus the bypass area meets the required flow control per flow control calculations included in Appendix B. 4. The undetained runoff from the target surface area being traded must not create a significant adverse impact to downstream drainage systems, salmonid habitat, or properties prior to convergence with runoff from the flow control facility Evaluation: Undetained runoff (0.084 acres) flows in a new pipe then meets the detained runoff at the culvert outlet in the roadside ditch and therefore does not create an adverse impact on the downstream system. 5. Mitigation trade proposals must be reviewed and approved with input from the City of Renton Evaluation: This proposal is submitted for review by the City of Renton. 6. The existing non-targeted surface area that is mitigated for purposes of the required flow control must be documented and tracked by CED. Documentation should clarify that future redevelopment of the existing non-targeted area used for mitigation trade will incur additional flow control mitigation requirements if the redevelopment exceeds Core Requirement #3 thresholds. This additional flow control mitigation must be met in addition to that previously required and provided for the mitigation trade. Applications must consider sizing flow control facilities sufficient for both the mitigation trade are and future development of the existing non-targeted area if feasible. Evaluation: Documentation to be tracked by CED. LPD Engineering, PLLC Page 12 Renton Fire Station #16 Technical Information Report, July 1, 2025 The flow control for TDA 1 is provided by a StormTech SC-740 Chamber System and two Detention Vaults, with associated flow control structures. Refer to Figure 7 – Proposed Modeled Conditions which shows the contributing areas to each of the detention facilities. The Western Washington Hydrology Model 2012 (WWHM) was used to model the detention facilities for the site. Illustration 1 below shows the routing of the facilities in the model for each detention facility. This model demonstrates that the release rates from the site are less than the allowable release rates required, see Table 1 below for detention facility details. See Appendix B for the WHMM report for each of the detention facilities. The result of the WWHM Model was a 48 Chamber SC-740 StormTech System, a 72 feet by 34 feet by 7 feet deep vault, and a 133 feet x 19 feet x 7 feet deep vault. Further details of the detention requirements are listed in Table 1. Table 1 – Detention Facility Details StormTech Chamber Detention Detention Vault 1 (South) Detention Vault 2 (North) Dimensions 70’ x 30’ x 3.5’ 72’ x 34’ x 7’ 133’ x 19’ x 7’ Total Available Storage Volume (cf) 4,158 17,136 17,689 LPD Engineering, PLLC Page 13 Renton Fire Station #16 Technical Information Report, July 1, 2025 Illustration 1 – Combined Outflow Overflow Conditions The unmitigated 100-year peak flow from the proposed site is 0.95, 1.13, and 0.43 cfs for Vault 1, Vault 2, and the StormTech, respectively. Per Figure 5.4.4.H Riser Inflow Curves in the 2022 RSWDM, for the proposed 12” riser this peak flow rate operates in the weir condition with a head of 0.22, 0.24, and 0.22 feet from the crest of riser for Vault 1, Vault 2, and the StormTech, respectively. See Appendix B for Riser Inflow Curve. Water Quality System Per Core Requirement #8, the proposed project improvements in TDA 1 result in more than 5,000 SF of new plus replaced pollution-generating impervious surface (PGIS), and therefore will require water quality treatment. As Fire Stations are considered a commercial land use, Enhanced Basic Water Quality Treatment is required. The proposed project improvements in TDA 2 result in less than 5,000 SF of new plus replaced pollution-generating impervious surface (PGIS) AND less than ¾ acre of new pollution-generating pervious surface. Per the RSWDM Exemptions from Core Requirement #8, this area meets Exemption 1 Surface Area and therefore water quality treatment for TDA 2 is not be required. Water quality treatment will be required for 48,201 SF (1.11 acres) of pollution-generating impervious surface which include the proposed concrete driveways, parking lot and parking areas. Due to the site elevations, certain areas of pollution-generating impervious surface were unable to be routed to water quality treatment. These areas include the northeastern area of the right-of-way frontage improvements pavement along SE 128th St and northeastern driveway access, which total 2,204 SF (0.051 acres) of PGIS surfaces. In lieu of treating these areas, 4,013 SF (0.092 acres) of the existing LPD Engineering, PLLC Page 14 Renton Fire Station #16 Technical Information Report, July 1, 2025 roadway along SE 128th will be treated by the northern water quality basin #3 shown in Figure 7 – Proposed Modeled Conditions. Water quality treatment will be provided by one Modular Wetland Systems (MWS), which have General Use Level Designation (GULD) approval by Ecology for enhanced treatment. This approval is provided in Appendix B for reference. The water quality facilities will be located downstream of the detention systems, per section 6.2.1 of the 2022 RSWDM, the water quality design flow rate will be the full 2-year release rate from the detention facility will be treated. Per Table 6.2.1.A, adjustment factor k has been applied to the water quality flow rate to modify it from the modeled rate. See Appendix B for the WWHM output for the water quality design flow rate for each facility. Refer to Figure 7 – Proposed Modeled Conditions for the proposed location of the three water quality basins. Sizing of the Modular Wetland System has been conducted by Contech Engineered Solutions and provided in Appendix B of this Report. SECTION 5 – CONVEYANCE SYSTEMS ANALYSIS AND DESIGN An analysis of the onsite conveyance system has been performed per section 1.2.4 of the 2022 RSWDM is provided in Appendix B. The new pipes and culverts will be designed to accommodate the 25-year peak flow from the tributary area. For conservative pipe sizing the 100-year peak flow will also be included in the backwater analysis. SECTION 6 – SPECIAL REPORTS AND STUDIES A Geotechnical Report has been prepared by GeoEngineers, Inc., dated March 18, 2025. This report is provided in Appendix F. SECTION 7 – OTHER PERMITS Coverage under the Construction Stormwater General Permit through the Department of Ecology will be required for the project because it disturbs over one (1) acre of land area. The NOI and public noticing required for this permit will be completed later in the design process, prior to construction. SECTION 8 – CSWPPP ANALYSIS AND DESIGN A Construction stormwater pollution prevention plan (CSWPP) including a Stormwater Pollution Prevention and Spill Control Plan (SWPPS) and a Temporary Erosion and Sediment Control (TESC) plan is provided in Appendix C. The TESC plan includes temporary sediment settling tanks, sized using the methodology from the 2022 RSWDM. A copy of the Sediment Facility Sizing Calculations worksheet and the associated output from MGS Flood used for the sediment tank sizing are included in Appendix B. The TESC plan will be considered the minimum for anticipated site conditions. The Contractor will be responsible for implementing all TESC measures and upgrading as necessary. The TESC facilities will be in place prior to any demolition or construction. LPD Engineering, PLLC Page 15 Renton Fire Station #16 Technical Information Report, July 1, 2025 SECTION 9 – FACILITY SUMMARIES, DECLARATION OF COVENANT, AND BOND QUANTITIES A Facility Summaries and Drainage Declaration of Covenant, and Bond Quantities Worksheet is provided in Appendix E. As a public agency, this project does not need to submit a Bond but the Bond Quantities Worksheet is required to determine the permitting cost. SECTION 10 – OPERATIONS AND MAINTENANCE MANUAL The Operations and Maintenance Manual is provided in Appendix D of this report. This will include maintenance recommendations associated with the conveyance pipes, catch basins, flow control structures, StormTech chamber detention facility, detention vault, and the Modular Wetland System (water quality facility). LPD Engineering, PLLC Page 16 Renton Fire Station #16 Technical Information Report, July 1, 2025 FIGURES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: Downstream Drainage Map 1 Figure 4: Downstream Drainage Map 2 Figure 5: Soils Map Figure 6: Proposed Conditions Figure 7: Proposed Modeled Conditions Figure 8: Existing Drainage Figure 9: Conveyance Tributary Areas 1932 First Ave, Suite 500 Seattle, Washington 98101 p. 206.725.1211 lpdengineering.com SITE VISIT REPORT Date: March 6, 2025 Project: Renton Fire Station #16 Time On-site: 5pm – 6pm LPD Field Rep: Marc Servizi Weather: 55° setting sun, dry. Attendees: Halcyon Bjornstad pastorhalcyon@lollc.org Donald Highley <dhighley@rentonrfa.org> Marie Hillard marie.hillard@gmail.com Michelle Langrehr <michelle@tca-inc.com> Purpose During the public presentation portion of the Hearing Examiner public meeting on February 25, Marie Hillard commented that the church was experiencing drainage problems near their Pre-School Building and would the new Fire Station make the drainage conditions better or worse? Marc Servizi agreed to meet on site to observe the conditions. Observations and Discussion · Pre-School Building Drainage Conditions o Shallow hand dug ditch around the west corner of the building. Contains shallow water. It appears that it would drain northerly, but the low point is adjacent to the building corner. The ditch would need to be dug deeper to the north to allow it actively drain. o A shallow perforated pipe has been installed in part of the ditch, presumably it is connected to the foundation drain. o Clean gravel installed against the building footing. Footing drain location and condition unknown. o Downspouts enter the ground at building corners. Connection point unknown. o The cut slope to the west has partially sloughed towards the ditch and is very wet. Soil that was excavated from the swale has been placed on the cut slope. o These conditions have been occurring as long as Marie and Halcyon have been involved with the church. o The church building is approximately 30’ from the property line. The ditch is about 23’ from the property line and 6’ – 8’ below grade at the property line. o Discussion with Marie, Marc: Guidance to the church: The footing drain and downspouts should be visually inspected and located. They both need to drain away from the building. The swale should be dug deeper to the north to allow it to drain. Both projects are a challenge, since the ground is generally flat and forested to the north before dropping into a swale draining further north. March 6, 2025 Site Visit Report Fire Station #16- Adjacent Church Property Page 2 · Upstream Conditions - Existing o Existing sheet flow across the fire station (currently vacant) is SW to NE. o Tributary area per map, below. o Marie and Halcyon have not observed surface sheet flow coming across the property line. o The sloughing appears to be sourced due to perched groundwater – approx. 5’ – 10’ below grade. o Because the future fire station site is mostly pervious, most of the runoff is likely moving as interflow, in the upper few feet of soil, and may be perched on the underlying glacial till layer (hard-pan). Marie agreed that this seemed for fit with their observations. · Upstream Conditions – Proposed o The new fire station will divert all impervious (ie roof and pavement) surface runoff to the ditch on 128th. o Only a small amount of landscape will drain towards the church property. o The new fire station will provide underground detention vaults. Both vaults include a foundation / footing drain which will collect perched groundwater to drain towards the ditch in 128th, so will divert at least some of the perched groundwater away from the preschool. Vault #1 is located directly adjacent to the preschool. · Summary o The new fire station will divert all of the runoff from impervious surfaces. This will also reduce the amount of water flowing as interflow within the soil. o Only a relatively small amount of runoff from Landscape areas would drain towards the property line. o Groundwater seepage will be reduced by the new fire station to underground vaults and utilities. o Marie and Pastor Halcyon were happy to hear the news and glad to welcome the new neighbors – especially for the pre-schoolers! March 6, 2025 Site Visit Report Fire Station #16- Adjacent Church Property Page 3 Photos: Picture #1 Location: West side of Pre-school building. . Picture #2 Location: North West side of Pre-school building. March 6, 2025 Site Visit Report Fire Station #16- Adjacent Church Property Page 4 Picture #3 Location: Future Fire Station site. Existing Drainage Map Submitted by: Marc Servizi, PE CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land Use (e.g., Subdivision / Short Subd.) Building (e.g., M/F / Commercial / SFR) Grading Right-of-Way Use Other _______________________ DFW HPA COE 404 DOE Dam Safety FEMA Floodplain COE Wetlands Other ________ Shoreline Management Structural Rockery/Vault/_____ ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final: Full Targeted Simplified Large Project Directed __________________ __________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final: Full Modified Simplified __________________ __________________ __________________ TBD Marc Servizi, PE LPD Engineering PLLC (206) 725 - 1211 Renton Regional Fire Station #16 Renton, WA 98059 X X X X X X 15815 SE 128th St 18002 108th Ave SE Renton, WA 98055 23 North 5 East 14 (425) 276-9500 Renton Regional Fire Authority REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: _____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream ________________________ Lake ______________________________ Wetlands ____________________________ Closed Depression ____________________ Floodplain ___________________________ Other _______________________________ _______________________________ Steep Slope __________________________ Erosion Hazard _______________________ Landslide Hazard ______________________ Coal Mine Hazard ______________________ Seismic Hazard _______________________ Habitat Protection ______________________ _____________________________________ N/A N/A May Creek Drainage Basin N/A None planned at this time. REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ Other________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No North Basin, TDA #1 1 TBD Glacial Till 5/7/2024 Soil Type, High Groundwater X X 8% to 15%low to moderate Flow Control Duration Standard REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: Infeasible due to high groundwater, low permeability soils. Fire Station Stormtech Chamber System, 2 Concrete Detention Vaults and 4 Modular Wetland Systems. REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ Other________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No South Basin - TDA #2 1 TBD 5/7/2024 #3: Exempt for less than 0.15 cfs increase. REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: Exempt for less than 0.15 cfs increase. N/A REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-5 Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust Control Flow Control Control Pollutants Protect Existing and Proposed BMPs/Facilities Maintain Protective BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize exposed surfaces Remove and restore Temporary ESC Facilities Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore operation of BMPs/Facilities as necessary Flag limits of sensitive areas and open space preservation areas Other _______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Description Water Quality Description On-site BMPs Description Detention Infiltration Regional Facility Shared Facility Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Full Dispersion Full Infiltration Limited Infiltration Rain Gardens Bioretention Permeable Pavement Basic Dispersion Soil Amendment Perforated Pipe Connection Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ X X X X X X X X X X X X X X X X X X StormTech System and (2) Detention Vaults Modular Wetland System REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6 Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other ____________________________ Cast in Place Vault Retaining Wall Rockery > 4′ High Structural on Steep Slope Other _______________________________ Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. ____________________________________________________________________________________ Signed/Date X X RENTON FIRE STATION 16 2VICINITY MAP 1932 First Ave Suite 500 Seattle, WA 98101 p. 206.725.1211 f. 206.973.5344 www.lpdengineering.comengineering pllc SE 132ND PL156TH AVE SESE 133RD ST156TH AVE SESE 128TH STSE 128TH ST 156TH AVE SESE 132ND ST 158TH AVE SESE 130TH ST SE 131ST ST SE 132ND ST SE 127TH ST160TH AVE SE160TH AVE SE 2024 LPD Engineering PLLC©1932 First AveSuite 500Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllcRENTON FIRE STATION 163DOWNSTREAMDRAINAGE MAP 1 1932 First Ave, Suite 500, Seattle, WA 98101 p. 206.725.1211 f. 206.973.5344 www.lpdengineering.comengineering pllc 2024 LPD Engineering PLLC© RENTON FIRE STATION 16 4DOWNSTREAM DRAINAGE MAP 2 Drainage from TDA #2 Only MAP UNIT SYMBOL KING COUNTY AREA, WASHINGTON (WA663) MAP UNIT NAME engineering pllc 7936 Seward Park Ave S, Seattle, WA 98118 p. 206.725.1211 f. 206.973.5344 www.lpdengineering.com RENTON FIRE STATION 16 5SOILS MAP SE 128TH ST AgC Alderwood Gravelly Sandy Loam, 8% to 15% slopes Bh Bellingham silt loam Sk Seattle muck W Water T2024 LPD Engineering PLLC©1932 First AveSuite 500Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllcRENTON FIRE STATION 166PROPOSED CONDITIONS T2025 LPD Engineering PLLC©1932 First AveSuite 500Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllcRENTON FIRE STATION 167PROPOSED MODELEDCONDITIONS FIGURE 8 EXISTING DRAINAGE CHURCH 1.65 Ac 0.2Ac 1.2Ac MAY CREEK BASIN CEDAR RIVER BASIN 2.5 Ac Hand dug swale T2024 LPD Engineering PLLC©1932 First AveSuite 500Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllcRENTON FIRE STATION 169CONVEYANCETRIBUTARY AREAS LPD Engineering, PLLC Page 17 Renton Fire Station #16 Technical Information Report, July 1, 2025 APPENDIX A Design Drawings