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Home My WebLink AboutExhibit 13_Drainage Report.pdf Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Preliminary Technical Information Report PREPARED FOR: Roger Hansen HHJ Architects, PLLC 601 St. Helens Avenue Tacoma, WA 98402 PROJECT: Walker Auto Dealership 3400 East Valley Road Renton, WA 98057 2180100.10 PREPARED BY: Bart Brynestad, PE Senior Engineer REVIEWED BY: J. Matthew Weber, PE Principal DATE: May 2018 RECEIVED 05/02/2018 amorganroth PLANNING DIVISION Preliminary Technical Information Report PREPARED FOR: Roger Hansen HHJ Architects, PLLC 601 St. Helens Avenue Tacoma, WA 98402 PROJECT: Walker Auto Dealership 3400 East Valley Road Renton, WA 98057 2180100.10 PREPARED BY: Bart Brynestad, PE Senior Engineer REVIEWED BY: J. Matthew Weber, PE Principal DATE: May 2018 I hereby state that this Preliminary Technical Information Report for the Walker Auto Dealership project has been prepared by me or under my supervision, and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that the City of Renton does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. Preliminary Technical Information Report Walker Auto Dealership i 2180100.10 Table of Contents 1.0 Project Overview ......................................................................................................................... 1-1 Purpose and Scope.......................................................................................................... 1-1 1.1 Existing Conditions........................................................................................................... 1-1 1.2 Post-Development Conditions ......................................................................................... 1-1 1.3 Section 1.0 Figures Figure 1-1 ......... TIR Worksheet Figure 1-2 ......... Site Location Figure 1-3 ......... Drainage Basin and Site Map Figure 1-4 ......... City of Renton Soils Survey 2.0 Conditions and Requirements Summary ................................................................................. 2-1 Core Requirements .......................................................................................................... 2-1 2.1 2.1.1 CR 1 – Discharge at the Natural Location .......................................................... 2-1 2.1.2 CR 2 – Offsite Analysis ....................................................................................... 2-1 2.1.3 CR 3 – Flow Control ............................................................................................ 2-1 2.1.4 CR 4 – Conveyance System ............................................................................... 2-1 2.1.5 CR 5 – Construction Stormwater Pollution Prevention ....................................... 2-1 2.1.6 CR 6 – Maintenance and Operations ................................................................. 2-1 2.1.7 CR 7 – Financial Guarantees and Liability ......................................................... 2-1 2.1.8 CR 8 – Water Quality Facilities ........................................................................... 2-1 2.1.9 CR 9 – Onsite Best Management Practices (BMPs) .......................................... 2-2 2.1.10 SR 1 – Other Adopted Area-Specific Requirements........................................... 2-2 2.1.11 SR 2 – Flood Hazard Area Delineation ............................................................... 2-2 2.1.12 SR 3 – Flood Protection Facilities ....................................................................... 2-3 2.1.13 SR 4 – Source Controls ...................................................................................... 2-3 2.1.14 SR 5 – Oil Control ............................................................................................... 2-3 2.1.15 SR 6 – Aquifer Protection Area ........................................................................... 2-3 Section 2.0 Figures Figure 2-1 ......... Flood Insurance Rate Map Figure 2-2 ......... City of Renton Groundwater Protection Areas 3.0 Offsite Analysis ........................................................................................................................... 3-1 Task 1 – Study Area Definition and Maps........................................................................ 3-1 3.1 Task 2 – Resource Review .............................................................................................. 3-1 3.2 Task 3 – Field Inspection ................................................................................................. 3-1 3.3 Task 4 – Drainage System Description and Problem Descriptions ................................. 3-1 3.4 Preliminary Technical Information Report Walker Auto Dealership ii 2180100.10 Section 3.0 Figures Figure 3-1 ......... City of Renton Effective FEMA Flood Insurance Rate Map 4.0 Flow Control and Water Quality Facility Analysis and Design ............................................... 4-1 Flow Control ..................................................................................................................... 4-1 4.1 4.1.1 Existing Site Hydrology (Part A) .......................................................................... 4-1 4.1.2 Developed Site Hydrology (Part B) ..................................................................... 4-1 4.1.3 Performance Standards (Part C) ........................................................................ 4-2 4.1.4 Flow Control System (Part D) ............................................................................. 4-2 Water Quality System (Part E) ......................................................................................... 4-2 4.2 Section 4.0 Figures Figure 4-1 ......... City of Renton Flow Control Application Map – Reference 15-A Figure 4-2 ......... Preliminary WWHM Flow Control Calculations 5.0 Conveyance System Analysis and Design ............................................................................... 5-1 6.0 Special Reports and Studies ..................................................................................................... 6-1 Section 6.0 Figures Figure 6-1 ......... Geotechnical Engineering Report Figure 6-2 ......... Critical Area Report 7.0 Other Permits .............................................................................................................................. 7-1 8.0 CSWPPP Analysis and Design .................................................................................................. 8-1 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant .................................... 9-1 10.0 Operations and Maintenance Plan .......................................................................................... 10-1 11.0 Conclusion ................................................................................................................................. 11-1 Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 1 Project Overview Preliminary Technical Information Report Walker Auto Dealership 1-1 2180100.10 1.0 Project Overview Purpose and Scope 1.1 This report accompanies the civil engineering plans and documents for the Walker Auto Dealership project site, a proposed commercial development project located at 3400 East Valley Road in the city of Renton, King County, Washington. The project site comprises Parcel No. 3023059067, which is 5.65 acres in size. The site is bordered to the north by East Valley Boat & RV Storage, to the east by Washington State Route (SR) 167, to the south by Bickman Group Landscaping, and to the west by East Valley Road. See Figure 1-1 for the TIR Worksheet and Figure 1-2 for a Site Location map. The site is located within the jurisdiction of the City of Renton, which has amended the 2016 King County Surface Water Design Manual (KCSWDM) as the 2016 City of Renton Surface Water Design Manual (CRSWDM). Per the CRSWDM, the Peak Rate Flow Control Standard shall be met, along with the Basic Enhanced Water Quality Treatment Menu. Existing Conditions 1.2 The site currently has a vacant, prefabricated, steel structure, while the remainder of the site is vacant. There are no existing trees on the site. A wetland is located along the east property line. This wetland was damaged by previous action at the east side of the site along SR 167. The wetland and reduced buffer will be restored by the applicant. The existing site is covered with pavement or hard packed dirt and gravel, and is impervious. There are two distinct drainage basins on the site. The larger west basin drains to the southwest corner of the site. Previously, a pumped system was used to discharge all stormwater from this basin into the public stormwater system in East Valley Road. The pump was recently removed, but stormwater still discharges to this system. The smaller east basin gently slopes to the east and drains to the existing wetland. There are no existing flow control facilities in either basin. The existing drainage patterns have been analyzed and are discussed in detail in the Level One Downstream Analysis (see Section 3.0). Post-Development Conditions 1.3 The project proposes development of the site into a new auto dealership, including removal of an existing building and construction of an approximately 64,935-square foot new building with some roof top parking. The interior space will consist of showroom/sales area, business offices, parts and storage, service and shop, storage area, and other supportive areas. Stormwater within the larger west basin will be collected in closed conveyances and treated by a proprietary (enhanced basic) stormwater treatment device prior to discharging to the public storm system in East Valley Road. Stormwater within the east basin will sheet flow into the linear bioretention cell for treatment prior to discharge to the adjacent wetland. These two basins will maintain the natural discharge points for stormwater leaving the site. See Figure 1-3 for a Drainage Basin and Site Map. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 1.0 Figures Figure 1-1 ......... TIR Worksheet Figure 1-2 ......... Site Location Figure 1-3 ......... Drainage Basin and Site Map Figure 1-4 ......... City of Renton Soils Survey Dale Walker 555 Grady Way Renton WA, 98057 Matt Weber AHBL, Inc. 253.383.2422 3400 E Valley Rd Renton, WA 98057 Walker Auto Dealership 30 23 N 05 E February 2016 February 2016 Black River Water Subbasin The City of Renton Peak Flow Rate Control Standard and Enhanced Basic Water Quality Existing Category III Wetland east of site Ur N/A N/A Existing Category III Wetland East Valley Road public stormwater system and wetland east of site 2 TBD TBD Peak Rate Flow Control Standard TBD Commercail Conveyance pipes, catch basins, Bioretention cell, and treatment unit. Treatment Unit Bioretention 2215 North 30th Street Suite 300 Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX WALKER AUTO DEALERSHIP VICINITY MAP 1-2 N SITE T EAST VALLEY ROADS.R. 167SW 34TH ST 12%6%24 22 23 118 DISPLAY DISPLAY DISPLAY DISPLAYDISPLAY 2 44 SERVICE/EMPLOYEESERVICE/EMPLOYEE10 DISPLAY 14 DISPLAY DISPLAY 22 DISPLAY 20 DISPLAY 20 7 DISPLAY11DISPLAY 6 CUSTOMERSERVICE DRIVE CAR WASH 2 13 DISPLAY3 8CUSTOMERSIGN BIKERAMP UP6 3 DISPLAY SERVICE/EMPLOYEESERVICE/EMPLOYEESERVICE/EMPLOYEE2020201819212121212020 20 21 2121222221 2 0 74 LF 12 " C P E P @ 0 . 5 0 % 113 LF 12" CPEP @ 0.49%108 LF 12" CPEP @ 0.49% 88 LF 12" CPEP @ 0.50% 87 LF 12" CPEP @ 0.50%60 LF 12" CPEP @ 1.45%116 LF 12" CPEP @ 0.49% 48 LF 12" CPEP @ 0.30% 97 LF 12" C P E P @ 0 . 4 1 % 14 LF 18" CPEP @ 0.25% DISCHARGE ADJACENT TO WETLAND 132 LF 12" CPEP @ 0.30%78 LF 12" CPEP @ 0.30%78 LF 12" CPEP @ 0 .30%80 LF 12" CPEP @ 0.30%41 LF 18" @ 0.25%400 LF BIORETENTION CELL 2' WIDTH 0.5' PONDING DEPTH WETLAND BOUNDARY WETLAND BUFFER 75.00' WETLAND BUFFER PROPOSED BUILDING FINISHED FLOOR: 22.0 PROPRIETARY TREATMENT UNIT FOR ENHANCED TREATMENT IE: 15.60 18" (E) IE: 12.59 18" (SW) CB #12 RIM: 20.84 IE: 17.79 12" (S) CB #4 RIM: 20.74 IE: 16.02 12" (NW) IE: 16.02 12" (SW) CB #6 RIM: 20.62 IE: 16.49 12" (N) IE: 16.49 12" (SW) CB #10 RIM: 20.58 IE: 18.53 12" (W) CB#1 48" TYPE 2 CB BIORETENTION OVERFLOW STRUCTURE RIM: 20.50 IE: 17.87 12" (E) CB #2 RIM: 20.48 IE: 15.63 12" (N) IE: 16.52 12" (E) IE: 15.63 18" (W) CB #9 RIM: 20.31 IE: 18.00 12" (W) IE: 18.00 12" (E) CB #8 RIM: 20.28 IE: 17.45 12" (E) IE: 17.45 12" (W) CB #14 RIM: 20.09 IE: 17.79 12" (W) CB #11 RIM: 19.81 IE: 16.92 12" (E) IE: 16.92 12" (N) IE: 16.92 12" (W) CB #13 RIM: 19.79 IE: 17.35 12" (E) IE: 17.35 12" (W) CB #3 RIM: 19.54 IE: 15.78 12" (NE) IE: 15.78 12" (S) CB #5 RIM: 19.43 IE: 16.25 12" (NE) IE: 16.25 12" (SE) CB #7 RIM: 18.93 IE: 16.88 12" (E) IE: 16.88 12" (S) OUTLET IE: 17.50 12" (W)R.O.W1 2 3 4 TEL FAX www.ahbl.comWEBTELFAXwww.ahbl.comWEBTELFAXwww.ahbl.comWEB 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB TACOMA SEATTLE SPOKANE TRI-CITIES Know what's below. before you dig.Call R 3 STKMKWBEB MAY 2, 2018 SITE PLAN REVIEW 2180100.10 601 ST. HELENS AVENUE TACOMA, WA98402 ROGER HANSEN HHJ ARCHITECTS, PLLC WALKER AUTO DEALERSHIP A PORTION OF THE NW 1/4 OF THE SE 1/4 OF SEC. 30, TWN. 23 N., RGE. 05 E. W.M. CITY OF RENTON, KING COUNTY, WASHINGTON. WALKER AUTO DEALERSHIP DATE: April 27, 2018 FILENAME: Q:\2018\2180100\10_CIV\CAD\_Site Plan Review\2180100-SH-STRM-GRAD.dwg C1.1 4 GRADING AND DRAINAGE PLAN N GRAPHIC SCALE 0 30 60 1" = 30 FEET 15 1 - 1 NOT TO SCALE BIORETENTION CELL EARTHWORK QUANTITIES CUT:600 CY FILL:14,300 CY NET: 13,700 CY IMPORT NOTE: THE ABOVE QUANTITIES ARE ESTIMATES ONLY INTENDED FOR THE PERMITTING PROCESS. DO NOT USE FOR BID PURPOSES. THE QUANTITIES DO NOT HAVE STRIPPING, COMPACTION, OR CUT OR FILL ADJUSTMENT FACTORS APPLIED TO THEM. NOTE: FILL MATERIAL SHALL BE STRUCTURAL FILL PER GEOTECHNICAL ENGINEER'S RECOMMENDATIONS. UP TO 20,000 CY OF CONTAMINATED MATERIAL WILL BE REMOVED FROM THE SITE. REFER TO SEPARATE REMEDIATION PLAN. PROJECT AREAS PARCEL AREA: 247,713 SF (5.69 AC) DISTURBED AREA: 209,808 SF (4.82 AC) 8'2' 1 31' BOTTOM OF BIORETENTION CELL OVERFLOW ELEVATION WASHED ROCK PERFORATED UNDERDRAIN BIORETENTION SOIL MIX (BSM) 1.00 1.5' 1 3 CATCH BASIN OVERFLOW STRUCTURE 1 3 1' GRAVEL SECTION WHEELSTOP PARKING LOT 2' West Developed Basin East Developed Basin 1-3 Drainage Basin and Site Map PROJECT SITE Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 2 Conditions and Requirements Summary Preliminary Technical Information Report Walker Auto Dealership 2-1 2180100.10 2.0 Conditions and Requirements Summary Core Requirements 2.1 2.1.1 CR 1 – Discharge at the Natural Location There are two existing basins on the site, each within a separate Threshold Discharge Area (TDA). All core requirements are required for both TDAs. The larger west basin drains to the southwest corner of the site. The smaller east basin gently slopes to the east and drains to the existing wetland. Both natural discharge locations are maintained. 2.1.2 CR 2 – Offsite Analysis A preliminary downstream analysis is included in Section 3.0 below. A full Level One Downstream analysis will be performed for the final Technical Information Report. The analysis will include:  Defining and mapping the study area.  Reviewing available information on the study area.  Field inspecting the study area. 2.1.3 CR 3 – Flow Control The project is located in a Peak Flow Rate Control Standard area. This flow control standard requires the peak flow rate under developed conditions to be equal to or less than the peak flow rate under existing conditions. Flow control is discussed in further detail in Section 4.0, Flow Control and Water Quality Facility Analysis and Design. 2.1.4 CR 4 – Conveyance System The proposed conveyance system will be designed to meet the requirements outlined in Section 1.2.4 of the CRSWDM. Refer to Section 5.0 for more information. 2.1.5 CR 5 – Construction Stormwater Pollution Prevention Onsite land disturbance will consist of clearing the site, demolition of several existing onsite buildings, and regrading of the site. A Construction Stormwater Pollution Prevention Plan (CSWPPP) will be included with the final engineering design. 2.1.6 CR 6 – Maintenance and Operations Maintenance and operations of all drainage facilities is the responsibility of the Owner. A completed Operations and Maintenance Manual will be included with a final engineering design. 2.1.7 CR 7 – Financial Guarantees and Liability All financial guarantee and liability requirements will be met by the owner and will be provided with the final engineering design. This project will provide a Drainage Facilities Restoration and Site Stabilization Financial Guarantee. 2.1.8 CR 8 – Water Quality Facilities The project site is subject to the Enhanced Basic Water Quality Treatment Menu per the CRSWDM. Design of these water quality facilities is discussed in Section 4.0. Preliminary Technical Information Report Walker Auto Dealership 2-2 2180100.10 2.1.9 CR 9 – Onsite Best Management Practices (BMPs) The W alker Auto Dealership project is classified as a Large Lot per Section 1.2.9.2 of the CRSWDM. The proposed project site will meet the Large Lot BMP Requirements outlined in Section 1.2.9.2.2 of the CRSWDM. Below is a discussion of the list approach for each type of surface proposed on the site. Landscape Areas  Post Construction Soil Quality and Depth will be used. Impervious Areas  Full Dispersion is not feasible because there are no existing native vegetated areas on the site.  Full Infiltration and Full Infiltration of Roof Runoff are not feasible because the existing fill and alluvial soils cannot support infiltration.  Limited Infiltration is not feasible because the existing fill and alluvial soils cannot support infiltration.  Bioretention per Onsite BMP standards is not feasible because the existing fill and alluvial soils cannot support infiltration. Note that the proposed bioretention cell has an underdrain and is not intended to infiltrate stormwater, and therefore does not meet the requirements for Onsite BMPs.  Permeable Pavement is not feasible because the existing fill and alluvial soils cannot support infiltration.  Basic Dispersion is not feasible because there are no well-established landscaped areas that can receive the runoff.  Reduced Impervious Surface Credit is not feasible for this site.  Native Growth Retention Credit and Tree Retention Credit are not feasible because there is no existing native vegetation or trees onsite.  Perforated Pipe Connection is not feasible because the existing fill and alluvial soils cannot support infiltration. 2.1.10 SR 1 – Other Adopted Area-Specific Requirements To our knowledge, there are no adopted area-specific requirements that are applicable to the project site. 2.1.11 SR 2 – Flood Hazard Area Delineation Flood Insurance Rate Map 53033C0979 F, Panel 979 of 1725, was consulted for this project and shows the project site within the Zone X area, which is described as areas determined to be outside of the 500-year floodplain. Refer to Figure 2-1 of this section for the Flood Insurance Rate Map. Preliminary Technical Information Report Walker Auto Dealership 2-3 2180100.10 2.1.12 SR 3 – Flood Protection Facilities The project site does not contain, nor is it adjacent to, any existing flood protection facilities. Project improvements do not include flood protection measures. 2.1.13 SR 4 – Source Controls The proposed project is classified as a commercial site. Water quality source controls applicable to the project site shall be evaluated and applied as described in the King County Stormwater Pollution Prevention Manual (KCSWPPM) and Renton Municipal Code IV. 2.1.14 SR 5 – Oil Control The project is not considered a high-use site; therefore, it is not subject to oil control requirements. 2.1.15 SR 6 – Aquifer Protection Area According to the City of Renton Public Works Department Groundwater Protection Areas map, Reference 15-B of the CRSWDM, the site is not located within an aquifer protection area. Refer to Figure 2-2 for the above referenced map. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 2.0 Figures Figure 2-1 ......... Flood Insurance Rate Map Figure 2-2 ......... City of Renton Groundwater Protection Areas PROJECT SITE PROJECT SITE Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 3 Offsite Analysis Preliminary Technical Information Report Walker Auto Dealership 3-1 2180100.10 3.0 Offsite Analysis Task 1 – Study Area Definition and Maps 3.1 There are two existing basins on the site, each within a separate TDA. All core requirements are required for both TDAs. The larger west basin drains to the southwest corner of the site. The smaller east basin gently slopes to the east and drains to the existing wetland. Both natural discharge locations will be maintained. There are no upstream tributary areas contributing stormwater to the onsite basin area. Task 2 – Resource Review 3.2 The following resources were reviewed to determine if there are any existing or potential problems in the study area:  Adopted Basin Plans: The project lies within the Black River Water Subbasin. Requirements for the Black River Water Subbasin will be followed where applicable.  Offsite Analysis Reports: AHBL staff has not located offsite analysis reports for projects near the W alker Auto Dealership project site.  FEMA Map: FEMA Flood Insurance Rate Map 53033C0979 F, Panel 979 of 1725, dated May 16, 1995 (see Figure 2-1), indicates that the project site lies outside the categorized flood zones.  City of Renton Effective FEMA Flood Insurance Rate Map: The project site is not located in a Flood Hazard Zone (see Figure 3-1).  Topographic survey.  As-builts of East Valley Road and SW 34th Street.  Renton online GIS Map. Task 3 – Field Inspection 3.3 A full field inspection of both downstreams will be performed prior to final design. Task 4 – Drainage System Description and Problem Descriptions 3.4 The west basin discharges to the public storm system within East Valley Road. The entire system is within closed conveyance ranging from 36- to 60-inch pipes. This drainage discharges to Springbrook Creek at SW 34th Street, approximately 0.45 mile downstream of the site. The east basin discharges to the wetland along the east property li ne. This wetland drains to the north along the SR 167 right-of-way toward Panther Creek, approximately 0.61 mile downstream of the site. There are no known signs of flooding, overtopping, or erosion. A full field inspection of both downstreams will be performed prior to final design. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 3.0 Figures Figure 3-1 ......... City of Renton Effective FEMA Flood Insurance Rate Map PROJECT SITE Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 4 Flow Control and Water Quality Facility Analysis and Design Preliminary Technical Information Report Walker Auto Dealership 4-1 2180100.10 4.0 Flow Control and Water Quality Facility Analysis and Design Flow Control 4.1 4.1.1 Existing Site Hydrology (Part A) The existing site is developed with existing buildings, asphalt, and gravel storage areas. The site is mostly fully impervious. The larger west basin drains to the southwest corner of the site. The smaller east basin gently slopes to the east and drains to the existing wetland. Both natural discharge locations will be maintained. The Western Washington Hydrology Model (WWHM) was used to model the existing site and determine peak flows. 4.1.2 Developed Site Hydrology (Part B) The west basin will maintain the natural discharge point to the west. Runoff will be collected in and conveyed to a treatment device at the southwest corner of the site before being discharged to the public storm system in East Valley Road. The east basin will maintain the natural discharge point to the east. Runoff from a portion of the parking lot will sheet flow to the linear bioretention cell. This bioretention cell will discharge via closed conveyance immediately adjacent to the wetland along the east property line. The project site is located within a Peak Rate Flow Control Standard area (see Figure 4-1). This standard requires that developed peak flows match existing flows for the 2-, 10-, and 100-year return period stormwater events. Under proposed conditions, net impervious area is planned to decrease, thus lowering peak flow rates, meeting the Peak Rate Flow Control Standard. Preliminary WWHM peak flow calculations are included as Figure 4-2. The annual peak flows and durations for the proposed site will be determined using the existing and developed surface areas shown below. Table 1 – Existing vs. Developed Site Hydrology for West Basin West Basin, acres Existing Proposed Pervious 0.000 0.395 Impervious 3.942 3.547 Table 2 – Existing vs. Developed Site Hydrology for East Basin East Basin, acres Existing Proposed Pervious, Buffer 0.000 0.870 Pervious, Landscape 0.000 0.150 Impervious 1.745 0.724 Preliminary Technical Information Report Walker Auto Dealership 4-2 2180100.10 4.1.3 Performance Standards (Part C) Area-Specific Flow Control Facility Standard The project site is located within a Peak Rate Flow Control Standard area. This standard requires that the proposed project site match existing peak flow rates for the 2-, 10-, and 100-year stormwater events (see Figure 4-1). Conveyance System Capacity Standards The onsite stormwater networks will be sized to convey and contain the 25-year peak flow and the 100-year runoff event, and may not create or aggravate a severe flooding problem or severe erosion problem, as described in Section 1.2.2 of the CRSWDM. Water Quality Treatment Menu In accordance with the 2016 CRSWDM, onsite flows will be treated to specifications provided by the Enhanced Basic Water Quality standards. The goal of this treatment menu is to reduce total suspended solids (TSS) by 80 percent and to reduce zinc concentration by 50 percent for a typical rainfall year. A bioretention cell will be used to treat runoff from the east basin before discharging to the wetland. The bioretention cell is sized to treat at least 91 percent of the WWHM influent file. A proprietary treatment unit with General Use Level Designation (GULD) approval for enhanced treatment will be used to treat stormwater from the west basin prior to discharge from the site. The unit will be sized according the GULD approval and the manufacturer’s recommen dations. Source Controls The proposed project consists of new parking and auto display and retail. Source control and erosion and sediment control measures during construction will be included in a CSWPPP to be submitted with the final engineering design. Post-construction source controls will be included in an Operation and Maintenance Plan to be submitted with the final engineering design. Oil Controls Not applicable. 4.1.4 Flow Control System (Part D) The proposed project site will have a greater percentage of pervious surface coverage than the existing site. This increase in pervious surface will decrease peak flows and satisfy the Peak Rate Flow Control Standard. WWHM calculations are provided in Figure 4-2 showing that the proposed peak flow rates are less than the existing conditions. No flow control facilities are required for either basin. Water Quality System (Part E) 4.2 In accordance with the 2016 CRSWDM, onsite flows will be treated to specifications provided by the Enhanced Basic Water Quality standards. The goal of this treatment menu is to reduce total suspended solids (TSS) by 80 percent and to reduce zinc concentration by 50 percent for a typical rainfall year. Preliminary Technical Information Report Walker Auto Dealership 4-3 2180100.10 A bioretention cell will be used to treat runoff from the east basin before discharging to the wetland. The bioretention cell is sized to treat at least 91 percent of the WWHM influent file. A proprietary treatment unit with GULD approval for enhanced treatment will be used to treat stormwater from the west basin prior to discharge from the site. The unit will be sized according the GULD approval and the manufacturer’s recommendations . Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 4.0 Figures Figure 4-1 ......... City of Renton Flow Control Application Map – Reference 15-A Figure 4-2 ......... Preliminary WWHM Flow Control Calculations PROJECT SITE WWHM2012 PROJECT REPORT DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 2 General Model Information Project Name:20180420 Prelim Site Name: Site Address: City: Report Date:4/30/2018 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/03/08 Version:4.2.14 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Low Flow Threshold for POC2:50 Percent of the 2 Year High Flow Threshold for POC2:50 Year DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 3 Landuse Basin Data Predeveloped Land Use Existing West Basin Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS FLAT 3.942 Impervious Total 3.942 Basin Total 3.942 Element Flows To: Surface Interflow Groundwater DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 4 Existing East Basin Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROADS FLAT 1.745 Impervious Total 1.745 Basin Total 1.745 Element Flows To: Surface Interflow Groundwater DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 5 Mitigated Land Use Proposed West Basin Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.395 Pervious Total 0.395 Impervious Land Use acre ROADS FLAT 3.547 Impervious Total 3.547 Basin Total 3.942 Element Flows To: Surface Interflow Groundwater DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 6 East Basin Buffer Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.87 Pervious Total 0.87 Impervious Land Use acre Impervious Total 0 Basin Total 0.87 Element Flows To: Surface Interflow Groundwater DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 7 Proposed East Basin Impervious Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.15 Pervious Total 0.15 Impervious Land Use acre ROADS FLAT 0.724 Impervious Total 0.724 Basin Total 0.874 Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 8 Routing Elements Predeveloped Routing DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 9 Mitigated Routing Bioretention 1 Bottom Length: 400.00 ft. Bottom Width: 2.00 ft. Material thickness of first layer: 1.5 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 1 Material type for second layer: GRAVEL Material thickness of third layer: 0 Material type for third layer: GRAVEL Underdrain used Underdrain Diameter (feet):0.67 Orifice Diameter (in.):0.67 Offset (in.):0.25 Flow Through Underdrain (ac-ft.):126.707 Total Outflow (ac-ft.):132.925 Percent Through Underdrain:95.32 Discharge Structure Riser Height:0.5 ft. Riser Diameter:48 in. Element Flows To: Outlet 1 Outlet 2 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.1620 0.0000 0.0000 0.0000 0.0385 0.1620 0.0003 0.0000 0.0000 0.0769 0.1597 0.0007 0.0000 0.0000 0.1154 0.1574 0.0011 0.0000 0.0000 0.1538 0.1551 0.0016 0.0000 0.0000 0.1923 0.1528 0.0021 0.0001 0.0000 0.2308 0.1505 0.0026 0.0002 0.0000 0.2692 0.1483 0.0032 0.0004 0.0000 0.3077 0.1460 0.0038 0.0005 0.0000 0.3462 0.1437 0.0044 0.0008 0.0000 0.3846 0.1415 0.0051 0.0009 0.0000 0.4231 0.1392 0.0058 0.0013 0.0000 0.4615 0.1369 0.0066 0.0017 0.0000 0.5000 0.1347 0.0074 0.0018 0.0000 0.5385 0.1324 0.0082 0.0025 0.0000 0.5769 0.1302 0.0091 0.0030 0.0000 0.6154 0.1279 0.0100 0.0031 0.0000 0.6538 0.1257 0.0109 0.0035 0.0000 0.6923 0.1234 0.0119 0.0039 0.0000 0.7308 0.1212 0.0129 0.0043 0.0000 0.7692 0.1189 0.0140 0.0046 0.0000 0.8077 0.1167 0.0151 0.0049 0.0000 0.8462 0.1144 0.0162 0.0052 0.0000 0.8846 0.1122 0.0174 0.0055 0.0000 0.9231 0.1100 0.0186 0.0057 0.0000 0.9615 0.1077 0.0199 0.0060 0.0000 1.0000 0.1055 0.0212 0.0062 0.0000 1.0385 0.1033 0.0225 0.0065 0.0000 1.0769 0.1011 0.0239 0.0067 0.0000 DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 10 1.1154 0.0988 0.0253 0.0069 0.0000 1.1538 0.0966 0.0267 0.0071 0.0000 1.1923 0.0944 0.0282 0.0073 0.0000 1.2308 0.0922 0.0298 0.0075 0.0000 1.2692 0.0900 0.0313 0.0077 0.0000 1.3077 0.0878 0.0329 0.0079 0.0000 1.3462 0.0856 0.0346 0.0081 0.0000 1.3846 0.0834 0.0362 0.0082 0.0000 1.4231 0.0812 0.0380 0.0084 0.0000 1.4615 0.0790 0.0397 0.0086 0.0000 1.5000 0.0768 0.0413 0.0087 0.0000 1.5385 0.0746 0.0430 0.0089 0.0000 1.5769 0.0724 0.0447 0.0091 0.0000 1.6154 0.0702 0.0464 0.0092 0.0000 1.6538 0.0680 0.0482 0.0094 0.0000 1.6923 0.0658 0.0500 0.0095 0.0000 1.7308 0.0636 0.0519 0.0097 0.0000 1.7692 0.0614 0.0538 0.0098 0.0000 1.8077 0.0593 0.0557 0.0100 0.0000 1.8462 0.0571 0.0576 0.0101 0.0000 1.8846 0.0549 0.0596 0.0103 0.0000 1.9231 0.0528 0.0616 0.0104 0.0000 1.9615 0.0506 0.0637 0.0106 0.0000 2.0000 0.0484 0.0658 0.0107 0.0000 2.0385 0.0463 0.0679 0.0108 0.0000 2.0769 0.0441 0.0701 0.0110 0.0000 2.1154 0.0419 0.0723 0.0111 0.0000 2.1538 0.0398 0.0745 0.0112 0.0000 2.1923 0.0376 0.0768 0.0114 0.0000 2.2308 0.0355 0.0791 0.0115 0.0000 2.2692 0.0333 0.0815 0.0116 0.0000 2.3077 0.0312 0.0839 0.0118 0.0000 2.3462 0.0290 0.0863 0.0121 0.0000 2.3846 0.0269 0.0887 0.0122 0.0000 2.4231 0.0248 0.0912 0.0123 0.0000 2.4615 0.0226 0.0938 0.0124 0.0000 2.5000 0.0205 0.0963 0.0125 0.0000 2.5000 0.0184 0.0963 0.0125 0.0000 Bioretention Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs) 2.5000 0.1620 0.0963 0.0000 0.2279 0.0000 2.5385 0.1643 0.1026 0.0000 0.2279 0.0000 2.5769 0.1665 0.1090 0.0000 0.2336 0.0000 2.6154 0.1688 0.1154 0.0000 0.2393 0.0000 2.6538 0.1711 0.1219 0.0000 0.2450 0.0000 2.6923 0.1734 0.1286 0.0000 0.2507 0.0000 2.7308 0.1757 0.1353 0.0000 0.2564 0.0000 2.7692 0.1780 0.1421 0.0000 0.2621 0.0000 2.8077 0.1803 0.1490 0.0000 0.2678 0.0000 2.8462 0.1827 0.1560 0.0000 0.2735 0.0000 2.8846 0.1850 0.1630 0.0000 0.2792 0.0000 2.9231 0.1873 0.1702 0.0000 0.2849 0.0000 2.9615 0.1896 0.1774 0.0000 0.2906 0.0000 3.0000 0.1919 0.1848 0.0000 0.2963 0.0000 3.0385 0.1942 0.1922 0.3203 0.3020 0.0000 3.0769 0.1966 0.1997 0.9055 0.3077 0.0000 3.1154 0.1989 0.2073 1.6629 0.3134 0.0000 DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 11 3.1538 0.2012 0.2150 2.5592 0.3191 0.0000 3.1923 0.2036 0.2228 3.5752 0.3248 0.0000 3.2308 0.2059 0.2307 4.6973 0.3305 0.0000 3.2692 0.2082 0.2386 5.9155 0.3362 0.0000 3.3077 0.2106 0.2467 7.2215 0.3419 0.0000 3.3462 0.2129 0.2548 8.6081 0.3476 0.0000 3.3846 0.2152 0.2631 10.069 0.3533 0.0000 3.4231 0.2176 0.2714 11.598 0.3590 0.0000 3.4615 0.2199 0.2798 13.190 0.3647 0.0000 3.5000 0.2223 0.2883 14.838 0.3704 0.0000 DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 12 Surface retention 1 Element Flows To: Outlet 1 Outlet 2 Bioretention 1 DRAFT20180420 Prelim 4/30/2018 2:17:48 PM Page 13 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:3.942 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.395 Total Impervious Area:3.547 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 1.502945 5 year 1.898394 10 year 2.167074 25 year 2.51559 50 year 2.782336 100 year 3.055559 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 1.377723 5 year 1.748814 10 year 2.001903 25 year 2.331175 50 year 2.58385 100 year 2.843191 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 1.947 1.809 1950 2.103 1.902 1951 1.216 1.129 1952 1.082 0.978 1953 1.168 1.056 1954 1.222 1.121 1955 1.386 1.265 1956 1.364 1.246 1957 1.547 1.430 1958 1.248 1.137 West Basin Existing Site Conditions West Basin Developed Site Conditions DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 14 1959 1.273 1.146 1960 1.249 1.162 1961 1.321 1.217 1962 1.151 1.044 1963 1.279 1.178 1964 1.254 1.133 1965 1.593 1.477 1966 1.065 0.973 1967 1.836 1.681 1968 2.088 1.913 1969 1.451 1.344 1970 1.400 1.284 1971 1.670 1.532 1972 1.724 1.614 1973 1.044 0.940 1974 1.523 1.406 1975 1.755 1.579 1976 1.180 1.089 1977 1.278 1.151 1978 1.563 1.410 1979 2.140 1.933 1980 1.920 1.807 1981 1.571 1.436 1982 2.215 2.042 1983 1.803 1.636 1984 1.137 1.042 1985 1.567 1.435 1986 1.358 1.233 1987 2.096 1.898 1988 1.271 1.144 1989 1.590 1.431 1990 2.678 2.558 1991 2.140 2.018 1992 1.126 1.032 1993 0.975 0.886 1994 1.061 0.955 1995 1.393 1.271 1996 1.482 1.381 1997 1.439 1.333 1998 1.459 1.325 1999 2.984 2.764 2000 1.485 1.366 2001 1.632 1.476 2002 1.904 1.773 2003 1.479 1.377 2004 2.792 2.580 2005 1.276 1.181 2006 1.127 1.048 2007 2.610 2.418 2008 2.102 1.982 2009 1.943 1.749 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 2.9845 2.7640 2 2.7923 2.5801 3 2.6783 2.5584 DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 15 4 2.6099 2.4176 5 2.2147 2.0420 6 2.1401 2.0179 7 2.1396 1.9822 8 2.1035 1.9329 9 2.1022 1.9126 10 2.0955 1.9018 11 2.0875 1.8982 12 1.9466 1.8088 13 1.9426 1.8067 14 1.9200 1.7728 15 1.9041 1.7490 16 1.8360 1.6811 17 1.8026 1.6362 18 1.7550 1.6144 19 1.7239 1.5795 20 1.6699 1.5323 21 1.6323 1.4767 22 1.5934 1.4763 23 1.5899 1.4360 24 1.5706 1.4346 25 1.5670 1.4307 26 1.5634 1.4296 27 1.5468 1.4101 28 1.5233 1.4059 29 1.4855 1.3811 30 1.4820 1.3775 31 1.4794 1.3655 32 1.4588 1.3440 33 1.4511 1.3333 34 1.4392 1.3255 35 1.4001 1.2844 36 1.3927 1.2709 37 1.3858 1.2650 38 1.3635 1.2463 39 1.3582 1.2326 40 1.3215 1.2167 41 1.2791 1.1806 42 1.2781 1.1778 43 1.2761 1.1625 44 1.2732 1.1507 45 1.2713 1.1458 46 1.2543 1.1440 47 1.2494 1.1371 48 1.2482 1.1326 49 1.2222 1.1287 50 1.2159 1.1210 51 1.1801 1.0886 52 1.1680 1.0560 53 1.1514 1.0483 54 1.1371 1.0444 55 1.1272 1.0417 56 1.1261 1.0317 57 1.0816 0.9776 58 1.0654 0.9726 59 1.0610 0.9547 60 1.0440 0.9395 61 0.9753 0.8861 DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 16 DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 17 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.7515 1806 1270 70 Pass 0.7720 1647 1156 70 Pass 0.7925 1475 1037 70 Pass 0.8130 1342 935 69 Pass 0.8335 1229 867 70 Pass 0.8540 1101 792 71 Pass 0.8746 1005 721 71 Pass 0.8951 920 659 71 Pass 0.9156 854 604 70 Pass 0.9361 789 560 70 Pass 0.9566 726 517 71 Pass 0.9771 665 473 71 Pass 0.9976 611 431 70 Pass 1.0182 571 401 70 Pass 1.0387 533 376 70 Pass 1.0592 488 344 70 Pass 1.0797 451 323 71 Pass 1.1002 420 297 70 Pass 1.1207 389 278 71 Pass 1.1412 364 254 69 Pass 1.1617 339 238 70 Pass 1.1823 316 215 68 Pass 1.2028 296 207 69 Pass 1.2233 272 191 70 Pass 1.2438 256 180 70 Pass 1.2643 238 163 68 Pass 1.2848 222 154 69 Pass 1.3053 206 142 68 Pass 1.3259 196 136 69 Pass 1.3464 181 125 69 Pass 1.3669 171 116 67 Pass 1.3874 161 109 67 Pass 1.4079 148 103 69 Pass 1.4284 139 99 71 Pass 1.4489 135 90 66 Pass 1.4695 122 85 69 Pass 1.4900 113 80 70 Pass 1.5105 108 77 71 Pass 1.5310 105 72 68 Pass 1.5515 100 67 67 Pass 1.5720 92 64 69 Pass 1.5925 87 61 70 Pass 1.6131 84 57 67 Pass 1.6336 73 53 72 Pass 1.6541 71 52 73 Pass 1.6746 66 52 78 Pass 1.6951 63 47 74 Pass 1.7156 62 46 74 Pass 1.7361 58 40 68 Pass 1.7566 54 38 70 Pass 1.7772 54 33 61 Pass 1.7977 52 32 61 Pass 1.8182 50 30 60 Pass DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 18 1.8387 46 26 56 Pass 1.8592 45 24 53 Pass 1.8797 40 24 60 Pass 1.9002 38 20 52 Pass 1.9208 33 17 51 Pass 1.9413 32 16 50 Pass 1.9618 29 13 44 Pass 1.9823 28 12 42 Pass 2.0028 25 11 44 Pass 2.0233 22 9 40 Pass 2.0438 21 8 38 Pass 2.0644 20 8 40 Pass 2.0849 17 8 47 Pass 2.1054 13 8 61 Pass 2.1259 12 8 66 Pass 2.1464 9 8 88 Pass 2.1669 9 8 88 Pass 2.1874 9 8 88 Pass 2.2080 9 8 88 Pass 2.2285 8 8 100 Pass 2.2490 8 8 100 Pass 2.2695 8 7 87 Pass 2.2900 8 7 87 Pass 2.3105 8 6 75 Pass 2.3310 8 6 75 Pass 2.3515 8 6 75 Pass 2.3721 7 6 85 Pass 2.3926 7 6 85 Pass 2.4131 7 6 85 Pass 2.4336 7 5 71 Pass 2.4541 7 5 71 Pass 2.4746 7 4 57 Pass 2.4951 6 4 66 Pass 2.5157 6 4 66 Pass 2.5362 6 3 50 Pass 2.5567 6 3 50 Pass 2.5772 6 2 33 Pass 2.5977 6 1 16 Pass 2.6182 5 1 20 Pass 2.6387 5 1 20 Pass 2.6593 4 1 25 Pass 2.6798 3 1 33 Pass 2.7003 3 1 33 Pass 2.7208 2 1 50 Pass 2.7413 2 1 50 Pass 2.7618 2 1 50 Pass 2.7823 2 0 0 Pass DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 19 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.4237 acre-feet On-line facility target flow:0.5597 cfs. Adjusted for 15 min:0.5597 cfs. Off-line facility target flow:0.3162 cfs. Adjusted for 15 min:0.3162 cfs. DRAFT20180420 Prelim 4/30/2018 2:18:22 PM Page 20 LID Report DRAFT20180420 Prelim 4/30/2018 2:19:22 PM Page 21 POC 2 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #2 Total Pervious Area:0 Total Impervious Area:1.745 Mitigated Landuse Totals for POC #2 Total Pervious Area:1.02 Total Impervious Area:0.724 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #2 Return Period Flow(cfs) 2 year 0.665307 5 year 0.84036 10 year 0.959296 25 year 1.113574 50 year 1.231654 100 year 1.352602 Flow Frequency Return Periods for Mitigated. POC #2 Return Period Flow(cfs) 2 year 0.142635 5 year 0.303256 10 year 0.449824 25 year 0.684929 50 year 0.89868 100 year 1.147383 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #2 Year Predeveloped Mitigated 1949 0.862 0.154 1950 0.931 0.188 1951 0.538 0.302 1952 0.479 0.042 1953 0.517 0.162 1954 0.541 0.076 1955 0.613 0.069 1956 0.604 0.240 1957 0.685 0.095 1958 0.553 0.123 1959 0.564 0.045 East Basin Existing Site Conditions East Basin Developed Site Conditions DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 22 1960 0.553 0.327 1961 0.585 0.348 1962 0.510 0.031 1963 0.566 0.143 1964 0.555 0.155 1965 0.705 0.199 1966 0.472 0.074 1967 0.813 0.175 1968 0.924 0.084 1969 0.642 0.096 1970 0.620 0.135 1971 0.739 0.150 1972 0.763 0.363 1973 0.462 0.168 1974 0.674 0.132 1975 0.777 0.103 1976 0.522 0.097 1977 0.566 0.053 1978 0.692 0.256 1979 0.947 0.031 1980 0.850 0.206 1981 0.695 0.080 1982 0.980 0.644 1983 0.798 0.098 1984 0.503 0.049 1985 0.694 0.064 1986 0.601 0.258 1987 0.928 0.317 1988 0.563 0.037 1989 0.704 0.030 1990 1.186 0.916 1991 0.947 0.501 1992 0.498 0.101 1993 0.432 0.042 1994 0.470 0.031 1995 0.617 0.218 1996 0.656 0.373 1997 0.637 0.381 1998 0.646 0.074 1999 1.321 0.274 2000 0.658 0.140 2001 0.723 0.027 2002 0.843 0.287 2003 0.655 0.113 2004 1.236 0.557 2005 0.565 0.157 2006 0.499 0.196 2007 1.155 0.840 2008 0.931 0.676 2009 0.860 0.414 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #2 Rank Predeveloped Mitigated 1 1.3211 0.9160 2 1.2361 0.8401 3 1.1856 0.6763 4 1.1553 0.6439 DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 23 5 0.9804 0.5571 6 0.9474 0.5013 7 0.9471 0.4137 8 0.9311 0.3811 9 0.9306 0.3729 10 0.9276 0.3625 11 0.9241 0.3478 12 0.8617 0.3268 13 0.8599 0.3170 14 0.8499 0.3025 15 0.8429 0.2873 16 0.8127 0.2735 17 0.7979 0.2578 18 0.7769 0.2558 19 0.7631 0.2400 20 0.7392 0.2181 21 0.7225 0.2060 22 0.7053 0.1988 23 0.7038 0.1963 24 0.6952 0.1881 25 0.6937 0.1750 26 0.6920 0.1676 27 0.6847 0.1621 28 0.6743 0.1571 29 0.6576 0.1546 30 0.6560 0.1541 31 0.6549 0.1505 32 0.6458 0.1435 33 0.6424 0.1405 34 0.6371 0.1348 35 0.6198 0.1319 36 0.6165 0.1228 37 0.6134 0.1135 38 0.6036 0.1027 39 0.6012 0.1009 40 0.5850 0.0985 41 0.5662 0.0967 42 0.5658 0.0956 43 0.5649 0.0954 44 0.5636 0.0840 45 0.5628 0.0798 46 0.5552 0.0758 47 0.5530 0.0743 48 0.5525 0.0740 49 0.5410 0.0692 50 0.5382 0.0642 51 0.5224 0.0534 52 0.5170 0.0489 53 0.5097 0.0452 54 0.5033 0.0423 55 0.4990 0.0420 56 0.4985 0.0372 57 0.4788 0.0310 58 0.4716 0.0309 59 0.4697 0.0309 60 0.4621 0.0303 61 0.4317 0.0275 DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 24 DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 25 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.3327 1812 102 5 Pass 0.3417 1653 95 5 Pass 0.3508 1482 92 6 Pass 0.3599 1359 85 6 Pass 0.3690 1235 79 6 Pass 0.3781 1102 71 6 Pass 0.3871 1003 63 6 Pass 0.3962 922 60 6 Pass 0.4053 854 51 5 Pass 0.4144 796 46 5 Pass 0.4235 728 44 6 Pass 0.4325 668 43 6 Pass 0.4416 611 42 6 Pass 0.4507 573 41 7 Pass 0.4598 537 37 6 Pass 0.4689 494 35 7 Pass 0.4779 451 33 7 Pass 0.4870 420 31 7 Pass 0.4961 389 28 7 Pass 0.5052 364 22 6 Pass 0.5143 339 21 6 Pass 0.5234 317 20 6 Pass 0.5324 296 19 6 Pass 0.5415 273 18 6 Pass 0.5506 256 14 5 Pass 0.5597 239 12 5 Pass 0.5688 223 12 5 Pass 0.5778 209 11 5 Pass 0.5869 196 11 5 Pass 0.5960 181 10 5 Pass 0.6051 171 8 4 Pass 0.6142 161 6 3 Pass 0.6232 148 6 4 Pass 0.6323 139 6 4 Pass 0.6414 135 6 4 Pass 0.6505 122 5 4 Pass 0.6596 113 5 4 Pass 0.6686 108 5 4 Pass 0.6777 105 3 2 Pass 0.6868 100 3 3 Pass 0.6959 93 3 3 Pass 0.7050 87 3 3 Pass 0.7140 84 3 3 Pass 0.7231 73 3 4 Pass 0.7322 71 3 4 Pass 0.7413 66 3 4 Pass 0.7504 63 3 4 Pass 0.7595 62 3 4 Pass 0.7685 58 3 5 Pass 0.7776 54 3 5 Pass 0.7867 54 2 3 Pass 0.7958 52 2 3 Pass 0.8049 50 2 4 Pass DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 26 0.8139 47 2 4 Pass 0.8230 45 2 4 Pass 0.8321 40 2 5 Pass 0.8412 39 1 2 Pass 0.8503 33 1 3 Pass 0.8593 32 1 3 Pass 0.8684 29 1 3 Pass 0.8775 28 1 3 Pass 0.8866 25 1 4 Pass 0.8957 22 1 4 Pass 0.9047 21 1 4 Pass 0.9138 20 1 5 Pass 0.9229 17 0 0 Pass 0.9320 14 0 0 Pass 0.9411 12 0 0 Pass 0.9501 9 0 0 Pass 0.9592 9 0 0 Pass 0.9683 9 0 0 Pass 0.9774 9 0 0 Pass 0.9865 8 0 0 Pass 0.9956 8 0 0 Pass 1.0046 8 0 0 Pass 1.0137 8 0 0 Pass 1.0228 8 0 0 Pass 1.0319 8 0 0 Pass 1.0410 8 0 0 Pass 1.0500 7 0 0 Pass 1.0591 7 0 0 Pass 1.0682 7 0 0 Pass 1.0773 7 0 0 Pass 1.0864 7 0 0 Pass 1.0954 7 0 0 Pass 1.1045 6 0 0 Pass 1.1136 6 0 0 Pass 1.1227 6 0 0 Pass 1.1318 6 0 0 Pass 1.1408 6 0 0 Pass 1.1499 6 0 0 Pass 1.1590 5 0 0 Pass 1.1681 5 0 0 Pass 1.1772 4 0 0 Pass 1.1862 3 0 0 Pass 1.1953 3 0 0 Pass 1.2044 2 0 0 Pass 1.2135 2 0 0 Pass 1.2226 2 0 0 Pass 1.2317 2 0 0 Pass DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 27 Water Quality Water Quality BMP Flow and Volume for POC #2 On-line facility volume:0.1687 acre-feet On-line facility target flow:0.2229 cfs. Adjusted for 15 min:0.2229 cfs. Off-line facility target flow:0.1259 cfs. Adjusted for 15 min:0.1259 cfs. DRAFT20180420 Prelim 4/30/2018 2:19:54 PM Page 28 LID Report DRAFT20180420 Prelim 4/30/2018 2:19:55 PM Page 29 POC 3 POC #3 was not reported because POC must exist in both scenarios and both scenarios must have been run. DRAFT20180420 Prelim 4/30/2018 2:19:55 PM Page 30 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. DRAFT20180420 Prelim 4/30/2018 2:19:55 PM Page 31 Appendix Predeveloped Schematic DRAFT20180420 Prelim 4/30/2018 2:19:56 PM Page 32 Mitigated Schematic DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 33 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 20180420 Prelim.wdm MESSU 25 Pre20180420 Prelim.MES 27 Pre20180420 Prelim.L61 28 Pre20180420 Prelim.L62 30 POC20180420 Prelim1.dat 31 POC20180420 Prelim2.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 IMPLND 1 COPY 501 COPY 502 DISPLY 1 DISPLY 2 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Existing West Basin MAX 1 2 30 9 2 Existing East Basin MAX 1 2 31 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 502 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 34 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 35 # - # *** RETS SURS 1 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Existing West Basin*** IMPLND 1 3.942 COPY 501 15 Existing East Basin*** IMPLND 1 1.745 COPY 502 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 36 EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 502 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 37 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 20180420 Prelim.wdm MESSU 25 Mit20180420 Prelim.MES 27 Mit20180420 Prelim.L61 28 Mit20180420 Prelim.L62 30 POC20180420 Prelim1.dat 31 POC20180420 Prelim2.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 16 IMPLND 1 GENER 2 RCHRES 1 RCHRES 2 COPY 501 COPY 2 COPY 502 COPY 602 DISPLY 1 DISPLY 2 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Proposed West Basin MAX 1 2 30 9 2 Surface retention 1 MAX 1 2 31 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 2 1 1 502 1 1 602 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** 2 24 END OPCODE PARM # # K *** 2 0. END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 16 C, Lawn, Flat 1 1 1 1 27 0 DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 38 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 39 # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Proposed East Basin Impervious*** PERLND 16 0.15 RCHRES 1 2 PERLND 16 0.15 RCHRES 1 3 IMPLND 1 0.724 RCHRES 1 5 Proposed West Basin*** PERLND 16 0.395 COPY 501 12 PERLND 16 0.395 COPY 501 13 IMPLND 1 3.547 COPY 501 15 East Basin Buffer*** PERLND 16 0.87 COPY 502 12 PERLND 16 0.87 COPY 602 12 PERLND 16 0.87 COPY 502 13 PERLND 16 0.87 COPY 602 13 ******Routing****** PERLND 16 0.15 COPY 2 12 IMPLND 1 0.724 COPY 2 15 PERLND 16 0.15 COPY 2 13 RCHRES 1 1 RCHRES 2 8 RCHRES 2 1 COPY 502 16 RCHRES 1 1 COPY 502 17 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 GENER 2 OUTPUT TIMSER .0011111 RCHRES 1 EXTNL OUTDGT 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Surface retentio-017 3 1 1 1 28 0 1 2 Bioretention 1 1 1 1 1 28 0 1 DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 40 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 2 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 6 0 0 0 1 0 0 0 2 1 2 2 2 2 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.01 0.0 0.0 0.5 0.0 2 2 0.08 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 5.0 6.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS *** User-Defined Variable Quantity Lines *** addr *** <------> *** kwd varnam optyp opn vari s1 s2 s3 tp multiply lc ls ac as agfn *** <****> <----> <----> <-> <----><-><-><-><-><--------> <><-> <><-> <--> *** UVQUAN vol2 RCHRES 2 VOL 4 UVQUAN v2m2 GLOBAL WORKSP 1 3 UVQUAN vpo2 GLOBAL WORKSP 2 3 UVQUAN v2d2 GENER 2 K 1 3 *** User-Defined Target Variable Names *** addr or addr or *** <------> <------> *** kwd varnam ct vari s1 s2 s3 frac oper vari s1 s2 s3 frac oper <****> <----><-> <----><-><-><-> <---> <--> <----><-><-><-> <---> <--> UVNAME v2m2 1 WORKSP 1 1.0 QUAN UVNAME vpo2 1 WORKSP 2 1.0 QUAN UVNAME v2d2 1 K 1 1.0 QUAN *** opt foplop dcdts yr mo dy hr mn d t vnam s1 s2 s3 ac quantity tc ts rp <****><-><--><><-><--> <> <> <> <><><> <----><-><-><-><-><--------> <> <-><-> GENER 2 v2m2 = 3985. *** Compute remaining available pore space GENER 2 vpo2 = v2m2 GENER 2 vpo2 -= vol2 *** Check to see if VPORA goes negative; if so set VPORA = 0.0 IF (vpo2 < 0.0) THEN GENER 2 vpo2 = 0.0 END IF DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 41 *** Infiltration volume GENER 2 v2d2 = vpo2 END SPEC-ACTIONS FTABLES FTABLE 2 67 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.161961 0.000000 0.000000 0.038462 0.161961 0.000342 0.000000 0.076923 0.159673 0.000721 0.000000 0.115385 0.157388 0.001138 0.000000 0.153846 0.155106 0.001592 0.000045 0.192308 0.152826 0.002084 0.000109 0.230769 0.150548 0.002614 0.000210 0.269231 0.148273 0.003181 0.000355 0.307692 0.146000 0.003787 0.000528 0.346154 0.143730 0.004429 0.000796 0.384615 0.141462 0.005110 0.000941 0.423077 0.139197 0.005829 0.001277 0.461538 0.136934 0.006586 0.001676 0.500000 0.134673 0.007380 0.001828 0.538462 0.132415 0.008213 0.002524 0.576923 0.130159 0.009084 0.002978 0.615385 0.127906 0.009992 0.003060 0.653846 0.125656 0.010939 0.003514 0.692308 0.123407 0.011924 0.003913 0.730769 0.121161 0.012948 0.004274 0.769231 0.118918 0.014009 0.004605 0.807692 0.116677 0.015109 0.004914 0.846154 0.114439 0.016248 0.005204 0.884615 0.112203 0.017424 0.005478 0.923077 0.109969 0.018640 0.005738 0.961538 0.107738 0.019893 0.005987 1.000000 0.105509 0.021185 0.006226 1.038462 0.103283 0.022516 0.006456 1.076923 0.101059 0.023886 0.006677 1.115385 0.098838 0.025294 0.006892 1.153846 0.096619 0.026740 0.007100 1.192308 0.094402 0.028226 0.007301 1.230769 0.092188 0.029750 0.007498 1.269231 0.089977 0.031313 0.007689 1.307692 0.087767 0.032915 0.007876 1.346154 0.085561 0.034556 0.008058 1.384615 0.083356 0.036236 0.008236 1.423077 0.081155 0.037955 0.008410 1.461538 0.078955 0.039713 0.008581 1.500000 0.076758 0.041344 0.008749 1.538462 0.074564 0.043010 0.008913 1.576923 0.072372 0.044712 0.009074 1.615385 0.070182 0.046449 0.009233 1.653846 0.067995 0.048222 0.009389 1.692308 0.065810 0.050031 0.009542 1.730769 0.063628 0.051876 0.009693 1.769231 0.061448 0.053756 0.009842 1.807692 0.059271 0.055672 0.009989 1.846154 0.057096 0.057624 0.010133 1.884615 0.054923 0.059611 0.010276 1.923077 0.052753 0.061635 0.010417 1.961538 0.050586 0.063695 0.010556 2.000000 0.048421 0.065790 0.010694 2.038462 0.046258 0.067922 0.010830 2.076923 0.044098 0.070089 0.010964 2.115385 0.041940 0.072293 0.011098 2.153846 0.039785 0.074533 0.011230 2.192308 0.037632 0.076809 0.011362 2.230769 0.035481 0.079121 0.011493 2.269231 0.033333 0.081470 0.011625 2.307692 0.031188 0.083855 0.011760 2.346154 0.029044 0.086276 0.012054 DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 42 2.384615 0.026904 0.088733 0.012172 2.423077 0.024766 0.091227 0.012289 2.461538 0.022630 0.093758 0.012404 2.500000 0.020496 0.096325 0.012519 2.500000 0.018365 0.202282 0.012519 END FTABLE 2 FTABLE 1 27 6 Depth Area Volume Outflow1 Outflow2 outflow 3 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.018365 0.000000 0.000000 0.000000 0.000000 0.038462 0.164250 0.006273 0.000000 0.227920 0.000000 0.076923 0.166543 0.012635 0.000000 0.233618 0.000000 0.115385 0.168837 0.019084 0.000000 0.239316 0.000000 0.153846 0.171135 0.025622 0.000000 0.245014 0.000000 0.192308 0.173434 0.032249 0.000000 0.250712 0.000000 0.230769 0.175736 0.038963 0.000000 0.256410 0.000000 0.269231 0.178041 0.045767 0.000000 0.262108 0.000000 0.307692 0.180348 0.052659 0.000000 0.267806 0.000000 0.346154 0.182657 0.059640 0.000000 0.273504 0.000000 0.384615 0.184969 0.066709 0.000000 0.279203 0.000000 0.423077 0.187283 0.073868 0.000000 0.284901 0.000000 0.461538 0.189600 0.081116 0.000000 0.290599 0.000000 0.500000 0.191919 0.088453 0.000000 0.296297 0.000000 0.538462 0.194241 0.095879 0.320299 0.301995 0.000000 0.576923 0.196565 0.103394 0.905527 0.307693 0.000000 0.615385 0.198891 0.110999 1.662909 0.313391 0.000000 0.653846 0.201220 0.118694 2.559248 0.319089 0.000000 0.692308 0.203552 0.126478 3.575168 0.324787 0.000000 0.730769 0.205886 0.134352 4.697313 0.330485 0.000000 0.769231 0.208222 0.142315 5.915519 0.336183 0.000000 0.807692 0.210561 0.150369 7.221491 0.341881 0.000000 0.846154 0.212902 0.158512 8.608088 0.347579 0.000000 0.884615 0.215246 0.166746 10.06890 0.353277 0.000000 0.923077 0.217592 0.175070 11.59796 0.358975 0.000000 0.961538 0.219940 0.183484 13.18961 0.364673 0.000000 1.000000 0.222291 0.191988 14.83834 0.370371 0.000000 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP WDM 2 PREC ENGL 1 RCHRES 1 EXTNL PREC WDM 1 EVAP ENGL 0.5 RCHRES 1 EXTNL POTEV WDM 1 EVAP ENGL 0.76 RCHRES 2 EXTNL POTEV END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL COPY 601 OUTPUT MEAN 1 1 48.4 WDM 901 FLOW ENGL REPL COPY 2 OUTPUT MEAN 1 1 48.4 WDM 702 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 802 FLOW ENGL REPL COPY 602 OUTPUT MEAN 1 1 48.4 WDM 902 FLOW ENGL REPL RCHRES 2 HYDR RO 1 1 1 WDM 1004 FLOW ENGL REPL RCHRES 2 HYDR STAGE 1 1 1 WDM 1005 STAG ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1006 STAG ENGL REPL RCHRES 1 HYDR O 1 1 1 WDM 1007 FLOW ENGL REPL END EXT TARGETS DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 43 MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 8 RCHRES OFLOW OVOL 2 RCHRES INFLOW IVOL END MASS-LINK 8 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 16 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 MASS-LINK 17 RCHRES OFLOW OVOL 1 COPY INPUT MEAN END MASS-LINK 17 END MASS-LINK END RUN DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 44 Predeveloped HSPF Message File DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 45 Mitigated HSPF Message File DRAFT20180420 Prelim 4/30/2018 2:19:57 PM Page 46 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. 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Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 5 Conveyance System Analysis and Design Preliminary Technical Information Report Walker Auto Dealership 5-1 2180100.10 5.0 Conveyance System Analysis and Design All conveyance systems will be sized to meet the requirements of Chapter 4 of the CRSWDM. Conveyance calculations will be provided with the final engineering design. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 6 Special Reports and Studies Preliminary Technical Information Report Walker Auto Dealership 6-1 2180100.10 6.0 Special Reports and Studies A Geotechnical Engineering Report dated April 27, 2018, by Migizi Group Inc. is included as Figure 6-1. A Critical Area Report dated April 2018, by PBS Environmental is included as Figure 6-2. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 6.0 Figures Figure 6-1 ......... Geotechnical Engineering Report Figure 6-2 ......... Critical Area Report Geotechnical Engineering Report Walker Renton Auto Dealership 3400 East Valley Road Renton, Washington P/N 302305-9067 April 27, 2018 prepared for: HHJ Architects, PLLC Attention: Roger Hansen 601 St Helens Tacoma Washington 98402 prepared by: Migizi Group, Inc. PO Box 44840 Tacoma, Washington 98448 (253) 537-9400 MGI Project P1238-T18 i TABLE OF CONTENTS Page No. 1.0 SITE AND PROJECT DESCRIPTION .............................................................................................. 1 2.0 EXPLORATORY METHODS ............................................................................................................ 2 2.1 Auger Boring Procedures...................................................................................................... 3 3.0 SITE CONDITIONS ............................................................................................................................ 3 3.1 Surface Conditions ................................................................................................................. 3 3.2 Soil Conditions ....................................................................................................................... 4 3.3 Groundwater Conditions ...................................................................................................... 5 3.4 Seismic Conditions ................................................................................................................. 5 3.5 Liquefaction Potential ........................................................................................................... 5 3.6 Infiltration Conditions ........................................................................................................... 6 4.0 CONCLUSIONS AND RECOMMENDATIONS............................................................................ 6 4.1 Site Preparation ...................................................................................................................... 7 4.2 Augercast Piles ....................................................................................................................... 9 4.3 Slab-On-Grade-Floors .......................................................................................................... 11 4.4 Drainage Systems ................................................................................................................. 11 4.5 Asphalt Pavement ................................................................................................................ 12 4.6 Structural Fill ........................................................................................................................ 13 5.0 RECOMMENDED ADDITIONAL SERVICES ............................................................................. 14 6.0 CLOSURE ........................................................................................................................................... 15 List of Tables Table 1. Approximate Locations and Depth of Explorations .............................................................................. 2 Table 2. Recommended Allowable Pile Capacities ............................................................................................... 9 List of Figures Figure 1. Topographic and Location Map Figure 2. Site and Exploration Plan APPENDIX A Soil Classification Chart and Key to Test Data .................................................................................................. A-1 Log of Auger Borings B-1 and B-2 ............................................................................................................. A-2…A-3 Page 1 of 15 MIGIZI GROUP, INC. PO Box 44840 PHONE (253) 537-9400 Tacoma, Washington 98448 FAX (253) 537-9401 April 17, 2018 HHJ Architects, PLLC 601 St Helens Tacoma, Washington 98402 Attention: Roger Hansen Subject: Geotechnical Engineering Report Walker Renton Auto Dealership 3400 East Valley Road Renton, Washington P/N 302305-9067 MGI Project P1238-T18 Dear Mr. Hansen: Migizi Group, Inc. (MGI) is pleased to submit this report describing the results of our geotechnical engineering evaluation of the proposed Walker Renton Auto Dealership development at 3400 East Valley Road in Renton, Washington. This report has been prepared for the exclusive use of HHJ Architects, PLLC, and their consultants, for specific application to this project, in accordance with generally accepted geotechnical engineering practice. 1.0 SITE AND PROJECT DESCRIPTION The project site consists of an irregularly-shaped, 5.65-acre, commercially-zoned parcel located towards the south end of the city limits of Renton, Washington, as shown on the enclosed Topographic and Location Map (Figure 1). The subject property is situated between East Valley Road and SR-167 in a heavily developed commercial area. The project site has previously been developed, being utilized as an auto junk yard. A 4,000-sf warehouse building and 1,160 sf radiator shop are still present towards the northwest corner of the project area, as well as paved parking facilities. The remainder of the site had been graded to accommodate storage of vehicles and auto parts, though these have previously been removed from the site. During this initial development of the site, the wetland area along the west side of SR-167 had been severely damaged, and in many cases had been filled. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 2 of 15 It is our understanding that improvement plans involve the demolition of existing site features and the repurposing of the property as an auto dealership. This will involve the construction of a new 50,000 to 60,000 sf two-story, wood-framed structure towards the center of the property, in addition to extensive pavements surrounding this facility. The new structure will contain a showroom/sales area, business offices, parts sales and storage, service and shop regions, storage and other supportive areas. In addition to the aforementioned improvements, the subject development will also entail the restoration of the existing wetland which was damaged by previous actions at the east side of the site along SR-167, and the establishment and maintaining of a new 75-foot buffer area from this wetland. Environmental cleanup will be performed in conjunction with new construction as appropriate, based on recommendations provided by Kane Environmental. 2.0 EXPLORATORY METHODS We explored surface and subsurface conditions at the project site on March 16, 2018. Our exploration and evaluation program comprised the following elements: • Surface reconnaissance of the site; • Two auger boring explorations (designated B-1 and B-2), advanced on March 16, 2016; and • A review of published geologic and seismologic maps and literature. Table 1 summarizes the approximate functional locations and termination depths of our subsurface explorations, and Figure 2 depicts their approximate relative locations. The following sections describe the procedures used for excavation of test pits. TABLE 1 APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS Exploration Functional Location Termination Depth (feet) B-1 B-2 East end of proposed building footprint Southwest corner of proposed building footprint 61½ 51½ The specific number and locations of our explorations were selected in relation to the existing site features, under the constraints of surface access, underground utility conflicts, and budget considerations. It should be realized that the explorations performed and utilized for this eva luation reveal subsurface conditions only at discrete locations across the project site and that actual conditions in other areas could vary. Furthermore, the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities have begun. If significant variations are observed at that time, we may need to modify our conclusions and recommendations contained in this report to reflect the actual site conditions. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 3 of 15 2.1 Auger Boring Procedures Our exploratory borings were advanced through the soil with a hollow-stem auger, using a truck- mounted drill rig, operated by an independent drilling firm working under subcontract to MGI. An engineering geologist from our firm continuously observed the boring, logged the subsurface conditions, and collected representative soil samples. All samples were stored in watertight containers and later transported to a laboratory for further visual examination and testing. After the borings were completed, the borehole was backfilled in accordance with state requirements. Throughout the drilling operation, soil samples were obtained at 2½ to 5-foot depth intervals by means of the Standard Penetration Test (SPT) per American Society for Testing and Materials (ASTM:D-1586), or using a large split-spoon sampler. This testing and sampling procedure consists of driving a standard 2-inch-outside-diameter steel split-spoon sampler 18 inches into the soil with a 140-pound hammer free-falling 30 inches. The number of blows struck during the final 12 inches is recorded on the boring log. If a total of 50 blows are struck within any 6 -inch interval, the driving is stopped, and the blow count is recorded as 50 blows for the actual penetration distance. The resulting blow count values indicate the relative density of granular soils and the relative consistency of cohesive soils. The soils were classified visually in general accordance with the system described in Figure A-1, which includes a key to our exploration logs. Summary logs of our explorations are included as Figures A-2 and A-3. The enclosed boring logs describe the vertical sequence of soils and materials encountered in the borings, based primarily on our field classifications and supported by our subsequent laboratory examination and testing. Where a soil contact was observed to be gradational, our logs indicate the average contact depth. Where a soil type changed between sample intervals, we inferred the contact depth. Our logs also graphically indicate the blow count, sample type, sample number, and approximate depth of each soil sample obtained from the boring, as well as any laboratory tests performed on these soil samples. If any groundwater was encountered in the borehole, the approximate groundwater depth is depicted on the boring logs. Groundwater depth estimates are typically based on the moisture content of soil samples, the wetted height on the drilling rods, and the water level measured in the borehole after the auger has been extracted. 3.0 SITE CONDITIONS The following sections present our observations, measurements, findings, and interpretations regarding, surface, soil, groundwater, and infiltration conditions. 3.1 Surface Conditions As previously indicated, the project site consists of an irregularly-shaped, 5.65-acre, commercially-zoned parcel, located towards the south end of the city limits of Renton, between East Valley Road and SR-167 in a heavily developed commercial area. The site is bound on the north by East Valley RV & Boat Storage, on the south by the Brickman Group storage yard, on the west by East Valley Road, and on the east by SR 167. The northwest corner of the project area retains an existing 4,000-sf warehouse building, a 1,160-sf radiator shop, and asphalt pavement parking facilities. The aforementioned structures were originally constructed in 1996. The remainder of the site had been graded and resurfaced with recycled concrete, to serve as a storage HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 4 of 15 location for automobile parts and debris. The entirety of the site is enclosed by a chain-link fence, with access to the interior being gained through a locked gate. Topographically, the site is relatively level with minimal grade changes being observed over its extent. Purportedly, the eastern margin of the site is a historic wetland region, which had been infringed upon by past developments. This portion of the site served as part of the larger basin for Panther Creek, which travels north and south of the project area along the east side of SR 167. No vegetation was observed on site outside of scattered weeds which have taken root within the existing gravel surfacing. No hydrological features were observed on site, such as seeps, springs, ponds and streams. Scattered ponding was observed across the southwest portion of the site at the time of our site visit. We believe that this is seasonal in nature, and not indicative of hydrogeological conditions onsite. 3.2 Soil Conditions We observed subsurface conditions through the advancement of two geotechnical borings within the footprint of the 50,000 to 60,000-sf structure proposed towards the interior of the site. These explorations extended 51½ to 61½ feet below existing grade, respectively, encountering relatively consistent subgrade conditions. Approximately 5 feet of fill soils were observed at surface elevations in both of our explorations, ranging in composition from recycled concrete to gravelly silty sand. Both of these material types were encountered in a medium dense to dense in situ condition. Underlying these fill soils, we encountered native, alluvial deposits. With depth, alluvial deposits encountered onsite exhibited alternating layers of poorly consolidated fine-grained soils, and moderately consolidated granular soils; highlighting the shifting, localized depositional environment across the project area. The uppermost fine-grained zone, observed immediately below existing fill material, contained a significant organic component. Both of our explorations encountered, below a depth of ± 31 feet, through their respective termination depths, moderately dense, fine silty sand. In the Geologic Map of the Tacoma 1:100,000-scale Quadrangle, as prepared by the Washington State Department of Natural Resources Division of Geology and Earth Resources (WSDNR) (2015), the project site is mapped as containing Qp, or peat, which directly overlies Qa, or Quaternary Alluvium. Peat, as per this publication, is described as loose, locally very soft and wet, organic and organic rich sediment, including muck, silt and clay. Alluvium, as it pertains to the geographic setting of the project area, refers to sedimentary deposits associated with the flood plains of the Duwamish/Green Rivers, and are typically comprised of loose, stratified to massively bedded fluvial silt, sand, and gravel that is typically, well rounded and moderately to well sorted and locally includes sandy to silty estuarine deposits. Our field observations and subsurface explorations generally conform with the geologic classification of the site performed by the WSDNR. The enclosed exploration logs (Appendix A) provide a detailed description of the soil strata encountered in our subsurface explorations. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 5 of 15 3.3 Groundwater Conditions At the time of our reconnaissance and subsurface explorations (March 16, 2018), we encountered groundwater seepage at a depth which ranged from 8 to 15 feet below existing grade . Groundwater levels were generally higher towards the southwest corner of the project area, where significant surficial ponding was observed at the time of our site visit. Given the fact that our explorations were performed within what is generally considered the rainy season (October 1st through April 30th), we do not anticipate that groundwater will rise much higher than that which we observed. Groundwater levels will fluctuate with localized geology and precipitation. 3.4 Seismic Conditions Based on our analysis of subsurface exploration logs and our review of published geologic maps, we interpret the onsite soil conditions to generally correspond with site class E, as defined by Table 20.3-1 in ASCE 7, per the 2015 International Building Code (IBC). Using 2015 IBC information on the USGS Design Summary Report website, Risk Category I/II/III seismic parameters for the site are as follows: Ss = 1.418 g SMS = 1.276 g SDS = 0.851 g S1 = 0.528 g SM1 = 1.266 g SD1 = 0.844 g Using the 2015 IBC information, MCER Response Spectrum Graph on the USGS Design Summary Report website, Risk Category I/II/III, Sa at a period of 0.2 seconds is 1.28 g and Sa at a period of 1.0 seconds is 1.27 g. The Design Response Spectrum Graph from the same website, using the same IBC information and Risk Category, Sa at a period of 0.2 seconds is 0.85 g and Sa at a period of 1.0 seconds is 0.84 g. 3.5 Liquefaction Potential Liquefaction is a sudden increase in pore water pressure and a sudden loss of soil shear strength caused by shear strains, as could result from an earthquake. Research has shown that saturated, loose, fine to medium sands with a fines (silt and clay) content less than about 20 percent are most susceptible to liquefaction. Subsurface explorations performed for this project indicate that the site is underlain by poorly consolidated alluvial soils, ranging in composition from a fine sand with silt to sandy silt; with intermittent layers or lenses of peat. Given the geologic/hydrogeolgic conditions of the project area, we interpret this site as having a moderate susceptibility to liquefaction. In Section 4.2 of this report, we provide recommendations for the preparation of the foundation subgrade which would help mitigate much of this risk, however, during a large-scale seismic event, some degree of liquefaction and related post-construction settlement should be anticipated. We recommend that the structure be designed to prevent catastrophic collapse during a seismic event. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 6 of 15 3.6 Infiltration Conditions As indicated in the Soil and Groundwater Conditions sections of this report, the site is underlain by fill material and poorly-drained, slowly permeable, alluvial soils, with a shallow groundwater table. As such, we do not interpret infiltration as being feasible for this project, and recommend that site produced stormwater be diverted to an existing storm system, managed through detention, or other appropriate means. 4.0 CONCLUSIONS AND RECOMMENDATIONS It is our understanding that improvement plans involve the demolition of existing site features and the repurposing of the property as an auto dealership. This will involve the constructi on of a new 50,000 to 60,000 sf two-story, wood-framed structure towards the center of the property, in addition to extensive pavements surrounding this facility. The new structure will contain a showroom/sales area, business offices, parts sales and storage, service and shop regions, storage and other supportive areas. In addition to the aforementioned improvements, the subject development will also entail the restoration of the existing wetland which was damaged by previous actions at the east side of the site along SR-167, and the establishment and maintaining of a new 75-foot buffer area from this wetland. Environmental cleanup will be performed in conjunction with new construction as appropriate, based on recommendations provided by Kane Environmental. We offer the following recommendations: • Feasibility: Based on our field explorations, research, and evaluations, the proposed structures and pavements appear feasible from a geotechnical standpoint. • Foundation Options: In order to address soil and liquefaction conditions within the proposed expansion area and limit settlement of the addition and new settlement of the existing structure, we recommend that all foundation elements be supported by augercast piles. Recommendations for augercast pile foundations are presented in Section 4.2. • Floor Options: In our opinion, soil-supported slab-on-grade floors can be used if the subgrades are properly prepared. However, there is a potential that liquefaction settlement of the underlying site soils could cause cracking and damage to soil-supported slab-on-grade floors during the design earthquake. If the potential for damage is not acceptable, we recommend that floor slabs be structurally supported. If used, soil supported floor sections should bear on medium dense or denser native soils or on properly compacted structural fill that extends down to medium dense or denser native soil. Recommendations for slab-on-grade floors are included in Section 4.3. Fill underlying floor slabs should be compacted to 95 percent (ASTM:D-1557). • Pavement: We recommend a conventional pavement section comprised of asphalt concrete over crushed rock base course over properly prepared subgrade. Because soft soils immediately underlie proposed pavements, subgrade preparation HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 7 of 15 generally should consist of an over-excavation of two feet, compaction of exposed subgrade soils, then replacement with a suitable structural fill. Compaction should be done in accordance with the structural fill recommendations presented in Section 4.6. All soil subgrades below 24 inches should be thoroughly compacted, then proof- rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over excavated to an additional maximum depth of 12 inches and replaced with a suitable structural fill material. The following sections of this report present our specific geotechnical conclusions and recommendations concerning site preparation, spread footings, slab-on-grade floors, pavement, and structural fill. The Washington State Department of Transportation (WSDOT) Standard Specifications and Standard Plans cited herein refer to WSDOT publications M41-10, Standard Specifications for Road, Bridge, and Municipal Construction, and M21 -01, Standard Plans for Road, Bridge, and Municipal Construction, respectively. 4.1 Site Preparation Preparation of the project site should involve erosion control, temporary drainage, clearing, stripping, excavations, cutting, subgrade compaction, and filling. Erosion Control: Before new construction begins, an appropriate erosion control system should be installed. This system should collect and filter all surface water runoff through silt fencing. We anticipate a system of berms and drainage ditches around construction areas will provide an adequate collection system. Silt fencing fabric should meet the requirements of WSDOT Standard Specification 9-33.2 Table 3. In addition, silt fencing should embed a minimum of 6 inches below existing grade. An erosion control system requires occasional observation and maintenance. Specifically, holes in the filter and areas where the filter has shifted above ground surface should be replaced or repaired as soon as they are identified. Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or near-surface water within the construction zones before stripping begins. Because the selection of an appropriate drainage system will depend on the water quantity, season, weather conditions, construction sequence, and contractor's methods, final decisions regarding drainage systems are best made in the field at the time of construction. Based on our current understanding of the construction plans, surface and subsurface conditions, we anticipate that curbs, berms, or ditches placed around the work areas will adequately intercept surface water runoff. Clearing and Stripping: After surface and near-surface water sources have been controlled, sod, topsoil, and root-rich soil should be stripped from the site. Our explorations and field observations indicate that no significant organic horizon is observed at surface elevations across the project area. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 8 of 15 Site Excavations: Based on our explorations, we expect that excavations will encounter moderately consolidated fill soils at shallow elevations, and poorly consolidated alluvial soils immediately beneath this material, both of which can be readily excavated using standard excavation equipment. Dewatering: Groundwater seepage was encountered in both of our subsurface explorations at a depth of 8 to 15 feet below existing grade, with higher groundwater tables being observed across regions exhibiting surficial ponding. If groundwater is encountered in excavations above the water table, or slightly below, we anticipate that an internal system of ditches, sumpholes, and pumps will be adequate to temporarily dewater shallow excavations. For excavations significantly below the water table, we anticipate that expensive dewatering equipment, such as well points, will be required to temporarily dewater excavations. Temporary Cut Slopes: All temporary soil slopes associated with site cutting or excavations should be adequately inclined to prevent sloughing and collapse. Temporary cut slopes in site soils should be no steeper than 1½H:1V and should conform to Washington Industrial Safety and Health Act (WISHA) regulations. Subgrade Compaction: Exposed subgrades for the foundations of the planned structures should be compacted to a firm, unyielding state before new concrete or fill soils are placed. Any localized zones of looser granular soils observed within a subgrade should be compacted to a density commensurate with the surrounding soils. In contrast, any organic, soft, or pumping soils observed within a subgrade should be over-excavated and replaced with a suitable structural fill material. Site Filling: Our conclusions regarding the reuse of onsite soils and our comments regarding wet- weather filling are presented subsequently. Regardless of soil type, all fill should be placed and compacted according to our recommendations presented in the Structural Fill section of this report. Specifically, building pad fill soil should be compacted to a uniform density of at least 95 percent (based on ASTM:D-1557). Onsite Soils: We offer the following evaluation of these onsite soils in relation to potential use as structural fill: • Surficial Organic Soil and Organic-Rich Topsoil: Where encountered, surficial organic soils, like duff, topsoil, root-rich soil, and organic-rich fill soils are not suitable for use as structural fill under any circumstances, due to high organic content. Consequently, this material can be used only for non-structural purposes, such as in landscaping areas. • Existing Fill Material: As described in the Soil Conditions section of this report, the uppermost 5-feet of soils encountered onsite are comprised of existing fill material placed during the original site development. This material ranged in composition between recycled concrete and gravelly silty sand. These materials should be considered moderately sensitive, and reuse should be confined to periods of extended dry weather. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 9 of 15 • Alluvial Soils: Underlying existing fill material, we encountered native alluvial soils exhibiting alternating layers of poorly consolidated fine -grained soils and moderately consolidated granular soils. The uppermost fine -grained layer is the only native soils which could be feasibly reused as structural fill throughout the course of this project. This soil group contains a high organic content, is extremely moisture sensitive, and is generally encountered in an over-saturated condition. Reuse of this material should be limited to landscaping areas. Permanent Slopes: All permanent cut slopes and fill slopes should be adequately inclined to reduce long-term raveling, sloughing, and erosion. We generally recommend that no permanent slopes be steeper than 2H:1V. For all soil types, the use of flatter slopes (such as 2½H:1V) would further reduce long-term erosion and facilitate revegetation. Slope Protection: We recommend that a permanent berm, swale, or curb be constructed along the top edge of all permanent slopes to intercept surface flow. Also, a hardy vegetative groundcover should be established as soon as feasible, to further protect the slopes from runoff water erosion. Alternatively, permanent slopes could be armored with quarry spalls or a geosynthetic erosion mat. 4.2 Augercast Piles Based on the soil conditions discussed above, we recommend that the new building be supported on augercast piles installed to a depth of 55 feet below the existing ground surface in the medium dense silty sands. The following table provides estimated allowable design capacities for 14-inch, 16-inch, and 18-inch diameter augercast concrete pilings installed to the aforementioned embedment depth: TABLE 2 RECOMMENDED ALLOWABLE PILE CAPACITIES 14-INCH, 16-INCH AND 18-INCH DIAMETER AUGERCAST CONCRETE PILES Pile Diameter (inches) Depth Below Existing Ground Surface (feet) Downward Capacity (tons) Uplift Capacity (tons) 14 55 66 26 16 55 80 30 18 55 98 34 The allowable pile capacities presented above apply to all long-term live and dead loads and may be increased by one-third when considering short-term loads such as wind or seismic influence. The allowable pile capacities are based on the strength of the supporting soils for the penetrations indicated and include a factor of safety of at least 2. The allowable uplift capacities indicated for augercast piles may be used provided that a reinforcing bar is installed the entire length of the pile. This bar should be centered in the pile. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 10 of 15 Static pile settlements are expected to be essentially elastic in nature and occur as loads are applied. Total static settlement of piles constructed as recommended are not expected to exceed 1 inch, while differential static settlements between comparably loaded piles are not expected to exceed about 50 percent of this value. The pile capacities provided above apply to single piles. If piles within groups are spaced at least three pile diameters on center, no reduction for pile group action need be made. The structural characteristics of the pile materials and allowable internal stresses may impose more stringent limitations and should be evaluated by the structural engineer. Lateral loadings due to wind or seismic forces can be resisted by uplift or lateral loading on the piles, or lateral soil resistance of the pile cap. The manner in which these loads are transferred into the piles will be a function of the design of the foundation system. Passive soil resistance of the pile cap may be computed using an equivalent fluid density of 220 pcf (pounds per cubic foot) for a level backfill surface, provided the backfill around the pile cap is compacted to at least 95 percent of maximum dry density per American Society for Testing and Materials (ASTM) D-1557. This value incorporates a factor of safety of about 1.5. Lateral capacities for augercast piling are dependent upon the characteristics of the reinforcing steel and the coefficient of subgrade reaction for the surrounding soils. We recommend that the pile stiffness, T, be computed using the formula T = (EI/f)1/5 where E equals the pile modulus of elasticity, I equals the pile moment of inertia, and f equals the soil coefficient of subgrade reaction. A value of 6 tcf (tons per cubic foot) should be used for f. For the recommended penetration, the maximum moment for piles fixed against rotation at the ground surface will occur at a depth equal to about 1.8 T and the magnitude of this moment, M, can be computed using the formula M = 0.25 PT where P is the lateral force applied at the ground surface. The moment will decrease to zero at a depth of about 4.5 T. The maximum pile deflection at the ground surface can be computed using the formula D = 0.93 (PT3/EI). Pile Installation: Augercast (cast-in-place) concrete piles should be installed using a continuous- flight, hollow-stem auger. As is common practice, the pile grout would be pumped under pressure through the hollow-stem as the auger is withdrawn. Reinforcing steel for bending and uplift would be placed in the fresh grout column immediately after withdrawal of the auger. No direct information regarding the capacity of augercast piles (e.g., driving resistance data) is obtained while this type of pile is being installed. Therefore, it is particularly important that the installation of augercast piles be carefully monitored by a qualified individual working under the direct supervision of a geotechnical engineer. It should be noted that the recommended pile penetration and allowable capacities presented above assumed uniform soil conditions. There may be unexpected variations in the depth and characteristics of the supporting soils across the site. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 11 of 15 Accordingly, we recommend that pile installation be monitored by a member of our staff who will observe installation procedures and evaluate the adequacy of individual pile installations. 4.3 Slab-On-Grade Floors In our opinion, soil-supported slab-on-grade floors can be used if the subgrades are properly prepared. However, there is a potential that liquefaction settlement of the underlying site soils could cause cracking and damage to soil-supported slab-on-grade floors during the design earthquake. If the potential for damage is not acceptable, we recommend that floor slabs be structurally supported. We offer the following comments and recommendations concerning soil-supported slab-on- grade floors. Floor Subbase: We recommend over-excavation of slab-on-grade floor subgrades to a minimum depth of 2 feet, then placement of properly compacted structural fill as a floor subbase. If floor construction occurs during wet conditions, it is likely that a geotextile fabric, placed between the structural fill floor subbase and native soils, will be necessary. All subbase fill should be compacted to a density of at least 95 percent (based on ASTM:D-1557). Capillary Break and Vapor Barrier: To retard the upward wicking of moisture beneath the floor slab, we recommend that a capillary break be placed over the subgrade. Ideally, this capillary break would consist of a 4-inch-thick layer of pea gravel or other clean, uniform, well-rounded gravel, such as “Gravel Backfill for Drains” per WSDOT Standard Specification 9-03.12(4), but clean angular gravel can be used if it adequately prevents capillary wicking. In addition, a layer of plastic sheeting (such as Crosstuff, Visqueen, or Moistop) should be placed over the capillary break to serve as a vapor barrier. During subsequent casting of the concrete slab, the contractor should exercise care to avoid puncturing this vapor barrier. Vertical Deflections: Due to elastic compression of subgrades, soil-supported slab-on-grade floors can deflect downwards when vertical loads are applied. In our opinion, a subgrade reaction modulus of 140 pounds per cubic inch can be used to estimate such deflections. 4.4 Drainage Systems In our opinion, the proposed expansion area should be provided with a permanent drainage system to reduce the risk of future moisture problems. We offer the following recommendations and comments for drainage design and construction purposes. Perimeter Drains: We recommend that the structure be encircled with a perimeter drain system to collect seepage water. This drain should consist of a 4-inch-diameter perforated pipe within an envelope of pea gravel or washed rock, extending at least 6 inches on all sides of the pipe, and the gravel envelope should be wrapped with filter fabric to reduce the migration of fines from the surrounding soils. Ideally, the drain invert would be installed no more than 8 inches above the base of the perimeter footings. HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 12 of 15 Subfloor Drains: We recommend that subfloor drains be included beneath the new building. These subfloor drains should consist of 4-inch-diameter perforated pipes surrounded by at least 6 inches of pea gravel and enveloped with filter fabric. A pattern of parallel pipes spaced no more than 20 feet apart and having inverts located about 12 inches below the capillary break layer would be appropriate, in our opinion. Discharge Considerations: If possible, all perimeter drains should discharge to a sewer system or other suitable location by gravity flow. Check valves should be installed along any drainpipes that discharge to a sewer system to prevent sewage backflow into the drain system. If gravity flow is not feasible, a pump system is recommended to discharge any water that enters the drainage system. Runoff Water: Roof-runoff and surface-runoff water should not discharge into the perimeter drain system. Instead, these sources should discharge into separate tightline pipes and be routed away from the building to a storm drain or other appropriate location. Grading and Capping: Final site grades should slope downward away from the buildings so that runoff water will flow by gravity to suitable collection points, rather than ponding near the building. Ideally, the area surrounding the building would be capped with concrete, asphalt, or low-permeability (silty) soils to minimize or preclude surface-water infiltration. 4.5 Asphalt Pavement Since asphalt pavements will be expanded during the course of the proposed development, we offer the following comments and recommendations for pavement design and construction. Subgrade Preparation: After removal of any organics underlying pavements, we recommend a conventional pavement section comprised of an asphalt concrete pavement over a crushed rock base course over a properly prepared (compacted) subgrade or a granular subbase. Given the relative loose/soft soil conditions observed across the project area, we recommend the over- excavation of 24 inches of the existing subgrade material underlying the new pavement sections, and replacement with a suitable structural fill subbase. Given the extent of the proposed paving operation and corresponding earthwork activities, we recommend limiting the subgrade preparation to times of dry weather. All soil subgrades below 24 inches should be thoroughly compacted, then proof-rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over excavated to an additional maximum depth of 12 inches and replaced with a suitable structural fill material. All structural fill should be compacted according to our recommendations given in the Structural Fill section. Specifically, the upper 2 feet of soils underlying pavement section should be compacted to at least 95 percent (based on ASTM D-1557), and all soils below 2 feet should be compacted to at least 90 percent. Pavement Materials: For the base course, we recommend using imported crushed rock, such as "Crushed Surfacing Top Course” per WSDOT Standard Specification 9-03.9(3). If a subbase HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 13 of 15 course is needed, we recommend using imported, clean, well-graded sand and gravel such as “Ballast” or “Gravel Borrow” per WSDOT Standard Specifications 9-03.9(1) and 9-03.14, respectively. Conventional Asphalt Sections: A conventional pavement section typically comprises an asphalt concrete pavement over a crushed rock base course. We recommend using the following conventional pavement sections: Minimum Thickness Pavement Course Automobile Parking Area Driveways Areas Subject to Frequent Truck Traffic Asphalt Concrete Pavement 2 inches 3 inches 4 inches Crushed Rock Base 4 inches 6 inches 6 inches Granular Fill Subbase (if needed) 12 inches 24 inches 24 inches Compaction and Observation: All subbase and base course material should be compacted to at least 95 percent of the Modified Proctor maximum dry density (ASTM D-1557), and all asphalt concrete should be compacted to at least 92 percent of the Rice value (ASTM D-2041). We recommend that an MGI representative be retained to observe the compaction of each course before any overlying layer is placed. For the subbase and pavement course, compaction is best observed by means of frequent density testing. For the base course, methodology observations and hand-probing are more appropriate than density testing. Pavement Life and Maintenance: No asphalt pavement is maintenance-free. The above described pavement sections present our minimum recommendations for an average level of performan ce during a 20-year design life, therefore, an average level of maintenance will likely be required. Furthermore, a 20-year pavement life typically assumes that an overlay will be placed after about 10 years. Thicker asphalt and/or thicker base and subbase courses would offer better long-term performance, but would cost more initially; thinner courses would be more susceptible to “alligator” cracking and other failure modes. As such, pavement design can be considered a compromise between a high initial cost and low maintenance costs versus a low initial cost and higher maintenance costs. 4.6 Structural Fill The term "structural fill" refers to any material placed under foundations, retaining walls, slab - on-grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and recommendations concerning structural fill are presented in the following paragraphs. Materials: Typical structural fill materials include clean sand, gravel, pea gravel, washed rock, crushed rock, well-graded mixtures of sand and gravel (commonly called "gravel borrow" or "pit- run"), and miscellaneous mixtures of silt, sand, and gravel. Recycled asphalt, concrete, and glass, which are derived from pulverizing the parent materials, are also potentially useful as structural fill in certain applications. Utilizing recycled content may require approval from the Tacoma Pierce County Health Department for placement in an aquifer recharge area. Soils used for HHJ Architects, PLLC – Walker Renton Auto Dealership, 3400 E Valley Rd, Renton, WA April 27, 2018 Geotechnical Engineering Report P1238-T18 Migizi Group, Inc. Page 14 of 15 structural fill should not contain any organic matter or debris, nor any individual particles greater than about 6 inches in diameter. Fill Placement: Clean sand, gravel, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be thoroughly compacted with a mechanical compactor. Compaction Criteria: Using the Modified Proctor test (ASTM:D-1557) as a standard, we recommend that structural fill used for various onsite applications be compacted to the following minimum densities: Fill Application Minimum Compaction Slab-on-grade floor subgrade (upper 2 feet) Slab-on-grade floor subgrade (below 2 feet) Asphaltic pavement base and subbase Asphaltic pavement subgrade (upper 2 feet) Asphaltic pavement subgrade (below 2 feet) 95 percent 90 percent 95 percent 95 percent 90 percent Subgrade Observation and Compaction Testing: Regardless of material or location, all structural fill should be placed over firm, unyielding subgrades prepared in accordance with the Site Preparation section of this report. The condition of all subgrades should be observed by geotechnical personnel before filling or construction begins. Also, fill soil compaction should be verified by means of in-place density tests performed during fill placement so that adequacy of soil compaction efforts may be evaluated as earthwork progresses. Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the "fines" content (that soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive t o small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points above or below optimum. For fill placement during wet-weather site work, we recommend using "clean" fill, which refers to soils that have a fines content of 5 percent or less (by weight) based on the soil fraction passing the U.S. No. 4 Sieve. 5.0 RECOMMENDED ADDITIONAL SERVICES Because the future performance and integrity of the structural elements will depend largely on proper site preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. Consequently, we recommend that MGI be retained to provide the following post-report services: • Review all construction plans and specifications to verify that our design criteria presented in this report have been properly integrated into the design; • Prepare a letter summarizing all review comments (if required); APPROXIMATE SITE LOCATION P.O. Box 44840 Tacoma, WA 98448 Location Job Number Figure DateTitle 3400 East Valley Road Renton, WA P/N 302305-9067 Topographic and Location Map 1 04/06/18 P1238-T18 APPENDIX A SOIL CLASSIFICATION CHART AND KEY TO TEST DATA LOG OF AUGER BORINGS CLAYEY GRAVELS, POORLY GRADED GRAVEL-SAND-CLAY MIXTURES SILTS AND CLAYSCOARSE GRAINED SOILSMore than Half > #200 sieveLIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 CLEAN GRAVELS WITH LITTLE OR NO FINES GRAVELS WITH OVER 15% FINES CLEAN SANDS WITH LITTLE OR NO FINES MORE THAN HALF COARSE FRACTION IS SMALLER THAN NO. 4 SIEVE MORE THAN HALF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE INORGANIC SILTS, MICACEOUS OR DIATOMACIOUS FINE SANDY OR SILTY SOILS, ELASTIC SILTS ORGANIC CLAYS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY OH INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS, OR CLAYEY SILTS WITH SLIGHT PLASTICITY CH SILTY GRAVELS, POORLY GRADED GRAVEL-SAND-SILT MIXTURES SANDS SILTS AND CLAYS Figure A-1 INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS E3RA R-Value Sieve Analysis Swell Test Cyclic Triaxial Unconsolidated Undrained Triaxial Torvane Shear Unconfined Compression (Shear Strength, ksf) Wash Analysis (with % Passing No. 200 Sieve) Water Level at Time of Drilling Water Level after Drilling(with date measured) RV SA SW TC TX TV UC (1.2) WA (20) Modified California Split Spoon Pushed Shelby Tube Auger Cuttings Grab Sample Sample Attempt with No Recovery Chemical Analysis Consolidation Compaction Direct Shear Permeability Pocket Penetrometer CA CN CP DS PM PP PtHIGHLY ORGANIC SOILS TYPICAL NAMES GRAVELS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS WELL GRADED GRAVELS, GRAVEL-SAND MIXTURES MAJOR DIVISIONS PEAT AND OTHER HIGHLY ORGANIC SOILS WELL GRADED SANDS, GRAVELLY SANDS POORLY GRADED SANDS, GRAVELLY SANDS SILTY SANDS, POOORLY GRADED SAND-SILT MIXTURES CLAYEY SANDS, POORLY GRADED SAND-CLAY MIXTURES POORLY GRADED GRAVELS, GRAVEL-SAND MIXTURES SOIL CLASSIFICATION CHART AND KEY TO TEST DATA GW GP GM GC SW SP SM SC ML FINE GRAINED SOILSMore than Half < #200 sieveLGD A NNNN02 GINT US LAB.GPJ 11/4/05INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS CL OL MH SANDS WITH OVER 15% FINES Migizi Group, Inc. SS S-1 SS S-2 SS S-3 SS S-4 SS S-5 SS S-6 SS S-7 SS S-8 6 6 12 12 12 18 18 18 11-19-12 (31) 6-3-6 (9) 3-3-4 (7) 1-2-2 (4) 2-1-2 (3) 2-5-6 (11) 2-3-12 (15) 4-1-1 (2) SM ML SM OH SM SP ML 2.0 5.5 7.0 9.0 13.0 17.5 31.0 Recycled Concrete (SM) Gray/brown silty sand with gravel (dense, damp) (Fill) (ML) Gray/brown silt with some organics (stiff, moist) (Alluvium) (SM) Gray silty sand with some gravel (loose, wet) (Alluvium) (OH) Gray organic silt (soft, wet) (Alluvium) (SM) Gray fine silty sand (very loose, wet) (Alluvium) (SP) Black fine to coarse sand (medium dense, wet) (Alluvium) With interbeds of silty sand (ML) Gray silt (soft, wet) (Alluvium) NOTES LOGGED BY ZLL DRILLING METHOD Truck Mounted Drill Rig DRILLING CONTRACTOR Holocene GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 3/16/18 COMPLETED 3/16/18 AT TIME OF DRILLING 15.00 ft AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION SAMPLE TYPENUMBERDEPTH(ft)0 5 10 15 20 25 30 35 (Continued Next Page) PAGE 1 OF 2 Figure A-2 BORING NUMBER B-1 CLIENT HHJ Architects, PLLC PROJECT NUMBER P1238-T18 PROJECT NAME Walker Renton Auto Dealership Geotech Report PROJECT LOCATION 3400 East Valley Road, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 4/5/18 15:42 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1238-T18\P1238-T18 BORING LOGS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 RECOVERY (in)(RQD)BLOWCOUNTS(N VALUE)U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION SS S-9 SS S-10 SS S-11 SS S-12 SS S-13 SS S-14 18 18 18 18 18 18 1-2-2 (4) 0-4-6 (10) 3-5-5 (10) 0-4-8 (12) 10-8-10 (18) 3-4-5 (9) ML SM 40.5 61.5 (ML) Gray silt (soft, wet) (Alluvium) (continued) (SM) Gray fine silty sand (medium dense, wet) (Alluvium) Grades to loose Bottom of borehole at 61.5 feet.SAMPLE TYPENUMBERDEPTH(ft)35 40 45 50 55 60 PAGE 2 OF 2 Figure A-2 BORING NUMBER B-1 CLIENT HHJ Architects, PLLC PROJECT NUMBER P1238-T18 PROJECT NAME Walker Renton Auto Dealership Geotech Report PROJECT LOCATION 3400 East Valley Road, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 4/5/18 15:42 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1238-T18\P1238-T18 BORING LOGS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 RECOVERY (in)(RQD)BLOWCOUNTS(N VALUE)U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION SS S-1 SS S-2 SS S-3 SS S-4 SS S-5 SS S-6 SS S-7 SS S-8 6 12 18 12 18 18 18 18 6-2-2 (4) 1-0-0 (0) 5-5-8 (13) 5-3-3 (6) 7-8-10 (18) 2-3-7 (10) 1-0-1 (1) 1-1-1 (2) SM OH SP- SM SP SM ML SM 1.5 5.0 7.0 12.5 20.0 22.5 32.5 Recycled Concrete (SM) Gray/brown fine silty sand (loose, moist) (Alluvium) (OH) Gray/brown organic silt (very soft, wet) (Alluvium) (SP-SM) Dark gray fine sand with silt and interbeds of silty sand (medium dense, wet) (Alluvium) (SP) Dark gray fine to medium sand (medium dense, wet) (Alluvium) (SM) Gray fine silty sand (medium dense, wet) (Alluvium) (ML) Gray silt (very soft, wet) (Alluvium) With shell debris (SM) Gray fine silty sand with shell debris (medium dense, wet) (Alluvium) NOTES LOGGED BY ZLL DRILLING METHOD Truck Mounted Drill Rig DRILLING CONTRACTOR Holocene GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 3/16/18 COMPLETED 3/16/18 AT TIME OF DRILLING 17.50 ft AT END OF DRILLING --- AFTER DRILLING --- HOLE SIZE 4.25" HSAGROUND ELEVATION SAMPLE TYPENUMBERDEPTH(ft)0 5 10 15 20 25 30 35 (Continued Next Page) PAGE 1 OF 2 Figure A-3 BORING NUMBER B-2 CLIENT HHJ Architects, PLLC PROJECT NUMBER P1238-T18 PROJECT NAME Walker Renton Auto Dealership Geotech Report PROJECT LOCATION 3400 East Valley Road, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 4/5/18 15:42 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1238-T18\P1238-T18 BORING LOGS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 RECOVERY (in)(RQD)BLOWCOUNTS(N VALUE)U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION SS S-9 SS S-10 SS S-11 SS S-12 18 18 18 18 3-4-6 (10) 3-5-3 (8) 4-5-5 (10) 7-9-9 (18) SM SM 40.0 51.5 (SM) Gray fine silty sand with shell debris (medium dense, wet) (Alluvium) (continued) (SM) Gray fine silty sand (loose, wet) (Alluvium) Grades to medium dense Bottom of borehole at 51.5 feet.SAMPLE TYPENUMBERDEPTH(ft)35 40 45 50 PAGE 2 OF 2 Figure A-3 BORING NUMBER B-2 CLIENT HHJ Architects, PLLC PROJECT NUMBER P1238-T18 PROJECT NAME Walker Renton Auto Dealership Geotech Report PROJECT LOCATION 3400 East Valley Road, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 4/5/18 15:42 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1238-T18\P1238-T18 BORING LOGS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 RECOVERY (in)(RQD)BLOWCOUNTS(N VALUE)U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION 314 WEST 15TH STREET VANCOUVER, WA 98660 360.695.3488 MAIN 866.727.0140 FAX PBSUSA.COM Critical Areas Report for the Dale Walker Property 3400 East Valley Road Renton, WA 98057 April 2018 PBS Project No. 41482.000 Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington I April 2108 PBS Project No. 41454.000 TABLE OF CONTENTS 1 INTRODUCTION .............................................................................................................................................. 1 2 SITE DESCRIPTION .......................................................................................................................................... 1 2.1 Location and Setting ................................................................................................................................................................ 1 2.2 Site History ................................................................................................................................................................................... 1 2.3 Hydrology ..................................................................................................................................................................................... 2 2.4 Soils ................................................................................................................................................................................................. 2 2.5 Vegetation Communities ........................................................................................................................................................ 2 2.5.1 Historic Vegetation Communities .......................................................................................................................... 2 2.5.2 Existing Vegetation ....................................................................................................................................................... 3 3 CRITICAL AREAS ............................................................................................................................................. 3 3.1 National and Local Wetland Inventories .......................................................................................................................... 3 3.2 Wetland Delineation Methods ............................................................................................................................................. 3 3.2.1 Rationale for Delineation Methods ........................................................................................................................ 3 3.2.2 Office Methods .............................................................................................................................................................. 3 3.2.3 Field Methods ................................................................................................................................................................. 3 3.2.4 Growing Season ............................................................................................................................................................. 4 3.2.5 Climate .............................................................................................................................................................................. 4 3.3 Delineation Results ................................................................................................................................................................... 5 3.3.1 Soils ..................................................................................................................................................................................... 5 3.3.2 Hydrology ......................................................................................................................................................................... 6 3.3.3 Vegetation ........................................................................................................................................................................ 6 3.4 Wetland Rating and Buffers .................................................................................................................................................. 6 3.5 Regulatory Framework ............................................................................................................................................................ 7 4 IMPACT ASSESSMENT .................................................................................................................................... 7 5 RESTORATION PLAN ...................................................................................................................................... 8 5.1 Goals and Objectives ................................................................................................................................................................ 8 5.2 Performance Standards ........................................................................................................................................................... 8 5.3 Restoration Activities................................................................................................................................................................ 8 5.3.1 Fill Removal/ Grading/ Site Preparation .............................................................................................................. 8 5.3.2 Native Plantings ............................................................................................................................................................. 8 5.3.3 Follow-up Weed Control ............................................................................................................................................ 8 5.4 Maintenance and Monitoring of Restoration ............................................................................................................... 10 5.5 Contingency Measures .......................................................................................................................................................... 10 6 REFERENCES .................................................................................................................................................. 11 Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington II April 2018 PBS Project No. 41454.000 SUPPORTING DATA TABLES Table 1. Precipitation Data Table 2. Wetland Characteristics, Rating and Buffers Table 3. Performance Standards Table 4. Planting Plan PHOTOGRAPHS FIGURES Figure 1. Site Vicinity Figure 2. City of Renton Mapped Wetlands and Streams Figure 3. National Wetland Inventory Figure 4. Wetland Delineation Map Figure 5. Restoration Planting Plan Figure 6. Mitigation Monitoring Plan APPENDICES APPENDIX A: Wetland Delineation Datasheets APPENDIX B: Wetland Rating Forms Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 1 April 2018 PBS Project No. 41475.000 1 INTRODUCTION PBS Engineering and Environmental, Inc. (PBS) has prepared the following Critical Area Report for a property recently purchased by Mr. Dale Walker and being proposed for development as a new car dealership. The site was operated as an auto junk yard and auto repair shop for at least 50 years prior to being purchased by Mr. Walker. Most recently the property was doing business as South End Auto Wrecking, Inc. Various forms of contamination have been identified at the site and cleanup efforts will likely include removal of some of the contaminated soils. Stemen Environmental is coordinating a cleanup of the site under Ecology’s voluntary cleanup program. Mr. Walker has cleared the vehicles and trash off the site in preparation for development of the lot. The City of Renton requested a wetland delineation prior to any excavation or grading of the site. Before PBS could conduct the delineation, Mr. Walker had someone clear the vegetation at the east edge of the property. The clearing extended across a City identified wetland at the east edge of the site onto the Washington State Department of Transportation (WSDOT) right-of-way for State Route 167. This report identifies the wetland boundary, assesses the impacts to the wetland from the clearing activity, and includes a restoration plan for restoring wetland vegetation. 2 SITE DESCRIPTION 2.1 Location and Setting The property is located at 3400 East Valley Road, inside the City limits of Renton, WA. It is in the NE quarter of Section 30, Township 23 North, Range 05 East. The property consists of a single tax lot (King County tax parcel 3023059067) totaling approximately 5.65 acres (Figure 1). The approximate center of the site is at latitude 47.449707, longitude -122.216895. The property is in the Lower Green – Duwamish watershed in the Duwamish-Green River Water Resource Inventory Area (WRIA 9). The Walker property borders East Valley Road on the west side, State Route 167 to the east, and commercial properties to the south and north. The property sits in a regional low-lying area that was once part of a large wetland complex at the junction of the Cedar, Black, and Green Rivers. An historic map shows a small stream running through the middle of the property from the southeast corner to the west side. The project site is relatively flat with elevations ranging from 16 feet above sea level near the northeast corner and the southwest corner to 24 feet near the middle of the site. Most of the surface drainage is towards the southwest corner, with some drainage flowing to the east. 2.2 Site History The property was used for agricultural land until the 1950’s or 1960’s Since then it has been used as an auto junkyard and auto repair facility. Historic aerials from 1936 and 1940 show agricultural fields across the entire area. No obvious wetlands are visible on these photos and any stream that may have been present has likely been ditched. Highway 167 was built in the 1960’s and a 1964 aerial shows the south half and the west third of the north half of the property cleared with fill placement likely. By 1968 the entire property is being used as an auto junkyard except for a strip of vegetation along the east edge. In 2008, WSDOT widened SR 167 extending the roadway approximately 30 feet to the west and constructing a rock gabion retaining wall just east of the subject property. The retaining wall was designed to limit impacts to a wetland that extended nearly a mile along the west edge of the roadway. In October of 2017, the eastern portion of the property and the adjacent WSDOT right-of-way was cleared of trees and shrubs. Some of the logs and brush were left in the wetland, some appear to have been collected in slash piles outside the wetland, and some appear to have been chipped in place. Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 2 April 2018 PBS Project No. 41475.000 WSDOT sent notification of the incident to Washington Department of Ecology, the City of Renton, the US Army Corps of Engineers, the Washington Department of Fish & Wildlife, and the Muckleshoot tribe. Mr. Walker is currently working with WSDOT on resolution of the unauthorized clearing and restoration of the wetland vegetation. 2.3 Hydrology The property is in the Panther Creek watershed. Panther Creek flows into Springbrook Creek, which in turn flows into the Black River and then the Green/Duwamish River. The site is part of the Duwamish – Green Water Resource Inventory Area (WRIA 9). The hydrology of this area has been dramatically changed over the last century with the lowering of Lake Washington which dried up much of the Black River, redirection of the Cedar River flows from the Black and Green Rivers into Lake Washington, and filling of vast areas of wetland and conversion of the floodplain and wetlands to commercial and industrial uses. Hydrology at the site currently comes primarily from direct precipitation, high groundwater, and stormwater runoff. There is a culvert connection under SR 167 near the south end of the property that allows water to pass through between the Panther Creek wetlands to the east of the Highway and the wetland between the west side of the highway and the subject property. Water level readings in wells installed by Stemen Environmental show water levels 7 to 10 feet below the ground surface across much of the site during the dry season and near the surface during the wet season, particularly in the southwest corner. Based on data from the wells, groundwater flow appears to be towards the west and the Green River. Surface flows on the site are towards the southwest corner and the east side of the property. Historic aerials show a stormwater pond constructed in 2011 in the southwest corner of the subject property. According to Mr. Stemen, water was pumped out of the pond east towards the southeast corner, where it was filtered in an oyster shell pit before entering the wetland. This stormwater treatment facility is visible on photos starting in 2012 and was approved by Ecology. The pumps have since been removed and water now overflows the stormwater pond across much of the southwest corner of the site. The remains of the stormwater pond and the oyster shell pit were found during the site visit. An east/west ditch across the property is visible on aerials in the southern half of the property. Portions of this ditch were still present during the site visit, though no direct connection to the wetland was observed. At the time of the site visit, there was shallow ponded water in much of the southwest corner and water up to 2 feet deep in the wetland on the WSDOT right-of-way. 2.4 Soils Soils are mapped as urban land across the subject property due to high levels of disturbance (NRCS 2017). To the west, across East Valley Road, soils are mapped as Tukwila Muck. To the east on the other side of SR 167, soils are mapped as Seattle Muck. Both soils are deep, poorly drained organic soils that formed in herbaceous and woody deposits in depressions and river valleys. Surface soil on the property is nearly all fill material. Some remnants of the original muck soils are found in the wetland in the WSDOT right-of-way. 2.5 Vegetation Communities 2.5.1 Historic Vegetation Communities The property would have probably originally supported a mix of upland forested and forested, scrub-shrub and emergent wetland communities. Black cottonwood (Populus balsamifera), western red-cedar (Thuja plicata), red alder (Alnus rubra). Pacific willow (Salix lucida ssp lasiandra) and Sitka spruce (Picea sitchensis) would have been present in the forested wetland areas. Shrubs likely included willows (Salix sp), red-osier dogwood (Cornus sericea), black twinberry (Lonicera involucrata), Douglas spirea (Spirea douglasii) and others. Sedges (Carex sp), rushes (Juncus sp, Scirpus sp) and a variety of other herbaceous plants would have also Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 3 April 2018 PBS Project No. 41475.000 been present. The original forest and wetlands were likely logged, cleared and drained over a century ago to make way for agricultural fields and then commercial and industrial development. 2.5.2 Existing Vegetation For the last 50 years or more, there has been very little vegetation on the site except for some narrow fringes of mostly weedy species along the edges. There was a forested wetland on the WSDOT right-of-way just east of the property. Based on vegetation on the properties to the north and south and remaining vegetation in th, this area, the vegetation in the right-of-way consisted of an overstory of black cottonwood and Pacific willow, with red-osier dogwood, Douglas spirea and Himalayan blackberry in the shrub layer and reed canary grass (Phalaris arundinacea), slough sedge (Carex obnupta), and horsetails (Equisetum sp) in the understory. Other species may also be present, but were not identifiable at the time of the site visit in December. 3 CRITICAL AREAS 3.1 National and Local Wetland Inventories The National Wetland Inventory (NWI) maps a 1.6 acre palustrine, forested, seasonally flooded wetland just east of the property along the west side of SR 167 extending north from the subject property. A 25-acre palustrine, emergent and scrub-shrub, semi-permanently flooded wetland is mapped on the east side of SR 157 that extends north to SR 405. Several other emergent and scrub-shrub wetlands are shown south of this larger wetland. A palustrine forested wetland associated with Panther Creek is also mapped along the east side of SR 167. All of these wetlands are part of a wetland complex associated with Panther Creek and Rolling Hills Creek that has been fragmented by SR 167 and other development. The City of Renton wetland maps show a 52-acre wetland on the east side of SR 167 and a 3-acre wetland on the west side of SR 167. While the NWI map shows wetland extending only halfway along the east side of the property, the City of Renton wetland maps show the wetland extending along the entire east edge of the property and continuing over 600 feet south of the property boundary. Figure 2 shows the City mapped wetlands and Figure 3 shows the NWI mapped wetlands. 3.2 Wetland Delineation Methods 3.2.1 Rationale for Delineation Methods Based upon guidance provided in the Corps of Engineers 1987 Wetland Delineation Manual (1987 Manual) and the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys and Coast Supplement (Version 2.0) (WMVC Regional Supplement), it is the best professional judgment of the PBS delineation team that the current wetlands in the study area still exist under reasonably “normal circumstances” as defined in the 1987 Manual and supplement despite the recent clearing. Wetland soils and hydrology are still present. Remnants of the cleared vegetation along with reference vegetation to the north and south allowed for inference of wetland vegetation at the site pre-clearing. Therefore, we delineated waters and wetlands on the project using methods recommended in the manual for normal circumstances. 3.2.2 Office Methods Office preparation for the delineation consisted of reviewing a variety of online sources including aerial photographs, City of Renton GIS layers, King County iMAP, soils maps and descriptions, weather history, site history, etc. 3.2.3 Field Methods Katharine Lee, a Professional Wetland Scientist, and Kevin Hood conducted a field visit on December 13, 2017. The wetland was delineated using the three-parameter approach as required in the WMVC Regional Supplement, with extrapolation of vegetation based on remaining vegetation, stumps and intact vegetation to the north and south. A Magellan handheld GPS unit with post-processing and sub-meter accuracy was used Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 4 April 2018 PBS Project No. 41475.000 to map the location of wetland flags and data plots. The wetland sits in a defined depression with a retaining wall on the east side along SR 167 and a fill prism on the west side. 3.2.3.1 Hydrology The presence of wetland hydrology was determined by evaluating a variety of direct and indirect indicators. In addition to direct hydrologic measurements, hydrologic indicators can be used to infer satisfaction of the wetland hydrology criterion. Field indicators of wetland hydrology listed in the Regional Supplement include, but are not limited to, visual observation of inundation or saturation, sediment deposition, hydric soil characteristics, watermarks, drift lines, oxidation around living roots and rhizomes, and water-stained leaves. To satisfy the hydrology criterion for wetlands, soils need to be inundated or saturated to the surface for at least 14 consecutive days during the growing season. The site visits occurred at the end of, or just outside the growing season for this area. Primary hydrologic indicators in the form of saturated soils, high groundwater and inundation were present at the time of the site visit. 3.2.3.2 Soils The presence of hydric soils was determined consistent with the WMVC Regional Supplement and current regulatory guidance. The supplement includes hydric soil indicators specific to this region. Soils were evaluated based on these indicators. The extent and depth of historic fill generally defines the current wetland boundary with the wetland extending into the edge of the fill. Fill material was a mix a silty, sandy, gravelly material with varying types of debris. 3.2.3.3 Vegetation No vegetation was present on the upland areas at the time of the site visit and while upland areas appeared to have recently been graded during the removal of vehicles, it does not appear any vegetation had been previously present based on historic aerials. The vegetation in the wetland had recently been cleared, removing all the trees and most of the shrubs. Stumps were still present along with a few shrubs and some herbaceous vegetation. Because of this, vegetation was not a reliable indicator of the wetland/upland boundary except offsite at the north and south edges. Species identifications and taxonomic nomenclature followed the USDA Plants Database. Each species' indicator status was assigned using the Western Mountains, Valleys, and Coast 2016 Regional Wetland Plant List (USAC 2017). A species indicator status refers to the relative frequency with which the species occurs in jurisdictional wetlands (Appendix E). An area satisfies the hydrophytic vegetation criteria when, under normal circumstances, more than 50 percent of the dominant species from each stratum are obligate wetland (OBL), facultative wetland (FACW), or facultative (FAC) species. 3.2.4 Growing Season The growing season is generally defined as the portion of the year when soil temperatures at approximately 20 inches below the soil surface are above biological zero or 5 degrees Celsius (US Department of Agriculture Soil Conservation Service 1985). When soil temperature data are not available, the Wetland Delineation Manual allows using the closest and best available weather station data to estimate the length of the growing season based on a 50% probability of a temperature of 28°F or higher (Environmental Laboratory 1987, USACE 2010). Using this approximation, the growing season in this region would be approximately 305 days long at least 50% of the time. Generally, this translates to the period of mid-February to mid-December. To meet the hydrology criteria at this site, soils would need to be saturated to the surface for at least 14 consecutive days during that interval. The site visits occurred at the very end of the growing season. 3.2.5 Climate King County has a predominantly temperate marine climate typical of much of the Puget Sound area. The property is in the Puget Sound lowlands climatic region. Summers are warm and relatively dry, and winters tend to be mild, but rather wet. Mean high temperatures for the Seattle Tacoma Airport (4.2miles west) range from 46°F in December and January to 76°F in July and August. Mean low temperatures range from 36°F in Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 5 April 2018 PBS Project No. 41475.000 December and January to 56°F in July and August (US Climate Normals 1912-2016). The wetland delineation occurred on December 13, 2017. Precipitation in the spring of 2017 was well above the normal range but this was followed by a very dry summer. The rainfall for the 6-month interval prior to the delineation was within the normal range. Precipitation levels are considered normal when the probability of that rainfall amount for a given month is greater than or equal to 30% either side of the mean, as displayed in the table below (Table 1). While precipitation in October and November was slightly above normal, precipitation for the interval of June through September was well below normal. There was 1.2 inches of rain for the 2 weeks in December prior to the delineation, which is somewhat low for that period. Table 1. Monthly precipitation in inches and “normal” ranges and averages for the Seattle Tacoma Airport, WA Month Seattle, WA 2017 Seattle Tacoma Airport, WA 1970- 2016 Above or Below Normal 30% chance will have Average Less than More than June 1.52 0.91 1.79 1.48 - July T 0.34 0.85 0.70 Below August 0.02 0.35 1.24 1.06 Below September 0.59 0.71 2.00 1.70 Below October 4.80 2.16 4.36 3.60 Above November 8.63 4.10 7.02 5.90 Above Total 14.04 8.57 17.26 14.44 Normal 3.3 Delineation Results One wetland (Wetland A) was mapped at the eastern edge of the property in a linear depression mostly within the WSDOT right-of-way. There is approximately 0.06 acres of wetland that extends onto the Walker property. This wetland had been mapped by WSDOT in 2004 and verified by PBS in 2007. More recent delineation and verification occurred in 2014/2015 as part of the WDOT direct connector project. The PBS mapped boundary was similar to the WSDOT previously mapped boundaries. One data plot was taken in the wetland (Plot 1) and one in the adjacent upland (Plot 2). Upland areas had no vegetation, fill material lacking hydric soil indicators, and no wetland hydrology. The upland/wetland boundary was identified primarily on the basis of wetland hydrology, hydric soil indicators and topography. The data sheets can be found in Appendix A. PBS also examined other areas of the property to make sure no other wetlands were present. A small stormwater pond is present in the southwest corner that was operational until very recently. Wetland vegetation in the form of willows and reed canary grass is present along the edge of this constructed pond. Soils are highly disturbed. It is PBS’s best professional judgement that this pond is not a jurisdictional wetland, having been constructed in fill about six years ago. Shallow ponding was also observed north of the stormwater pond in an area with highly compacted gravel soils and pavement and no vegetation. This area did not meet the definition of a wetland. 3.3.1 Soils Soils in Plot 1 consisted primarily of fill material. Two inches of recent wood chippings were present at the surface. From 2 to 6 inches, the soil was sandy fill material with a matrix color of 10YR 3/2. Between 6 and 12 inches there was similar sandy, gravelly fill that had a matrix color of 2.5Y 4/1 with 2 percent redoximorphic concentrations of 7.5YR 4/4. Below 12 inches, the matrix color remained the same with 5 percent Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 6 April 2018 PBS Project No. 41475.000 redoximorphic concentrations of 7.5YR 4/4 and 2 percent concentrations of 10YR 4/6. Some cobbles were present at depth. The soil met the criteria for Hydric Soil Indicator F3: Depleted Matrix as defined in the Corps of Engineers Regional Supplement. Organic soils were not found in the top 18 inches at the plot but appeared to be present further into the wetland. The corresponding upland soil at Plot 2 was sandy gravelly fill material that also had a matrix value of 10YR 3/2 to a depth of 10 inches with matrix colors of 10YR 4/2 and 10YR 4/1 below but no redoximorphic concentrations in the top 16 inches. Well logs from the two wells closest to the wetland did not have information on the surface soils but found moist silts and sandy soils at a depth of 5 feet. No organic soils were documented in the logs, which if historically present, were probably above 5 feet in depth. Unfortunately, the logs were not useful in trying to determine the depth of fill on the property. 3.3.2 Hydrology Wetland hydrology was present in the form of inundation up to 2 feet in depth, water in the soil test pits near the surface, and saturation. No detectable flow was observed. At the time of the site visit, no flow was observed coming into the wetland from the culvert under SR 167. Some minor surface flow was detected from the property into the wetland in the northeast corner. Hydrologic inputs appear to be primarily from high groundwater and direct precipitation. 3.3.3 Vegetation Stumps of black cottonwood and Pacific willow were observed in the wetland along with remnants of Douglas spirea, red-osier dogwood and what appears to be Sitka willow (Salix sitchensis). Himalayan blackberry was also present. Reed canary grass had about 20 percent coverage in the wetland. Wetland vegetation on the property to the north consisted of an overstory of black cottonwood, and a shrub layer of red-osier dogwood, willows, Douglas spirea and Himalayan blackberry. Reed canary grass dominated the understory with some common sedge (Carex obnupta) and horsetails. Adjacent upland vegetation also had a canopy of black cottonwood with an understory of Himalayan blackberry, reed canary grass and tansy ragwort (Senecio jacobaea) with an occasional sword fern (Polystichum munitum). The wetland on the property to the south was dominated by willows and reed canary grass with the wetland sandwiched between the retaining wall to the east and a steep fill slope to the west. As mentioned previously no vegetation was present on the subject property west of the wetland. . 3.4 Wetland Rating and Buffers The wetland was rated using the 2014 version of the Washington State Wetland Rating System for Western Washington (Hruby, 2014) as a Category III wetland. Despite the fact that the wetland was once part of the larger Panther Creek wetland to the east, it is now effectively separated and was considered a separate wetland for the purposes of rating. The culvert under SR 167 at the property is 180 feet long and at an elevation that it would only engage during very high water levels. Table 2 lists the characteristics of the wetland. Figure 5 shows the wetland boundary, data plot locations and buffers. City of Renton buffers for Category III wetlands with a habitat score of 5 to 7 are 100 feet. The wetland rates relatively high for water quality because of the urban setting and poor water quality in the vicinity, moderate for hydrology functions, and moderately low for habitat functions. Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 7 April 2018 PBS Project No. 41475.000 Table 2. Waters/wetlands characteristics Characteristic Wetland A Cowardin Classification Palustrine Forested / Scrub-Shrub Size –(Acres) ~ 3 acres HGM Classes Depression WA State Wetland Rating Scores Water Quality 8 Hydrology 6 Habitat 5 Total Score 19 Wetland Category Based on Score III Special Characteristics Category N/A City of Renton Buffers 100 ft Additional Building Setback 15 ft 3.5 Regulatory Framework Wetland A is assumed to be under Federal, State and City of Renton jurisdiction. Impacts to the wetland would trigger both a City of Renton permit and a federal Army Corps of Engineers permit and review by other agencies. Impacts to buffers are regulated only at the local level. The City of Renton allows buffers to be reduced by 25 percent if the development follows certain mitigation measures which include:  The reduced buffer will function at a higher level than the standard buffer, and  The buffer has less than fifteen percent slopes and no direct or indirect, short-term or long-term, adverse impacts to regulated wetlands, and  The proposal shall rely on a site-specific evaluation and documentation of buffer adequacy based upon the document “Wetlands in Washington State” (Ecology Publication No. 04-06-008, April 2005) or similar approaches, and  The proposed buffer standard is based on consideration of the best available science. 4 IMPACT ASSESSMENT All trees and most shrubs were cleared from Wetland A between the north and south property corners east to the SR 167 retaining wall on the WSDOT right-of-way. Clearing occurred over approximately 19,000 square feet (0.44 acres). All but approximately 2,500 square feet of wetland clearing occurred on the WSDOT right-of- way. Some of the logs were left in the wetland and other material was either piled in uplands or chipped on site. Aside from some wood chips, it did not appear that any grading or filling had occurred in the wetland, though this was difficult to determine accurately since we had not seen the site prior to disturbance and water levels in the wetland at the time of the site visit were high enough to obscure ground disturbance. It is likely that operation of equipment in or adjacent to the wetland caused some ground disturbance, though fortunately the clearing occurred at the end of an extended dry period when most of the wetland was dry. At least a dozen trees greater than 6 inches diameter were removed. Some of the stumps appeared to have been ground down to the soil surface. Because soil disturbance appears to have been limited, herbaceous vegetation is already starting to recover and many of the trees and shrubs are expected to re-sprout from root crowns. Several wetland functions have been impacted by the clearing. Despite the urban and industrialized context of the site, the wetland performs some important wetland functions. The ability of the wetland to provide water quality functions has been diminished by the loss of vegetation. The loss of vegetation structure has also greatly reduced habitat functions. The narrow strip of forest and shrubs provided a corridor for wildlife in a heavily developed landscape. The cover provided by vegetation is now gone, effectively breaking the corridor. Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 8 April 2018 PBS Project No. 41475.000 5 RESTORATION PLAN 5.1 Goals and Objectives Mr. Walker is working with WSDOT on restoration of the wetland in the WSDOT right-of-way. The restoration will be completed per WSDOT specifications either by WSDOT or by Mr. Walker under WSDOT supervision. The goal of the restoration plan for the buffer will be to create a functioning buffer that protects and enhances the wetland functions through planting and control of invasives. Nearly the entire buffer was being used for junk vehicle storage with little to no native vegetation present. We are proposing a reduction in the standard buffer from 100 feet to 75 feet through enhancement of the remaining buffer to include planting of native trees, shrubs and understory vegetation. Some of the surface fill soils will be removed as part of the site clean-up effort. Placement of compost will help improve surface soil conditions and protect water quality in the wetland. 5.2 Performance Standards Table 3 shows the performance standards that will be used to measure restoration success in the buffer. Table 3. Performance Standards Thresholds Parameter Year 1 Year 3 Year 5 Survival of planted trees 90% 80% 70% Survival of planted shrubs/ferns 90% 80% 70% Plant diversity - # of native species >6 >6 >6 Percent cover invasives1 < 10% 1. Invasives include Japanese knotweed, Himalayan blackberry, and any other species listed on the King County noxious weed list. Reed canary grass is ubiquitous in this area and control is likely not feasible. 5.3 Restoration Activities 5.3.1 Fill Removal/ Grading/ Site Preparation Within the 75-foot buffer some contaminated fill material will likely be removed as part of the site clean-up effort. Clean soil backfill may be placed as necessary depending on the depth of the removal. The final buffer area will be graded to provide some microtopographic relief. Large wood may be placed near the wetland edge for habitat improvement. Two inches of compost will be spread throughout the wetland buffer area to improve soil conditions. 5.3.2 Native Plantings The restoration area has been divided into three planting zones. Zone A is the WSDOT wetland area that is will be restored per WSDOT requirements. Zone B is the wetland edge that is rarely inundated, and Zone C is the buffer zone. Zone B will be seeded with a wetland seed mix. Zone C will be seeded with an upland erosion control mix. Table 4 is the planting plan and Figure 5 shows the planting zones. Planting will occur in the spring of 2018. Planting of Zone A may need to be delayed until water levels have come down far enough to allow access by the planting crews. 5.3.3 Follow-up Weed Control Himalayan blackberry will be removed throughout the wetland and buffer area where present. Other species that will be removed if they appear in the restoration area include scotch broom, tansy ragwort, thistles, and any other species on the King County noxious weed list. Reed canary grass is currently present it the wetland and may spread into the buffer. Efforts will be made to control the grass, but success of the restoration will not be dependent on control of this species. Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 9 April 2018 PBS Project No. 41475.000 Table 4. Planting Plan for the Walker Property. All of Zone A and a third of Zone B is on WSDOT right-of-way. The planting plan for the WSDOT areas are currently under review and subject to change. Common Name Scientific Name Strata Number Size Spacing Zone A –Seasonally Inundated Wetland (12,200 sq ft, 0.28 acres) Entirely on WSDOT ROW Pacific willow Salix lucida ssp lasiandra T 20 2 gal or stake 6 to 8 feet apart Sitka willow Salix sitchensis ST 40 2 gal. or stake Black twinberry Lonicera involucrata S 40 1 gal. pot or bareroot 12” min. height randomize and avoid disturbing native volunteers Red-osier dogwood Cornus sericea S 40 Douglas spirea Spirea douglasii S 40 Subtotal 180 Zone B –Wetland Edge (8,400sq ft, 0.19 acres) 3,000 sf on WSDOT ROW Western red-cedar Thuja plicata T 8 2 or 5 gal. 6 to 8 feet apart avoiding stumps and live shrubs Red alder Alnus rubra T 18 2 gal. or stake Sitka willow Salix sitchensis ST 18 2 gal. or stake Crabapple Malus fusca ST 16 2 gal >12’ spacing Cluster rose Rosa pisocarpa S 30 1 gal Randomize in groups of 3 or 4 Red-osier dogwood Cornus sericea S 30 Douglas spirea Spirea douglasii S 30 Subtotal 150 Zone B– Wetland seed mix (8,400 sq ft, 0.19 acres) 3000 sf on WSDOT ROW Sunmark “Marsh” seed mix or equivalent Common rush Juncus effusus H 10% Small-fruited bullrush Scirpus microcarpus H 25% Slough sedge Carex obnupta H 15% Awlfruit sedge Carex stipata H 20% Common spikerush Eleocharis palustris H 10% Fowl managrass Glyceria striata H 20% 5 lb Zone C – Buffer (32,000 sq ft, 0.73 acres) Western red cedar Thuja plicata T 10 2 or 5 gal Approx. 12 ft spacing As shown on plans Douglas-fir Pseudotsuga menziesii T 15 2 or 5 gal Red alder Alnus rubra T 10 1 or 2 gal Bitter cherry Prunus emarginata T 10 2 gal Beaked hazelnut Corylus cornuta ST 15 2 gal. Vine maple Acer circinatum ST 20 2 gal. Nootka rose Rosa nutkana S 40 1 gal. Randomize in groups of 3 or 4 – at least 3’ spacing, 6’ from trees Snowberry Symphoricarpos albus S 40 1 gal. Low Oregon grape Berberis nervosa S 40 1 gal. Swordfern Polystichum munitum F 50 1 gal >3’ spacing Subtotal 250 Zone C– Upland seed mix (32,000 sq ft, 0.78acres) Blue wild rye Elymus glaucus H 30% Native red fescue Festuca rubra H 30% Tufted hairgrass Deschampsia cespitosa H 20% Meadow barley Hordeum brachyantherum H 20% 30lbs TOTAL AREA = 1.2 acres TOTAL PLANTS 580 Strata: H=herbaceous, F=fern, S=shrub, ST=small tree, T=tree Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 10 April 2018 PBS Project No. 41475.000 5.4 Maintenance and Monitoring of Restoration Per City of Renton Code, the restoration plantings must be monitoring annually for 3 to 5 years or until performance standards have been met. We are proposing a baseline monitoring, yearly monitoring in years 1,2 and 3 and then a final monitoring in Year 5 if needed. Monitoring may need to be continued beyond 5 years if performance standards are not being met. Once planting is complete, a Baseline Monitoring Report will be submitted to the City that includes an as-built drawing and a more detailed Monitoring Plan. The as- built report will document any grading and site preparation activities, as well as the new plantings. Specific monitoring protocol will be provided in the Baseline Monitoring Report. Once approved by the City, this plan will form the basis for evaluating the success of the critical area restoration. During the first two years, all planted stock will be replaced either in kind or with another approved native species if diseased, dead or dying. Weeding and removal of invasives will need to occur at least twice a year during the monitoring period. Native volunteers will not be removed. Monitoring will occur near the end of the growing season to document vigor and survival of planted stock. Reports will be due to the City before the end of each calendar year in Years 1, 2, 3, and 5. The monitoring report will include the following basic information:  A tally of planted trees and shrubs in each plot to identify mortality or poor vigor.  Estimates of native species cover by species  Vigor and mortality of planted stock  Percent cover of invasive weed species  Assessment of other non-natives to determine if control is needed  Photographs at established photo points  Recommended contingency measures to replace mortality or control weeds.  Observations on the overall status of the restoration area and any unauthorized activities. A total of 6 10-foot radius circular plots will be established throughout the buffer restoration to evaluate percent cover. The plot centers will be marked with a piece of rebar and flagging. Figure 6 shows approximate locations of photo points and plots. The locations may be modified during baseline monitoring. Monitoring of the WSDOT property will be done according to WSDOT specifications. 5.5 Contingency Measures Contingency measures will be triggered if the performance standard thresholds are not being met as documented during the yearly monitoring. All planted stock mortality in the first year will be replaced either in-kind or with a replacement species approved by the wetland biologist. Some species substitutions may be needed if the original species is not performing well. Any replacement plantings will occur either in the fall or spring. Additional weed control will be triggered if invasive species become established that threaten the success of the restoration. Control of reed canary grass will be limited due to difficulty of control. Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 11 April 2018 PBS Project No. 41475.000 6 REFERENCES Anchor Environmental, LLC. 2007. I-405, Tukwila to Renton Improvement Project Wetland Biology Report. Prepared for WA Dept of Transportation, Urban Corridors Office. Blaine Tech Services. 2017. Well Monitoring Data. 3400 E. Valley Rd., Renton, WA. Code Publishing Co. 2017. City of Renton Municipal Code. Accessed online at: http://www.codepublishing.com/WA/Renton/#!/Renton04/Renton0403/Renton0403050.html#4-3-050 Cowardin, L.M., Carter, V., Golet, F.C., and La Roe, E.T. 1979. Classification of Wetlands and Deepwater Habitats of the United States. FWS/OBS79/31. US Fish and Wildlife Service, Office of Biological Services, Washington, D.C. DOWL Surveying. 2017. Monitoring Well Survey. 3400 East Valley Road, Renton. WA. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1. U.S. Department of the Army, Corps of Engineers, Waterways Experiment Station, Vicksburg, Mississippi. Google Earth. 2017. Online aerial photographs. Hruby, T. 2014. Washington State Wetland Rating System for Western Washington: 2014 Update. Washington State Department of Ecology Publication # 14-06-029. Olympia, Washington. Kane Environmental, Inc. 2017. Figure 1. Groundwater Elevation Contours, from report titled: Phase II Environmental Site Assessment, 3400 East Valley Road, Renton, WA. Kane Environmental, Inc. 08/2017. Soil Boring Logs. 3400 E. Valley Road. King County IMAP. 2017. Accessed online at: http://www.kingcounty.gov/operations/GIS/Maps/iMAP.aspx Lichvar, R.W., D.L. Banks, W.N. Kirchner, and N.C. Melvin. 2016. The National Wetland Plant List: 2016 wetland ratings. Phytoneuron 2016-30: 1-17. Published 28 April 2016. ISSN 2153 733X Munsell Color. 2000. Munsell soil color charts. Gretagmacbeth, New Windsor, New York. NRCS Web Soil Survey. 2017. Accessed on-line at: http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx Pojar J. and A. MacKinnon. 2004. Plants of the Pacific Northwest Coast - Revised. Lonepine Publishing U.S. Army Corps of Engineers. 2010. Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0). ed. J.S. Wakeley, R.W. Lichvar, and C.V. Noble. ERDC/EL TR-10-3. Vicksburg, MS. U.S. Army Corps of Engineer Research and Development Center. US Department of Agriculture, Natural Resource Conservation Service. 2017. Regional climatic data, WETS. Accessed online at: http://agacis.rcc-acis.org/?fips=53033 USDA Natural Resources Conservation Service. 2017. Plants National Database. Accessed online at: http://plants.usda.gov/java/ US Fish & Wildlife Service. 2017 National Wetlands Inventory. Accessed online at: https://www.fws.gov/wetlands/Data/Mapper.html WA State Department of Ecology. 2014. Reissuance of Coverage under the Industrial Stormwater General Permit. WAR000021 Dale Walker Property Critical Areas Report 3400 E. Valley Rd Renton, Washington 12 April 2018 PBS Project No. 41475.000 WA State Department of Ecology. 2017. WA State Water Quality Atlas. Accessed online at: WA Department of Fish and Wildlife (WDFW). 2017.Priority Habitats and Species on the Web. Accessed online at: http://apps.wdfw.wa.gov/phsontheweb/ WA State Department of Transportation (WSDOT). 2015. I-405 / SR 167 Interchange Direct Connector Project. Request for Proposal Appendix P5: Critical Area Variance. Accessed online at: ftp://ftp.wsdot.wa.gov/contracts/8811-SR167InterchangeDirectConnector/ConformedRFP /AppendicesConformed/P/P05_CriticalAreaVariance/CriticalAreaPermit_LUA15-000522.pdf WSDOT. 2015. Corps of Engineers Permit NWS-2014-29 JARPA Drawings: Sheet 2 of 20. WSDOT. 2017. Email from Linda Cooley dated 10/18/17 regarding unauthorized clearing of WSDOT right-of- way. WTU Herbarium Image Collection. 2017. Burke Museum of Natural History and Culture. Accessed online at: http://biology.burke.washington.edu/herbarium/imagecollection.php PHOTOGRAPHS Photo 1. Google Earth aerial of property taken in early 2017 prior to removal of vehicles and clearing. Photo 2. Google Earth street view looking southwest from the west edge of SR 167 showing trees in wetland prior to clearing. N Stormwater pond Oyster shell pit Ditch Wetland Photo 3. WSDOT photo looking north taken on October 18, 2017 shortly after clearing. Note very little ponding in wetland. Photo 4. View to southeast showing water levels in cleared area in December. Photo 5. Buffer area just north of property. Photo 6. View of wetland on the property just north of the subject property. Photo 7. Wetland just south of property. Photo 8. View to north of wetland showing current condition of wetland with WSDOT retaining wall to the right. Photo 9. Closeup of wetland with WSDOT retaining wall in background. Photo 10. Stumps and logs in wetland. Photo 11. View to west of cleared yard and slash/trash piles. Photo 12. Wetland soil pit. Photo 13. South end of wetland on property with steep gradient at edge of fill Photo 14. View to north of stormwater pond with willows growing along edge. Water is no longer being pumped and water is ponded outside of edges of pond. Photo 15. View to north of water ponded near the west edge in area of compact gravel and pavement Photo 16. Remnants of ditch that ran west to east across the center of the site. FIGURES PROJECT VICINITY MAP Dale Walker Property Renton, WA FIGURE 1 PROJECT # 41482 DATE APRIL 2018 Project Site N CITY OF RENTON WATERS / WETLANDS Dale Walker Property Renton, WA FIGURE 2 PROJECT # 41482 DATE APRIL 2018 Project Site N NATIONAL WETLAND INVENTORY Dale Walker Property Renton, WA FIGURE 3 PROJECT # 41482 DATE APRIL 2018 Project Site N WETLAND DELINEATION MAP Dale Walker Property Renton, WA FIGURE 4 PROJECT # 41482 DATE APRIL 2018 20 20 Proposed 75’ reduced buffer KEY: Property boundary City of Renton mapped wetlands 10’ elevation contours PBS mapped wetland on property Proposed 75’ reduced buffer line Wetland Data Plot 1 Upland Data Plot 2 180’ culvert SR 167 Project Site N Wetland A RESTORATION PLANTING PLAN Dale Walker Property Renton, WA FIGURE 5 PROJECT # 41482 DATE APRIL 2018 SR 167 KEY: Wetland Boundary Property boundary Zone A – Seasonally Inundated Zone B – Wetland edge Zone C – 75’ Buffer Plantings Habitat Logs 0 25 50 Approximate Scale A B C Proposed 75’ Buffer N SR 167 Planting on WSDOT right‐of‐ way will be undertaken per WSDOT specifications either by WSDOT or under WSDOT supervision KEY: Property boundary Zone A – Seasonally Inundated Zone B – Wetland edge Zone C – 75’ Buffer Plantings Habitat Logs Monitoring Plots Photo Points RESTORATION MONITORING PLAN Dale Walker Property Renton, WA FIGURE 6 PROJECT # 41482 DATE APRIL 2018 SR 167 1 1 1 2 3 4 6 1 Proposed 75’ Buffer A B C N 0 25 50 Approximate Scale 7 15 8 This figure shows monitoring on the Walker property only. WSDOT will coordinate monitoring on their property. APPENDIX A Wetland Delineation Datasheets Project/Site: City/County: King Sampling Date: Applicant/Owner: State: Sampling Point: Investigator(s): Local relief: Slope (%): 0 Subregion (LRR): Lat: Long: Datum: Soil Map Unit Name: NWI classification: Are climatic / hydrologic conditions on the site typical for this time of year? Yes X No 0 , or Hydrology significantly disturbed? , or Hydrology naturally problematic? Yes X No SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes No Hydric Soil Present? Yes No Wetland Hydrology Present? Yes No Yes X No Remarks: VEGETATION Absolute Dominant Indicator Dominance Test worksheet: Tree Stratum (Plot size: 30 ft) % Cover Species?Status Number of Dominant Species 1.40 Yes FAC That Are OBL, FACW, or FAC: (A) 2.30 Yes FACW 3.0 Total Number of Dominant 4.0 Species Across All Strata: (B) Total Cover: 70 Sapling/Shrub Stratum (Plot size: 30 ft)Percent of Dominant Species 1.15 Yes FAC That Are OBL, FACW, or FAC: (A/B) 2.10 Yes FACW Prevalence Index worksheet: 3.20 Yes FACW Total % Cover of: Multiply by: 4.0 OBL species 0 x 1 = 0 5.0 FACW species 80 x 2 = 160 Total Cover: 45 FAC species 55 x 3 = 165 Herb Stratum (Plot size: 5 ft)FACU species 0 x 4 = 0 1.20 Yes FACW UPL species 0 x 5 = 0 2.0 Column Totals:135 (A)325 (B) 3.0 Prevalence Index = B/A = 4.0 Rapid Test for Hydrophytic Vegetation 5.0 X Dominance Test is >50% 6.0 X Prevalence Index is ≤3.01 7.0 8.0 Total Cover: 20 Wetland Non-Vascular Plants1 Woody Vine Stratum (Plot Size: 5 ft)Problematic Hydrophytic Vegetation1 (Explain) 1.0 2.0 Total Cover: 0 Hydrophytic Vegetation % Bare Ground in Herb Stratum %Present? Yes X No Remarks: WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys and Coast Region 3400 East Valley Rd 12/13/2017 Dale Walker WA Plot 1 Katharine Lee, Kevin Hood Section/Township/Range:S30 T23N R5E Landform (hillslope, terrace etc.): Valley concave A 47.450 -122.215940 WGS 84 Urban ne forested / scru (If no, explain in Remarks) Are Vegetation X ,Soil Are “Normal Circumstances” present? (If needed, explain any answers in remarks)Are Vegetation ,Soil Populus balsamifera 6 Salix lucida ssp lasiandra X Is the Sampled Area within a wetland?X X Wetland is remnant of large floodplain wetland that is sandwiched between SR 167 retaining wall and fill prism. Wetland was recently cleared but enough vegetation remained to determine what species had been present. 6 Rubus armeniacus 100% Spiraea douglasii Cornus alba Phalaris arundinacea Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) 1Indicators of hydric soil and wetland hydrology must be present. 2.41 80 All trees and most shrubs were recently cut down. Except for reed canary grass, all coverages are estimates based on stumps and remnants of shrubs. Intact portions of the wetland to the north and south were used as reference SOIL Sampling Point: Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Color (moist) % Color (moist) % Type1 Loc2 chips from clearing 0-4 10YR 3/2 100 sandy loam fill material 4-10 10YR 4/1 98 7.5YR 4/4 2 C M sandy gravelly loam fill material 10-18 10YR 4/1 93 7.5YR 4/4 5 C M sandy gravelly loam fill material 10YR 4/6 2 C M cobbles 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix. 2Location: PL=Pore Lining, RC=Root Channel, M=Matrix. Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3: Histosol (A1) Sandy Redox (S5) 2 cm Muck (A10) Histic Epipedon (A2) Stripped Matrix (S6) Red Parent Material (TF2) Black Histic (A3)Loamy Mucky Mineral (F1) (except MLRA 1)Very shallow dark surface (TF12) Hydrogen Sulfide (A4) Loamy Gleyed Matrix (F2) Other (Explain in Remarks) Depleted Below Dark Surface (A11)X Depleted Matrix (F3) Thick Dark Surface (A12) Redox Dark Surface (F6) Sandy Mucky Mineral (S1) Depleted Dark Surface (F7) 3Indicators of hydrophytic vegetation and Sandy Gleyed Matrix (S4) Redox Depressions (F8) wetland hydrology must be present. Restrictive Layer (if present): Type:Hydric Soil Present? Depth (Yes No Remarks: HYDROLOGY Wetland Hydrology Indicators: Primary Indicators (any one indicator is sufficient) Secondary Indicators (2 or more required) Surface Water (A1)Water-Stained Leaves (B9) (except NW coast)Water-Stained Leaves (B9) (NW coast) High Water Table (A2) Salt Crust (B11) Drainage Patterns (B10) Saturation (A3) Aquatic Invertebrates (B13) Dry-Season Water Table (C2) Water Marks (B1)Hydrogen Sulfide Odor (C1) Saturation Visible on Aerial Imagery (C9) Sediment Deposits (B2)Oxidized Rhizospheres along Living Roots (C3)Geomorphic Position (D2) Drift Deposits (B3) Presence of Reduced Iron (C4) Shallow Aquitard (D3) Algal Mat or Crust (B4) Recent Iron Reduction in Tilled Soils (C6) Frost-Heave Hummocks (D4) Iron Deposits (B5)Stunted or Stressed Plants (D1) (LRR A)FAC-Neutral Test (D5) Surface Soil Cracks (B6) Other (Explain in Remarks) Raised Ant Mounds (D6) (LRR A) Inundation Visible on Aerial Imagery (B7) Sparsely Vegetated Concave Surface (B8) Field Observations: Surface Water Present? Yes No X Depth (in): Water Table Present? Yes X No Depth (in): 10"Wetland Hydrology Present? Saturation Present? Yes X No Depth (in): 0"Yes No (includes capillary fringe) Remarks: +2 Plot 1 Depth (in.) Matrix Redox Features Texture Remarks Soils to 18 inch appear to be fill material. Do not resemble historic muck soils. X X X X Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Ponding up to 2 feet deep further into wetland Project/Site: City/County: King Sampling Date: Applicant/Owner: State: Sampling Point: Investigator(s): Local relief: Slope (%): 0.05 Subregion (LRR): Lat: Long: Datum: Soil Map Unit Name: NWI classification: Are climatic / hydrologic conditions on the site typical for this time of year? Yes X No 0 , or Hydrology significantly disturbed? , or Hydrology naturally problematic? Yes X No SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes No X Hydric Soil Present? Yes No X Wetland Hydrology Present? Yes No X Yes No Remarks: VEGETATION Absolute Dominant Indicator Dominance Test worksheet: Tree Stratum (Plot size: 30 ft) % Cover Species?Status Number of Dominant Species 1.0 That Are OBL, FACW, or FAC: (A) 2.0 3.0 Total Number of Dominant 4.0 Species Across All Strata: (B) Total Cover: 0 Sapling/Shrub Stratum (Plot size: 30 ft)Percent of Dominant Species 1.0 That Are OBL, FACW, or FAC: (A/B) 2.0 Prevalence Index worksheet: 3.0 Total % Cover of: Multiply by: 4.0 OBL species 0 x 1 = 0 5.0 FACW species 0 x 2 = 0 Total Cover: 0 FAC species 0 x 3 = 0 Herb Stratum (Plot size: 5 ft)FACU species 0 x 4 = 0 1.0 UPL species 0 x 5 = 0 2.0 Column Totals:0 (A)0 (B) 3.0 Prevalence Index = B/A = 4.0 Rapid Test for Hydrophytic Vegetation 5.0 Dominance Test is >50% 6.0 Prevalence Index is ≤3.01 7.0 8.0 Total Cover: 0 Wetland Non-Vascular Plants1 Woody Vine Stratum (Plot Size: 5 ft)Problematic Hydrophytic Vegetation1 (Explain) 1.0 2.0 Total Cover: 0 Hydrophytic Vegetation % Bare Ground in Herb Stratum %Present? Yes No X Remarks: WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys and Coast Region 3400 East Valley Rd 12/13/2017 Dale Walker WA Plot 1 Katharine Lee, Kevin Hood Section/Township/Range:S30 T23N R5E Landform (hillslope, terrace etc.): Valley slope A 47.44980 -122.216030 WGS 84 Not mapped None (If no, explain in Remarks) Are Vegetation X ,Soil Are “Normal Circumstances” present? (If needed, explain any answers in remarks)Are Vegetation ,Soil 0 Is the Sampled Area within a wetland?X Site recently graded. No vegetation present prior to grading. Auto junkyard 0 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) 1Indicators of hydric soil and wetland hydrology must be present. #DIV/0! 100 No vegetation present SOIL Sampling Point: Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Color (moist) % Color (moist) % Type1 Loc2 10YR 3/2 100 sandy gravelly loam fill 10-14 10YR 4/2 100 sandy gravelly loam fill, some cobbles 14-18 10YR 4/1 98 7.5YR4/4 2 C M sandy gravelly loam fill, some cobbles 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix. 2Location: PL=Pore Lining, RC=Root Channel, M=Matrix. Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3: Histosol (A1) Sandy Redox (S5) 2 cm Muck (A10) Histic Epipedon (A2) Stripped Matrix (S6) Red Parent Material (TF2) Black Histic (A3)Loamy Mucky Mineral (F1) (except MLRA 1)Very shallow dark surface (TF12) Hydrogen Sulfide (A4) Loamy Gleyed Matrix (F2) Other (Explain in Remarks) Depleted Below Dark Surface (A11) Depleted Matrix (F3) Thick Dark Surface (A12) Redox Dark Surface (F6) Sandy Mucky Mineral (S1) Depleted Dark Surface (F7) 3Indicators of hydrophytic vegetation and Sandy Gleyed Matrix (S4) Redox Depressions (F8) wetland hydrology must be present. Restrictive Layer (if present): Type:Hydric Soil Present? Depth (Yes No Remarks: HYDROLOGY Wetland Hydrology Indicators: Primary Indicators (any one indicator is sufficient) Secondary Indicators (2 or more required) Surface Water (A1)Water-Stained Leaves (B9) (except NW coast)Water-Stained Leaves (B9) (NW coast) High Water Table (A2) Salt Crust (B11) Drainage Patterns (B10) Saturation (A3) Aquatic Invertebrates (B13) Dry-Season Water Table (C2) Water Marks (B1)Hydrogen Sulfide Odor (C1) Saturation Visible on Aerial Imagery (C9) Sediment Deposits (B2)Oxidized Rhizospheres along Living Roots (C3)Geomorphic Position (D2) Drift Deposits (B3) Presence of Reduced Iron (C4) Shallow Aquitard (D3) Algal Mat or Crust (B4) Recent Iron Reduction in Tilled Soils (C6) Frost-Heave Hummocks (D4) Iron Deposits (B5)Stunted or Stressed Plants (D1) (LRR A)FAC-Neutral Test (D5) Surface Soil Cracks (B6) Other (Explain in Remarks) Raised Ant Mounds (D6) (LRR A) Inundation Visible on Aerial Imagery (B7) Sparsely Vegetated Concave Surface (B8) Field Observations: Surface Water Present? Yes No X Depth (in): Water Table Present? Yes No X Depth (in):Wetland Hydrology Present? Saturation Present? Yes X No Depth (in): 14"Yes No (includes capillary fringe) Remarks: 0-10 Plot 1 Depth (in.) Matrix Redox Features Texture Remarks X Edge of wetland X Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: APPENDIX B Wetland Rating Forms Washington State Wetland Rating Project Name: Dale Walker - Renton Date(s) of Site Visit(s): 12/13/2017 Rated by: Katharine Lee Trained by Ecology? Yes HGM Class used for Ratin Depressional Multiple HGM Classes? No DEPRESSIONAL WETLANDS Wetland Name A Total Size (acres) WATER QUALITY FUNCTIONS D 1.1 Surface flow out Depression/flat with no outlet -3 Intermittent or constricted permanent outlet - 2 Un- or slightly constricted permanent outlet - 1 Flat with no outlet or outlet it ditch- 1 2 D 1.2 Surface soils Soil is clay or organic yes = 4, no = 0 4 D 1.3 Persistent, Ungrazed, Unmowed Vegetation > = 95% area - 5 > = 1/2 area - 3 > = 1/10 area - 1 < 1/10 area - 0 3 D 1.4 Seasonal Ponding > 2 months > 1/2 total area of wetland - 4 >1/4 total area of wetland - 2 < 1/4 total area of wetland - 0 2 11 M D 2.1 Stormwater discharges Wetland receives stormwater discharge Yes=1 No = 0 1 D 2.2 Buffer land use >10% of 150 ft buffer in pollutant Yes=1 generating land uses No = 0 1 D 2.3 Septic systems Septic systems present Yes=1 No = 0 0 D 2.4 Other pollutants Other pollutant sources present : L ist Yes=1 No = 0 1 Contamination 3 H D 3.1 Discharge to 303(d) list waters Direct (<1 mi) discharge to 303(d) water Yes=1 No=0 0 D 3.2 303(d) list Basin or sub- basin Wetland in 303(d) list basin or sub-basin Yes=1 No=0 1 D 3.3 TMDL watershed Site identified as important to water quality (i.e. TMDL Yes = 2 No=0 1 Green River temp 2 H Improving Water Quality : Score Based on Ratings 8 Site Potential: Does the site have the potential to improve water quality? Landscape Potential: Does the landscape have the potential to support the water quality function of the site? Rating of Value: Is the water quality improvement provided by the site valuable to society? Total for D1 (H=12-16; M=6-11; L=0-5) Rating of Site Potential Total for D2 (H=3-4; M= 1-2; L=0) Rating of Landscape Potential Total for D3 (H=2-4; M=1; L=0) Rating of Value PBS Engineering and Environmental Table 1 Page 1 Washington State Wetland Rating HYDROLOGIC FUNCTIONS Wetland Name A Site Potential: Does the site have the potential to reduce flooding and erosion? D 4.1 Surface water flow out No surface water outlet - 4 Intermittent/ highly constricted outlet - 2 Flat with no outlet or outlet is ditch - 1 Unconstricted outlet - 0 2 D 4.2 Depth of storage 3 ft or more - 7 2 ft to 3 ft - 5 0.5 to < 2 ft - 3 headwater wetland - 3 flat w/small depressions - 1 < 0.5 ft - 0 3 D 4.3 Watershed storage Basin is < 10 times area of wetland - 5 Basin is 10 to 100 times bigger - 3 Basin is > 100 times bigger - 0 Entire wetland is in Flats class - 5 0 5 L Landscape Potential: Does the landscape have the potential to support the hydrologic functions of the site? D 5.1 Stormwater discharges Wetland receives stormwater discharge Yes=1 No = 0 1 D 5.2 Buffer land use >10% of 150 ft buffer in pollutant Yes=1 generating land uses No = 0 1 D 5.3 Basin land use >25% contributing basin in intensive land use Yes=1 No = 0 1 3 H Rating of Value: Are the hydrologic functions provided by the site valuable to society? D 6.1 Flooding Flooding occurs: In sub-basin immediately down-gradient - 2 In sub-basing farther down-gradient - 1 From groundwater in sub-basin - 1 Wetland outflow not related to flooding - 0 No problems with flooding downstream - 0 1 D 6.2 Flood storage Site is critical part of regional flood control plan Yes - 2 No - 0 0 1 M Hydrologic : Score Based on Ratings 6 Total for D4 (H=12-16; M=6-11; L=0-5) Rating of Site Potential Total for D5 (H=3; M= 1-2; L=0) Rating of Landscape Potential Total for D3 (H=2-4; M=1; L=0) Rating of Value PBS Engineering and Environmental Table 1 Page 2 Washington State Wetland Rating HABITAT FUNCTIONS Wetland Name A H 1.1 Vegetation structure Number of Cowardin classes >10% or >1/4 ac: Aquatic bed, emergent plants, scrub/shrub,forested, forested with at least 3 strata >20% area. >= 4 types = 4, 3 types = 2, 2 types = 1, 1 type = 0 1 Forested, emergent H 1.2 Hydro-period Permanently flooded or inundated Seasonally flooded or inundated Occasionally flooded or inundated Saturated only Permanent stream in or adjacent Seasonal stream in or adjacent >= 4 types = 3, 3 types = 2 2 types = 1 lake-fringe = 2, freshwater tidal = 2 2 Seasonally inundated Saturated only Perm. Stream H 1.3 Plant species diversity Number of species covering at least 10 sq ft. Do not count reed canarygrass, purple loosestrife, Canada thistle, Eurasian milfoil > 19 species = 2 5-19 = 1 < 5 =0 1 H 1.4 Habitat interspersion None = 0 low=1 moderate = 2 high = 3 If 4 or more plant classes, rating is always high. 2 H 1.5 Special habitats Count number of special habitat features: _ large downed woody debris _ standing snags _ undercut banks or overhanging vegetation _ stable steep banks of fine material for beaver OR recent beaver activity _ >1/3 ac thin-stemmed persistent vegetation _ <25% cover by invasives in each stratum 3 large wood standing snags recent beaver 9 M H 2.1 Accessible habitat Habitat in 1km polygon abutting wetland using: %undisturbed+[(%mod+low intensity/2)] >1/3 of polygon - 3 20-33% of polygon - 2 10-19% of polygon - 1 <10% of polylgon - 0 0 H 2.2 Undisturbed Habitat Undisturbed habitat in 1 km polygon using: %undisturbed+[(% mod + low intensity)/2] >50% of polygon - 3 10-50% of polygon in 1-3 patches - 2 10-50% of polygon in >3 patches - 1 <10% of polygon - 0 1 H 2.3 Land Use Intensity >50% high intensity - (-2) < or = 50% high intensity - 0 -2 -1 L Total for H1 (H=15-18; M=7-14; L=0-6) Site Potential: Does the site have the potential to provide habitat? Rating of Site Potential Total for H2 (H=4-6; M= 1-3; L=<1) Rating of Landscape Potential Landscape Potential: Does the landscape have the potential to support the habitat functions of the site? PBS Engineering and Environmental Table 1 Page 3 Washington State Wetland Rating HABITAT FUNCTIONS (continued) Wetland Name A H 3.1 Habitat for species with legal status Site meets any habitat criteria (see manual) - 2 Site has 1 or 2 priority habitats within 100 m - 1 Site does not meet criteria above - 0 1 1 M Habitat: Score Based on Ratings 5 TOTAL SCORE BASED ON RATINGS 19 OVERALL WETLAND CATEGORY III Wetland A Site Potential M Landscape Potential H Value H Rating 8 Site Potential L Landscape Potential H Value M Rating 6 Site Potential M Landscape Potential L Value M Rating 5 Total 19 Category III Total for H3 (H=2; M= 1; L=0) Rating of Value Rating of Value: Is the habitat provided by the site valuable to society? Water QualityHydrologicHabitatPBS Engineering and Environmental Table 1 Page 4 Cowardin Plant Classes & Hydroperiods Dale Walker Property Renton, WA Rating Figure A PROJECT # 41482 DATE JAN 2018 Approximate Scale 0 200 400 SR 167 Cowardin classes KEY: Property boundary Cowardin Forested Emergent Hydroperiods Seasonally inundated Saturated only Hydroperiods SR 167 Outlet to Panther Creek 150-FOOT AREA AROUND WETLAND Dale Walker Property Renton, WA Rating Figure B PROJECT # 41482 DATE JAN 2018 KEY: Property boundary 150-foot area around wetland >80% of area in pollution generation surfaces SR 167 ACCESSIBLE / UNDISTURBED HABITAT Dale Walker Property Renton, WA Rating Figure C PROJECT # 41482 DATE JAN 2018 SR 167 KEY: Total area 1km radius = 1,500 acres Accessible habitat = 6 acres (0.4%) Undisturbed habitat = (75+10+4+22+14+8=133) + Moderate & Low Intensity ((12+12+35+45+2+32+7=145)/2=73) = 206 acres (14%) WA DOE 303d & TMDL LISTINGS Dale Walker Property Renton, WA Rating Figure D PROJECT # 41482 DATE JAN 2018 Black River (1.2 miles) listed for Dissolved Oxygen, Bioassessment, Bacteria (Cat 5) Temperature (Cat 4) SR 167 Subject Property Subject Property Flow path Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 7 Other Permits Preliminary Technical Information Report Walker Auto Dealership 7-1 2180100.10 7.0 Other Permits Required permits for the project may include a Construction Stormwater National Pollutant Discharge Elimination System (NPDES) Permit for the proposed construction, a City of Renton commercial building permit, and a City of Renton grading permit. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 8 CSWPPP Analysis and Design Preliminary Technical Information Report Walker Auto Dealership 8-1 2180100.10 8.0 CSWPPP Analysis and Design A CSWPPP will be included with the final engineering design. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 9 Bond Quantities, Facility Summaries, and Declaration of Covenant Preliminary Technical Information Report Walker Auto Dealership 9-1 2180100.10 9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant The required forms will be included with the final engineering design. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 10 Operations and Maintenance Plan Preliminary Technical Information Report Walker Auto Dealership 10-1 2180100.10 10.0 Operations and Maintenance Plan The drainage facilities detailed in this report will be privately owned and maintained. A detailed Operations and Maintenance Manual will be included with the final engineering design. Preliminary Technical Information Report Walker Auto Dealership 2180100.10 Section 11 Conclusion Preliminary Technical Information Report Walker Auto Dealership 11-1 2180100.10 11.0 Conclusion This Walker Auto Dealership site has been designed to meet the 2016 King County Surface Water Design Manual (KCSWDM), amended by the City of Renton as the 2016 City of Renton Surface Water Design Manual (CRSWDM). The site utilizes water quality facilities to treat stormwater draining from the site. It was determined using these criteria that:  The site will meet the Peak Rate Flow Control Standard for flow control.  Water quality facilities will be designed to meet the required Enhanced Basic Water Quality Treatment Level for the site.  Pipe networks will be designed to be of adequate size to effectively convey the 25-year storm event and to contain the 100-year storm event. This analysis is based on data and records either supplied to or obtained by AHBL. These documents are referenced within the text of the analysis. The analysis has been prepared utilizing procedures and practices within the standard accepted practices of the industry. We conclude that this project, as schematically represented, will not create any new problems within the downstream drain age system. This project will not noticeably aggravate any existing downstream problems due to either water quality or quantity. AHBL, Inc. Bart Brynestad, PE Senior Engineer BEB/lsk May 2018 Q:\2018\2180100\WORDPROC\Reports\20180501 Rpt (Prelim TIR) 2180100.10.docx