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HomeMy WebLinkAbout20250805_PLN1308_Drainage Report Drainage Report Quail Ridge SP PFN: for KJR Family LLC Attn: John Robinett 131 Colby Ave Everett, WA 98201 SITE LOCATION: XXXX 1961h PI NE Arlington, WA 98223 TPN: 01052300099900 Ak #M• S + " 38935 '.iY LOCI e Prepared by: Joseph M. Smeby, P.E. Job No: 24-0701 Preliminary: July, 2025 Quail Ridge 24-0701 July 2025 Page-1 TABLE OF CONTENTS ITEM PAGE TABLE OF CONTENTS.................................................................................................... 1 LISTOF FIGURES............................................................................................................2 1. INTRODUCTION...........................................................................................................3 A. DRAINAGE FACILITY SUMMARY TABLE..........................................4 2. EXISTING SITE CONDITIONS.....................................................................................5 3. DEVELOPED SITE CONDITIONS................................................................................6 4. OFFSITE DRAINAGE ANALYSIS.................................................................................7 5. STORMWATER CONTROL PLAN ...............................................................................8 A. i. SITE HYDROLOGY...............................................................................9 ii. STANDARDS........................................................................................9 iii. FLOW CONTROL ANALYSIS............................................................ 10 iv. WATER QUALITY ANALYSIS........................................................... 10 v. CONVEYANCE SYSTEM ANALYSIS ................................................ 11 Al. General Site Infiltration Analysis 6. SWPPP....................................................................................................................... 11 7. PROJECT OVERVIEW............................................................................................... 15 APPENDIX A - STORMWATER CALCULATIONS.............................................................A-1 APPENDIX B — GEOTECHNICAL REPORT ................................................................B-1 Quail Ridge 24-0701 July 2025 Page-2 LIST OF FIGURES ITEM PAGE FIGURE 1 VICINITY MAP........................................................................................... 1 FIGURE 2 EXISTING DRAINAGE BASIN MAP .........................................................2 FIGURE 3 DEVELOPED DRAINAGE BASIN MAP ....................................................3 FIGURE 4 OFF-SITE TRIBUTARY MAP....................................................................4 Quail Ridge 24-0701 July 2025 Page-3 1. INTRODUCTION This document is intended to provide the engineering information necessary to support the Not short plat for this project which includes the development of Tract 999 into two lots totaling 0.89 acres with the two future lots being designed for disturbance for SFRs and driveways. The lots will take access from the existing private road 196th PI NE. This project will include 2 new lots with driveway access. The proposed improvements for this project will not require any improvements as part of the short plat since all of the existing infrastructure was constructed as part of the original subdivision. Runoff from all new impervious and pervious surfaces will be dispersed on- site. The Geotechnical Engineer for this project, Cobalt Geoscience, LLC has prepared a report summarizing their findings in the field. They found a till layer consisting of weather till to 4-feet over hardpan with mottling at 3' or shallower. 5' of fill was also logged in TP- 3. The site is located on Tract 999 of the Quail Ridge subdivision on 196th PI NE and west of 95th Ave NE, in the City of Arlington, and in Section 13, Township 31 N, Range 5E, Willamette Meridian. See Figure 1 - Vicinity Map. Quail Ridge 24-0701 July 2025 Page-4 A. DRAINAGE INFORMATION SUMMARY FORM Project: Quail Ridge Short Plat PFN: Engineer: Omega Engineering, Inc. 2707 Wetmore Ave Total site area: 13.08 acres Everett, WA 98201 Offsite area: 0.00 acres Attention: Joseph Smeby, P.E. Project area: 0.88 acres Applicant: KJR Family, LLC 1311 Colby Ave Everett, WA 98201 New Lots/Units: 2 Attention: John Robinettd Drainage Basin Information Basin A On-site Developed Area 0.88 acres Off-site Improved Area 0.00 acres Types of storage proposed on site Sheet Flow Disp Approximate total storage volume 0 Soil Types Type C Soils Basin Data Existing Basin 2-year 0.044 cfs 50-year 0.219 cfs 100- ear 0.284 cfs Developed Basin Vault Discharge) 2-year 0.141 cfs 50- ear 0.310 cfs 100- ear 0.373 cfs Quail Ridge 24-0701 July 2025 Page-5 2. EXISTING SITE CONDITIONS The site is located on 196th PI NE and west of 951h Ave NE, in the City of Arlington, and in Section 13, Township 31 N, Range 5E, Willamette Meridian. See Figure 1 - Vicinity Map. Land use around the site is primarily native with single-family homes in the Quail Ridge development. The parcel associated with this project currently is Tract 999 which was platted as a future development tract which contains areas for the two future lots along with critical areas and other open space. The area of the Tract for the new lots has been cleared and contains pasture or brush/blackberries. 196th PI NE was constructed as part of the original subdivision so no new frontage improvements will be required. The existing developable site is irregular in shape made up of one tract. The grades on the site, in the area of the future lots, are moderate with the steepest slopes approximately 8%. The vegetation found on the existing property consists of pasture grasses or brush. A site visit was conducted in July 2025. The weather was clear with temperatures in the 70's. No surface water was observed on this site. The soil hydrologic types for this site have been identified as Type C from the Snohomish County Soil Survey Map, see figure 4. These soils, Tokul gravelly medial loam typically consists of weathered medial loam over hardpan at around 33". This soil type is identified as a Till soil (Type C/D) in the 2021 DOE Manual. Based on the geotechnical findings for this project the site does not have infiltration capacity due to the shallow mottling logged in the test pits at less than 3'. Refer to the Geotech report in Appendix B. This project proposes to build 2 new SFRs. Approximately 14% of the future lots 1 & 2 will be impervious surface with the remaining area to be landscaped or left as pasture. Quail Ridge 24-0701 July 2025 Page-6 3. DEVELOPED SITE CONDITIONS This development proposes to cover the site with 14% impervious surfaces. The runoff from these surfaces will be dispersed on-site via splash blocks, sheet flow dispersion or level spreaders. Per the project Geotech's report, there is a shallow mottling layer at less than 3 feet making infiltration infeasible. Based on the recommendations of the project Geotechnical Engineer in the soils report, no infiltration will be used for this project. However, roof downspout dispersion, sheet flow dispersion and soil amendments will be utilized for on-site LID BMPs prior to the runoff leaving either lot. Quail Ridge 24-0701 July 2025 Page-7 4. OFFSITE ANALYSIS DEFINE STUDY AREA: From observations made during the field visit, and the topographic survey, no significant areas drain onto this project site, this is due to the existing road being constructed and low areas to the east and west of the lot areas. Runoff from the future lots 1 & 2 drain either to the east or west respectively. Runoff from lot 1 drains to the east and is collected by the detention system constructed as part of the Quail Ridge subdivision. The pond discharges into a critical area buffer and wetland near the northeast corner of Tract 999. The wetland drains to the north/northwest for approximately 1000-feet before reaching the '/4 mile downstream point for this project. The area of the wetland is in a broad low area which is densely vegetated. The runoff from Lot 2 drains to the west and is collected by a wetland the cuts through Tract 999 and flows to the north/northwest. The wetland flows for approximately 1,200 feet before it reaches the '/4 mile downstream point for this project. This point is near where the wetland crosses a PUD parcel that is long and narrow running north/south. This wetland area is a narrow low area which is also densely vegetated. Since the flow paths do not combine within '/4 mile of the site lots 1 & 2 are considered to be in two separate TDA. However, the drainage design for this project will be completed considering the site a single threshold discharge area which is more conservative since the improvements cannot be split to meet the required thresholds. REVIEW AVAILABLE INFORMATION: The City and County GIS Maps were reviewed along with the original plat documents to identify two existing wetlands in Tract 999. These are the closest critical areas to the project. FIELD INSPECTION: This site slopes to the east and west depending on what side of 196t" PI NE you are on. Each future lot area appeared in good condition with no indications of standing water or erosion issues were noticed at the time of the field visit. DESCRIPTION OF DRAINAGE SYSTEM AND ANY EXISTING OR PREDICTED PROBLEMS: The downstream systems for this project appear in good condition. The systems consist of overland flow to a wetland or overland flow to man-made detention with outfall to wetland. Each critical area flows easily to the north/northwest. Since this project will disperse runoff over the future lots and the current site is pasture/lawn, the runoff flow rates from the developed conditions will only be slightly higher than in the current conditions for the site. Quail Ridge 24-0701 July 2025 Page-8 5. STORMWATER CONTROL PLAN A. On-Site Stormwater BMPs As documented in Section 1 of this report this project is required to meet Minimum Requirements 1-9. As a result, per Table 1.1 in Section 2.5.5 of Volume I in the 2024 DOESWMMWW this project is required to provide BMPs per List#2. Lawn/Landscaping Areas: BMP T5.13 will be used over all disturbed/converted pervious surfaces to remain after mass grading and prior to final site stabilization. Roofs: Full Dispersion: Infeasible due to lack of 100-foot native vegetation flow path prior to the runoff leaving the site or being collected by the existing detention pond or wetlands. Roof Downspout Infiltration: The project geotech found soils with mottling at less than 3- feet. Therefore, infeasible based on Geotech recommendations. Sheet flow or concentrated flow dispersion: Feasible, runoff from the future roof areas will be dispersed via splash blocks (50-foot vegetated flow path) or dispersion trench (25' vegetated flow path). Perforated Stubout Connection: Not selected since higher priority BMP was found feasible. Other Hard Surfaces: Full Dispersion: Infeasible due to lack of 100-foot native vegetation flow path prior to the runoff leaving the site or being collected by the existing detention pond or wetlands. Permeable Pavement: The project geotech found soils with mottling at less than 3-feet. In addition, 5' of fill was found in TP-3. Therefore, infeasible based on Geotech recommendations. Bioretention: Not feasible refer to infiltration discussion above. Sheet Flow Dispersion: Feasible, all driveway, walk and patio surfaces will be designed to sheet flow over the adjacent amended soils and vegetation on-site. B. FLOW CONTROL SYSTEM This project proposes to construct less than 10,000 sf of new/replaced effective impervious surfaces, convert less than 3/4 acre or 2.5 acres of forest to lawn or pasture respectively. Therefore, if the proposed improvements are found to increase the peak 100-year flow rate from the developed site by less than 0.15 cfs Quail Ridge 24-0701 July 2025 Page-9 over the current land cover conditions using the WWHM2012 software and 15- minute time steps, then this project would be considered exempt from this MR. Using the WWHM2012 software the existing and developed 100-year flows for lots 1 & 2 combined are 0.28 & 0.37 cfs respectively. This results in an increase of 0.09 cfs which is less than the 0.15 cfs threshold, so as noted, this project is exempt from flow control D. WATER QUALITY SYSTEM This project proposes to construct less than 5,000 sf of effective impervious surfaces and is exempt from this MR. Quail Ridge 24-0701 July 2025 Page-10 6. SWPPP NARRATIVE The intent of this section is to provide the information necessary to support the engineering plans to implement a design that will reduce, eliminate, or prevent the discharge of stormwater pollutants, meet or exceed the water quality and sediment management standards for the City and State, and prevent adverse impacts to the receiving waters for this project. Note: this narrative is intended to support the SWPPP that is included with the Drainage Plans also a part of this submittal package to the city. A. SITE GRADING/EROSION CONTROL RISK ASSESSMENT Area proposed to be cleared/worked: 0.88 acres Average slope for the site: 8% (Area of Disturbance Only) Erosion Hazard of Soil Slight to Moderate Critical Areas downslope Yes Site is upstream of an ESA Stream No Based on the above information and the fact that significant areas of vegetation can be retained along the perimeter of the area of disturbance, and that if site conditions warrant, additional BMP's can be implemented as corrective measures the Risk Category for this site is Low Risk. Quail Ridge 24-0701 July 2025 Page-1 1 B. SWPPP Minimum Elements 1: Preserve Vegetation and Mark Clearing Limits The first step in the construction process is for the contractor to flag or fence the limits of clearing/disturbance prior to any other construction activity. The engineering plans locate and provide the square footages for the areas of grading, clearing, impervious surfaces and un-disturbed areas on the proposed site. Existing vegetation can be preserved around the perimeter of the site during the initial construction phases on this project. Approximately 90% of the entire site will be cleared or disturbed for this project. 2: Establish Construction Access The SWPPP calls for the proposed construction entrance to be installed as the second step after the staking of clearing limits. At this time winter work is expected during the wet season. 3: Control Flow Rates This project is exempt from MR 7 and by retaining as much existing vegetation as possible during the SFR construction the runoff from this project will be attenuated. 4: Install Sediment Controls This site SWPPP proposes to construct/maintain gravel entrances, vegetative buffer, silt fencing or a brush barrier if necessary. The construction of these features should be completed before the clearing and grading of the site. Mulch will also be used on the exposed soil as necessary to limit erosion. 5: Stabilize Soils The "Construction Sequence" calls for the stabilization of soils that remain unworked for certain lengths of time based on the time of year. Stabilization techniques may include but not limited to mulching, plastic sheeting or hydroseeding, notes have been added to the plan regarding protection for the stockpile area if necessary. Stockpile areas have been identified on the SWPPP and are setback a minimum of 25-feet from any down slope property line. 6: Protect Slopes All disturbed slopes on site during construction are required to be protected with mulch or other means as specified in the construction sequence. No concentrated runoff or significant amounts of sheet flow will be directed to new cut or fill slopes during construction. 7: Protect Drain Inlets All existing catch basins adjacent to this project w/in 196t" PI NE and immediately downslope will be protected with inlet protection. No new CBs are proposed. 8: Stabilize Channels and Outlets All new/temporary or existing channels/outlets will be protected with check dams and rock pads as appropriate. Quail Ridge 24-0701 July 2025 Page-12 9: Control Pollutants No outside chemicals are expected to be necessary for the construction of this project. All vehicles working on and around the site would need to meet the State requirements for emissions. Vehicle fueling locations will be used to limit the potential impacts from any spills and concrete washout areas will also be provided well away from the detention vault. 10: Control DeWatering DeWatering may be necessary during construction of this project. However, the existing vegetation retained on site will be available to spread any water from construction for filtration and disposal 11: Maintain BMPs The construction supervisor will be responsible for maintaining all BMPs during construction and working with the City to relocate or add BMPs as necessary as site conditions change. 12: Manage the Project It will be the responsibility of the Contractor and Developer to manage this project and coordinate with the City Inspector and Engineer. Inspection and Monitoring: Site inspections shall be done by a person who is knowledgeable in the principles and practices of erosion and sediment control. The person must have skills to first assess the site conditions and construction activities that could impact the quality of stormwater, and second assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. Whenever inspection and/or monitoring reveals that the BMPs identified in the Construction SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible. Maintaining an Updated Construction SWPPP: The construction SWPPP shall be retained on-site or within reasonable access to the site. The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven days following inspection. 13: Protect On-Site Stormwater Management BMPs for Runoff from Hard Surfaces The use of on-site management BMPs for this project will allow for the installation of the roof dispersion BMPs and sheet flow dispersion of driveways and soil amendments at the time of building permit. Quail Ridge 24-0701 July 2025 Page-13 7. PROJECT OVERVIEW This project proposes to construct 2 new SFRs/Units on the site. Approximately 0.88 acres of the site will be developed/disturbed under this project. All the new impervious and pervious surfaces will be dispersed on-site to provide mitigation prior to the runoff leaving the site. The existing ground cover of pasture/grass and brush will be converted to landscaping and impervious surfaces because of this project. The site grades for this project range from 5-8%. Site grading will be necessary to create driveways and lot building pads for the future SFRs. An off-site septic easement is provided for both lots on the west side of the project. New water meters will be installed for each lot. Quail Ridge 24-0701 July 2025 Page-14 N URN <a SITE 9 200TH Fv L �ti o G � P2 �9 196TH s rn T p rn m OG 190TH P x VICINITY MAP SCALE 1" 2000' FIG. 1 OMEGA VICINITY MAP ENGINEERING, INC. QUAIL RIDGE SP 2707 WETMORE"E. DATE JOB NO. SCALE SHEET Everett, WA 98201(o)425.387.3820 (f) 425.259.1958 7/31/25 24-0701 1 = 2000, 1 OF 1 \ & DRAINAGE \ \ EASEMENT \ \ \ EXISTING l 20' ACCESS I \ & DRAINAGE \ _ EASEMENT \ 9 S G 9 LOT EXISTING \ Io' UE \ \ 1�2 A V v0 \ ti� EXISTING \ —X A P P R bol55 E X. W LOT 5 / N FIG. 2 OMEGA EXISTING BASIN MAP ENGINEERING, INC. QUAIL RIDGE SP 2707 WETMORE AVE. DATE JOB NO. SCALE SHEET Everett, WA 98201 „ (o)425.387.3820 (f) 425.259.1958 7/31/25 24-0701 1 = 60' 1 OF 1 \ & DRAINAGE \ \ EASEMENT \ \ 1 \ EXISTING 20' ACCESS I & DRAINAGE \ _ EASEMENT / PROP. D/W \ PCA 99, / (7 2 0 SF) � �50 gao \ LOT 6 PROP. DEW \ — pF� R0P. SFTR (715 SF) \ (2\000 SFy LO 1 EXISTING \ 21,984 s \ 1 o' uE \ \ \ \ PROP. SFR 4" STEEL CAST G\ \ems \\ (2,000 6'� WTH (2) CARRI CRIES\T �T ti \ \ LOT 2 EXISTING \ —� V 16,921 SF Io' \ \ Q7 w PROP. SEPTIC APPR SERVICE LI �(TYP )/ Q�Po�RRP5�5o EX. W LOT 5 PF N FIG. 3 OMEGA DEVELOPED BASIN MAP ENGINEERING, INC. QUAIL RIDGE SP 2707 WETMORE AVE. DATE JOB NO. SCALE SHEET Everett, WA 98201 „ (o)425.387.3820 (f) 425.259.1958 7/31/25 24-0701 1 = 60' 1 OF 1 3 Soil Map—Snohomish County Area,Washington 3 (QUAIL RIDGE SP) 566470 5%490 566510 566530 566550 566570 566590 566610 566630 5%650 48o 10'30"N _:ram 1 48o 10'3TN Nor t ` �AL 48o 10'26'N — 1 48o 10'26"N vs 566470 566490 566510 566530 566550 565M 565590 566610 566630 566650 3 3 lV e Map Scale:1:897 if printed on A landscape(11"x 8.5")sheet Meters N 0 10 20 40 60 Feet 0 40 80 160 240 Map projection:Web Mercator Comer coordinates:WG584 Edge tics:UTM Zone 1ON WGSS84 usm Natural Resources Web Soil Survey 7/31/2025 Conservation Service National Cooperative Soil Survey Page 1 of 3 Soil Map—Snohomish County Area,Washington QUAIL RIDGE SP Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 72 Tokul gravelly medial loam,0 1.5 44.6% to 8 percent slopes 73 Tokul gravelly medial loam,8 1.9 55.4% to 15 percent slopes Totals for Area of Interest 3.4 100.0% USDA Natural Resources Web Soil Survey 7/31/2025 Conservation Service National Cooperative Soil Survey Page 3 of 3 APPENDIX A STORMWATER CALCULATIONS Quail Ridge 24-0701 July 2025 Page-15 WWHM2012 PROJECT REPORT General Model Information WWHM2012 Project Name: default[11] Site Name: QUAIL RIDGE SP Site Address: City: ARLINGTON Report Date: 7/31/2025 Gage: Everett Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.200 Version Date: 2025/05/13 Version: 4.3.2 POC Thresholds Low Flow Threshold for POC1: 50 Percent of the 2 Year High Flow Threshold for POC1: 50 Year default[11] 7/31/2025 10:29:15 AM Page 2 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Pasture, Flat 0.88 Pervious Total 0.88 Impervious Land Use acre Impervious Total 0 Basin Total 0.88 Element Flow Componants: Surface I nterflow Groundwater Componant Flows To: POC 1 POC 1 default[11] 7/31/2025 10:29:15 AM Page 3 Mitigated Land Use Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Pasture, Flat 0.76 Pervious Total 0.76 Impervious Land Use acre ROOF TOPS FLAT 0.09 DRIVEWAYS FLAT 0.03 Impervious Total 0.12 Basin Total 0.88 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 default[11] 7/31/2025 10:29:15 AM Page 4 Routing Elements Predeveloped Routing default[11] 7/31/2025 10:29:15 AM Page 5 Mitigated Routing default[11] 7/31/2025 10:29:15 AM Page 6 Analysis Results POC 1 0.22 u ,.o Cunuladva Pmbabiity ,.o w 0.17 I u + 0.12 u o., �u.•T+ o., 000A Il 0.07 " + + +++ 000o n + 0.02 10E-5 10E-4 10E-3 10E-2 10E-1 1 1 11ri o.m a.o, Porcont Timo Exceeding6 0.5 1 2 5 10 ZO 30 50 70 BO 90 95 95 W 99.5 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area: 0.88 Total Impervious Area: 0 Mitigated Landuse Totals for POC #1 Total Pervious Area: 0.76 Total Impervious Area: 0.12 Flow Frequency Method: Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.043676 5 year 0.078777 10 year 0.111466 25 year 0.166377 50 year 0.219217 100 year 0.284228 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.092335 5 year 0.14325 10 year 0.185495 25 year 0.249949 50 year 0.306928 100 year 0.372408 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.069 0.128 1950 0.061 0.126 1951 0.038 0.079 1952 0.037 0.085 1953 0.035 0.107 1954 0.178 0.250 1955 0.065 0.124 1956 0.039 0.061 1957 0.069 0.115 1958 0.137 0.262 default[11] 7/31/2025 10:29:15 AM Page 7 1959 0.037 0.080 1960 0.050 0.102 1961 0.383 0.514 1962 0.046 0.086 1963 0.102 0.167 1964 0.057 0.081 1965 0.028 0.056 1966 0.018 0.058 1967 0.041 0.124 1968 0.046 0.092 1969 0.240 0.335 1970 0.028 0.066 1971 0.052 0.104 1972 0.058 0.140 1973 0.035 0.103 1974 0.091 0.144 1975 0.047 0.111 1976 0.032 0.070 1977 0.023 0.054 1978 0.025 0.058 1979 0.123 0.183 1980 0.047 0.084 1981 0.025 0.064 1982 0.038 0.065 1983 0.077 0.106 1984 0.034 0.081 1985 0.046 0.094 1986 0.113 0.180 1987 0.044 0.099 1988 0.024 0.080 1989 0.041 0.096 1990 0.030 0.066 1991 0.031 0.062 1992 0.034 0.088 1993 0.027 0.064 1994 0.025 0.054 1995 0.032 0.054 1996 0.068 0.112 1997 0.144 0.194 1998 0.034 0.106 1999 0.026 0.055 2000 0.029 0.136 2001 0.010 0.045 2002 0.030 0.045 2003 0.024 0.060 2004 0.040 0.124 2005 0.029 0.062 2006 0.099 0.148 2007 0.078 0.130 2008 0.081 0.101 2009 0.024 0.068 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.3831 0.5143 2 0.2398 0.3347 3 0.1779 0.2622 default[11] 7/31/2025 10:29:44 AM Page 8 4 0.1444 0.2504 5 0.1372 0.1943 6 0.1232 0.1832 7 0.1133 0.1799 8 0.1019 0.1670 9 0.0986 0.1485 10 0.0911 0.1438 11 0.0811 0.1395 12 0.0780 0.1360 13 0.0769 0.1305 14 0.0695 0.1283 15 0.0686 0.1261 16 0.0680 0.1245 17 0.0652 0.1242 18 0.0610 0.1235 19 0.0582 0.1148 20 0.0566 0.1120 21 0.0517 0.1107 22 0.0503 0.1072 23 0.0474 0.1064 24 0.0468 0.1063 25 0.0465 0.1037 26 0.0456 0.1035 27 0.0455 0.1015 28 0.0442 0.1009 29 0.0414 0.0992 30 0.0409 0.0960 31 0.0400 0.0940 32 0.0392 0.0920 33 0.0383 0.0882 34 0.0380 0.0862 35 0.0368 0.0855 36 0.0367 0.0837 37 0.0349 0.0815 38 0.0346 0.0807 39 0.0344 0.0805 40 0.0337 0.0797 41 0.0336 0.0792 42 0.0325 0.0696 43 0.0323 0.0683 44 0.0313 0.0662 45 0.0304 0.0660 46 0.0302 0.0653 47 0.0293 0.0643 48 0.0287 0.0641 49 0.0283 0.0621 50 0.0276 0.0619 51 0.0269 0.0613 52 0.0258 0.0596 53 0.0251 0.0582 54 0.0251 0.0578 55 0.0247 0.0559 56 0.0244 0.0555 57 0.0237 0.0545 58 0.0235 0.0544 59 0.0231 0.0535 60 0.0182 0.0455 61 0.0097 0.0449 default[11] 7/31/2025 10:29:44 AM Page 9 default[11] 7/31/2025 10:29:44 AM Page 10 Duration Flows The Duration Matching Failed Flow(cfs) Predev Mit Percentage Pass/Fail 0.0218 8138 18491 227 Fail 0.0238 5668 14514 256 Fail 0.0258 3993 11407 285 Fail 0.0278 3003 9073 302 Fail 0.0298 2212 7195 325 Fail 0.0318 1684 5730 340 Fail 0.0338 1360 4667 343 Fail 0.0358 1122 3762 335 Fail 0.0378 953 3074 322 Fail 0.0398 804 2562 318 Fail 0.0418 695 2138 307 Fail 0.0438 632 1800 284 Fail 0.0458 570 1539 270 Fail 0.0478 518 1331 256 Fail 0.0498 476 1173 246 Fail 0.0517 431 1018 236 Fail 0.0537 394 889 225 Fail 0.0557 369 796 215 Fail 0.0577 346 725 209 Fail 0.0597 322 667 207 Fail 0.0617 294 600 204 Fail 0.0637 265 530 200 Fail 0.0657 239 489 204 Fail 0.0677 215 447 207 Fail 0.0697 192 404 210 Fail 0.0717 169 364 215 Fail 0.0737 148 324 218 Fail 0.0757 118 296 250 Fail 0.0777 91 266 292 Fail 0.0797 68 246 361 Fail 0.0816 54 221 409 Fail 0.0836 46 204 443 Fail 0.0856 36 178 494 Fail 0.0876 26 157 603 Fail 0.0896 19 142 747 Fail 0.0916 17 133 782 Fail 0.0936 16 123 768 Fail 0.0956 16 113 706 Fail 0.0976 14 101 721 Fail 0.0996 13 91 700 Fail 0.1016 11 81 736 Fail 0.1036 10 74 740 Fail 0.1056 9 67 744 Fail 0.1076 9 57 633 Fail 0.1096 9 53 588 Fail 0.1116 9 49 544 Fail 0.1135 8 47 587 Fail 0.1155 8 42 525 Fail 0.1175 7 41 585 Fail 0.1195 7 40 571 Fail 0.1215 7 39 557 Fail 0.1235 6 37 616 Fail 0.1255 6 32 533 Fail 0.1275 6 31 516 Fail default[11] 7/31/2025 10:29:44 AM Page 11 0.1295 6 28 466 Fail 0.1315 6 26 433 Fail 0.1335 6 24 400 Fail 0.1355 6 22 366 Fail 0.1375 5 21 419 Fail 0.1395 5 20 400 Fail 0.1415 5 18 360 Fail 0.1435 5 18 360 Fail 0.1454 4 16 400 Fail 0.1474 4 15 375 Fail 0.1494 4 14 350 Fail 0.1514 4 14 350 Fail 0.1534 4 14 350 Fail 0.1554 4 14 350 Fail 0.1574 4 12 300 Fail 0.1594 4 12 300 Fail 0.1614 4 12 300 Fail 0.1634 4 12 300 Fail 0.1654 4 11 275 Fail 0.1674 4 10 250 Fail 0.1694 4 10 250 Fail 0.1714 4 8 200 Fail 0.1734 4 8 200 Fail 0.1754 4 8 200 Fail 0.1773 4 8 200 Fail 0.1793 3 8 266 Fail 0.1813 3 7 233 Fail 0.1833 3 6 200 Fail 0.1853 3 6 200 Fail 0.1873 3 6 200 Fail 0.1893 3 6 200 Fail 0.1913 3 6 200 Fail 0.1933 3 6 200 Fail 0.1953 3 5 166 Fail 0.1973 3 5 166 Fail 0.1993 3 5 166 Fail 0.2013 3 5 166 Fail 0.2033 3 5 166 Fail 0.2053 3 5 166 Fail 0.2073 3 5 166 Fail 0.2092 3 5 166 Fail 0.2112 3 5 166 Fail 0.2132 3 5 166 Fail 0.2152 3 5 166 Fail 0.2172 3 5 166 Fail 0.2192 3 5 166 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. default[11] 7/31/2025 10:29:44 AM Page 12 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0 acre-feet On-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off-line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. default[11] 7/31/2025 10:29:44 AM Page 13 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. default[11] 7/31/2025 10:29:44 AM Page 14 Appendix Predeveloped Schematic Basin 1 �1 0.88ac default[11] 7/31/2025 10:29:44 AM Page 15 Mitigated Schematic Basin 1 0.88ac default[11] 7/31/2025 10:29:44 AM Page 16 Predeveloped UC/ 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 default[ll] .wdm MESSU 25 Predefault[ll] .MES 27 Predefault[ll] .L61 28 Predefault[ll] .L62 30 POCdefault[11] 1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 13 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 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 *** 13 C, Pasture, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 13 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 ********* 13 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO default[111 7/31/2025 10:29:45 AM Page 17 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 13 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 13 0 4.5 0.06 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 13 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 13 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATEI <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 13 0 0 0 0 2.5 1 0 END PWAT-STATEI END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATEI <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATEI default[11] 7/31/2025 10:29:45 AM Page 18 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 13 0.88 COPY 501 12 PERLND 13 0.88 COPY 501 13 ******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 <-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 Al A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARMl 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 EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1.2 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1.2 IMPLND 1 999 EXTNL PREC default[11] 7/31/2025 10:29:45 AM Page 19 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 END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** 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 END MASS-LINK END RUN default[11] 7/31/2025 10:29:45 AM Page 20 Mitigated UC/ 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 default[ll] .wdm MESSU 25 Mitdefault[ll] .MES 27 Mitdefault[ll] .L61 28 Mitdefault[ll] .L62 30 POCdefault[11] 1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 13 IMPLND 4 IMPLND 5 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 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 *** 13 C, Pasture, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 13 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 ********* 13 0 0 4 0 0 0 0 0 0 0 0 0 1 9 default[111 7/31/2025 10:29:45 AM Page 21 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 13 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 13 0 4.5 0.06 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 13 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 13 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATEI <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 13 0 0 0 0 2.5 1 0 END PWAT-STATEI END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 5 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 4 1 9 5 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 *** 4 0 0 0 0 0 5 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 5 400 0.01 0. 1 0.1 default[111 7/31/2025 10:29:45 AM Page 22 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 5 0 0 END IWAT-PARM3 IWAT-STATEI <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 5 0 0 END IWAT-STATEI END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 13 0.76 COPY 501 12 PERLND 13 0.76 COPY 501 13 IMPLND 4 0.09 COPY 501 15 IMPLND 5 0.03 COPY 501 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 <-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 Al 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 default[11] 7/31/2025 10:29:45 AM Page 23 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 EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1.2 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1.2 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 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 END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** 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 END MASS-LINK END RUN default[11] 7/31/2025 10:29:45 AM Page 24 Predeveloped HSPF Message File default[11] 7/31/2025 10:29:45 AM Page 25 Mitigated HSPF Message File default[11] 7/31/2025 10:29:45 AM Page 26 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright© by : Clear Creek Solutions, Inc. 2005-2025; All Rights Reserved. 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 default[11] 7/31/2025 10:29:45 AM Page 27 APPENDIX B Geotechnical Assessment L�2COBALT Cobalt Geosciences,LLC GEOSCI LTCES P.O.Box1792 North Bend,WA 98045 July 14,2025 KJR Family LLC John Robinett Jrobinett2500(@aol.com RE: Geotechnical Evaluation Proposed Development Two Lots at Quail Ridge 196th Place NE Arlington,Washington In accordance with your authorization,Cobalt Geosciences,LLC has prepared this report to discuss the results of our geotechnical evaluation at the referenced site. The purpose of our evaluation was to provide recommendations for foundation design, grading, and earthwork. Site & Project Description The site is located at 93xx 196th Place NE in Arlington,Washington. The site includes two small tracts along 196th Place NE(Figure 1). Both of the properties are undeveloped and previously graded during plat development. The properties are vegetated with grasses,blackberry vines,understory,bushes,and sparse trees. The site areas are mostly level with local slopes to the east and west of the two properties,extending downward to the east and west,respectively.The site areas are along the margins of 196th Place NE west of 95th Avenue NE. The proposed development includes a new residence and driveway on each property. Stormwater will include infiltration or other systems depending on feasibility. Site grading may include cuts and fills of 3 feet or less and foundation loads are expected to be light. We should be provided with the final plans to verify that our recommendations remain valid and do not require updating. Area Geology The Geologic Map of the Arlington East Quadrangle,indicates that the site is underlain by Vashon Glacial Till. Vashon Glacial Till includes mixtures of silt, sand, clay, and gravel. These materials are usually impermeable and are typically dense to very dense below a weathered zone. Soil & Groundwater Conditions As part of our evaluation, we excavated three test pits, where accessible. The explorations encountered approximately 6 inches of grass and topsoil underlain by approximately 3 to 6.5 feet of loose to medium dense, silty-fine to medium grained sand trace gravel (Fill in TP-3 over Weathered Glacial Till). www.cobaltgeo.com (2o6)331-1097 July 14,2025 Page 2 of to Geotechnical Evaluation These materials were underlain by dense to very dense, silty-fine to medium grained sand trace gravel(Vashon Glacial Till),which continued to the termination depths of the explorations. While groundwater was not observed, the soils were locally mottled. Additionally, there is a detention pond to the east, indicating that groundwater becomes perched in this area. Minor interflow may develop within the upper glacial till soils, likely where the soils become relatively dense. Water table elevations often fluctuate over time. The groundwater level will depend on a variety of factors that may include seasonal precipitation, irrigation, land use, climatic conditions and soil permeability. Water levels at the time of the field investigation may be different from those encountered during the construction phase of the project. Erosion Hazard The Natural Resources Conservation Services (NRCS) maps for Snohomish County indicate that the site is underlain by Tokul gravelly medial loam(o to 8 percent slopes). Based on our experience, the site soils would have a slight to moderate erosion potential in a disturbed state depending on the slope magnitude. It is our opinion that soil erosion potential at this project site can be reduced through landscaping and surface water runoff control. Typically,erosion of exposed soils will be most noticeable during periods of rainfall and may be controlled by the use of normal temporary erosion control measures, such as silt fences, hay bales, mulching, control ditches and diversion trenches. The typical wet weather season, with regard to site grading, is from October 31st to April ist. Erosion control measures should be in place before the onset of wet weather. Seismic Hazard The overall subsurface profile corresponds to a Site Class D as defined by Table 1613.5.2 of the International Building Code(IBC). A Site Class D applies to an overall profile consisting of medium dense to very dense soils within the upper too feet. We referenced the U.S.Geological Survey(USGS)Earthquake Hazards Program Website to obtain values for Ss,S,,FQ,and F,,. The USGS website includes the most updated published data on seismic conditions. The following tables provide seismic parameters from the USGS web site referenced parameters from ASCE 7-16 and ASCE 7-22. Seismic Design Parameters(ASCE 7-16) Site Spectral Spectral Site Design Spectral Design Class Acceleration Acceleration Coefficients Response Parameters PGA at 0.2 sec. at 1.o sec. (g) (g) Fa Fv SDS SD1 D 1.031 0.368 1.0 Null 0.747 Null 0.438 www.cobaltgeo.com (206)331-1097 July 14,2025 Page 3 of 10 Geotechnical Evaluation Seismic Design Parameters(ASCE 7-22) Site Spectral Spectral Site Design Spectral Design Class Acceleration Acceleration Coefficients Response Parameters PGAM at 0.2 sec. at 1.o sec. (g) (g) Fa F, SDs SDl D 1.14 0.34 - - 0.9 0.51 0.53 Additional seismic considerations include liquefaction potential and amplification of ground motions by soft/loose soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table. The site has a low likelihood of liquefaction. For items listed as "Null' see Section 11.4.8 of the ASCE. Conclusions and Recommendations General The site is underlain by areas of fill and at depth by glacial till which becomes denser with depth. The proposed residential structures may be supported on shallow foundation systems bearing on medium dense or firmer native soils or on structural fill placed on the native soils. Local overexcavation of loose weathered native soils may be necessary depending on the proposed elevations and locations of the new footings. Significant removal of fill will be necessary in the area of the eastern structure,where mass grading historically occurred. Pin piles could be used in lieu of excavations,if desired. We recommend dispersion devices or direct/perforated connection to utility conveyance. We can provide additional input once a civil plan is prepared. Site Preparation Trees, shrubs and other vegetation should be removed prior to stripping of surficial organic-rich soil and fill. Based on observations from the site investigation program, it is anticipated that the stripping depth will be 6 to 12 inches. Deeper excavations will be necessary in areas of existing foundation systems(where present),larger trees where roots persist,and in any areas underlain by undocumented fill. The native soils consist of silty-sand with gravel. Most of the native soils may be used as structural fill provided they achieve compaction requirements and are within 3 percent of the optimum moisture. Some of these soils may only be suitable for use as fill during the summer months, as they will be above the optimum moisture levels in their current state. These soils are HIGHLY moisture sensitive and may degrade during periods of wet weather and under equipment traffic. www.cobaltgeo.com (2o6)331-1097 July 14,2025 Page 4 of 10 Geotechnical Evaluation Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill should be placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of the modified proctor maximum dry density, as determined by the ASTM D 1557 test method. Temporary Excavations Based on our understanding of the project,we anticipate that the grading could include local cuts on the order of approximately 3 feet or less for foundation and most of the utility placement. Temporary excavations should be sloped no steeper than 1.5H:1V (Horizontal:Vertical) in loose native soils and fill,1H:1V in medium dense native soils and 3/4H:1V in dense to very dense native soils. If an excavation is subject to heavy vibration or surcharge loads, we recommend that the excavations be sloped no steeper than 2H:1V,where room permits. Temporary cuts should be in accordance with the Washington Administrative Code(WAC)Part N, Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified person during construction activities and the inspections should be documented in daily reports. The contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope erosion during construction. Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the slopes should be closely monitored until the permanent retaining systems or slope configurations are complete. Materials should not be stored or equipment operated within 10 feet of the top of any temporary cut slope. Soil conditions may not be completely known from the geotechnical investigation. In the case of temporary cuts, the existing soil conditions may not be completely revealed until the excavation work exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes will need to be re-evaluated by the geotechnical engineer so that supplemental recommendations can be made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be adjustable,to deal with unanticipated conditions, so that the project can proceed and required deadlines can be met. If any variations or undesirable conditions are encountered during construction, we should be notified so that supplemental recommendations can be made. If room constraints or groundwater conditions do not permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring systems may be required. The contractor should be responsible for developing temporary shoring systems, if needed. We recommend that Cobalt Geosciences and the project structural engineer review temporary shoring designs prior to installation,to verify the suitability of the proposed systems. Foundation Design The proposed structures may be supported on shallow spread footing foundation systems bearing on undisturbed medium dense or firmer native soils or on properly compacted structural fill placed on the suitable native soils. Any undocumented fill and/or loose native soils should be removed and replaced with structural fill below foundation elements. Structural fill below footings should consist of clean angular rock 5/8 to 4 inches in size. We should verify soil conditions during foundation excavation work. www.cobaltgeo.com (2o6)331-1097 July 14,2025 Page 5 of 10 Geotechnical Evaluation For shallow foundation support,we recommend widths of at least 16 and 24 inches, respectively, for continuous wall and isolated column footings supporting the proposed structure. Provided that the footings are supported as recommended above, a net allowable bearing pressure of 2,500 pounds per square foot(psf)may be used for design. All fill should be removed below the new buildings,where present. Note that fill was significantly thick within the eastern lot. A 1/3 increase in the above value may be used for short duration loads,such as those imposed by wind and seismic events. Structural fill placed on bearing, native subgrade should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Footing excavations should be inspected to verify that the foundations will bear on suitable material. Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or adjacent exterior grade,whichever is lower. Interior footings should have a minimum depth of 12 inches below pad subgrade(soil grade)or adjacent exterior grade,whichever is lower. If constructed as recommended,the total foundation settlement is not expected to exceed 1 inch. Differential settlement,along a 25-foot exterior wall footing,or between adjoining column footings, should be less than 1/2 inch. This translates to an angular distortion of 0.002. Most settlement is expected to occur during construction, as the loads are applied. However, additional post- construction settlement may occur if the foundation soils are flooded or saturated. All footing excavations should be observed by a qualified geotechnical consultant. Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.4o acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can also be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot(pcf)acting against the appropriate vertical footing faces(neglect the upper 12 inches below grade in exterior areas). The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Any extremely wet or dry materials,or any loose or disturbed materials at the bottom of the footing excavations,should be removed prior to placing concrete.The potential for wetting or drying of the bearing materials can be reduced by pouring concrete as soon as possible after completing the footing excavation and evaluating the bearing surface by the geotechnical engineer or his representative. Concrete Retaining Walls The following table,titled Wall Design Criteria,presents the recommended soil related design parameters for retaining walls with a level backslope. Contact Cobalt if an alternate retaining wall system is used. This has been included for new cast in place walls. Wall Design Criteria "At-rest"Conditions(Lateral Earth Pressure—EFD+) 55 pcf(Equivalent Fluid Density) "Active"Conditions(Lateral Earth Pressure—EFD+) 35 pcf(Equivalent Fluid Density) Seismic Increase for "At-rest" Conditions 12H*(Uniform Distribution) (Lateral Earth Pressure) www.cobaltgeo.com (2o6)331-1097 July 14,2025 Page 6 of io Geotechnical Evaluation Seismic Increase for "Active" Conditions 6H*(Uniform Distribution) (Lateral Earth Pressure) Passive Earth Pressure on Low Side of Wall Neglect upper 12 inches,then 250 pcf EFD+ (Allowable,includes F.S.=1.5) Soil-Footing Coefficient of Sliding Friction(Allowable; 0.40 includes F.S.=1.5) *H is the height of the wall;Increase based on one in 500 year seismic event (10 percent probability of being exceeded in 50 years), +EFD—Equivalent Fluid Density The stated lateral earth pressures do not include the effects of hydrostatic pressure generated by water accumulation behind the retaining walls. Uniform horizontal lateral active and at-rest pressures on the retaining walls from vertical surcharges behind the wall may be calculated using active and at-rest lateral earth pressure coefficients of 0.3 and 0.5,respectively. A soil unit weight of 125 pcf may be used to calculate vertical earth surcharges. To reduce the potential for the buildup of water pressure against the walls, continuous footing drains (with cleanouts) should be provided at the bases of the walls. The footing drains should consist of a minimum 4-inch diameter perforated pipe, sloped to drain, with perforations placed down and enveloped by a minimum 6 inches of pea gravel in all directions. The backfill adjacent to and extending a lateral distance behind the walls at least 2 feet should consist of free-draining granular material. All free draining backfill should contain less than 3 percent fines (passing the U.S. Standard No. 200 Sieve)based upon the fraction passing the U.S. Standard No.4 Sieve with at least 30 percent of the material being retained on the U.S. Standard No. 4 Sieve. The primary purpose of the free-draining material is the reduction of hydrostatic pressure. Some potential for the moisture to contact the back face of the wall may exist,even with treatment, which may require that more extensive waterproofing be specified for walls, which require interior moisture sensitive finishes. We recommend that the backfill be compacted to at least go percent of the maximum dry density based on ASTM Test Method D1557. In place density tests should be performed to verify adequate compaction. Soil compactors place transient surcharges on the backfill. Consequently,only light hand operated equipment is recommended within 3 feet of walls so that excessive stress is not imposed on the walls. Stormwater Management Feasibility The near surface weathered glacial till has very limited capacity for infiltration of runoff. The soil becomes mottled and very dense at shallow depths. Infiltration is not recommended in fill,which was significant within the eastern lot. The denser till at these depths acts as an aquitard. We recommend that most of the runoff(roof areas and pavements)be routed to City infrastructure via a perforated or tightline connection per City requirements. Local permeable pavements and biortetention could be utilized to manage runoff in the shallow weathered soils. We can provide additional recommendations once a civil plan has been prepared. If possible,systems should have overflow to an approved conveyance. www.cobaltgeo.com (2o6)331-1097 July 14,2025 Page 7 of io Geotechnical Evaluation Slab-on-Grade We recommend that the upper 12 inches of the native soils within slab areas be re-compacted to at least 95 percent of the modified proctor(ASTM D1557 Test Method). Often,a vapor barrier is considered below concrete slab areas.However,the usage of a vapor barrier could result in curling of the concrete slab at joints. Floor covers sensitive to moisture typically requires the usage of a vapor barrier. A materials or structural engineer should be consulted regarding the detailing of the vapor barrier below concrete slabs. Exterior slabs typically do not utilize vapor barriers. The American Concrete Institutes ACI 36oR-o6 Design of Slabs on Grade and ACI 302.1R-04 Guide for Concrete Floor and Slab Construction are recommended references for vapor barrier selection and floor slab detailing. Slabs on grade may be designed using a coefficient of subgrade reaction of 210 pounds per cubic inch (pci) assuming the slab-on-grade base course is underlain by structural fill placed and compacted as outlined above. A 4-to 6-inch-thick capillary break layer should be placed over the prepared subgrade. This material should consist of pea gravel or 5/8 inch clean angular rock. A perimeter drainage system is recommended unless interior slab areas are elevated a minimum of 12 inches above adjacent exterior grades. If installed, a perimeter drainage system should consist of a 4-inch diameter perforated drain pipe surrounded by a minimum 6 inches of drain rock wrapped in a non-woven geosynthetic filter fabric to reduce migration of soil particles into the drainage system. The perimeter drainage system should discharge by gravity flow to a suitable stormwater system. Exterior grades surrounding buildings should be sloped at a minimum of one percent to facilitate surface water flow away from the building and preferably with a relatively impermeable surface cover immediately adjacent to the building. Erosion and Sediment Control Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands,streams,lakes,drainage systems,and adjacent properties. Erosion and sediment control measures should be implemented,and these measures should be in general accordance with local regulations. At a minimum,the following basic recommendations should be incorporated into the design of the erosion and sediment control features for the site: • Schedule the soil, foundation,utility, and other work requiring excavation or the disturbance of the site soils, to take place during the dry season (generally May through September). However, provided precautions are taken using Best Management Practices (BMP's),grading activities can be completed during the wet season(generally October through April). • All site work should be completed and stabilized as quickly as possible. • Additional perimeter erosion and sediment control features may be required to reduce the possibility of sediment entering the surface water. This may include additional silt fences,silt fences with a higher Apparent Opening Size(AOS),construction of a berm, or other filtration systems. • Any runoff generated by dewatering discharge should be treated through construction of a sediment trap if there is sufficient space. If space is limited other filtration methods will need to be incorporated. www.cobaltgeo.com (2o6)331-1097 July 14,2025 Page 8 of io Geotechnical Evaluation Utilities Utility trenches should be excavated according to accepted engineering practices following OSHA (Occupational Safety and Health Administration) standards,by a contractor experienced in such work. The contractor is responsible for the safety of open trenches. Traffic and vibration adjacent to trench walls should be reduced; cyclic wetting and drying of excavation side slopes should be avoided. Depending upon the location and depth of some utility trenches, groundwater flow into open excavations could be experienced, especially during or shortly following periods of precipitation. In general,silty and sandy soils were encountered at shallow depths in the explorations at this site. These soils have low cohesion and density and will have a tendency to cave or slough in excavations. Shoring or sloping back trench sidewalls is required within these soils in excavations greater than 4 feet deep. All utility trench backfill should consist of imported structural fill or suitable on site soils. Utility trench backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. The upper 5 feet of utility trench backfill placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Below 5 feet,utility trench backfill in pavement areas should be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557• Pipe bedding should be in accordance with the pipe manufacturer's recommendations. The contractor is responsible for removing all water-sensitive soils from the trenches regardless of the backfill location and compaction requirements. Depending on the depth and location of the proposed utilities,we anticipate the need to re-compact existing fill soils below the utility structures and pipes. The contractor should use appropriate equipment and methods to avoid damage to the utilities and/or structures during fill placement and compaction procedures. CONSTRUCTION FIELD REVIEWS Cobalt Geosciences should be retained to provide part time field review during construction in order to verify that the soil conditions encountered are consistent with our design assumptions and that the intent of our recommendations is being met.This will require field and engineering review to: ■ Monitor and test structural fill placement and soil compaction ■ Observe bearing capacity at foundation locations ■ Observe slab-on-grade preparation ■ Observe soil conditions at stormwater system locations(if utilized) ■ Monitor foundation drainage placement ■ Observe excavation stability Geotechnical design services should also be anticipated during the subsequent final design phase to support the structural design and address specific issues arising during this phase. Field and engineering review services will also be required during the construction phase in order to provide a Final Letter for the project. www.cobaltgeo.com (206)331-1097 July 14,2025 Page 9 of io Geotechnical Evaluation CLOSURE This report was prepared for the exclusive use of KJR Family LLC and their appointed consultants. Any use of this report or the material contained herein by third parties, or for other than the intended purpose,should first be approved in writing by Cobalt Geosciences,LLC. The recommendations contained in this report are based on assumed continuity of soils with those of our test holes and assumed structural loads. Cobalt Geosciences should be provided with final architectural and civil drawings when they become available in order that we may review our design recommendations and advise of any revisions,if necessary. Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the responsibility of KJR Family LLC who is identified as "the Client" within the Statement of General Conditions,and its agents to review the conditions and to notify Cobalt Geosciences should any of these not be satisfied. Sincerely, Cobalt Geosciences,LLC �HONr P yy q \o E�ginwn -0 , 3- �c�\ 2513 �. �0 54896 �r���@mod c eo�o IST �SS�ONAL�- ILLIP HASERMA� 7/14/2025 Phil Haberman,PE,LG,LEG Principal www.cobaltgeo.com (206)331-1097 July 14,2025 Page io of io Geotechnical Evaluation Statement of General Conditions USE OF THIS REPORT: This report has been prepared for the sole benefit of the Client or its agent and may not be used by any third party without the express written consent of Cobalt Geosciences and the Client.Any use which a third party makes of this report is the responsibility of such third parry. BASIS OF THE REPORT: The information, opinions, and/or recommendations made in this report are in accordance with Cobalt Geosciences present understanding of the site specific project as described by the Client.The applicability of these is restricted to the site conditions encountered at the time of the investigation or study. If the proposed site specific project differs or is modified from what is described in this report or if the site conditions are altered, this report is no longer valid unless Cobalt Geosciences is requested by the Client to review and revise the report to reflect the differing or modified project specifics and/or the altered site conditions. STANDARD OF CARE: Preparation of this report, and all associated work, was carried out in accordance with the normally accepted standard of care in the state of execution for the specific professional service provided to the Client.No other warranty is made. INTERPRETATION OF SITE CONDITIONS: Soil, rock, or other material descriptions, and statements regarding their condition,made in this report are based on site conditions encountered by Cobalt Geosciences at the time of the work and at the specific testing and/or sampling locations. Classifications and statements of condition have been made in accordance with normally accepted practices which are judgmental in nature; no specific description should be considered exact,but rather reflective of the anticipated material behavior. Extrapolation of in situ conditions can only be made to some limited extent beyond the sampling or test points. The extent depends on variability of the soil, rock and groundwater conditions as influenced by geological processes, construction activity,and site use. VARYING OR UNEXPECTED CONDITIONS: Should any site or subsurface conditions be encountered that are different from those described in this report or encountered at the test locations, Cobalt Geosciences must be notified immediately to assess if the varying or unexpected conditions are substantial and if reassessments of the report conclusions or recommendations are required. Cobalt Geosciences will not be responsible to any party for damages incurred as a result of failing to notify Cobalt Geosciences that differing site or sub-surface conditions are present upon becoming aware of such conditions. PLANNING,DESIGN,OR CONSTRUCTION:Development or design plans and specifications should be reviewed by Cobalt Geosciences, sufficiently ahead of initiating the next project stage (property acquisition,tender, construction, etc),to confirm that this report completely addresses the elaborated project specifics and that the contents of this report have been properly interpreted. Specialty quality assurance services (field observations and testing) during construction are a necessary part of the evaluation of sub-subsurface conditions and site preparation works.Site work relating to the recommendations included in this report should only be carried out in the presence of a qualified geotechnical engineer;Cobalt Geosciences cannot be responsible for site work carried out without being present. www.cobaltgeo.com (2o6)331-1097 PLACE • � t VOW WWI • . 5� Approximate Test TP-1 Pit Location N Sno.Co.GIS Map A Cobalt Geosciences,LLC Proposed Development Site Image P.O.Box 82243 _ . Quail Ridge lg6th Place NE Kenmore,WA 98028 (206)331-1097 GEOSCIENCES Arlington, Washington Figure i www.cobaltgeo.com cobaltgeoogmail.com Basement or Shallow Foundation Wall 1-1�X Slab on Grade 12"Free Draining Backfill and/or Drainage Mat Attached to Wall Backfill Soils Compacted per Geotechnical Report Native Soils Benched as Required Filter Fabric Over Rock (Mirafi 14oN) 0 --� 3//4"Washed Rock or Clean Angular Rock 4"Diameter Perforated Pipe Not to Scale Cobalt Geosciences,LLC PO Box 1792 Typical Foundation Drain Detail North Bend,WA 9So45 COBALTAttachment (2o6)331-1097 GEOSCIENCES www.cobaltgeo.com phil(@cobaltgeo.com Unified Soil Classification System (USCS) MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION GW Clean Gravels 5,1 Well-graded gravels,gravels,gravel-sand mixtures,little or no fines Gravels (less than 5% LM GP (more than 50% fines) Poorly graded gravels,gravel-sand mixtures,little or no fines of coarse fraction -7 GM retained on No.4 Gravels with Silty gravels,gravel-sand-silt mixtures COARSE sieve) Fines GRAINED (more than 12% GC SOILS fines) Clayey gravels,gravel-sand-clay mixtures (more than 50% sw retained on Clean Sands Well-graded sands,gravelly sands,little or no fines No.200 sieve) Sands (less than 5% SP (50%or more fines) Poorly graded sand,gravelly sands,little or no fines of coarse fraction passes the No.4 sM sieve) Sands with Fines Silty sands,sand-silt mixtures (more than 12% sc fines) Clayey sands,sand-clay mixtures ML Inorganic silts of low to medium plasticity,sandy silts,gravelly silts, or clayey silts with slight plasticity Silts and Clays Inorganic cL Inorganic clays of low to medium plasticity,gravelly clays,sandy clays (liquid limit less FINE GRAINED than 50) silty clays,lean clays SOILS oL Organic Organic silts and organic silty clays of low plasticity (50%or more passes the MH Inorganic silts,micaceous or diatomaceous fine sands or silty soils, No.200 sieve) elastic silt Silts and Clays Inorganic CH (liquid limit 50 or Inorganic clays of medium to high plasticity,sandy fat clay, more) or gravelly fat clay OH Organic Organic clays of medium to high plasticity,organic silts HIGHLY ORGANIC Primarily organic matter,dark in color, PT SOILS and organic odor Peat,humus,swamp soils with high organic content(ASTM D4427) Classification of Soil Constituents Grain Size Definitions Description Sieve Number and/or Size MAJOR constituents compose more than 50 percent, Fines <#200(o.o8 mm) by weight,of the soil. Major constituents are capitalized (i.e.,SAND). Sand -Fine #200 to#40(0.08 to 0.4 mm) Minor constituents compose 12 to 50 percent of the soil -Medium #40 to#10(0.4 to 2 mm) and precede the major constituents(i.e.,silty SAND). -Coarse #10 to#4(2 to 5 mm) Minor constituents preceded by"slightly"compose 5 to 12 percent of the soil(i.e.,slightly silty SAND). Gravel -Fine #4 to 3/4 inch(5 to 19 mm) Trace constituents compose o to 5 percent of the soil -Coarse 3/4 to 3 inches(19 to 76 mm) (i.e.,slightly silty SAND,trace gravel). Cobbles 3 to 12 inches(75 to 305 mm) Boulders >12 inches(305 mm) Relative Density Consistency (Coarse Grained Soils) (Fine Grained Soils) N,SPT, Relative N,SPT, Relative Moisture Content Definitions Blows/FT Density Blows/FT Consistency 0-4 Very loose Under 2 Very soft 4-10 Loose 2-4 Soft Dry Absence of moisture,dusty,dry to the touch 10-30 Medium dense 4-8 Medium stiff 30-50 Dense 8-15 Stiff Moist Damp but no visible water Over 50 Very dense 15-3o Very stiff Over 3o Hard Wet Visible free water,from below water table Cobalt Geosciences,LLC P.O.Box 82243 �7 Kenmore,WA98028 Soil Classification Chart Figure Ci (2o6)331-1097 _ www.cobalt eg o.com cobaltgeoPgmail.com Test Pit TP-1 Date: July 2025 Depth: 5' Groundwater: None Contractor: Cobalt Elevation: Logged By: KK Checked By: PH 0) o Moisture Content(%) N Q 5 Plastic I I Liquid U E 3 Limit Limit L � L N Material Description o c G ? o DCP Equivalent N-Value G 0 10 20 30 40 50 ------ -- TosoilVegetation -------------------------------- 1 SM Loose to medium dense,silty-fine to medium grained sand with gravel dark yellowish brown to grayish brown,dry to moist. 2 (Weathered Glacial Till) 3 Locally mottled 4 Dense to very dense,silty-fine to medium grained sand with gravel SM grayish brown, moist. (Glacial Till) End of Test Pit 5' 6 7 8 9 10 Cobalt Geosciences,LLC Proposed Development P.O.Box 82243 Quail Ridge 1 6th Place NE Exploration en ore,WA 98028 COBALT Q o� 9 )331-1097 • S C I E N C E S Arlington, Washington Logs www.cobaltgeo.com cobaltgeoogmail.com Test Pit TP-2 Date: July 2025 Depth: 5' Groundwater: None Contractor: Cobalt Elevation: Logged By: KK Checked By: PH 0) o Moisture Content(%) N Q 5 Plastic I I Liquid U E 3 Limit Limit L � L N Material Description o c G ? o DCP Equivalent N-Value G 0 10 20 30 40 50 ------ -- To�soilVegetation -------------------------------- 1 SM Loose to medium dense,silty-fine to medium grained sand with gravel dark yellowish brown to grayish brown,dry to moist. 2 (Weathered Glacial Till) TV 3 Locally mottled ———— ———— SM --------------------------------------------- Dense to very dense,silty fine to medium grained sand with gravel grayish brown, moist. (Glacial Till) End of Test Pit 5' 6 7 8 9 10 Cobalt Geosciences,LLC Proposed Development P.O.Box 82243 • _ Quail e ace il Rid 1 6th Place NE Exploration en ore,WA 98028 Q o� 9 )331-1097 • Arlington, Washington LOgS www.cobaltgeo.com cobaltgeoogmail.com Test Pit TP-3 Date: July 2025 Depth: 8' Groundwater: None Contractor: Cobalt Elevation: Logged By: KK Checked By: PH 0) o Moisture Content(%) N Q 5 Plastic I I Liquid U E 3 Limit Limit L � L N Material Description o c G ? o DCP Equivalent N-Value G 0 10 20 30 40 50 ------ -------------------------------- 1 SM Loose to medium dense,silty-fine to medium grained sand with gravel dark yellowish brown to grayish brown,dry to moist. 2 (Fill) 3 4 5 ------ ---- SM Loose to medium silty-fine to medium grained sand with gravel b dark yellowish brown to grayish brown,dry to moist. •' (Weathered Glacial Till) --- ---- :: :'--- ------- rydens -------------------------------- SM Dense to very dense,silty fine to medium grained sand with gravel grayish brown,moist. (Glacial Till) End of Test Pit 8' 9 10 Cobalt Geosciences,LLC Proposed Development P.O.Box 82243 • _ Quail e ace il Rid 1 6th Place NE Exploration en ore,wa 98028 Q o� 9 )331-1097 • Arlington, Washington LOgS www.cobaltgeo.com cobaltgeoogmail.com