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Home My WebLink AboutEx09_Geotechnical_Report Gary A. Flowers, PLLC Geological & Geotechnical Consulting 5205 23rd Avenue W Everett, WA 98203 Gary A. Flowers, PLLC. 5205 23rd Avenue W Everett, Washington 98203 206-819-4304 1 October 27, 2021 Project No. 21021 Xiao Zhang 440 Maple Ave SW Apt. B201 Renton, WA 98057-2801 Subject: Geotechnical Services Report Shum Short Plat 1157 Queen Ave NE Renton, Washington This report summarizes the results of our geological and infiltration evaluation of the property located at the above noted address in Renton, WA. Infiltration testing was provided in general accordance with the 2017 Renton Storm Water Design Manual. EXISTING CONDITIONS The property is currently undeveloped and is flat lying with a barely discernible downward slope from west to east. Overall relief is on the order of 2 feet. The site is primarily vegetated with tall field grass, an area of blackberry bushes in the southeast corner, a cedar hedge along the south property line and a few deciduous trees. At the time of our study there was no evidence of standing or flowing water on the parcel. Subsurface Exploration In order to confirm subsurface conditions on th e property a series of 3 exploration pits were excavated on October 13, 2021. Logs of the exploration pits are attached with this report. Generally, medium dense to very dense silty sand with gravel was observed on the site. This sediment is interpreted to be Vashon age lodgement till. Lodgement till is a nonhomogeneous mixture of sand and gravel in a silt/clay matrix. This material was deposited in front of the advancing ice sheet on the order of 13,500 years ago and subsequently overrun by the ice which is thought to have been in excess of 3,000 feet thick in this area. The result is a densely consolidated soil with high strength and low permeability characteristics. Ground water seepage was not observed in any of the exploration pits and no caving conditions were observed within the sidewalls of the exploration pits. DocuSign Envelope ID: B58AD446-584F-46BF-8420-90761B7E491E Shum 2 Lot Short Plat Geotechnical Services Report 1157 Queen Avenue NE, Renton, Washington Gary A. Flowers, PLLC. 5205 23rd Avenue W Everett, Washington 98203 206-819-4304 2 Mappings According to the Geologic Map of King County, Washington, by Booth, Troost and Wisher, March 2007, the site is mapped as Vashon age glacial till (Qvt). Our explorations are in agreement with the published geology map of the area. Infiltration of Storm Water We understand that infiltration of storm water on-site was to be considered for the project. Our subsurface explorations were located in order to encompass both potential building sites should the short plat be granted. In order to verify whether or not there was any infiltration potential within the observed sediments an infiltration test was performed on these soils. Testing was completed in general accordance with City of Renton 2017 Storm Water Design Manual and Reference 6-A for a small scale pilot infiltration test (PIT). Based on our current understanding storm water would be infiltrated into one or more infiltration trenches approximately 3 feet below existing grade. As such, the infiltration testing was completed at a depth which included the planned receptor soils. The pit was excavated to a depth of 3.1 feet and the bottom measured 4.7 feet long and 4.1 feet wide for a total area of 19.27 square feet. Presoaking and testing was completed using a garden hose running into an 4-foot long, 4-inch diameter, perforated, pvc pipe with a cap for a splash plate on the bottom end. The pvc pipe was marked in half-inch increments as required. Water was then added to the pit for the pre-soak period and maintained at a depth of 12 to 14 inches for 6 hours. It should be noted that little to no water flow was required in order to maintain the water depth. In fact, at the lowest water flow setting attainable with the available equipment the water level continued to rise throughout the soak period. Following the pre-soak, the water flow was shut off to allow the water level to adjust to the required 6-inch head. After 2 hours the water level had only reduced by less than 1 inch. Due to the conditions detailed above, the constant head test was not performed. The falling head test was then performed for an hour. During the falling head test the water level reduced by approximately .5 inches in one hour even with a 12-inch head instead of a 6-inch head. Based on the results of our explorations that encountered glacial till sediments at shallow depth, the measured infiltration rate and the required correction factors for testing, geometry and plugging, it is our opinion that the design infiltration rate is nil and no consideration should be given to infiltration of storm water on this property. This is typical for sites that are underlain by glacial till sediments. DocuSign Envelope ID: B58AD446-584F-46BF-8420-90761B7E491E Shum 2 Lot Short Plat Geotechnical Services Report 1157 Queen Avenue NE, Renton, Washington Gary A. Flowers, PLLC. 5205 23rd Avenue W Everett, Washington 98203 206-819-4304 3 SUMMARY Our findings and recommendations provided in this report were prepared in accordance with generally accepted principles of engineering geology and geotechnical engineering as practiced in the Puget Sound area at the time this report was submitted. We make no other warranty, either express or implied. Thank you for the opportunity to be of service. Should you have any questions please do not hesitate to contact our office. Respectfully submitted, Gary A. Flowers, P.G., P.E.G. Principal Engineering Geologist Attachments: Exploration Pit Logs Site & Exploration Plan DocuSign Envelope ID: B58AD446-584F-46BF-8420-90761B7E491E Shum 2 Lot Short Plat Geotechnical Services Report 1157 Queen Avenue NE, Renton, Washington Gary A. Flowers, PLLC. 5205 23rd Avenue W Everett, Washington 98203 206-819-4304 4 EXPLORATION PIT LOGS Shum 2 Lot Short Plat 1157 Queen Avenue NE Renton, WA EP-1 Approximate elevation 432 feet 0.0’ – 1.0’ Loose, moist, grayish-black, silty SAND (topsoil) and grass sod 1.0’ – 2.5’ Medium dense, light brown, silty sand with gravel (glacial till) [SM] 2.5’ – 4.0’ Very dense, light brown, silty sand with gravel (glacial till) [SM] Bottom of pit at 4.0 feet on 10/13/2021. No ground water. No caving. EP-2 Approximate elevation 432 feet 0.0’ – 1.0’ Loose, moist, grayish-black, silty SAND (topsoil) and grass sod 1.0’ – 2.5’ Medium dense, light brown, silty sand with gravel (glacial till) [SM] 2.5’ – 4.0’ Very dense, light brown, silty sand with gravel (glacial till) [SM] Bottom of pit at 4.0 feet on 10/13/2021. No ground water. No caving. EP-3 Approximate elevation 431 feet 0.0’ – 1.0’ Loose, moist, grayish-black, silty SAND (topsoil) and grass sod 1.0’ – 2.5’ Medium dense, light brown, silty sand with gravel (glacial till) [SM] 2.5’ – 4.0’ Very dense, light brown, silty sand with gravel (glacial till) [SM] Bottom of pit at 4.0 feet on 10/13/2021. No ground water. No caving. IP-1 Approximate elevation 430 feet 0.0’ – 1.0’ Loose, moist, grayish-black, silty SAND (topsoil) and grass sod 1.0’ – 2.5’ Medium dense, light brown, silty sand with gravel (glacial till) [SM] 2.5’ – 3.1’ Very dense, light brown, silty sand with gravel (glacial till) [SM] Bottom of pit at 4.0 feet on 10/13/2021. No ground water. No caving. DocuSign Envelope ID: B58AD446-584F-46BF-8420-90761B7E491E 30.02'30.02'NE 12TH STREET N87°59'46"W 2,625.71'(M)(R1)210.16'210.16'N00°15'00"W 240.18'S00°15'59"E 240.18'1,506.81'(C)(R1) 134.07'(C)(R1) W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D) FOUND PUNCH ON 1 1/2" BRASS DISK IN IN CASE DOWN 0.7' 08-30-21 UNION AVE. NEFOUND 1/8" PIN IN CONC MON IN CASE DOWN 1.5' 08-30-21MONROE AVE. NE805.92'(C)(R1) FOUND TACK IN CONC MON IN CASE DOWN 2.1' 08-30-21 MONROE AVE. NE178.91'(R1) 178.92'(M) TREE CANOPY/DRIP LINE FENCE LINE (TYPE AS NOTED)x BUILDING LINE TELEPHONE RISERTJR MONUMENT (FOUND AS NOTED) SIGN DECIDUOUS TREE CONIFEROUS TREE WATER VALVE FIRE HYDRANT HOSE BIB STORM DRAIN MANHOLE STORM CATCH BASIN SEWER MANHOLE POWER POLE/LIGHT POLE GUY ANCHOR GAS METER S D GM WV POWER OVERHEAD LINEOP SANITARY SEWER PIPESS STORM DRAIN PIPESD CONCRETE PAVING ASPHALT PAVING REBAR (FOUND AS NOTED) POST OR BOLLARD GAS VALVEGV F FIR TREE M MAPLE TREE LEGEND LEGEND (C) (M) P/L CLF CALCULATED DIMENSION MEASURED DIMENSION PROPERTY LINE CHAIN LINK FENCE WATER LINE PER RECORD DATAW(D)xxxxxxxxxxxxxxxxxxxxxxxx x x x x x x x x xxxxxxxxxxxxxxxxxxxN00°15'00"W 20.02'N87°59'46"W 20.02'QUEEN AVEWV WV 18"F 20"F 14"F 30"F 26"F 30"F S 32"F 26"F 30"F 60"MA 12"DEC 16"DEC 30"F 10"M WV TJR WMS 8"DEC(2) FOUND 1/2" REBAR AND CAP AT GRADE "MHT 9470" E. 0.1' 09-02-21 FOUND 1/2" REBAR AND CAP IN 5" X 5" CONC "MHT 9470" E. 0.1' 09-02-21 FOUND BARE 1/4" REBAR W. 0.5' 09-02-21 xxOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOP5' TALL CLF x5' TALL CLF VERTICAL CURB5' TALL CLFCONC SLAB TREE CANOPY LINE (TYP) TREE CANOPY LINE (TYP) TREE CANOPY LINE (TYP)5' TALL CLFGATE5' TALL CLFCEDAR HEDGE 430 43243 2 432OPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOP ~PIERCE AVE NEPARCEL A KING COUNTY BOUNDARY LINE ADJUSTMENT REC.NO. 9802099012 SSMH TOP 432.03 IE 427.63 (8" PVC (OUT-N) BOTTOM STRUCTURE ELEV. 427.66 NO CHANNEL SSMH TOP 434.25 8" PVC (W), 8" CONC (N), 8" CONC (S) CENTER CHANNEL ELEV. 425.43 CATCH BASIN TOP 433.33 6" CONC IE 432.30 (IN-W) 8" CMP IE 431.28 (OUT-S)SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS~SD SD SD SDSDSDSDTBM 1 TOP REBAR/CAP EL = 434.36'430.5429.8432.7430.1430.6432.1432.5432.46432.17432.9 2433.15433.82434.04433.84433.41433.39433.51432.44430. 0431.3433.4434.7432.6431.6429.7430.3431.7430.3430.3432.6432.0N87°59'50"W 134.14'(C) 134.13'(R1) N87°59'46"W 114.15'S00°15'59"E 131.11'S00°15'00"E 111.09'430 4324344344344304 3 0 432430430 5' TALL CLF0.5' 0.6' FENCE CROSSES P/L FENCE 0.1' S. OF P/LFENCE 0.2' S. OF P/L 1.8' CONC DRIVECONC WALKTBM 2 TOP REBAR/CAP EL = 430.64' 4.8' 30.00' 30.00'W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D)W(D) CATCH BASIN TOP 433.61 6" CONC IE 432.30 (OUT-E)SSSS~30.00' 30.00' 3.3' 10.7' 9.8'REVISIONOFSHEET NO.DRAWING FILE:PROJECT NUMBER:NUMBER: SCALE: DATE:DESIGN:DRAWN:CHECKED: REVISIONS:APPD.SV-TP-OWDV01880001.dwgSave Date: Plot Date: 9/21/2021 2:46 PM 9/24/2021 10:35 AM By: Arj P:\O\OWDV01880001\0400CAD\SV\BASES\SV-TP-OWDV01880001.dwg Aaron JenningsBy: File: POR. NW 1/4, NE 1/4, SEC. 9, TWP. 23 N., RGE. 5 E., W.M. TOPOGRAPHIC SURVEY FOR SHUM PROPERTY HOI-FUNG SHUM 17723 110TH PLACE SE, RENTON, WA 98055SEPTEMBER 24, 2021ARJ1"=10'OWDV0188-0000111® 20300 Woodinville Snohomish Rd. NE, Ste A Woodinville Washington 98072 Phone: 425.415.2000 NORTH 1. INSTRUMENTATION FOR THIS SURVEY WAS A TRIMBLE TOTAL STATION. PROCEDURES USED IN THIS SURVEY WERE FIELD TRAVERSE, MEETING OR EXCEEDING STANDARDS SET BY WAC 332-130-090. 2. PRIMARY CONTROL POINTS AND ACCESSIBLE MONUMENT POSITIONS WERE FIELD MEASURED UTILIZING GLOBAL POSITIONING SYSTEM (GPS) SURVEY TECHNIQUES USING TRIMBLE EQUIPMENT. MONUMENT POSITIONS THAT WERE NOT DIRECTLY OBSERVED USING GPS SURVEY TECHNIQUES WERE TIED INTO THE CONTROL POINTS UTILIZING TRIMBLE ELECTRONIC TOTAL STATIONS FOR THE MEASUREMENT OF BOTH ANGLES AND DISTANCES. THIS SURVEY MEETS OR EXCEEDS THE STANDARDS SET BY WAC 332-130-090. 3. THE INFORMATION DEPICTED ON THIS MAP REPRESENTS THE RESULTS OF A SURVEY MADE ON SEPTEMBER 3, 2021 AND CAN ONLY BE CONSIDERED AS INDICATING THE GENERAL CONDITION EXISTING AT THAT TIME. 4. NO EASEMENTS, RESTRICTIONS OR RESERVATION OF RECORD WHICH WOULD BE DISCLOSED BY TITLE REPORT ARE SHOWN. 5. CONTOUR INTERVAL: 2 FOOT PARCEL A OF KING COUNTY BOUNDARY LINE ADJUSTMENT, RECORDED UNDER RECORDING NO. 9802099012, RECORDS OF KING COUNTY, WASHINGTON. NAVD 88 BASED ON GPS OBSERVATIONS. SITE BENCH MARKS: TBM 1: TOP OF REBAR AND CAP, SET IN ASPH DRIVE, 46'± SW OF SW CORNER OF SUBJECT PROPERTY ON SITE AS SHOWN ELEVATION = 434.36' TBM 2: TOP OF REBAR AND CAP, SET IN MIDDLE OF SUBJECT PROPERTY AS SHOWN ELEVATION = 430.64' EROF GI E OY DU Call: TOLL FREE 1-800-424-5555CLLABCALL BEFORE YOU DIG 1. KING COUNTY BOUNDARY LINE ADJUSTMENT, RECORDED UNDER RECORDING NO. 9802099012, RECORDS OF KING COUNTY, WASHINGTON. 09-24-21 GARY A. FLOWERS, PLLC PROJECT NO. 21021 SHUM PARCEL - 1157 QUEEN AVE NE IP-1 EP-3 EP-2EP-1 DocuSign Envelope ID: B58AD446-584F-46BF-8420-90761B7E491E