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Home My WebLink AboutMiscRenton 14 Plat 6201 NE 4th Street Renton, Washington 98059 K.C parcel #1423205-9070 & 9064 Preliminary Drainage Report January 25, 2016 Prepared for: Kendall Homes, Inc. Attn: Kevin Murray 612 South Lucile Street Seattle, Washington 98108 (260) 395-7173 office kevinm@kendallhomesnw.com Prepared by: Offe Engineers, PLLC Darrell Offe, P.E. 13932 SE 159th Place Renton, Washington 98058-7832 (425) 260-3412 office darrell.offe@comcast.net Table of Contents • Section 1: Technical Information Worksheet • Section 2: Project Overview • Section 3: Drainage Review Requirements (CORE requirement review) • Section 4: Special Reports and Studies • Section 5: Other Permits • Section 6: Declaration of Covenant(s) Section 1: Technical Information Worksheet City of Renton TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner: Kendall Homes, Inc. Address: 612 South Lucile Street Seattle, WA 98108 Phone: Project Engineer: Darrell Offe, P.E. Company: Offe Engineers, PLLC Address/Phone: 13932 SE 159th Place Renton, WA 98058 (425) 260-3412 Part 3 TYPE OF PERMIT APPLICATION Subdivision X Subdivision LJ Grading D Commercial D Other Part 2 PROJECT LOCATION AND DESCRIPTION Project Name: Renton 14 Plat Location Township: 23 North Range: 5 East Section: 14 Part 4 OTHER REVIEWS AND PERMITS 0 DFWHPA D Shoreline Management D COE 404 Rockery D DOE Dam Safety Structural Vaults D FEMA Floodplain D Other LJ COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community Renton East Highlands Drainage Basin Maplewood Creek/ Cedar River / Lake Washington Part6 SITE CHARACTERISTICS D River D Floodplain D Seeps/Springs [J Stream D High Groundwater Table n Critical Stream Reach [J Groundwater Recharge D Depressions/Swales D Other [l Lake ,, Steep Slopes L...i I Part 7 SOI LS Soil Type Slopes Qvt 5-100/o D Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE D Ch. 4 -Downstream Analysis D D D D D D Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION LJ Sedimentation Facilities C Stabilized Construction Entrance n Perimeter Runoff Control ~ [l Clearing and Grading Restrictions D Cover Practices D Construction Sequence D Other Erosion Potential Erosive Velocities minor LIMITATION/SITE CONSTRAINT MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION D Stabilize Exposed Surface D Remove and Restore Temporary ESC Facilities D Clean and Remove All Silt and Debris ,-. L.J Ensure Operation of Permanent Facilities D Flag Limits of SAO and open space preservation areas ,c L...! Other I Part 10 SURFACE WATER SYSTEM J Grass Lined Detention/WQ Infiltration Method of Analysis Channel Vault [ Depression 2009 City of Renton - I Pipe System L: KCRTS C Open Channel D Energy Dissipater D Waiver Compensation/Mitigati ,, Wetland on of Eliminated Site r, Dry Pond c_J D Regional L_: Storage C Stream Detention Brief Description of System Operation: Catch basin within curb line of proposed public streets to collect runoff and convey into a stormwater vault located on the southwest corner of project. Vault will discharge to the south within an existing drainage course. Facility Related Site Limitations Reference Facility Limitation I Part 11 STRUCTURAL ANALYSIS Part12 EASEMENTS/TRACTS I Cast in Place Vault D Retaining Wall Rockery > 4' High D Structural on Steep Slope D Other Drainage Easement LJ Access Easement Tract D Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. Section 2: Project Overview This proposed project is to create 15 single family lots from two existing King County tax parcels (#142305- 9070 & 9064) located in the easterly portion of the Renton Highlands. The property addresses are: 6201 and 6207 NE 4th Street. The project consists of two parcels having 210,594 square feet (4.83 acres). The property has three existing residences located on it: two of which will be removed and the third (6201 NE 4th Street) will be retained after development. The current property has multi uses: the northerly area of the westerly parcel is used to grow Christmas trees, the southerly and mid portion of the project is fenced for agricultural use, the three residences having lawn and landscaping for single family use. A new access road will be provided along the westerly side with the extension of NE 3'' Court onto the property. Access to the developed project will be from this access point. An emergency access point will be provided to NE 4th Street. This project will be reviewed for drainage under the 2009 King County Surface Water Drainage Manual and the City of Renton Amendments. The project will install a storm water vault in the southwest corner to provide storm water detention and water quality. The storm water facility will discharge at the natural discharge point (SW corner of property). The property is served by King County Water District #90 for water service. The property is flat with very gentle grade from the northeast corner to the southwest corner, at the natural discharge point. The soils were found to be Alderwood Series (Glacial Till) soils. There is a high ground water table on the property due to the hard compact soils just below the grass. These soils allow for minimal infiltration of runoff. The proposed developed stormwater mitigation will be to provide a storm water facility to treat developed runoff flows and water quality treatment. Renton 14 Plat =, i -:,, '" L .., -. _J ~ --SE_,,_/'~ • I .c ' .t ~ z:: I,-·· _.-i ..,. ' ~ . ,W-· --,:,.. z -i;\1 v· .. IC. >, (:.. -':1: ;-· ~----~ Ir" • --· · , ~· l •, --"'~ _J u-! I ~--· --LI ' ~ c:. -~ --~ I ~.l! I --; . i i ··---' ·.; -1 :>-.. (...I! ..... z.. J;. __ ----4,o, --i, , l,;.<,\s . I ,-c, :--· - I'-·-'- &.i· i,,1 • 9i ic.r c ' . -...-} -, i..... ·---..:.__ n:-• <1• "="'~-. ~ - " ,, ~. d1 . _NB >llll Pl ' "'"'~-!~ i . i (,~, .. I , I 1 I 1---· t.1£. ,uJ.---;t " u I ·1· _,l ... L (j 1 , ' . L:· ii ,_ ~ .. +··-':--'~-..L.----1 •,.... ' I t · · j i I ... ,. 1_J 'L ___ .i : l t- '1 ., ·~ -·- ·-· ;a I i",, ·1 ~-~-~ --] -. 1 I. ' I r-· _.w, I jZ Di -··01 ....... --~ --··· ' +-· I ' ___ _, _ .. 1 ;j . l. ,I i _J f 0\,((,-~ I l. _ _____. __ _L ·-., 1',,t/ I, .~"', ,'.~" ' __ ]. ~.-!!tJ .' ... f .~\. ·:-Eu .. :.:'~ I ., r::..J i I '. - ' ~~ -:-1 .cfj -~ 'V. _.fJ..-r: n ........ ~;/. r-· J -----, i . . , . ........, i .1 ;../,., --"~~ '\i ~ JI -~ -~- '-· '.:;[ "'T ----: The rifonnallon mclldedon lhs map l1as been wmpied by King County stafffrcm a variety of sotrces and 1s su~ect 10 charge wthout notice. Kiny Cm1rrt y makes rKJ iepr esentations or w<1rrarllies. express or 1m~ied. as to accuracy. completeness. tirle iness or rights to 1he use of s1ich 1nforn"0tion. Thsdoc.urt'V'lnt r:; not 1rt€nded for use asa strvey pro:tuct King C:01Jrty shall not be iabie ior any general. special. 11d1rect. 1nc•de ntal. orconsequent,ai darn ages 1nclud1ng. but no! lrn1ted to lost revenues or \:isl profits resulting from the use t~ misuse of the intom1aton conlamed oo this map Any sale of this map or111format1onontl1ismap 1s prohi:J1tP.d except hy written permss1011 of Kmg Gounty Date: 2/2/2016 Notes: -- ;,! --....--,--.-- ~ ' I ., -t ' -I "' tl:' ,,. •l '. ,, •)"i _ _... __ _ ~'.~ " .- ',L 1-'-~1~ ,;rr.. r· ' ! i I . .L I 1 L .~.........+-'1 I --:--': I NJ J}t.111 ; _ . ' Ii - N A .... , .I 1, ., : I ,I '.J ' ,I Kim-1 County tQ King County GISCENTER Section 3: Drainage Review Requirements Project Characteristics: Total Site Area = 210,594 square feet Offsite Improvements: Installation of a 12" storm pipe extension along NE 4th Street Total Improvement: Value of development cost in excess of $100,000 Developed Impervious = 91,848 square feet (new plus replaced) Drainage Review: Based upon Table 1.1.2.A., the project drainage review meets "Full Drainage Review". Sections Attached: Core Requirement #1 -Discharge Natural Location Core Requirement #2 -Offsite Analysis Core Requirement #3 -Flow Control Core Requirement #4 -Conveyance System Core Requirement #5 -Erosion & Sediment Control Core Requirement #6 -Maintenance & Operations Core Requirement #7 -Financial Guarantees & Liability Core Requirement #8 -Water Quality Special Requirement #1 -other Adopted Requirements Special Requirement #2 -Flood Hazard Area Delineation Special Requirement #3 -Flood Protection Facilities Special Requirement #4 -Source Control Special Requirement #5 -Oil Control Core Requirement #1 -Discharge at Natural Location The subject property naturally sheet fiows from the easterly property line to the southwest corner. The natural discharge point is the southwest corner of the property. The property to the east (abutting) sheet flows onto the subject property. A drainage swale and conveyance system will be installed along the easterly property line to bypass this offsite flow from entering the project. The bypass line will discharge at the southwest corner, at the natural discharge point. The discharge for the proposed project will be from a storm water facility (vault) located in the southwest corner with a 12" pipe conveying flows from the vault to the natural discharge point. The facility will be located within a Tract of property owned by the homeowners association with the maintenance of the facility will provided by the City of Renton. -·;··, -~-.. , .,_, ,j}~_§f}l ;17;!'~. '=-··· ' Core Requirement #2 -Offsite Analysis The subject property discharges in the southwest corner at the natural discharge point. The flow continues to the southwest into a heavily vegetated area of un-developed property. Along the flow path offsite, the flow becomes concentrated and forms a channel within the open space area in the northeast corner of Quincy Avenue NE and NE 2"d Street, photos A. There is an inlet structure on the north side of NE2nd Street that conveys the flow across the street and into an open space area to the south. The inlet structure is clean and exposed and does not appear to have a capacity issue. The flow then continues in a southwest direction within the open space crossing NE 1" Place at Orcas Avenue NE, photos B. The inlet on the north side of NE 1" Place is covered in leaves and small tree branches. The inlet is conveying flows at the time of observation. The flow continues to the southwest in behind a developed property of single family homes. Access to the channel in this area was difficult to follow the channel. The flow (channel) is exposed on the north side of a King County park property (un-developed) on the south side of the single family development. The flow continues to the south across the King County parcel within a well-defined channel. The channel enters an inlet structure to the north of 148"' Place SE, photos C. The inlet is clean and maintained -no debris or obstacles blocking inlet. At this point, the flow enters a closed storm system flowing south through an older development. The system was not followed beyond this point downstream. Point C is located over 3,800 feet downstream of the property. The downstream system from the subject property to point C (north of 148'h Place SE) appears to have adequate capacity to convey the developed runoff from the project. DOWNSTREAM MAPS Pg. 53 12652 I I : -. , I I \'1 !154161 'i 15418. I ---1k .. ,... J:, ' '" 0 • I mop -Lt 11211 i ... ! ;] a, 0 ' • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • N I • • • • • / 3\~j JO.GJ i '-..,;.-_ 131885 . 3(10 i I '. ;j ; _;--~--I \ 5702 .~703 . 131690 131891 "1'":c''"''.'::"-f-C-<J ~1318!12 B § -1 :,.d, -~ ___ Ji ' Pg. 53 101 \ I t'i2D7 ' 'i:n ,. 1 :;: .::;K .:. c _5. 1 ~ NE-4th· / 15409 ! \ I :\ : :I/ i,smi 1 ;'. 1 I _J 1\ i 1541~ Sz.p :621a :s,:2~ 0230 ~;C4 116 · 115356 ! 11'3358, ~ 116354 112 1 '11€357 116359 t -;;;/;:f-~1"". "'"' 'lS CX) 1'- Cl 0.. · mzk\ !...__~I "1363,0 m1~ 1392D J 13930 : 139~8 J 1394.6 14000 _I 14008 14016 _J 14024 I 1402Jr' , f ' ,1,14708 SE 138th Pl ' ,~1125! ' i . 14825 '~>' · ~ 13900,., 14010 14B06 14B02-• 14129 J ' !4130 14121,-' 141J' SE 142nd St '4705, 14216 •2JD 14)02 1022~; H)~1 .J, ,i' · 11 ' ; ' i : ' 14925. 1_".~J: .1_:~1_,1, 150~5 :,, ,50_,_3 :i 15-105.JI 15\n 11 1512-,, . i I ·I ,··1 .J ---..J: · ... I ' I • I 11 · L_ r L ..... 1_· 1 _ . ' ~-_,..: ____ _ 141JQ4 i '-,. .,.I 1 ~ 14103 I -·: i----114/0;·,,_,..:, 14Qj4 I i--,' ! ____ {f 140241 I 141d2 14k! 1~!.F I Hj32 -f .. ._, __ ' LU ~ 14125 I i:i: -~ ~ ; 0 ~ 14131 :./ 1 14104 . .-;,,· ·'\ '\ ] 14_1.1~ ,-c?;,0,- 14!~0 15115 -~ 15124i 1511? _.....-... ,··/: 15 i21 --~-- 15125 i -~ --_,_.,---- -~.--, ''-9",1 '.4S07,: 149;5., 1'1923' ----. _, -:.::.~ ...... .,,-··-, ;;~ ... ---.__· --~;-.._ __ '$W3 :c.•J2G ,~9:2€, SE 143rd Pl 1~0()3 15011 1 15D30 m m 15406 .. ·---~ ,i • .. -. 12S1~1 "i ! I 1~~-~.I t ' l·\12D 14na I ' J ' J.5213, 1381 ~ ·-~:::::.~· '"'----100 l, 1361 \, --,.P,-· •------ RI "<_37~-! '.\I' I-- } I ----l I ·.L- 152JO j '--, i 14035 , 14/05:_; !5Y.i9 115~15" -' • I :---i·h. .,./ ;-.__~~; . 15252' , 1tz~a 152J1 .. '--><> . ..:,. . _ _,.--' 1S403 PHOTOS PHOTO A -Quincy Avenue NE and NE 2nd Street PHOTO B -Orcas Avenue NE and NE 1st Place PHOTO C -at the north end of 148th Place SE Core Requirement #3 -Flow Control The property is located within the City of Renton Flow Control Duration Standards (Forested Conditions) basin. Based upon the City of Renton Drainage Manual, the following steps are required to determine the mitigation of storm water runoff of the developed project: Full Dispersion -N/G (no good) -The property does not have adequate flow path lengths to allow for full dispersion; Full Infiltration -N/G -The soils have been classified by the Geotechnical Engineer as "fine loamy sands" with a low permeability rate; Alderwood Series soils w/ high ground water present. These soils are not adequate for full infiltration per the Drainage Manual. The Geotechnical Engineer does not recommend infiltration or retention of onsite runoff due to the high ground water table and poor draining soils. Limited Infiltration -N/G-With the presents of a high ground water table, the use of infiltration BMP's is not recommended by the geotechnical Engineer or allowed by the City manual. Limited Dispersion -N/G -The soils, the high ground water table and the lack of available flow path do not allow for these types of BMP's. Perforated Pipe Connection -This BMP will be used on the lots as each house connects to the onsite stormwater facility. The project will be sized for a stonm water facility (vault) to provide runoff control. The facility sizing calculations can be found attached to this section. From the proposed site conditions, the KCRTS model was used to compute the existing and developed runoffs from the project. A storm water volume was calculated as 44,736 cubic feet of detention storage required. The proposed vault (within the active (detention) portion) is 511.00' overflow -503.00' outlet (8.00' active storage). The detention portion of the vault would be 120' x 48' (wide) x 8.00' deep OR 46,080 cubic feet. The proposed vault is adequately sized for flow control for the proposed development. PROPOSED BMP'S C.2.11 PERrORATED PIPE CONNECTION CJ TEXT OF INSTRUCTIONS Your property contains a stormwater management ffow control BMP (best management practice} called a "pertorated pipe connection," which was installed to reduce the stormwater runoff impacts of some or all of the impervious surface on your propeity. A perforated pipe connection is a length of drainage conveyance pipe with holes in the bottom, designed to "leak" runoff. conveyed by the pipe, into a gravel filled trench where it can be soaked into the surrounding soi!. The connection is intended to provide oppo1tunity for infiltration of any runoff that is being conveyed from an impervious surface (usually a roof) to a local drainage system such as a ditch or roadway pipe system. The size and composition of the peliorated pipe connection as depicted by the flow conu·ol BMP site plan and design details must be maintained and may not be changed without written approval either from the King County Water and Land Resources Division or through a future development permit from King County. The soil overtop of the perforated portion of the system must not be compacted or covered with lmpervious materials. FrGl'RE C.2.11.A PERFORATED PIPE CONNECTION FOR A SDiGLE FA.MILY RESIDENCE 7 . . I filter fabric L crandomfill 6" 8 . bcc-::'c -:-_ -:-.=o=)(;::·=-_:::_:::, ::t_!-1-6" perf pipe 1 L" mm _! -:,· >;;;: -=' ~ -1 1/:::i". -3/.(" washed rock 'J-"]' -"J_ J, - u. ~ J r ~ w -~ -~ - '-1 -., r u -, .. ,.l .. o----24" min--J TRENCH X-SECTION NTS PLAN VIEW OF ROOF NTS 2009 Su1face Water Desjgn Manual -App~ndix C C-Sl slope__. ,.- / 'J to road drainage system 2' X 10' level trench w/perf pipe 1/9/?JJ(J9 DETENTION CALCULATIONS Renton 14 Plat January 21, 2016 A(T) 210,594 sq. feet Developed Condition Impervious Pervious Proposed R/W 39724 sq. feet (sg. feet) (sg. feet) asphalt (PGIS) 19263 sidewalk 8955 landscaping 11506 Tracts A -vault 11764 sq. feet landscape 0 11764 B -access 3131 sq. feet aspahlt (PGIS) 2700 landscaping 431 C -utility 566 sq. feet structure 566 landscaping 0 Lot.s 155409 sq. feet House, patio, walks <3,400 per lot> 51000 Driveway (PGIS) <600 per lot> 9000 Landscaping 95409 119110 91484 Acres 2.10 2.73 (PGIS) 0.71 30963 sq. feet Predeveloped Conditions Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Welland Impervious Area 4.83 acres 0.00 acres 0.00 acres 0.00 acres 0.00 acres 0.00 acres 0.00 acres 0.00 acres Total Scale Factor : 0.80 Hourly 4.83 acres Reduced Time Series: Predev.tsf Compute Time Series Modify User Input ? )) File for computed Time Series [.TSF] Flow Frequency Analysis Time Series File:predev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak (CFS) 0.356 2 2/09/01 18:00 0.058 7 1/05/02 16:00 0. 226 4 2/28/03 16:00 0.041 8 3/03/04 3:00 0.207 5 1/05/05 10:00 0 .167 6 1/18/06 21:00 0. 289 3 11/24/06 5:00 0.421 1 1/09/08 7:00 Computed Peaks -----Flow Frequency Analysis------- --Peaks Rank Return Prob (CFS) Period 0.421 1 100.00 0.990 0.356 2 25.00 0. 960 0.289 3 10.00 0.900 0.226 4 5.00 0.800 0.207 5 3.00 0.667 0.167 6 2.00 0.500 0.058 7 1. 30 0.231 0.041 8 1.10 0.091 0.399 50.00 0.980 Developed Conditions _3,·::: -_:::; : .•.• -.., ... -::··-, Area Till Forest 0.00 acres Till Pasture 0.00 acres Till Grass 2.73 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 2.10 acres Total Scale Factor : 0.80 Hourly 4.83 acres Reduced Time Series: Dev.ts! Compute Time Series Modify User Input _, I ? I I I » File for computed Time Series (.TSF] Flow Frequency Analysis Time Series File:dev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- Flow Rate Rank Time of Peak (CFS) 0. 87 6 4 2/09/01 2:00 0.474 B 12/03/01 17:00 0.764 7 9/10/03 15:00 0.944 3 8/26/04 1:00 0.769 6 10/28/04 18: 00 0.795 5 10/22/05 17:00 1. 06 2 11/21/06 9: 00 l. 65 1 1/09/08 7:00 Computed Peaks -----Flow Frequency Analysis------- --Peaks Rank Return Prob (CFS) Period l. 65 1 100.00 0.990 1. 06 2 25.00 0. 960 0.944 3 10.00 0.900 0.876 4 5.00 0.800 0. 7 95 5 3.00 0. 667 0. 769 6 2.00 0.500 0. 764 7 1. 30 0.231 0. 4 74 8 1.10 0.091 1.45 50.00 0.980 Detention Facility Design Retention/Detention Faci.2_ity Type of Facility: Detention Pond Side Slope: 3.00 H:lV Pond Bottom ~ength: 51. 00 ft Pond Bottom Width: 48.00 ft Pond Bottom Area: 2448. sq. Top Area at 1 ft. FB: 10710. sq. ft 0.246 acres Effective Storage Depth: 8.00 ft 100.00 ft 44736. cu. ft Stage O Elevatior.: , JOWINI~ Storage Volume~=~~;;.:;..:..::;..:...,,.,,,,.....::.:c.:...,,.:c..::~~~~~~--=-~~~-'~·\\::,-~~ Riser Head: Riser Diameter: NUTil.ber of orifices: Orifice# l 2 Height (ft) 0.00 5.30 1.027 ac-ft 8.00 12.00 2 Diameter tin) 1.13 1. 75 ft inches Full Head Discharge (CFS) D. 097 0.136 Top Notch Weir: Rectangular Length: 1.00 in Weir Height: 7.35 ft O~tflow Rating Curve: None Pipe Diameter (in) 4. 0 Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 100.00 C. 0.000 0.000 0.00 0.01 100.01 25. 0.001 0.004 0.00 0.02 100.02 4 9. 0.001 0.005 0.00 0.04 100. 04 98. 0.002 0.006 0.00 0.05 100.05 123. 0.003 0.007 0.00 0.06 100.06 148. 0.003 0.008 0.00 0.07 100.07 173. 0.004 0. 009 0.00 0.08 100.08 198. 0.005 0.010 0.00 0.09 100.09 223. 0.005 0. Oll 0.00 0.25 100.25 631. 0.014 0. 017 0.00 0.41 100.41 1054. 0.024 0.022 0.00 0.56 100.56 1466. 0.034 0.026 0.00 0.72 100.72 1921. 0.044 0.029 0.00 0.86 100.88 2392. 0.055 0.032 0.00 1. 03 101.03 2850. 0.065 0.035 0.00 1.19 101.19 3354. 0. 077 0.037 0.00 1. 35 101.35 3876. 0.089 0.040 0.00 1. 51 1.01. SJ 441S. 0. 101 I), 042 o. on 1. 66 101. 66 4937. 0.113 0.044 0.00 l.82 101.82 5512. 0. 2.27 0.046 0.00 1. 98 101.98 6105. 0 .140 .J. 048 0.00 2.13 102.13 6678. 0.153 0.050 ;J. 00 'OQ :..,(...j 102.29 7308. C. 168 0.DS2 o.oc ;::: • 45 102.45 7957. 0.183 0. '.)54 0.00 2.60 102.60 3S83. 0 .197 0.055 0.00 2.76 102. 76 927 l. J.213 0.057 0.00 0 0' :::.. _,,:. 102.92 9979. 0. 229 0.059 0.00 3.07 103. 07 10662. 0.245 0.060 0.00 Q~..J\ tz-e.\;;, Surf Area (sq. ft) 2448. 2454. ::2460. 2472. 2478. 2484. 2490. 2496. 2502. 2599. 2698. 2792. 2894. 2999. 3098. 3206. 3316. .3427. 3533. 3648. 376S. 3877. 3997. 4119. 1±236. 4362. 4489. 461' . 3.23 103.23 11410. 0.262 0. 062 0.00 4742. 3.39 103.39 1217 9. 0.280 0.063 0.00 4875. 3. 54 103.54 12920. 0.297 0.065 0.00 5002. 3.70 103.70 13731. 0.315 0.066 0.00 5139. 3. 86 103.86 14565. 0.334 0.067 0.00 5277. 4. 02 104.02 15420. 0.354 0.069 0.00 5418. 4.17 104 .17 16243. 0.373 0.070 0.00 5551. 4.33 104.33 17142. 0. 394 0. 071 0.00 5695. 4.49 104.49 18065. 0.415 0.073 0.00 5841. 4. 64 104. 64 18952. 0.435 0.074 0.00 5979. 4.80 104.80 19920. 0.457 0.075 0.00 6129. 4. 96 104. 96 20913. 0.480 0.076 0.00 6280. 5.11 105 .11 21866. 0.502 0.078 0.00 6423. 5.27 105.27 22906. 0.526 0.079 0.00 6578. 5.30 105.30 23104. 0.530 0.079 0.00 6607. 5.32 105.32 23236. 0.533 0.080 0.00 6627. 5.34 105.34 23369. 0.536 0.082 0.00 664 7. 5.35 105.35 23435. 0.538 0.085 0.00 6656. 5.37 105.37 23569. 0.541 0.090 0.00 6676. 5.39 105.39 23702. 0.544 0.095 0.00 6696. 5. 41 105.41 23836. 0.547 0.102 0.00 6715. 5.43 105.43 23971. 0.550 0.110 0.00 6735. 5. 45 105.45 24106. 0.553 0.112 0.00 6755. 5.46 105.46 24173. 0.555 0.114 0.00 6764. 5. 62 105. 62 25268. 0.580 0.128 0.00 6923. 5. 78 105.78 26389. 0.606 0.140 D.00 7084. 5.93 105.93 27463. 0.630 0.150 0.00 7236. 6.09 106.09 28634. 0.657 0.159 0.00 7401. 6.25 106.25 29831. 0.685 0.167 0.00 7567. 6.41 106.41 31055. 0. 713 0.174 0.00 7735. 6.56 106.56 32227. 0.740 0.181 0.00 7894. 6.72 106.72 33504. 0. 7 69 0 .188 0.00 8065. 6. 88 106.88 34808. 0. 799 0.194 0.00 8239. 7.03 107.03 36057. 0.828 0.200 0.00 8403. 7.19 107.19 37415. 0.859 0.206 0.00 8580. 7.35 107.35 38802. 0.891 0.212 0.00 8759. 7.43 107.43 39507. 0.907 0.220 0.00 884 9. 7.51 107.51 40218. 0. 923 0. 229 0.00 8939. 7.59 107.59 40937. 0.940 0.240 0.00 9030. 7. 68 107. 68 417 54. 0.959 0.254 0.00 9133. 7.76 107.76 42489. 0.975 0.268 0.00 9225. 7.84 107.84 43230. 0.992 0.285 0.00 9318. 7.92 107. 92 4397 9. 1. 010 0.302 0.00 9411. 8.00 108.00 44736. 1. 027 0.320 0.00 9504. 8.10 108.10 45692. 1. 049 0.631 0.00 9621. 8.20 108.20 46660. 1. 071 1. 200 0.00 9739. 8.30 108.30 4 7 640. 1. 094 1. 930 0.00 9858. 8. 40 108.40 48632. 1.116 2.720 0.00 9978. 8.50 108.50 49636. 1.139 3.010 0.00 10098. 8. 60 108.60 50652. 1.163 3.270 0.00 10219. 8.70 108.70 51680. 1.186 3.510 0.00 10341. 8.80 108.80 52720. l.210 3.730 0.00 10463. 8. 90 108.90 53772. 1. 234 3.930 0.00 10586. 9.00 109.00 54837. 1. 259 4.130 0.00 10710. 9.10 109.10 55914. 1. 284 4.320 0.00 10835. 9.20 109.20 57004. 1. 309 4.500 0.00 10960. 9.30 109.30 58106. l. 334 4.670 0.00 11086. 9.40 109.40 59221. 1. 360 4.830 0.00 11213. 9.50 109.50 60349. 1. 385 4.990 0.00 11340. 9. 60 109.60 61489. 1. 412 5.150 0.00 114 68. 9. 70 109.70 62642. 1. 438 5.300 0.00 11597. 9.80 109.80 63809. 1. 465 5.440 0.00 11727. 9.90 109.90 64988. 1. 492 5.590 0.00 11857. Hyd l 2 3 4 5 6 7 8 Inflow l. 65 0.83 l. 06 0.51 0.57 0. 79 0.94 Outflow Target Cale 0.42 :..52 ******* 0.38 ******* 0.33 ******* 0.17 ******* 0.17 ******* 0.09 ******* 0.07 Elev Peak Stage 8.24 8.02 8.00 6.23 6.31 5.35 3.88 108.24 108. 02 108.00 106.23 106.31 105.35 103.88 0.42 ******* 0.06 3.15 103.15 Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:RDout Storage (C·o-Ftl (Ac-Ft) 47093. 1.081 44913. 1.031 44770. 1.028 29659. 30303. 23451. 14685. 11034. 0.681 0. 696 0.538 0.337 0.253 Inflow/Outflow Analysis Peak Inflow Discharge: Peak Outflow Discharge: Peak Reservoir Stage: 1.65 CFS at 7:00 on Jan 9 in Year 8 1.52 CFS at 8:00 on Jan 9 in Year 8 8.24 Ft Peak Reservoir Elev: 108.24 Ft Peak Reservoir Storage: 47093. Cu-Ft 1.081 Ac-Ft Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence Probability CFS % % % 0.005 32820 53.523 53.523 46.477 0.016 0.027 0.037 0.048 0.058 0.069 0.080 0.090 0.101 0.111 0.122 0.133 0.143 0.154 0 .164 0.175 0.186 0.196 0.207 0 .217 0.228 0.238 0.249 0. 260 0.270 0.281 0. 291 0.302 o. 313 0.323 0.334 0.344 0.355 6719 5325 5812 4047 2440 1428 1158 51 27 15 55 75 37 49 55 34 11 15 18 17 9 9 6 3 5 3 3 3 4 3 2 0 0 10.957 10.414 9.478 6.600 3.979 2.329 1. 888 0.083 0.044 0.024 0.090 0.122 0.060 0.080 0.090 0.055 0.018 0.024 0.029 0.028 0.015 0.015 0.010 0.005 0.008 0.005 0.005 0.005 0.007 0.005 0.003 0.000 0.000 64. 480 74.894 84.372 90.972 94.951 97.280 99.168 99.251 99. 296 99.320 99.410 99.532 99.592 99.672 9 9. 7 62 99.817 99.835 99.860 99.889 99.917 99.932 99.946 99.956 99. 961 99. 969 99.974 99. 97 9 99.984 99.990 99.995 99.998 99.998 99.998 35.520 25.106 15.628 9.028 5. 049 2. 720 0.832 0. 749 0.705 0.680 0.590 0.468 0.408 0.328 0.238 0.183 0.165 0.140 0 .111 0.083 0.068 0.054 0.044 0.039 0.031 0.026 0.021 0.016 0.010 0.005 0.002 0.002 0.002 0.465E+00 0.355E+00 0.251E+OO 0.156E+OO 0.903E-01 0.505E-01 0.272E-01 0.832E-02 0.749E-02 0.705E-02 0.680E-02 0.590E-02 0.468E-02 0.408E-02 0.328E-02 0.238E-02 0.183E-02 0.165E-02 0.140E-02 O. lllE-02 0.832E-03 0.685E-03 0.538E-03 0.440E-03 0.391E-03 0.310E-03 0.261E-03 0.212E-03 0.163E-03 0.978E-04 0.489E-04 0.163E-04 0.163E-04 0 .163E-04 0.366 0 0.000 99.998 0.002 0.163E-Ot; 0.376 0 0.000 99.998 0.002 0.163E-04 =iuration Comparison ~~aylsis Base File: predev.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time--------------Check of Tolerance------- Cutoff Base New %Change Probability 0.083 O.lOE-01 0.79E-02 -23.4 I O.lOE-01 0.104 0.70E-02 0.69E-02 -0.2 I 0.70E-02 0.125 0.47E-02 0.56E-02 17.9 I 0. 4 7E-02 0.146 0. 31E-02 0.38E-02 24.2 I 0.31E-02 0.167 0. 21E-02 0. 21E-02 3.2 I 0.21E-02 0.188 0.15E-02 0.16E-02 4.3 0.15E-02 0.209 O.lOE-02 O.lOE-02 0.0 O.lOE-02 0.230 0.78E-03 0.65E-03 -16.7 0.78E-03 0.251 0.57E-03 0.44E-03 -22.9 0.57E-03 0. 272 0.33E-03 0.31E-03 -5.0 0.33E-03 0.293 0.20E-03 0.21E-03 8.3 0.20E-03 0. 313 0.15E-03 0.98E-04 -33.3 0.15E-03 0.334 ! 0.98E-04 0.16E-04 -83.3 0.98E-04 0.355 0.16E-04 0.16E-04 0.0 0.16E-04 Maximum positive excursion= 0.013 cfs ( 9.5%) occurring at 0.133 cfs on the Base Data:predev.tsf and at 0.145 cfs on the New Data:rdout.tsf Maximum negative excursion= 0.014 cfs (-15.4%) occurring at 0.094 cfs on the Base Data:predev.tsf and at 0.079 cfs on the New Data:rdout.tsf Route Time Series through Facility Inflow Time Series File:dev.tsf outflow Time series File:RDout Inflow/Outflow Analysis Peak Inflow Discharge: 1. 65 Peak Outflow Discharge: 1. 52 Peak Reservoir Stage: 8.24 Peak Reservoir Elev: 108.24 Peak Reservoir Storage: 47093. 1. 081 CFS at 7:00 CFS at 8:00 Ft Ft Cu-Ft Ac-Ft Flow Duration from Time Series File:rdout.tsf Base 0.083 0.104 0.125 0.146 0 .167 0.188 0.209 0.230 0.251 0.272 0.293 0.313 0.334 0.355 on Jan 9 on Jan 9 Cutoff Count Frequency CDF Exceedence Probability CFS % % % 0.005 32820 53.523 53.523 4 6. 4 77 0.465E+OO 0.016 6719 10.957 64.480 35.520 0.355E+00 0. 027 6386 10. 414 74.894 25.106 0.251E+OO 0.037 5812 9.478 84.372 15.628 0.156E+OO 0.048 4047 6.600 90.972 9.028 0.903E-01 0.058 2440 3.979 94. 951 5.049 0.505E-01 0.069 1428 2.329 97.280 2. 720 0.272E-01 0.080 1158 1.888 99. c68 0.832 0.832E-02 0.090 51 0.083 99.251 0.749 0.749E-02 0.101 27 0.044 99.296 0.705 0. 705E-02 0 .111 15 0.024 99.320 0.680 0.680E-02 0 .122 55 0.090 99.410 0.590 0.590E-02 0.133 75 0.122 99.532 0.468 0.468E-02 0.143 37 0.060 99.592 0.408 0.408E-02 New %Change 0. 079 -5.4 0.104 -0.3 0.132 5.8 0.156 6.6 0.169 1. 0 0 .191 1. 7 0.209 0.3 0.221 -4.0 0.235 -6.2 0.268 -1. 3 0. 296 1. 3 0.306 -2.5 0.315 -5.9 0.377 6.1 in Year 8 in Year 8 0.154 49 O.GBO 99.672 C.328 0.328~-02 0.164 55 0.090 99, ·7 62 0. 238 0.238E-02 0.175 34 J.055 99.817 0.183 0.183E-02 0. 2-86 11 0.018 99.835 0. 165 C. l ESE-O;:: 0 .196 15 0.024 99.860 0.140 0.14CE-02 0.207 13 0.029 99.889 ,J.111 O.lllE-02 0. 217 17 0. 028 99.917 0.083 0.832E-03 0.228 9 0.015 99.932 0.068 0.685E-03 0.238 9 0.015 99. 94 6 0.054 0.538E-03 0.249 6 0.010 99.956 0.044 0.440E-03 0.260 3 0.005 99.961 0.039 0.391E-03 0 .270 5 0.008 99. 969 0.031 0.31DE-03 0.281 3 0.005 99.974 0.026 0.261E-03 0.291 3 0.005 99. 97 9 0. 021 0.212E-03 0.302 3 0.005 99.984 0.016 0.163E-03 0.313 4 0.007 99.990 0.010 0.978E-04 0.323 3 0.005 99.995 0.005 0.4891'-04 C.334 2 0.003 99.998 0.002 0.163E-04 0.344 0 0.000 99.998 0. 002 0.163E-04 0.355 0 0.000 99.998 0. 002 0.163E-04 0.366 0 0.000 99.998 0.002 0.163E-04 0.376 0 0.000 99.998 0.002 0.163E-04 Core Requirement #4 -Conveyance System The proposed on-site conveyance improvements will include a catch basins and storm pipe being conveyed to the proposed storm water vault. The proposed new houses and the existing house will connect into the vault via a 6" PVC tight line. The outfall storm pipe that discharges the storm water facility will be sized at the time of the civil engineering utility plans with calculations. Based upon the outlet fiows form the detention volume sizing, a 12" outfall at 0.50% slope will provide adequate capacity for this project. Core Requirement #5 -Erosion and Sediment Control A Temporary Erosion and Sediment Control Plan implementing the Best Management Practices will be included within the final engineering plan submittal. The project does exceed the State Department of Ecology requirements of clearing/grading over 1.0 acres in size; therefore a SWPPP plan and NPDES permit will be provided as part of the final engineering plan submittal. Core Requirement #6 -Maintenance and Operations The on-site storm system will be maintained by the City of Renton. Tract A, storm water treatment tract, will be owned by the HOA. The private storm stubs to the individual lots and the proposed perforated pipe connection (BMP) will be owned and maintained by the individual property owners. The maintenance and operations for the private system will be included within the Declaration of Covenants for the individual BMP's provided on the project and the final civil construction plans. Core Requirement #7-Financial Guarantees and Liability The Financial Guarantees and Liabilities will be required prior to the project being finalized by the City of Renton. Bond Quantity worksheets will be provided at time of final engineering plan submittal. Core Requirement #8 -Water Quality The proposed project will include the installation of a wet sump (dead storage) within the proposed storm water vault for water quality treatment. Check project for Water Quality Exemption: Section 1.2.8.1 Surface Area Exemptions: Project creates greaterthan 5,000 square feet of new PGIS (30,963 sq. feet proposed PGIS) -new roads, emergency access paving, and new proposed driveways. Therefore water quality treatment is required. Water Quality Sizing -calculations for the water quality volume are attached to this section. The calculated volume required is 13,117 cubic feet of dead storage. Cell #1 of the storm water vault will contain the water quality portion of required volume. Proposed Cell #1 volume: 24' wide x 120' long x 4.6' -volume provided = 13,248 cubic feet. WATER QUALITY CALCULATIONS Wetpool Sizing Calculations Per 2009 King County Stormwater Management Manual Project Name: Renton 14 Plat Project Number: Facility Description: Water Quality Sizing ((01/21/2016)) Step 1: Identify required wetpool volume factor (f). f= 3 Per KCSWDM 6.4.1.1 ---- Step 2: Determine rainfall (R) for the mean annual storm. R= 0.039 Per KCSWDM Fig. 6.4.1.A Step 3: Calculate runoff from the mean annual storm (V,) for the developed site. V, = (0.9A; + 0.25A,9 + 0.1 QA,,+ 0.01A,,) x (R) where: A = Impervious Surface Area= 91,484 s.f. A,9 = Till Grass Area = 119,110 s.f. A,, = Till Forest Area = a s.f. A,, = Outwash Area = a s.f. V, = 4,372 c.f. Step 4: Calculate required wetpool volume (Vb)- Vb = f x V, vb= 13,117 c.f. Special Core Requirements Special Requirement# 1 -Other Adopted Requirements There are no other adopted site specific plans for this property Special Requirement #2-Flood Hazard Area Delineation The proposed project is NOT located adjacent or near a 100-year flood plain Special Requirement #3 -Flood Protection Facilities The project does not rely on a flood control facility as part of the discharge to Lake Washington Special Requirement #4 -Source Control This project is a single-family residence. It is NOT a commercial project subject to possible pollutants. Project is exempt from source control. Special Requirement #5-Oil Control The project is NOT a high-use site or the re-development of a high-use site. Project is exempt from oil control. Section 4: Special Reports and Studies Geotechnical Report prepared by Terra Associates, Inc. dated November 23, 2015 GEOTECHNICAL REPORT • GEOTECHNICAL REPORT Kendall Homes Plat 6207 NE 4th Street Renton, Washington Project No. T-7290 Terra Associates, Inc. Prepared for: Kendall Homes/Jacob Alexander Homes Seattle, Washington November 23, 2015 TERRA ASSOCIATES, Inc. Mr. Kevin Mun-ay Kendall Homes/Jacob Alexander Homes 612 S. Lucile Street Seattle, Washington 98108 Subject: Geotechnical Report Kendall Homes Plat 6207 NE 4th Street Renton, Washington Dear Mr. Mun-ay: November 23, 20!5 Pr0ject No. T-7290 As requested, we haYe conducted a gectechnical engineering study for the subj.,ct project The attached rep011 presents our findings and recommendations for the geotechnical aspects of project design and construction. Our field exploration indicates the site is generally underlain by six to ten inches of organics overlying two and one-half to three feet of medium dense to dense silty sand with gravel (weathered till) over very dense silty sand with gravel (unweathered glacial till) to the termination of the test pits. We did not observe any groundwater during our exploration. In our opinion, soil conditions observed at the site will be suitable for support of the proposed development provided the recommendations present in this report are incorporated into project design and construction. We trust the infonnation presented in this report is sufficient for your cun-entneeds. If you have any questions or require additional information. please call. Sincerely )'ours, TERRA.ASSOCIATES, INC. .-' <. ·-· ,;/ .. · ., )_'.,,,,..-------.,---"\:' -; / / / Jx ,/ l -, ;:-;.. -' :'(..// / . ./. ' . Carnlyn S:i)ecker. P.E. Project Engineer 12}~1! 11 Hh ,\veriut> NF. 5tF, l 3\J, Kirki,rnd \\J~h1ngtor, qHu_;:....;. Phone (425) 821-7777 • Fa, ,42s, ~.21-4B4 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Figures TABLE OF CONTENTS Page No. Project Description .......... . ... I Scope ofWork .................................... . ...... I Site Conditions .......................... . .2 3.1 Surface ..................... . . ........... 2 3.2 Subsurface .... . . ............................................... 2 3 .3 Groundwater. ..................... .. Geological Hazards ...... .. 4.1 Seismic Considerations ...... 4.2 4.3 4.4 4.5 Erosion Hazard Areas ......... . Lands! ide Hazard Areas .. . Steep Slope Hazard Areas ................... . Coal Mine Hazard Areas ..... . Discussion and Recommendations ........ . 5. I General .................................. . 5.2 Site Preparation and Grading ...... . 5.3 Excavation ................................... . . .... 2 3 . .. 3 . .. 3 .. 4 .. 4 5 ... 5 . .................................................... 5 . ...... 6 .. ................ 7 5.4 Foundation Support .......................................................... . 7 . ... 8 8 5.5 Floor Slab-on-Grade ............................................ . 5.6 Stormwater Detention Pond ................................. . 5.7 Lateral Earth Pressure for Below-Grade Walls ...... . 8 5.8 Drainage ............................. . .......... 9 5.9 Utilities ....................... . .. ···················· 9 5. IO Pavement.. .......... .. .......... 10 Additional Services ........ . .. ........ IO Limitations .................... . . ....................................... 10 Vicinity Map ......................................................... . .. ..... Figure I Exploration Location Plan ........................ . .. ................................................ Figure 2 Typical Wall Drainage Detail... .... . . .............................. Figure 3 Appendix Field Exploration and Laboratory Testing .................................................... . .. ........ Appendix A 1.0 PROJECT DESCRIPTION Geotechnical Report Kendall Homes Plat 6207 NE 4th Street Renton, Washington The project consists of redeveloping the approximately 4.8-acre site with 15 residential building lots, access roadways, a stormwater detention pond, and utilities. Based on the layout prepared by Offe Engineers, dated August 12, 20 J 5, the stormwater detention pond will be located in the southwest comer of the site. Grading plans were not available at the time of this report. Based on the existing topography, we expect the grading to establish lot and roadway elevations will include cuts and fills of one to five feet throughout the site. We expect that the residential structures constructed on the lots will be two-to three-story, wood-framed buildings with their main floor levels framed over a crawl space. Attached garage floors will be constructed at grade. Structural loading should be relatively light; with bearing walls caring loads of 2 to 3 kips per foot and isolated columns caring maximum loads of 30 to 40 kips. The recommendations in the following sections of this report are based on our understanding of the preceding design features. We should review final design drawings as they become available to verify that our recommendations have been properly interpreted and to supplement them, if required. 2.0 SCOPE OF WORK Our work was completed in accordance with our authorized proposal dated August 18, 2015. On November 12, 2015, we observed soil conditions at 7 test pits excavated between 7 and 9 feet below existing site grades. Using the information obtained from the subsurface exploration and laboratory testing, we performed analyses to develop geotechnical recommendations for project design and construction. Specifically, this report addresses the following: • Soil and groundwater conditions • Seismic design parameters per 2012 International Building Code (IBC) • Geologic Hazards per current City of Renton Municipal Code • Site preparation and grading • Excavation • Foundations • Floor slabs at grade • Infiltration feasibility • Stormwater detention pond • Lateral earth pressure for below-grade building walls • Drainage • Utilities • Pavement November 23, 20 l 5 Project No. T-7290 It should be noted that recommendations outlined in this report regarding drainage are associated with soil strength, design earth pressures, erosion, and stability. Design and performance issues with respect to moisture as it relates to the structure environment are beyond Terra Associates' purview. A building envelope specialist or contractor should be consulted to address these issues, as needed. 3.0 3.1 SITE CONDITIONS Surface The project site consists of 2 tax parcels totaling approximately 4.8 acres located at 6207 NE 4th Street and 620 I NE 4th Street in Renton, Washington. The approximate site location is shown on Figure l. The site is currently occupied by two single-family homes, a mobile home, a couple of outbuildings, and associated access and landscaping. There are a few mature trees scattered around the property and along the property line. The remainder of the site is cuvered with grass and weeds. Site wpography consists of a slight slope that descends from the northeast to the southwest with an overall relief of approximately ten feet. 3.2 Subsurface In general, the soil conditions we observed in the test pits consisted of six to ten inches of organics overlying three and one-half to five and one-half feet of medium dense to dense silty sand with gravel (weathered till) over very dense silty sand with gravel (unweathered glacial till) to the termination of the test pits. The Geologic Map of the Renton Quadrangle, King County, Washington by D.R. Mullineaux (1965), maps the site as Ground Moraine Deposits (Qgt). Soil conditions observed in the test pits are generally consistent with the mapped geology. The preceding discussion is intended to be a general review of the soil conditions encountered. For more detailed descriptions, please refer to the Test Pit Logs in Appendix A. 3.3 Groundwater We did not observe any groundwater during our site exploration. However, we would expect that shallow perched groundwater develops at the site berween the weathered and unweathered till stratums during the wet winter months. Typically, surface water that infiltrates through the upper weathered soil zone becomes perched on the underlying, denser till. The denser till has a relatively low permeability that impedes the downward migration of the infiltrated surface water. As a result, groundwater will accumulate, and when combined with a positive gradient, will tend to flow laterally along the till contact. Locally, such seepage is referred to as interflow. Page No. 2 November 23, 2015 Project No. T-7290 Fluctuations in groundwater seepage levels will occur and should be expected on a seasonal and annual basis. Typically, groundwater seepage reaches maximum levels during and shortly following the wet winter months. GEOLOGICAL HAZARDS 4.1 Seismic Considerations Section 4.3.050.G.5.d of the City of Renton Municipal Code (RMC) defines a seismic hazard as: '"i. Low Seismic Hazard (SL): Areas underlain by dense soils or bedrock. These soils generally have site classifications of A through D, as defined in the International Building Code, 2012. ii. High Seismic Hazard (SH): Areas underlain by soft or loose, saturated soils. These soils generally have site classifications E or F. as defined in the International Building Code, 2012." Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations. Liquefaction mainly affects geologically recent deposits of fine-grained sand that is below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction; thus, eliminating the soil's strength. Based on the soil conditions we observed the site soils would be classified as type "C" by the International Building Code, therefore the site is a low seismic hazard area as defined by the City of Renton. In our opinion, the risk for liquefaction to occur at this site during an earthquake is negligible. Based on soil conditions observed in the test pits and our knowledge of the area geology, per Chapter 16 of the 2012 International Building Code (!BC), site class "C" should be used in structural design. Based on this site class, in accordance with the 2012 !BC, the following parameters should be used in computing seismic forces: Seismic Design Parameters (/BC 20/2) I Spe<:(i:,,l_.i:esponse acceleration (Short Period_!,_ SM'--_ i 1.377 -•· Spectral response acceleration (I -Second Period), SM 1 0.671 Five percent damped .2 second period,. S0 , -------------·--·------__ 0.918_ Five nercent damned 1.0 second oeriod, Sm 0.448 Values determined using the United States Geological Survey (USGS) Ground Motion Parameter Calculator accessed on November 21, 2015 at the web site http://earthquake.usgs.gov/designmaps/us/application.php. 4.2 Erosion Hazard Areas Section 4.3.050.G.5.c of the RMC defines an erosion hazard as: "i. Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service) as having slight or moderate erosion potential, and a slope less than J 5 percent. Page No. 3 November 23, 2015 Project No. T-7290 ii. High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource Conservation Service (fom1erly C.S. Soil Conservation Service) as having severe or very severe erosion potential, and a slope more than 15 percent." The soils observed on-site are classified as Alderwood gravelly sandy loam 8 to 15 percent slopes by the United States Department of Agriculture Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service. Over most of the site with the existing slope gradients, these soils will have a slight to moderate potential for erosion when exposed. Therefore, in our opinion, the site is a low erosion hazard as defined by the RMC. Erosion protection measures as required by the City of Renton will need to be in place prior to starting grading activities on the site. This would include perimeter silt fencing to contain erosion on-site and cover measures to prevent or reduce soil erosion during and following construction. 4.3 Landslide Hazard Areas Section 4.3.050.G.5.b of the RMC defines a landslide hazard area as: "i. Low Landslide Hazard (LL): Areas with slopes less than 15 percent. ii. Medium Landslide Hazard (LM): Areas with slopes between 15 percent and 40 percent and underlain by soils that consist largely of sand, gravel, or glacial till. iii. High Landslide Hazards (LH): Areas with slopes greater than 40 percent, and areas with slopes between 15 percent and 40 percent and underlain by soils consisting largely of silt and clay. iv. Very High Landslide Hazards (LV): Areas of known mapped or identified landslide deposits." The site slopes are less than 15 percent, therefore, the site would be classified as a Low Landslide Hazard by the RMC. 4.4 Sll'CP Slope Hazard Areas Section 4.3.050.g.5.a of the RMC defines a steep slope hazard area as: "i. Sensitive Slopes: A hillside, or portion thereof, characterized by: (a) an average slope of 25 percent to less than 40 percent as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of 40 percent or greater with a vertical rise of less than 15 feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; (c) abuning an average slope of25 percent to 40 percent as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. This definition excludes engineered retaining walls. ii. Protected Slopes: A hillside, or portion thereof, characterized by an average slope of 40 percent or greater grade and having a minimum vertical rise of 15 feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City." None of the above conditions are present at the site, therefore, it is our opinion that the site does not contain a steep slope hazard as defined by the RMC. Page No. 4 4.5 Coal Mine Hazard Areas Section 4.3.050.g.5.e of the RMC defines a coal mine hazard area as: November 23, 2015 Project No. T-7290 "i. Low Coal Mine Hazards (CL): Areas with no known mine workings and no predicted subsidence. While no mines are known in these areas, undocumented mining is known to have occurred. ii. Medium Coal Mine Hazards (CM): Areas where mine workings are deeper than 200 feet for steeply dipping seams, or deeper than 15 times the thickness of the seam or workings for gently dipping seams. These areas may be affected by subsidence. iii. High Coal Mine Hazard (CH): Areas with abandoned and improperly sealed mme openings and areas underlain by mine workings shallower than 200 feet in depth for steeply dipping seams, or shallower than 15 times the thickness of the seam or workings for gently dipping seams. These areas may be affected by collapse or other subsidence." We have reviewed the coal mme maps for the area and used the King County !map sensitive area map to determine if any coal mine workings are within the site. Based on our review, the site is not mapped on the coal mine maps and the King County !map sensitive area map shows the nearest coal mine hazard to be over 13,000 feet southwest of the project site. We did not observe any evidence of underground tunnels or shafts during our site exploration. Based on this review, in our opinion, the site would be classified as a Low Coal Mine Hazard Area as defined by the RMC. 5.0 5.1 DISCUSSION AND RECOMMENDATIONS General Based on our study, there are no geotechnical considerations that would preclude development of the site, as currently planned. The residential buildings can be supported on conventional spread footings bearing on competent inorganic native soils or on structural fill placed and compacted above the native soils. Pavement and floor slabs can be similarly supported. The native soils encountered at the site contain a sufficient amount of soil fines that will make them difficult to compact as structural fill when too wet. The ability to use native soil from site excavations as structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction. If grading activities will take place during winter, the owner should be prepared to import clean granular material for use as structural fill and backfill. The following sections provide detailed recommendations regarding the preceding issues and other geotechnical design considerations. These recommendations should be incorporated into the final design drawings and construction specifications. Page No. 5 5.2 Site Prqiarntion and Grading November 23, 2015 Project No. T-7290 To prepare the site for construction, all vegetation, organic surface soils, and other deleterious material should be stripped and removed from below the building lots and roadway areas. Surface stripping depths of approximately six to ten inches should be expected to remove the organic surface soils. In the developed portions of the site, demolition of existing structures should include removal of existing foundations and abandonment of underground septic systems and other buried utilities. Abandoned utility pipes that fall outside of new building areas can be left in place provided they are sealed to prevent intrusion of groundwater seepage and soil. Organic topsoil will not be suitable for use as structural fill, but may be used for limited depths in nonstructural areas. Once clearing and stripping operations are complete, cut and fill operations can be initiated to establish desired grades. Prior to placing fill, all exposed bearing surfaces should be observed by a representative of Terra Associates to verify soil conditions are as expected and suitable for support of new fill. Our representative may request a proofroll using heavy rubber-tired equipment to determine if any isolated soft and yielding areas are present. If excessively yielding areas are observed, and they cannot be stabilized in place by compaction, the affected soils should be excavated and removed to firm bearing and grade restored with new structural fill. Beneath embankment fills or roadway subgrade if the depth of excavation to remove unstable soils is excessive, the use of geotextile fabrics, such as Mirafi 500X, or an equivalent fabric, can be used in conjunction with clean granular structural fill. Our experience has shown that, in general, a minimum of 18 inches of a clean, granular structural fill placed and compacted over the geotextile fabric should establish a stable bearing surface. The native soils encountered at the site contain a sufficient amount of soil fines that will make them difficult to compact as structural fill when too wet or too dry. The ability to use native soils from site excavations as structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction. If wet soils are encountered, the contractor will need to dry the soils by aeration during dry weather conditions. Alternatively, the use of an additive such as Portland cement or lime to stabilize the soil moisture can be considered. If the soil is amended, additional Best Management Practices (BMPs) addressing the potential for elevated pH levels will need to be included in the Storm Water Pollution Prevention Program (SWPPP) prepared with the Temporary Erosion and Sedimentation Control (TESC) plan. If grading activities are planned during the wet winter months, or if they are initiated during the summer and extend into fall and winter, the owner should be prepared to import wet weather structural fill. For this purpose, we recommend importing a granular soil that meets the following grading requirements: ._.!'.!rcent Passing . __ _ 100 _____ u.s~ ~~~~:Size .. -.~. . .... ,.[[" .. No. 4 . i ---·-------------- 75 maximum r-----No. 200 , 5 maximum* * Based on the 3/4-inch fraction. Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural fill. Page No. 6 5.5 Floor Slab-on-Grade November 23, 20 l 5 Project No. T-7290 Slab-on-grade floors may be supported on subgrade prepared as recommended in Section 5.2 of this report. Immediately below the floor slab, we recommend placing a four-inch thick capillary break layer composed of clean, coarse sand or fine gravel that has less than three percent passing the No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor transmission. Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or fine gravel to protect it from damage during construction, and to aid in uniform curing of the concrete slab. It should be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will not be effective in assisting uniform curing of the slab and can actually serve as a water supply for moisture bleeding through the slab, potentially affecting floor coverings. Therefore, in our opinion, covering the membrane with a layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the layer cannot be effectively drained. We recommend floor designers and contractors refer to the 2003 American Concrete Institute (ACI) Manual of Concrete Practice, Part 2, 302. l R-96, for further information regarding vapor barrier installation below slab-on-grade floors. 5.6 Stormwater Detention Pond The preliminary plans show a stormwater detention pond in the southwest comer of the site. Design details were not available at the time of this report. As we understand, the pond will be built by a combination of below-grade excavation and cast-in-place retaining walls around the north, west, and south sides of the pond. Interior pond slopes below the maximum stored water level should be graded to a minimum slope gradient of 3: l. The portion of the slope above the maximum water surface along with exterior slopes can be graded to a minimum inclination of 2: I. Soils used for construction of containment berms should consist of on-site silty sand with gravel till that is compacted structurally as recommended in Section 5.2 of this report. Cobbles in excess of six inches in diameter should be removed from the soil when used for construction of the pond containment berm. 5.7 Lateral Earth Pressure on Below Grade Walls The magnitude of earth pressures developing on below-grade walls will depend on the quality and compaction of the wall backfill. We recommend placing and compacting wall backfill as structural fill, as described in Section 5.2 of this report. To prevent overstressing the walls during backfilling, heavy construction machinery should not be operated within five feet of the wall. Wall backfill in this zone should be compacted with hand-operated equipment. To prevent hydrostatic pressure development, wall drainage must also be installed. A typical wall drainage detail is shown on Figure 3. Page No. 8 November 23, 2015 Project No. T-7290 With wall backfill placed and compacted as recommended, and drainage properly installed, we recommend designing unrestrained walls for an active earth pressure equivalent to a fluid weighing 35 pounds per cubic foot (pcf). For restrained walls, an additional unifonn load of 100 psfshould be added to the 35 pcf. To account for typical traffic surcharge loading, the walls can be designed for an additional imaginary height of two feet (two- foot soil surcharge). For evaluation of wall perfo,mance under seismic loading, a unifonn pressure equivalent to 8H psf, where H is the height of the below-grade portion of the wall should be applied in addition to the static lateral earth pressure. These values assume a horizontal backfill condition and that no other surcharge loading, sloping embankments, or adjacent buildings will act on the wall. If such conditions exist, then the imposed loading must be included in the wall design. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.4 of this report. 5.8 Drainage Surface Final exterior grades should promote free and positive drainage away from the site at all times. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building areas. We recommend providing a positive drainage gradient away from the building perimeters. lf this gradient cannot be provided, surface water should be collected adjacent to the structures and disposed to appropriate storm facilities. Subsurface We recommend installing perimeter foundation drains adjacent to shallow foundations. The drains can be laid to grade at an invert elevation equivalent to the bottom of footing grade. The drains can consist of four-inch diameter perforated PVC pipe that is enveloped in washed pea gravel-sized drainage aggregate. The aggregate should extend six inches above and to the sides of the pipe. Roof and foundation drains should be tightlined separately to the stonn drains. All drains should be provided with cleanouts at easily accessible locations. Infiltration The glacial till soils composed of silty sand with gravel characteristically exhibits low permeability and would not be a suitable receptor soil for discharge of development stormwater using infiltration/retention facilities. Even low impact development methods such as rain gardens and penneable pavements would mound and overtop during rain events. We recommend using conventional stonnwater management methods for this site. 5.9 Utilities Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) or the City of Renton specifications. As a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 5.2 of this report. As noted, depending on the soil moisture when excavated most inorganic native soils on the site should be suitable for use as backfill material during dry weather conditions. However, if utility construction takes place during the wet winter months, it will likely be necessary to import suitable wet weather fill for utility trench backfilling. Page No. 9 5.10 Pavement November 23, 2015 Project No. T-7290 Pavement subgrade should be prepared as described in the Section 5.2 of this report. Regardless of the degree of relative compaction achieved, the subgrade must be fom and relatively unyielding before paving. The subgrade should be proofrolled with heavy rubber-tire construction equipment such as a loaded JO-yard dump truck to verify this condition. The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic conditions to which it will be subjected. For residential access, with traffic consisting mainly of light passenger vehicles with only occasional heavy traffic, and with a stable subgrade prepared as recommended, we recommend the following pavement sections: • Two inches of hot mix asphalt (HMA) over four inches of crushed rock base (CRB) • Four inches full depth HMA The paving materials used should confonn to the Washington State Department of Transportation (WSDOT) specifications for \!,-inch class HMA and CRB. Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be subject to premature failure as a result of surface water infiltrating into the suhgrade soils and reducing their supporting capability. For optimum pavement performance, we recommend surface drainage gradients of at least two percent Some degree of longitudinal and transverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracks when they occur. 6.0 ADDITIONAL SERVICES Terra Associates, Inc. should review the final design drawings and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and implemented in project design. We should also provide geotechnical service during construction to observe compliance with our design concepts, specifications, and recommendations. This will allow for design changes if subsurface conditions differ from those anticipated prior to the start of construction. 7.0 LIMITATIONS We prepared this report in accordance with generally accepted geotechnical engineering practices. No other warranty, expressed or implied, is made. This report is the copyrighted property of Terra Associates, Inc. and is intended for specific application to the Kendall Homes Plat project. This report is for the exclusive use of Kendall Homes/Jacob Alexander Homes and its authorized representatives. The analyses and recommendations present in this report are based on data obtained from the test pits done on- site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations appear evident, Terra Associates, Inc. should be requested to reevaluate the recommendations in this report prior to proceeding with construction. Page No. 10 , SE 1'Hith St , NE 10th St SE 116th St w 1! Q, 0 .c u ·c II .., NE 1th Pl NE 8th St ----1 l L -: ~ \ l :! .\J I 'R I r I I w ct : r~1~~th$t ! ~ w I I > n Z I < 3 111 I o Qi: > I ' ;;; ' < I _.. i I I ~ ,, I ; I II) ' SITE r--~--- SE 132nd.St SE 133rd St NE 1st St t ___ ..,_, si \athPt ~ I""' SE 139th Pl ~ 11{ -0 i:: = 1 ~ http .//www. wsdot. wa. gov/data/tools/geoportal/ j " ' s, 128th S ... r IIJ Vl Ill > 11{ = 0 <I) ~ J• (fl ~ Q. ~ i, ,J>~ -Sf 132ndSt SE-135th.St " UJ t ~ ii ! 'tJ J{ . C: r~ 1000 &@F)IYi)~ ATE SCALE IN FEET ACCESSED 11/13/15 . Te rra VIC INI TY MAP KENDA LL HOMES PLAT RENTON, WASHINGTON A ssociates Inc. Consultants 1n Geotechnica l ~ng 1neering Geology and En vironme ntal E arth Science s Proj . No.T-7290 Date NOV 2015 Figure 1 12" MINIMUM 3/4" MINUS WASHED GRAVEL 1-lt-1 SLOPE TO DRAIN 12" f ,-i--~---=-~=='--~----·---/. ·--·- I111-1 / 1!11 I, / COMPACTED i STRUCTURAL FILL ! : I SEE NOTE 7~ I ,. / .! I l'- 6"(MIN.) -I i-J--~~---~-4-_ r 12" OVER PIPE EXCAVATED SLOPE (SEE REPORT TEXT FOR APPROPRIATE INCLINATIONS) -------~.~ 1 ~) /·--' l. ---------;__/- / I / L 3" BELOW PIPE 4" DIAMETER PERFORATED PVC PIPE .J NOTTO SCALE NOTE: MIRADRAIN G100N PREFABRICATED DRAINAGE PANELS OR SIMILAR PRODUCT CAN BE SUBSTITUTED FOR THE 12-INCH WIDE GRAVEL DRAIN BEHIND WALL DRAINAGE PANELS SHOULD EXTEND A MINIMUM OF SIX INCHES INTO 12-INCH THICK DRAINAGE GRAVEL LAYER OVER PERFORATED DRAIN PIPE. ___ /-_.-.:-i Terra ~ Associates Inc. t· __ t..,~~->,/ Consultants in Geotechnical ~ngineering Geology and TYPICAL WALL DRAINAGE DETAIL KENDALL HOMES PLAT RENTON, WASHINGTON Environmental Earth Sciences Proj. No.T-7290 I Date NOV 2015 I Figure 3 ·- APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING Kendall Homes Plat Renton, Washington On November 12, 2015, we completed our site exploration by observing soil conditions at 7 test pits. The test pits were excavated using a minihoe to a maximum depth of nine feet below existing site grades. Test pit locations were determined in the field by measurements from existing site features. The approximate location of the test pits is shown on the attached Exploration Location Plan, Figure 2. Test Pit Logs are attached as Figures A-2 through A-8. An engineering geologist from our office conducted the field exploration. Our representative classified the soil conditions encountered, maintained a log of each test pit, obtained representative soil samples, and recorded water levels observed during excavation. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure A-1. Representative soil samples obtained from the test pits were placed in closed containers and taken to our laboratory for further examination and testing. The moisture content of each sample was measured and is reported on the individual Test Pit Logs. Grain size analyses were performed on selected samples. The results of the analyses are shown on Figure A-9. Project No. T · 7290 MAJOR DIVISIONS TYPICAL DESCRIPTION I LEDER i 1 SYMBOL i -------------. I ----,-------------------------------- GRAVELS I Gra:~~:~ess I__ GW I Well-graded gravels, grav~-sand mixtu~e~, littleor no ~nes VI ..J i5 VI 0 w z ~ (!) w VI 0:: ~ () ~ .91 I than 5% , I 0 ~~~=r~:~r;~;~n l. ___ !1n_"_s) ___ _i __ --~fJ_ __ 1 Poorly-graded gravels, gravel-san~:1xtures, little or no fines. is larger than No. I . , GM I Silty gravels, gravel-sand-silt mixtures, non-plastic fines 4 sieve 11 Gravels with I-_ _ _______ _ , fines i GC ; Clayey gravels, gravel-sand-clay mixtures, plastic fines. i ---------------------~-------------------- .. ---------- : Mor!~h~~~O% I C?i:~!::f s :: ] ::~;'.;~ae:e~~~~d~~~d~s;:~t::~:~ 1 i.t'.'.~;:r o~ 0 n~n:ns~~-- I of coarse fraction I -· -----r-------------- is smaller than 1 , 1 SM Silty sands, sand-silt mixtures, non-plastic fines. Sandswith 1 1 __________________ _ No. 4 sieve i fines --· -· ---------~-----f-----+------------------------------··-- SC Clayey sands, sand-clay mixtures, plastic fines. r-ML I inorganic silts, rock flour, clayey silts with slight plasticity 1ii a, VI E N ...J !!!. ·w 1 _____ I __________ -.. -,----------------·- ! Inorganic clays of low to medium plasticity. (Lean clay) SIL TS AND CLAYS i5 "' a, Liquid Limit is less than 50% ,.,, ·c > ' 2.~ I 0 "'"' w E o lf-------------------~ ~ ?3 I CL Ol MH ------·-------·---.. Organic silts and organic clays of low plasticity I I ~ ~ 0 I ~ ffi ~ ·1' SIL TS AND CLAYS j Inorganic silts, elastic. -----f-----------------_________ _, z £ ~ Liquid Limit is greater than 50% LL (]) - --. -~ . J_ Inorganic clays of high plasticity. (Fat clay) 1 CH 1------+-----------------______ __, j o~_ J Organic clays of high plasticity -~IGH~;~~~;~I~-;;;~; ! -PT ! Peat. --------------- ·------------· ---------------------~'~----~·----------------, DEFINITION OF TERMS AND SYMBOLS VI I Standard Penetration I 2" OUTSIDE DIAMETER SPILT SPOON SAMPLER VI Density Resistance in Blows/Foot w ..J I z Very Loose 2.4" INSIDE DIAMETER RING SAMPLER OR 0 0-4 SHELBY TUBE SAMPLER iii Loose 4-10 w Medium Dense 10-30 ::c y WATER LEVEL (Date) 0 Dense 30-50 0 Very Dense >50 Tr TORVANE READINGS, tsf ----------- Standard Penetration Pp PENETROMETER READING, tsf Consistanc,y _Resistance in Blows/Foot w I DD DRY DENS In', pounds per cubic foot > iii I Very Soft 0-2 w Soft 2-4 LL LIQUID LIMIT, percent ::c I 0 I Medium Stiff 4-8 () I Stiff 8-16 Pl PLASTIC INDEX I Very Stiff 16-32 I Hard >32 N STANDARD PENETRATION, blows per foot I __ /T-! Terra UNIFIED SOIL CLASSIFICATION SYSTEM ~i·1 Associates Inc. KENDALL HOMES PLAT RENTON, WASHINGTON ~-· ~7 Consultants in Geotechnical ~ngineenng Geology and Proj. No.T-7290 I Date NOV 2015 I Figure A-1 Environmental Earth Sciences ----------···-·-----·----- LOG OF TEST PIT NO. 1 FIGUREA-2 PROJECT NAME: Kendall Homes Plat PROJ. NO: T-7290 LOGGED BY: JCS LOCATION: Renton, Washington SURFACE CONDS: Lawn APPROX. ELEV: 525 Feet DATE LOGGED: November 12, 2015 DEPTH TO GROUNDWATER: NIA DEPTH TO CAVING: NIA t i C. w C 2· 3--: 5 6 7 8- 9- 10 · I DESCRIPTION (10 inches SOD and TOPSOIL) Red-brown silty SAND with grave!, fine to medium grained, moist (SM) Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. (SM) (Weathered till) Gray to gray-brown silty SAND with gravel, fine to medium grained, moist. (SM) (Unweathered Glacial till) r Test pit terminated at approximately 7 feet. ' No groundwater seepage. CONSISTENCY/ - RELATIVE DENSITY i ' ;: Medium Dense Medium Dense to Dense Very Dense 13.8 REMARKS J "' Terra Associates, Inc. ! NOTE. This subsurface information pertains only to this test pit location and should not be interpreted as being indicative of other locations at the site ' __ ... ,--· Consultants in Geotechnical Engineering 1 Geology and ' Environmental Earth Sciences _____ _J --------"---- LOG OF TEST PIT NO. 2 FIGUREA-3 PROJECT NAME: Kendall Homes Plat PROJ. NO: T-7290 LOGGED BY: JCS LOCATION: Renton, Washington SURFACE CONDS: Pasture Grass APPROX ELEV· .illl.5..£.e.el I , __ D_A_T_E_L_O_G_G_E_D_: _N_o_v_e_m_b_e_r _12_,_2_0_1_5 __ o_E_P_T_H_T_o_G_Ro_uN_D_w_AT_E_R_:_N_i_A ____ D_E_P_TH_rn_ CA:N~: N/; ~ 1- 2 I ' I 3-! 4- ,_ 6- 7 0 ; ; DESCRIPTION CONSISTENCY/ i<: ~ REMARKS I i. RELATIVE DENSITY -tu ~ ~ ~ 2 (6 inches SOD and TOPSOIL) Red-brown silty SAND with gravel. fine to medium grained, moist, numerous fine roots. (SM) Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. (SM) (Weathered till) Gray silty SAND with gravel. fine to medium grnined, moist. (SM) (Unweathered Glacial till) Test pit terminated at approximately 9 feet. No groundwater seepage. Medium Dense Medium Dense to Dense Very Dense g ._ 24.1 12.2 NOTE: This subsurface information pertains only to this test pit location and should not be mterpreted as being indicative of other locations at the site Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and Environmental Earth Sciences ---------------------------~ I~--------·--------· I LOG OF TEST PIT NO. 3 FIGURE:l LOGGED BY: JCS T~ I PROJ. NO: T-7290 PROJECT NAME; Kendall Homes Plat LOCATION: Renton. Washington DATE LOGGED: November 12. 2015 SURFACE CONDS: Pasture Grass DEPTH TO GROUNDWATER: NIA APPROX. ELEV: 506 Feet DEPTH TO CAVING: NIA ' ;:-i .... ~i ... w 0 1 - 3-- 4 5 6 7- 6 C ' 10 ci z w _, .. "' :; DESCRIPTION (8 inches SOD and TOPSOIL) Red-brown silty SAND with gravel, fine to medium grained, moist, numerous fine roots. (SM) Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. (SM) {Weathered till) Gray silty SAND with gravel, fine to medium grained, moist. (SM) (Unweathered Glacial till) Test pit terminated at approximately 9 feet. No groundwater seepage. NOTE: This subsurface information pertains only to this test pit location and should not be interpreted as being indicative of other locations at the site L__ ____ _ CONSISTENCY/ RELATIVE DENSITY Medium Dense Medium Dense to Dense Very Dense ;;:: "' t:. z ~ w .. REMARKS ,-. ;: w " 0 0 .. 12.2 ---------- Terra Associates, Inc. Consultants 1n Geotechnical Engineering Geology and Environmental Earth Sciences LOG OF TEST PIT NO. 4 FIGURE A-5 PROJECT NAME: Kendall Homes Plat LOCATION: Renton, Washington DATE LOGGED: November 12. 2015 PROJ, NO: T-7290 LOGGED BY: JCS SURFACE CONDS: Pasture Grass APPROX, ELEV: 516 Feet DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING: N/A ;:, ci z !:. ' w :,: ~ .... l'.L C. " w :ii C i- a.- 6·- 8 9 DESCRIPTION (6 inches SOD and TOPSOIL) Red-brown silty SAND with gravel, fine to medium grained, moist, 1.5-foot diameter boulder. (SM) Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. {SM) (Weathered till) Gray silty SANO with gravel, fine to medium grained, moist (SM) (Unweathered Glacial till) Test pit terminated at approximately 7 feet. No groundwater seepage. CONSISTENCY/ RELATIVE DENSITY Medium Dense Medium Dense to Dense Very Dense >----~---~·------------------------· NOTE: This subsurface information pertains only to this test pit location and should not be interpreted as being indicative of other locattons at the site. -·--------------~--- (c r z ~ w "-REMARKS .... ;: w "' <) 0 C. Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and Environmental Earth Sciences --------------------------------------------~I LOG OF TEST PIT NO. 5 FIGUREA-6 PROJ. NO: T-7290 LOGGED BY: JCS SURFACE CONDS: Pasture Grass PROJECT NAME: Kendall Homes Plat LOCATION: Renton. Washington DATE LOGGED: November 12. 2015 DEPTH TO GROUNDWATER: N/A ~ .. ,, "~· "' -I DEPTH TO CAVING: NIA 2- 4 5 7- B- 9 10 -, d z w i 2 ---------------- DESCRlPTION (6 inches SOD and TOPSOIL) Red-brown silty SAND with gravet, fine to medium grained, moist. (SM) Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. (SM) (Weathered till) Gray silty SANO with gravel, fine to medium grained. moist. (SM) (Unweathered Glacial till) Test pit terminated at approximately 8 feet. No groundwater seepage. NOTE: This subsurface information pertains only to this test pit location and should not be interpreted as being indicative of other locations at the site ----------- CONSISTENCY{ RELATIVE DENSITY Medium Dense Medium Dense to Dense Very Dense ; -"7 ,• '· ~ -~, . 20 1 7.7 ;;:-I ~ I z w £L ~ 0 ~ REMARKS ___ ______j Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and Environmental Earth Sciences ------------------ ------·-------·-·--------- LOG OF TEST PIT NO. 6 FIGURE A-7 PROJECT NAME: Kendall Homes Plat LOCATION: Renton. Washington DATE LOGGED: November 12., 2015 PROJ. NO: T-7290 LOGGED BY: JCS SURFACE CONDS: Grasses APPROX. ELEV: 520 Feet DEPTH TO GROUNDWATER: NIA DEPTH TO CAVING: NIA ;c !!,. i: .. w C 1- 2- 3 4-, r; --' ., 6- 8 8-- 10- ci z w -' .. " :is 2 DESCRIPTION (6 inches SOD and TOPSOIL) Red-brov,m silty SAND with gravel, fine to medium grained, wet. (SM} Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. (SM) (Weathered till) Gray silty SAND with gravel, fine to medium grained, moist. (SM) (Unweathered Glacial till) Test pit terminated at approximately 8 feet. No groundwater seepage. CONSISTENCY! RELATIVE DENSITY Medium Dense Medium Dense to Dense Very Dense e----------------------·---------------------- NOTE: This subsurface information pertains only to this test pit location and should not be interpreted as being indicative of other locations at the site. , ' "'' ',1···'- , ,.- ii: U) !:, z g w .. REMARKS ... ;: w " " 0 .. 27.4 11.2 Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and Environmental Earth Sciences ·--·--1 LOG OF TEST PIT NO. 7 FIGURE A-8 PROJECT NAME: Kendall Homes Plat LOCATION: Renton, Washington DATE LOGGED: November 12, 2015 PROJ. NO: T-7290 LOGGED BY: JCS SURFACE CONDS: Grasses APPROX. ELEV: 518 Feet DEPTH TO GROUNDWATER: NIA DEPTH TO CAVING: N/A 2- 3 4 5 6~ i 7- 8 9- 10-. DESCRIPTION (6 inches SOD and TOPSOIL) Red-brown silty SAND with gravel, fine to medium grained, wet. (SM) Gray-brown silty SAND with gravel, fine to medium grained, moist, mottled. (SM) (Weathered till) Gray silty SAND with gravel, fine to medium grained, moist. (SM) (Unweathered Glacial till) Test pit terminated at approximately 8 feet. No groundwater seepage. NOTE: This subsurface information pertains only to this test pit location and should not be interpreted as being indicative of other locations at ttie site. ------·--------------------- CONSISTENCY/ RELATIVE DENSITY Medium Dense Medium Dense to Dense Very Dense IL ~ :i w 0. ... w " g .. REMARKS Terra Associates, Inc. Consultants in Geotechn ical Engineering Geology and Environmental Earth Sciences Particle Size Distribution Report 90 80 70 0:: 60 w z I ! u:: f-50 z ,---, w I u 0:: w 40 a. I I -i--1-- 30 i I i !11 _: ___ ~ -I : I Li_;_~ , i : i I f1-[-i I 1 _ I! 1 I I '' i I I , ._II·_ i -; ii ! . i i -~I - i -•-;- GRAIN SIZE -mm. % Gravel I o/o Sand %+3" I, , 0 O.O C_of;e . _ ~~"!--(~;:e_M_~-:-i~_m ____ ;-~"-_: __ J_ __ _ "'i o.o 9.1 _7_:4 -r 10.0 --21-:-2--26-2 LIi 0.0 L8 18.6 20.1 19.l 22.9 ::,:1_~LL -!-_P__!:____i:>_as_ _ [)so ____ j Dso. [)30 1 1 _(lJ_ _,_ _ 9j37±_ 1.0661 j ~0.3929 _ . 0.1236 ' I 5.7023 0.6780 0.3689 0.1122 ::'.+----------~-,-----; LIi 7.1013 2.0494 1.0055 o Silty SAND with gravel D Silty SAND with gravel LI Silty SAND with ave! ------- Material Description 0.2175 1 Project No. T-7290 Client: Kendall Homes/Jacob Alexander Homes 'Project: Kendall Homes Plat 1 Renton, Washington Location: Test Pit TP-2 Location: Test Pit TP-2 Location: Test Pit TP-5 Tested By: fQ Depth: -2 feet Depth: -6 feet Depth: -3 feet Terra Associates, Inc. _____ Kirklancl, WA -I ' I I I I % Fines Silt C:lay 23.7 26.1 -------- 17.5 Dto __ Cc_ __ -_ Cu_ -1 ---!---- uses SM SM SM AASHTO ·1 Remarks: 1 oTestedon 11/13/2015 I oTested on 11/13/20 I 5 LI Tested on 11/13/2015 :1 lj :1 Figure A-9 Section 5: Other Permits None at this time Section 6: Declaration of Covenants The proposed storm water BMP covenants will be provided as part of the final engineering plan submittal for City review and approval. RECORDING REQUESTED BY AND WHEN RECORDED MAIL TO: CITY CLERK'S OFFICE CITY OF RENTON 1055 SOUTH GRADY WAY RENTON. WA 98057 DECLARATION OF COVENANT FOR MAINTENANCE AND INSPECTION OF FLOW CONTROL BMPS Grantor: -------------- Grantee: City of Renton Legal Description:--------------------------- Additional Legal(s) on:------------------------- Assessor's Tax Parcel ID#:------------------------ IN CONSIDERATION of the approved City ofRenton(check one of the following) D residential building permit, D commercial building permit, D clearing and grading permit, D subdivision permit, or D short subdivision permit for Application File No. LUA/SWP ________ relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covcnants(covenant) with City or Renton, a political subdivision of the state of Washington, that hc/she(they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 8 below with regard to the Property. Grantor(s) hereby grants(grant), covenants(covenant), and agrees(agree) as follows: 1. Grantor(s) or his/her(their) successors in interest and assigns ("Owners") shall retain, uphold, and protect the stonnwater management devices, features, pathways, limits, and restrictions, known as flow control best management practices ("BMPs"), shown on the approved Flow Control BMP Site Plan for the Property attached hereto and incorporated herein as Exhibit A. 2. The Owners shall at their own cost, operate, maintain, and keep in good repair, the Property's BMPs as described in the approved Design and Maintenance Details for each BMP attached hereto and incorporated herein as Exhibit B. 3. City or Renton shall provide at least 30 days written notice to the Owners that entry on the Property is planned for the inspection of the BMPs. After the 30 days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting the BMPs. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the BMPs and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen days of receiving the City's notice of inspection. Within 30 days of giving this notice, the Owners, or the engineer on: behalf of the Owners, shall provide the engineer's report to the City of Renton. If the report is not provided in a timely manner as specified above, the City of Renton may inspect the BMPs without further notice. 4. If the City determines from its inspection, or from an engincds report provided in accordance with Paragraph 3, that maintenance, repair, restoration, and/or mitigation work is required for the BMPs, The City shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (Work) required under RMC 4-6-030. The City shall also set a reasonable deadline for completing the Work or providing an engineer's report that verifies completion of the Work. After the deadline has IN WITNESS WHEREOF, this Declaration of Covenant for the Maintenance and Inspection of Flow Control BMPs is executed this __ day of _________ , 20 . GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: __________________ , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this __ day of _________ ., 20 __ Printed name Notary Public in and for the State of Washington, residing at My appointment expires _________ _