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Home My WebLink AboutLUA16-000217_REPORT 01Denis Law Mayor April 4, 2016 Michael Crowson Mundy Jo Holdings, LLC 2800 156'h Avenue SE, Suite 120 Bellevue, WA 98007 Community & Economic Development Department C.E."Chip"Vincent, Administrator Subject: Alternate Procedural Request -Alternative Street Pavement Section Nantucket Avenue Short Plat (UlS-001403 and LUAlG-000217) Dear Mr. Crowson, We have reviewed your request to construct an alternative pavement design for the private roadway within the Nantucket Subdivision from the required four inches (4") of asphalt over six inches (6") of crushed rock to the requested two inches (2") HMA over four inches (4") crushed rock base over twelve inches (12") minimum of pit run gravel base. Per RMC 4-9-250.E.2, the City of Renton has reviewed the alternative request and the geotechnical report analysis enclosed. Based upon the geotechnical analysis provided, the alternative pavement design provides an increase in structural strength of the roadway from the Code required pavement section. In addition, it does not alter the suitability, effectiveness, durability, safety, maintainability, or environmental protection of the private street. Therefore, the alternative pavement section is approved. Note that this approved alternative pavement section is only applicable to the private street within this project. The decision to approve the alternative design will become final if not appealed in writing together with the required fee to: Hearing Examiner, City of Renton, 1055 South Grady Way, Renton, WA 98057 on or before 5:00 pm on April 18, 2016. Additional information regarding the appeal process may be obtained from the City Clerk's office, Renton City Hall-7'h Floor, 425-430-6510. If you have any further questions regarding utility or drainage requirements for this project, please contact Jan Illian at 425-430-7261 or jillian@rentonwa.gov. / L,.A;'.:-{.A.4--'.......,.._..,, ~ --;,. ,, UU.,0<3... ·rA._. Brianne Bannwarth, // (____.,V.., Development Engineering Manager Enclosures: Nantucket Short Plat, Private Drive P~vement Section prepared by Terra Associates., Inc. on March 16, 2016 cc: Jennifer Henning, CED Planning Director Jan Illian, CED Plan Reviewer Patrick Decaro, CED Site Inspector Renton City Hall • 1055 South Grady Way • Renton, Washington 98057 • rentonwa.gov ' DESIGN MEMORANDUM To: Michael Crowson Mundy Jo Holdings, LLC From: Ted Schepper, P.E. Subject: Private Drive Pavement Section ~========c..c..;;===--- R e f: Terra Geotechnical Report, 11-4-15 Michael: TERRA ASSOCIATES, Inc. Date: Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences March 16, 2016 Project Number: T-730::.::3:..;-2=-------- Project Name: Nantucket Short Plat Renton, Washington In the referenced report we had provided a recommended pavement section consisting of 2 inches of Y, inch hot mix asphalt (HMA) over 4 inches of crushed rock base (CRB) for the private access drive on the east side of the project This section was to be constructed over a prepared stable subgrade consisting of onsite native mineral soils. Laboratory testing to determine the supporting strength of the subgrade as measured by the California Bearing Ratio (CBR) indicates compacted non-yielding subgrade consisting of the native silty sand soils would exhibit a CBR equivalent to 26. This CBR would correlate to a subgrade modulus (M,) of 25,000 psi. Back calculation to determine the design traffic that could be supported by the section determined that the section would be structurally adequate for an 18-kip equivalent single axle load (ESAL) of 100,000. This ESAL represents an 80,000 pound tractor trailer rig traversing the pavement structure approximately 4 times a day, 365 days a year over a 30 year design life. The section is more than adequate to support traffic loading including emergency response vehicles such as fire trucks that could be expected for the short plat. As we understand preparation of the road subgrade will be completed shortly. As you are aware the current over optimum moisture content of the native soils will not allow for compacting the soils to a stable non-yielding condition. To prepare a stable grade, we recommend that the unstable wet soils be removed to firm and stable subgrade and grade restored using a pit run gravel base. Based on conditions observed in the field the gravel base thickness would be a minimum of 12-inches. If conditions warrant a geotextile separation/reinforcement fabric such as Mirafi SOOX should be placed on the native soil grade followed by placement of the gravel base. When including this pit run as a gravel sub-base in the pavement section the structural capacity of the section as measured by the section structural number (SN) will be greater than the City of Renton required section consisting of 4-inches of HMA over 6-inches of CRB. Please call if you have any questions or require additional information. Attachments: CBR Laboratory Test Results Pavement Design Section Calculations j 12220 113~ Ave NE, Suite 130, Kirkland, Washington 98034 Phone No. (425) 821-7777 Fax: 821-4334 Sample Number: Sample Location: Soil Type: uses Classlflcation: Grain Size Distribution: Gravel Fraction: Sand Fraction: Fines Fraction: Laboratory Moisture Density: Method of Test Maximum Dry Density (pcf) Optimum Moisture Content(%) California Bearing Ratio (CBR): Remolded Unit Weight (pcf): Remolded Moisture Content(%): Surcharge Weight (lbs.): Percent Swell ( 48 hrs. soak) CBR .1" penetration CBR .2" penetration California Bearing Ratio Soil Tests Summary Nantucket Short Plat Renton, Washington 1 Private Drive Subgrade Silty Sand SM 7.7% 51.6% 40.7% See attached proctor curve. ASTM 01557 117.6 13.2 115.7 13.2 10 0.15 21 26 TERRA ASSOCIATES, INC. Laboratory Moisture Density Curve 124.0 ~-------------~-----------~ Project Name: Nantucket Short Plat L-j-Method of Test: ASTM D 1557 122.0 120.0 118.0 116.0 114.0 112.0 110.0 108.0 Project Number: 7303-2 =f Maximum Dry Density (pcf): 117.6 Sample 1.0.: C , Optimum Moisture Content(%): 13.2 Sample Location: Road Subgrade + Sieve Analysis Soil Type: Brown silty sand (SM) =t US Standard Sieve Percent Passing _': 3/4" 98.3 ' ---· 3/8" - I --r· ----r-1=1=-#4 95.9 92.3 40.7 ----1--#200 --------- Zero Air Voids --\,\'---~t~~~-1--.u __ /,::'.:'-1--ti.:t.:t.t.-,'-_ _,_'-~-,--1--·1--·h-,_,-_1-,.1---1-. .u.,·.t.t.ttt;::';::',::',::',jj_jj.·. ,_,___,'-_ 1 -,.G_s=_2 __ 6_5~-~~-' -• ··1--H·-•+·l-l-~ --•-,-, -l-1--l--l-1-1-1--1--1--W1--1- -1+1--l--l--l--le+-l-1-1-H-1-1-l-+-l--!-e+-1--1--1--l--l-1--1-1-1--• --1-l--l--l--l-l-+-++-++++-1--1--1--1--l-+<--l-l+i+i-l-+-I-I-I--I--I--I -H-l-++~-1--i-l--l-_1.,.. ----W--W--l+-1--+-1-+--H-~1--1--l-_µ__l---hl-l-1--1-11-'-1--'-+--l+-l-+-4- 1-'--'hh--U+-I-W.-W.-l--l--LLhl-hl-1.--l--L .. --1- -·'-1--1-HH ,, - .J...L -L.L. -_, ' " -.Ll-J.."-1--1--L LI. 1--l--LLiLLJ--'---l--Ll-W.-LW-. ·--1-I-·---1-,1--1-l--1-1- \_ -•. 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'-1--'_-!'-'+--l--i-l-. =-Hl-1--1--hl-C-1----l+t+H--f--H--1--l--l---l---1--1---1--!--1-,l--l--l-l-H--j.-j.-!l--hl-l -h -_ 1-1-.1--i-~kl-+r.1-.l.-.1-.l-_ _ _ _ _ 1-_ _,_ --I- ---------l---l-LLLl--l--l---1~!~~~~~~:,_-1----1--1-1--"41--h---l---,-l-l--l---1-++-I=' --r-+· __ :~tl=t/::' 1--C-l--l--,C-l--1-+--l--1--1 L.LI--LLL.U... ... -..• -i-l--1--l--1--i---+-l--1--i-l-++i-1--!-+i-l--l--i--4-----,---I-__ ,1..,1.. -L 1 I--LLJ..Ll--hl--+-1-W+-1-1--l--HC-l--l--l--LHI-I-Lll+-l+-1-W-1-I C-1--1-1---1--l--ll-1-i--- ·----1-L. --1---1--C Il--l--l--l--l--H-+-1--1-1 --'--- _JJ.l--l--++-Ll-'--1-LW_ -· ~t~ -:1 --+ ------------j ~ --f--------' ' --- -'-- --1--~ - I --. - 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Moisture Conll!nt (%) AASHTO --Pavement Analysis Program (2) Nantucket Short Plat -Private Access Road !!MA Section ********************** Flexible Analysis******************** * Structural Number * Design E 18 1 s • Reliability * Overall Deviation * Resilient Modulus * Initial Serviceability * Terminal Serviceablity Layer Number Ht,.'A CRB Layer Coefficient a (i) 0.44 0.14 Design Life= 30 years Drainage Coefficient ==== Cd ==·• 1. 00 1. 00 1. 39 100,000 90.00 percent 0.45 25,000.0 psi 4.50 2.00 Layer Thickness === t ;,;::== 2.0 4.0 Total SN'"" a(i)*Cd*t 0.88 0.56 ==S::.::l:"'11!=== 1.44 > 1.39 80,000 pound GVW Semi-Tractor Trailer Truck Factor= 2.39 Number of trucks representing Design ESAL of 100,000 •100,000/(JQ X 365 X 2.39) •• 3. 82 trucks per day Structural Number (SN) o:£ section vith 12 inches o:f gravel sub-base. SN (2 X .11) + (4 x .14) + (12 X .1) 2. 64 SN o:f City o:f Renton Section SN = ( 4 X • 4 4) + ( 6 X , 14) = 2. 60 - 2800 156 Avenue SE Suite 120 Beilevue WA 98007 206-972-6 711 mcrowson@mjhdevco.com e 0 To: Brianne Bannwarth, City of Renton • J_:' __ ,_,-c"";; __ ".:'.',:::,='¥1~--" "">'\," . MWRIJr:J'o tloldings; ttcr ~' I I I 1111 I I ~ J'-' ~ f\, Jan Illian, City of Renton ~\ 1~ Michaei Crowson, Mundy Jo Holdings, LLC '\0 cc: From: Date: March 18 2016 Re: Nantucket Subdivision; R-383005 Request for Modification I am pieased to submit this formal Modification Request to change the Nantucket private drive road section. In addition to this Modification request memo I am submitting the pavement section design dated March 16, 2016, private drive detail, and geotechnical report dated November 4, 2015. I know you have many projects under review and construction so I want to share the bnef history of this prQJect, Nantucket Short Plat We, Renton Park Ave. LLC, purchased this prQJect from Violette Sh1llam in late 2015, long after the engineering drawings were approved. The geotechnical letter that supported the engineering design was brief and mainly focused on infiltration. The letter didn't address the design aspects of the project Thus we hired Terra Associates to complete a detailed geotechnical report to evaluate the specific site conditions as it relates to the soil. groundwater, drywell infiltrallon, building foundation and pavement design. After clearing the site, obsenving the on-site material, and starting utility construction it was apparent we needed to consider an alternate road section for the private drive. Therefore, with guidance from Jan related to the modification process. we asked Terra Associates to complete a site and soil specific pavement section design for the private drive. The private drive pavement section design memo and supporting calculations by Ted Schepper, owner of Terra Associates, are attached. We are requesting the private drive pavement section be changed to 2-inches HMA over 4-inches Crushed Rock Base over 12-inches minimum of pit run gravel base. Based on conditions at the time of placement, a Mirafi 500X fabric may be underlain before the gravel base is placed This road section would replace the previously approved 4-inches HMA over 6-inches Crushed Surfacing Top Course. In essence, we are proposing to replace the proposed 10-inch road section with an 18-inch road section of different composition and higher structurai number The details of the soil and pavement design are included as part of the pavement design memo by Terra Associates. I have included a private drive detail that highlights the proposed section in drawing format As well as proposing a road section with a higher structural number, it should also be noted that this private drive will only serve 5 single family homes, is a dead-end drive, and will be maintained by a home owners association per a condition of the plat It is understood that emergency vehicles will use the private dlive from time-to-time given the hammerhead tum around at the end of the drive but based on the nature of the traffic volume, type of vehicle traffic, and proposed road section the private dnve will be more than adequate. Page 1 Based on the specific soil conditions, detailed soil analysis and pavement design, as well as the proposed use we are asking for your consideration of the proposed change to the private drive road section. As it relates to RMC 4-9-250, the proposed pavement section modification doesn't compromise any of the following: a. Substantially implements the policy direction of the policies and objectives of the Comprehensive Plan Land Use Element and the Community Design Element and the proposed modification is the minimum adJustment necessary to implement these policies and objectives; b. Will meet the obJectives and safety, function. appearance, environmental protection and maintainability intended by the Code requirements. based upon sound engineering Judgment. c. Will not be injurious to other property(ies) in the vicimty; d. Conforms to the intent and purpose of the Code; e Can be shown to be justified and required for the use and situation intended; and f Will not create adverse impacts to other property(ies) in the vicinity Upon your review of this request and review of the attached materials should you have any questions or concerns please do not hesitate to email me at mcrowson@mjhd~vco com or call me anytime at 206-972-6711. Thank you in advance for taking the time to review and consider this request. Attachment(s): Check for Modification Request $154.50 Pavement Design Memorandum dated 3116/2016 Private Drive Road Section Detail & Approved Sheet 5 Road drawing Nantucket Geotechnical Report dated November 4, 2015. • Page2 DESIGN ME1VIORANDUM To: Michael Crowson :vl.undy ,Jo Holdings, LLC From: Ted Schepper, P.E. Subject: Private Drive Pavement Section Ref: Terra Geotechnical Report, 11-4-15 Michael: TERRA ASSOCIATES, Inc. Date: Consultants In Geotechnlnl EnginePring, Geology and Environmental Earth Sciences Project Number: March 16, 2016 T-7303-2 Project Name: Nantucket Short Plat Renton, Washington In the referenced report we had provided a recommended pavement section consisting of 2 inches of Y, inch hot mix asphalt (HMA) over 4 inches of crushed rock base (CRB) for the private access drive on the east side of the project. This section was lo be constructed over a prepared stable subgrade consisting of onsite native mineral soils. Laboratory testing to determine the supporting strength of the subgrade as measured by the California Bearing Ratio (CBR) indicates compacted non-yielding subgrade consisting of the native silty sand soils would exhibit a CBR equivalent to 26. This CBR would correlate to a subgrade modulus (M,) of 25,000 psi. Back calculation to determine the design traffic that could be supported by the section dctennined that the section would be structurally adequate for an l 8-kip equivalent single axle load (ESAL) of I 00,000. This ESAL represents an 80,000 pound tractor trailer rig traversing the pavement structure approximately 4 times a day, 365 days a year over a 30 year design life. The section is more than adequate to support traffic loading including emergency response vehicles such as fire trucks that could be expected for the short plat. As we understand preparation of the road subgradc will be completed shortly. As you are awan: the current over optimum moisture content of the naliw soils will not allow for compacting the soils to a stable non-yielding condition. To prepare a stable grade, we recommend that the unstable wet soils be removed lo firm and stable subgradc and grade restored using a pit run gravel base. Based on conditions observed in the field the gravel base thickness would be a minimum of 12-inches. If conditions warrant a geotextile separation/reinforcement fabric such as Mirafi 500X should be placed on the native soil grade followed by placement of I.he gravel base. When including this pit run as a gravel sub-base in the pavement section the structural capacity of the section as measured hy the section structural number (SN) will be greater than the City of Renton required section consisting of 4-inches of HMA over 6-inchcs of CRB. Laboratory test results and pavement design section calculations supporting the above arc attached for City of Renton Public Works review. Please call if you have any questions nr require additional information. Attachments: CBR Laboratory Test Results Pavement Design Section Calculations 12220 l !3'' Ave NE, Suite 130, Kirkland, Washington 98034 Phone No. (425) 821 ·7777 Fax: 821-4334 J Sample Number: Sample Location: Soil Type: uses Classification: Grain Size Distribution: Gravel Fraction: Sand Fraction: Fines Fraction: Laboratory Moisture Density: Method of Test: Maximum Dry Density (pct) Optimum Moisture Content (%} California Bearing Ratio (CBR): Remolded Unit Weight (pcf): Remolded Moisture Content(%): Surcharge Weight (lbs.): Percent Swell ( 48 hrs. soak) CBR . 1" penetration CBR .2" penetration California Bearing Ratio Soil Tests Summary Nantucket Short Plat Renton, Washington 1 Private Drive Subgrade Silty Sand SM 7.7% 51.6% 40.7% See attached proctor curve. ASTM 01557 117.6 13.2 115.7 13.2 10 0.15 21 26 ;:-u .9, ;:, ·;; C .3 1:' Cl 124.0 122.0 120.0 118.0 116.0 114.0 112.0 TERRA ASSOCIATES, INC. Laboratory Moisture Density Curve Project Name: Nantucket Short Plat Project Number: 7303-2 1Sample I.D.: C Sample Location: Road Subgrade Soil Type: Brown silty sand (SM) ' 't ' Method of Test: ASTM O 155 7 Maximum Dry Density (pct): 117.6 Optimum Moisture Content(%): 13.2 Sieve Analysis US Standard Sieve 3/4" 318" #4 #200 'I Percent Passing 98.3 95.9 92.3 40.7 'i '' 110.0 108.0 8.0 10.0 '' 12.0 '' 14.0 16.0 18.0 20.0 22.0 Moisturo Content ('Y.) =========================== AASHTO --Pavement Analysis Program (2) Nantucket Short Plat -Private Access Road HMA Section ********************** Flexible Analysis******************** -;.-St nicturn.l :t-binbcr * 8csiqn E l8's * Reli<Jb.i Li.ty * Overall Ceviation -Resilie11t Mudulua ln~tia: Serviceability .,,. Terninal Se.i·viceabLL ty ; ,.:Jy1?.Y' '.'LIT;Der HYJ'\ CR3 ~ .. 1.yQr Cocfficie:n·.: a (l) 0.44 0.14 :)Ps ~ qn L: fc = 30 y0ars Drair:a1Je C0pff_ic-lf:r:t "C:d 1 . C 0 1. co l. l') 10~.000 90. 00 perc(:n-:: 0.45 /.5,JOO.O pD~. 4.. SC 2.GC La.ycr 'ff",.i.ckn<=s-S -=== +-=== 2.J 0.88 0.56 no,ooc oouna GVW Semi-Trac·tor ~rai.l.er ~ruck Pactor ?.3S Dl'.1rnter of tr1,..;_c%.s reprns~:!n~:in9 i)cs.i.gn :::.:SA.L \;,:f. :OD, ~)()(J lOO,OC0/(30 x 365 x 2.39) 3.82 tr~cks per day Structura1 Number (SN) of section with 12 inches 0£ grave1 sub-base. SN (2 X .,1!J) r (,1 X .l-1) +. (12 X .1) 2.64 SN of City of Renton Section SN ( 4 X • H) + ( 6 x .14) 2.60 }9 fl.\ Die.\VE 24 N., RANGE 5 EAST, W.M., CITY OF RENTON, WASHINGTON EXISTING lJllLl1Y LOCATIO -- --~ -~- LOT DRAINAGE -SFF SHEET 8 "· ------~---···"--------- I I r--· :1·1 29' ACCESS & PUBLIC UTILITY EASEMENT u~ <§ j&"! 0:: ~:: 0 z,w WI~ on. 18.0' APPROXIMATE ONLY. IT RESPONSIBILITY TO DETEF HORIZONTAL LOCATION 01 UTILIITES PRIOR TO COM! RlPRESENTATION IS MADI ARE SHOWN HEREON. T RESPONSIBILITY FOR UTII. NOT SHOWN IN THEIR PF l__G.~LL BEFORE YOU DIG: I 11 .o· ~---"·-······-J-._, ... , , o· I 13. · 0.50' VERT. CURB 4"MIN. CLASS "8" ASPHAL!IC CONCRFlT . I\ / \ & GUTTER \ PAVEMENT-2-2· LIFTS REQUIRED (\ we ti \ '-6"MIN. CRUSHED SURFACING TOP COURSE '. w \_CRUSHED SURFACING BASE COURSE TO BE DETERMINED BY FIFLD CONDITIONS '· PRIVATE ACCESS STREET L11 ~Ml+. 4 ri ·c~-~ ?ropo9c, ,.:.,,.,,.~---""'"'- \ 2..11 ? rf \Ll)f'l &iilJW(l. !1 • <-~ l z 2 "' z 'j' "' ; I z 2 z '" 0: ~ 0 I: (j ::; " ,..: "' :Ii ~ u, " z ii z ~ N a. l: "' z " 0 .... oi ~ z 0 ~ u w "' r " "' ' r ;{ w ,5 "' !i w •'; I .... ~ 0 z Q .... o; 0 a. "' '-----~ /. ;sc !·¥ ~ r {-; ,,_.,, '-~~ ,n,r ';;~'-- l V!d l.LICHS B>i'.J(li.N~N l_1i l -''I '' .,. ._, -------- -I -~ ., ., < 'I" TERRA ASSOCIATES, Inc. Consu!t.a.nts ln (Jt:otechnic;:i.! EnginPeffng, Geology and Renton -Park Avenue, LLC c/o Mr. Michael Crowson Mundy Jo Holdings, LLC 2800-156th Avenue SE, Suite 120 Bellevue, Washington 98007 Subject: Geotechnical Engineering Study Nantucket Short Plat 2802 and 2820 Park Avenue North Renton, Washington Dear Mr. Crowson: Environmental Earth Scicno'.s November 4, 2015 Project No. T-7303-1 As requested, we performed a geotechnical engineering study for the subject project. The proposed project is an eight-lot residential subdivision with associated utility and access improvements. Building plans are currently unavailable; however, we anticipate that the buildings will be two-story wood-frame structures with their main floor levels constructed at grade or framed over a crawl space. A site plan prepared by Offe Engineers titled Road/Storm Details and Notes, dated May 5, 2015, indicates surface runoff from the lots will be managed using individual-lot infiltration systems consisting of drywells. Runoff collected from paved access improvements will be routed to a detention vault in the southwestern portion of the site. The purpose of our work was to investigate subsurface conditions at the site in order to tlevelop geotechnical recommendations for project design and construction. Using the results of our field study and laboratory testing, analyses were undertaken to develop geotechnical recommendations for project design and construction. Specifically, this report addresses the following: • Soil and groundwater conditions • Seismic design parameters per the current International Building Code (IBC) • Foundations • Drywell infiltration " Pavements 12220 ! 1 '.Hh /wu:ut: Ste -130, Kit kl:. nd., V\/ashingtun 9BOJ4 Phone (42,'i) !121-7777 • Fa>. ( ii214U4 Mr. Michael Crowson November 4, 2015 The recommendations in the following sections of this report are based on our understanding of the preceding design features. We should review design drawings as they become available to verify that our recommendations have been properly interpreted and to supplement them, if required. SITE DESCRIPTION The site is an approximately 1.43-acre assemblage of 2 residential parcels located northeast of and adjacent to the intersection of Park Avenue North and North 28th Street in Renton, Washington. The site location is shown on the attached Vicinity Map, Figure 1. Both parcels arc occupied by a single-family residence. Site vegetation consists primarily of grass lawn, landscape vegetation, mature fruit trees, and mature coniforous trees. Existing surface grades arc relatively flat. SUBSURJ<'ACE CONDITIONS We investigated subsurface conditions at the site by excavating 4 test pits to maximum depths of about IO to 10.5 feet below existing surface grades using a track-mounted excavator. We supplemented this information by reviewing the logs of three test pits excavated in the southwestern portion of the site presented in a report by Robert M. Pride, LLC, dated November 7, 2014. The approximate locations of the test pits are shown on the attached Exploration Location Plan, Figure 2. The Test Pit Logs arc attached as Figures 4 through 7. The test pit logs prepared by Robert M. Pride, LLC arc attached. The soils observed in our test pits generally consist of about four to seven feet of silty fine sand to fine sandy silt overlying sand to sand with sill that are interpreted to be glacial recessional outwash deposits. The soils arc generally in a medium dense to dense and dry to moist condition. The soil conditions observed in our test pits are generally consistent with those observed in the on-site test pits completed by others. The Pre/iminwy geologic map of Seattle and vicinity Washing/Un, by H. H. Waldron, et.al. ( I 962) shows the site soils mapped as Vashon recessional outwash comprised of fine !o medium sand (Qys). The native srlils that we observed in the test pits are generally consistent with this map unit. The United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS) has mapped the site soils as Indianola loamy sand 5 /0 15 percent slopes {lnC). This soil unit is described as somewhat excessively drained soils fom1cd in sandy glacial outwash. The soils that we observed in tlic test pils are generally consistent with this mapped soil unit. Groundwater We did not observe groundwater seepage or indications of seasonally fluctuating 1,,,rounJwater levels in the test pits. This is consistent with conditions observed in the on-site test pits completed by others. Project No. T-7303-J Page No. 2 Mr. Michael Crowson November 4, 2015 DISCUSSION Soil Bearing Capacity In our opinion, the medium dense to dense native soils observed beneath the surficial topsoil layer are suitable for support of residential building loads using conventional spread footing foundations. We recommend designing foundations bearing on native soils or on new structural !ill placed and compacted as recommended below for a net allowable bearing capacity of 2,500 pounds per square foot (psf). For short-tcnn loads, such as wind and seismic, a one-third increase in this allowable capacity can be used. With the anticipated loads and this bearing stress applied, building settlements should be less than one-half inch. For detennination of seismic forces, per the 2012 International Building Code (lBC), site class "D" should be used. For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth pressures acting on the sides of the footings can also be considered. We recommend calculating this lateral resistance using an eqnivalent fluid weight of 300 pounds per cubic foot (pd). We recommend not including the upper 12 inches of soil in this computation because it can be affected by weather or disturbed by future grading activity. This value assumes the foundation will be constructed neat against competent soil or backfilled with structural fill. The recommended friction and passive values include a safety factor of L5. Structural Fill A representative of Terra Associates, Inc. should examine all bearing surfaces to verify that conditions encountered are as anticipated and are suitable for placement of structural !ill or direct support of building and pavement elements. Our representative may request proofrolling exposed surfaces with a heavy rubber-tired vehicle to dctcnnine if any isolated soft and yielding areas are present. If unstable yielding areas are observed, they should be cu! to finn bearing soil and filled to grade with structural fill. If the depth of excavation to remove unstable inorganic soils is excessive, use of geotextile fabric such as Mirafi SOOX or equivalent in conjunction with structural Iii! can be considered in order to limit the depth of removal. In general, our experience has shown that a minimum of l8 inches of clean, granular structural !ill over the geotextile fabric should establish a stable bearing surface. The upper approximately four to seven feet of soil at the site contain a sufficient amount of fines such that they will be difficult to compact as structural lill when too w"t or too dry. Accordingly, the ability to use these soils from site excavations as structural fill will depend on their moisture content and tbc prevailing weather conditions al the time of construction. If grading activities will take place during the winter season, or if they are initiated during the summer and extend into fall and winter, the owner should be prepared to import free-draining granular material for use as strnctural !ill and backfill. For this purpose, we recommend importing a granular soil that meets the following gradational requirements: U.S. Sieve Size 6 inches No,4 No. 200 * Based on the 314-inch fraction. Percent lOO 75 maximum 5 maximum* Project No, T-7303-1 Page No. 3 Mr. Michael Crowson '-i(JVember 4, 2015 Prior to nso, Terra Associates, [nc. should examine and test all materials imported to the site for use as strnctural filL Structural fill should be placed in unifonn loose layers not exceeding 12 inches and compacted to a minimum of 95 percent of the soil's maximum dry density, as delcnnined by American Society for Testing and Materials (ASTM) Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction should be within minus one lo plus three percent of its optimum, as determined by this ASTM standard. ln nonstructural areas, the degree of compaction can be reduced to 9() percenL Drywell Infiltration Based on our study, it is our opinion that soil conditions observed below depths of about 4 to 7 foet arc favorable for infiltrating runoff from the individual lots using drywells. The results of grain size analyses indicate that these soils fall into the category of sand when classified using USDA textural analysis, with a predominant particle size consisting of medium-to coarse-grained sand. The results ofthc grain size analyses are attached as Figures 8 and 9. The City of Renton has adopted the 2009 King County Surface Water Design Manual (SWDM) for design, construction, and maintenance of stonnwaler management systems and facilities, including drywells. Therefore, drywell design and construction should follow the specifications given in Appendix C, Section C.2.2.4 (Use of Drywells for Full Infiltration) and Figure C.2.2.C (Typical Drywel! Infiltration System) of the 2009 SWDM. Pavements Pavements should be constructed on a subgrade consisting of finn native soil or properly placed and compacted structural filL Regardless of the degree of relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. Proofrolling the subgrade with heavy construction equipment should be completed 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 traffic consisting mainly of light passenger vehicles with only occasional heavy traffic, and with a stable subgrade prepared as recommended, we recommend the following pctvement sections: • Two inches of hot mix asphalt (l !MA) over four inches of crushed rock base (CRB) • 3 Y:, inches foll Jcp1h HMA over prepared subgrade The paving materials used should confonn to the Washington State Department of Transportation (WSDOT) specifieations for \',-inch class HMA and urn. Project No. T-7303-1 Page No. 4 ML Michael Crowson November 4, 2015 Long-tenn 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 subgrade soils and reducing their supporting capability. For optimum pavement performance, we recommend surface drainage gradients of al 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. 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 properly of Terra Associates, Inc., and is intended for specific application to the Nantucket Short Plat project in Renton, Washington. This report is for the exclusive use of Renton -Park Avenue, LLC and their authorized representatives. The analyses and recommendations presented in this report are based on data obtained from the on-site test pits. 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. We trust the information presented is sufficient for your current needs. If you have any questions or require additional infonnation, please call. Sincerely yours, TERRA ASSOCIATES, INC. Project No. T-7303-l Page No. S I SI S ll''il ii P I 11 tilh SI Sd11thSt REFERENCE WSDOT GEOPORTAL (2015) Terra Associates, Inc. Cor;suilants in Gecter;hnic.11 Enginemipg Geology and Environment;;! Earth Sc:ences N 3-Gth St N '.!~th St D~ ~4t!J St SE 76111 St N 34th St N 3'3rd Pl uJ Ncc24,h St z ',.:J z ., ;, ,:; VICINITY MAP NANTUCKET SHORT PLAT RENTON, VVASHINGTON CJ ,n SE UU! " ~! s: , \D'~ ~; "'' ? •:: ,:; u; Proj No.T-7303-1 Date NOV 2015 Figure 1 r I I I !/ § "'I 4 n. 1::/ I I I --i I I __ _/_ NORTH 28th STREET ------------------ REFERENCE: SITE PLAN BY OFFE ENGINEERS NOTE: THIS SITE PLAN IS SCHEMATIC, ALL LOCATIONS AND DIMENSIONS ARE APPROXIMATE. IT IS INTENDED FOR REFERENCE ONLY AND SHOULD NOT BE USED FOR DESIGN OR CONSTRUCTION PURPOSES. LEGEND: tlllljjj APPROXIMATE TEST PIT LOCATION (TERRA 2015) ~APPROXIMATE TEST PIT LOCATION (RMP,LLC 2014) 0 50 100 APPROXIMATE SCALE IN FEET Terra Associates, Inc. EXPLORATION LOCATION PLAN NANTUCKET SHORT PLAT RENTON, WASHINGTON Consultants in Geotechnical Engineering Geology and t:1w1ronmental Earth Sciences Proj. No.T-7303-1 Dale NOV 2015 Figure 2 MAJOR DIVISIONS I LEITER TYPICAL DESCRIPTION I SYMBOL Clean ! GW Well-graded gravels, gravel-sand mixtures, little or no fines. GRAVELS Gravels (less ~ More than 50% than 5% (/) "' fines) GP Poorly-graded gravels, gravel-sand mi.>ctures, little or no fines. .... Ol ~ <l) of coarse fraction 0 El .!:! (/) ~~ is larger than No. GM Silty gravels, gravel-sand-silt mixtures. non-plastic fines. C 4 sieve Gravels with w 2 i fines z (Q ·-GC Clayey gravels, gravel-sand-clay mixtures, plastic fines. ~ E "' 0 ,'i! 0 t') ON Clean Sands SW Well-graded sands, sands with gravel, little or no fines. "' 0 w cz SANOS (less than .. _ (,f) ro C I Poorly-graded sands, sands wi1h gravel, little or no fines. ll: £ ro More than 50% 5% fines) SP < a, .c I of coarse fraction 0 ~-·-~---u 0 2 is smaller than Sands with SM Silty sands, sand-silt mb<tures, non-plastic fines No. 4 sieve fines SC Clayey sands, sand-day mixtures, plastic fines. ~ _']! ML Inorganic silts, rod< flour, clayey silts with slight plasticity. iii "' (I) EN SIL TS ANO CLA VS ' .... ~ ·w CL Inorganic clays of low to medium plasticity. (Lean clay) 0 .~ ;1; Liquid Limit is less than 50% ·--· <fl Cl .ffi -~ OL Organic silts and organic clays of low plasticrty. "' "' I w Ea z *~ - ~ 0 . MH Inorganic silts, elastrc. '° 0 t') C: z SIL TS AND CLAYS w n, C CH Inorganic clays of high plasticity. (Fat clay) z .c to Liquid Limit is greater than 50% -.c -;:;:: a, -~ 0 OH Organic clays of high plasticity. 2 --- HIGHLY ORGANIC SOILS PT Peat. ------ DEFINITION OF TERMS AND SYMBOLS (/) Standard Penetration I 2" OUTSIDE DIAMETER SPILT SPOON SAMPLER u, Density Resistance in Blows/Foot w .... I 2.4" INSIDE DIAMETER RING SAMPLER CR :z Very Loose 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 Consis{anqy_ Resistance In BlowsJFoot w DD ORY DENSITY, pounds per cubic foot > iii Very Soft 02 w Soi\ 2-4 LL LIQUID LIMIT, percent ::c 0 Medium Stiff 4-8 0 Stiff 8-16 Pl PLASTIC INDEX Very Stiff 16-32 ! Hard >32 N STANDARD PENETRATION, blows per foot ~Terra UNIFIED SOIL CLASSIFICATION SYSTEM ' NANTUCKET SHORT PLAT Associates Inc. RENTON, WASHINGTON Constiitants in Geotechnlcal ingineering No.T-7303-1 I Date NOV 2015 j Geo!our and Proj Figure 3 Environmenfa Earth Sciences LOG OF TEST PIT NO. 1 FIGURE4 PROJECT NAME: Nanl!J.cisl!Lfillort Plat PROJ. NO: T-7303-_i ___ LOGGED BY: JCS LOCATION: _RenlQn,__V\IJ!,Sb)ng!Qn ___ ----SURFACE CONDS: lllwn ----APPROX. ELEV: 2.125 .FL DATE LOGGED: OctoberZ2 •. 20j5 _ --DEPTH TO GROUNDWATER: 1'1/A___-DEPTH TO C;::A::V;IN::G;:-==N=/A====·-.::.··-1 G:' I i ~ w ... ..J '=-a. ::! :c .. .... "' a. ~ w 0 "' 1 -- 2 G 3 4 5 7- 8 9 I 10 11 ' I I DESCRIPTION (6 inct,es SOD and TOPSOIL) Light brovm silty SAND to SAND with silt, trace of fine gravel, dry, scattered roots. (SM/SP-SM) Light gray~brown silty fine SANO, trace of gravel, dry, weakly cemented, trace of cobbles. (SM) Brown fine to medium SAND to fine to medium SAND with silt, dry to moist, trace of roots. (SP/SP~SM) Test pit tenninated at 1 O feet. No groundwater seepage_ NOTE This s11bsurface 1nformat1on pertains only to this te$1: pit location and should not be interpreted as being indicative of other locations at the site I I I ! i I i I I I I I ! i CONSISTENCY/ I ~ RELATIVE DENSITY I ;= I ! I I ' ; :i ~ ; USDA TEXTURAL CLASSIFICATION +---t ~ I I Medium Dense ! I I i I ! I I I 75 ' Sandy Loam I I ! I Medium Dense I I to Dense I I I I I I ! I 5.7 I Sand ! I I l I I ~ Terra Associates, Inc. Consu!tants in Geotechnical En.gineerir:g Geology and Environmental Earth Sciences - . --------··------------------------~ LOG OF TEST PIT NO. 2 FIGURES PROJECT NAME: NantucketShort Plat PROJ. NO: T-7303-1 LOGGED BY: JUL ... -. LOCATION: .Renton. Wfillh1ng!Qn... SURFACE CONDS: Lawn APPROX. ELEV: 2m.5.. ....... . DATE LOGGED: October 22, 2015. DEPTH TO GROUNDWATER: NA DEPTH TO CAVING: .NA. w >' ~ Q. '!, " J: <( >-., .. ~ w 6 0 "' 2 3 4 5 6 ; 7 ; B 10 11 DESCRIPTION (4 inches SOD and TOPSOIL) Brown silty SAND with gravel, moist (SM) Light gray-brown SILT with tine sand to fine sandy silt. trace of fine gravel, dry to rnoist, weakly cemented_ \ML} j : CONSISTENCY/ ; ~ ' ! RE~TIVE DENS!n i ~ I ' ' i Medium Dense Dense Gray-br.;;;;, fine SAND with s,lt and gravel to siltyiine --. ·· 1 SAND with gravel, moist, scattered cobbles, 1.5-foot 13.3 diameter boulder_ (SP .. SM/SM) Gray-brown fine to medium SANO to fine to medium SAND with sflt, trace of fine gravel. moist. (SP/SP-SM) fest pit temiinated at 10 feet No groundwater seepage. Medium Dense to Dense 7.0 I USDA TEXTURAL CLASSIFICATION Sand Terra Associates, Inc. NU r E. l"h11, subsl.Jrface 1rtormabon pen ams only to this rest pit k.ic.at;m nnd should 1,01 be 1nt,;,rpretBd as being indicative cf other locations at 1he site Consultants tn Geotechnical Erigineenng Geology and Environmental Earth Sciences .J LOG OF TEST PIT NO. 3 FIGURE 6 PROJECT NAME: 1'1antucl<et stlQ!i!'Jal._. - LOCATION: Renton Washjngton ·----PROJ.NO: T,7303-,L __ LOGGEDBY: JCS. __ _ SURFACE CONOS: Lawn ... -APPROX. ELEV: 2QlL ·-·-· DATE LOGGED: Qct.o.b..eL22 2015 DEPTH TO GROUNDWATER: MA____ DEPTH TO CAVING: ]IJ"'A'--- .: I ~j ,:; ' >-I 0. w " 2 3 5 - 8 . 10 11 ' G C ' ' I I I I ' ' I ' ' DESCRIPTION Brown silty SAND with gravel, moist. (SM) Light gray-brown fine sandy SILT to silty fine SANO, trace of fine gravel, dry to moist, weakly cemented_ (MUSM) Gray-brown fine SAND 'With silt and gravel to silty fine SAND with gravel, moist, scattered cobbles. (SP-SM/SM) Gray-brown fine to medium SAND to fine to medium SAND wllh silt, trace of fine gravel, moist (SP/SP-SM) . .. -----·----·------~-----~-~---------- Gray-brown fine to medium SANO with gravel, moist. (SP) Test pit terminated at 10 feet No groundwater seepage. NOTE: This subsurface intormabon pertains only to this test pit location and should not be interpreted as being indicat!ve o! other locations at the site I i 1 CONSISTENCY/ i ' RELATIVE DENSITY : : i ' Medium Dense Dense Medium Dense to Dense Dense ·--· ' ' I i:. ;:: 8.1 ii: "' I::. z w .. ... w " () 0 .. I i USDA TEXTURAL CLASSIFICATION ' - Sand I 9 9 ' Terra Associates, Inc. Consultants in Geotechn1cal Engineenng Geology and Environmental Earth Scierces .. ------~--------------~------------------------' LOG OF TEST PIT NO. 4 FIGURE 7 PROJECT NAME: N,mtuck<at Short Plat PROJ. NO: T ,7303,.1 LOGGED BY: JCS LOCATION: _RentQn~Washington SURFACE CONDS: Lawn APPROX. ELEV: 20,L ... DATE LOGGED: October22.2015 OEPTHTO GROUNDWATER: Nii... DEPTH TO CAVING: NA·-············ ~' ... !:. :,: ... a. "' 0 I I 2 3 4 .; 5 8 ; 9 10 11 12 "' _, a. :; " "' _, 0 "' DESCRIPTION (6 inct,es SOD and TOPSOIL) Brown silty SANO with gravel. moist, numerous roots. (SM) Light gray fine sandy SILT to silty fine SANO. dry, weakly cemented, scattered mottling. (MUSM) Gray~brown fine to medium SAND with silt. moist. (SP- SM) Gray-brown fine to medium SAND to fine to medium SAND with silt scattered graveL moist. (SP) est pit ferrninated at 10.5 feet No groundwater seepage NOTE fh·s subsurface informaiJon pertains only to this test pit location and should not ne interpreted dS being :ndicative of ottier loqt1ons at the s.1te CONSISTENCY/ ~ RELATIVE DENSITY 1 - USDA TEXTURAL CLASSIFICATION Medium Dense Dense ;: 13 3 58 Sand Terra Associates, Inc. Consultants m Geotechnical Engineering r}eology and Environmerita! Earth Suenr..es a:: w z Li: f-z w l) a:: w a. Particle Size Distribution Report N SI E-mm. % Ston••I % +J" I % Gravel 1 % Sand I % Silt r-·-· __ . _1 _ Coal'!lll_ ___ M._edium__ Fine f\l. C!":_J:rs, • Med •• Fine _\I. Fin~ Crs. Fine 0 0 , 0 0 ! 0 0 3.9 1.9 , 2.2 IS. I 22.6 11.3 40.0 0.0 ! __ Q.O ·o:o. _ 60 9 _ _1.8 -~,-42.9: 28 7 ~-4~6_· -8.0 0.0 0.0 0.0 0.2 1.4 1.6 2.8 6.2 9.3 78.5 Material Description "' '-·-·-·----------····----·-·-·· .. O silty SAND uses SM SP-SM ML D SAND wjth silt A SILT with sand ·------·-·-·----~ I Project No. T-7303-1 Client: Renton -Park Avenue, LLC !Remarks: I Project: Nantucket Short Plat - 1 o Tested 10-26-15 ! j luTested 10-26-15 o Location: TP-1 Depth: 2' ·1ii1:. Tested 10-26-15 o Location: Tl'-1 Depth: 8' A Location: TP-2 Depth: 4.5' lf"'--""--~~~----''-=""-'~-~----------------1' Terra Associates, Inc. jl __ .. _J Figure Kirkland WA Tested By: FQ ,%Clay ' 3.34 AASHTO 8 Particle Size Distribution Report 100 ! 90 ' 80 70 r O'. w 60 }··· ~·- z u:: i I-50 ·I z w ' I t) O'. w 40 , t''' Q_ 30 ' ... 20 .. 10 . I I G ' i I I I , ' I I I I I ' : i I I l I l. ... ' '. ' ' ' 100 i' Ii I ' i I '! I. . i .,.. ~ I i ' ' I I I I I ;I I ;1 ' ' I I I .. ..1. I I I I I .. I I I I I I i I I ! I '· II I I II I I lt . j__ :... ! ... 11 I I I I ---·-· ·"L. I I I 10 I . if i I I u . , ' ! ··-· .,J ... •.•.. ' ' ------~ '' ...... I i I I i ' i i . T I ' I I ,. . ' ' I " r -i '' .. .. ,. .. .. ... ! ' ' I I i . ........... I I i I . ' . .... ·T i I ' ' I , ,!I,-,. I l , :;1 i'.i i i I I i . i i 0.1 0.01 GRAIN SIZE -mm. % Stonesj %+3" %Gravel j %Sand I Fine iV. Crs. Crs~ Med. Fine _ Y: Fin_~ Crs. t1;,, Silt Fine 6.3 Coarse Medium 3.1 J 3.6 28.4 46.8 0 0.0 0.0 0.0 LL CJ SAl\lD with silt CJ SAND with silt 6 S,\!\D wilh silt 0.0 PL 2.2 Pas 0.7828 l.1694 2.9563 4.5 t'" 4.2 t JJ.3 36.8 28.1 16.l i 35.7 20.} 7.1 D50 Dao. ..... 0.4325 0.3314 0.5590 !.2451 0.3879 0.8261 Material Description -··-,·---·------------.--------· I Project No. T-7303-! Client: Renton. Park Avenue, LLC !Project: l\lantuckel Short Plat ID Location: TP-2 Depth: 7' c Location: TP-J Depth: 7' ,,:, Location: TP-4 Depth: I 0.5 Terra Associates, Inc. 8,8 4.0 i D15 r i 0.2584 0.2166 0.3889 .D.10. 0.2227 0.1799 0.2131 7.0 l .27 2.!5 uses SP-SM SP-SM SW-SM I ·:'Remarks: II ll<)Tcs\c<l J0-26-lS I !jnTcstcd I0-26-15 ''r,, rested 10-26-15 \i I 1 -.. . . . " .. . ... 0.001 %Clay _Cu 2.23 3.67 7.01 AASHTO Kirkland WA Figura 9 Tested By: FQ ~c,bert_M .. Pride, J,LC November 7, 2014 Mr. Darrell Offe Offe Engineers 13932 SE 159th Place Renton, WA 98058 Re: Geotechnical Recommendations Proposed Residential Development 2800 Park Avenue North Renton, Washington Dear Mr. Offe, Consultin~_neer This report provides recommendations for onsite storm water infiltration on this proposed nine lot subdivision located on the northeast corner of Park Avenue and North 28th Street in Renton. It is understood that a detention tank is also being proposed for contaminated water storage on the west side of the project site. Site and Subsurface Conditions This rectangular property covers nearly two acres ofland that has a gentle slope from the east to west side. An existing residence is situated on this property near the south end that will be removed as part of this new development. A new roadway will extend toward the north end of this development to provide access to these new residences. Geologic research of mapping by Booth in 2007 shows this area of Renton is underlain by recessional deposits consisting of silty sands, sands and gravels (Qvr). Field exploration consisted of excavating four exploratory test pits and documenting subsoil conditions in an open excavation located south of Lot #1. Summary logs of these test pits are described below and their locations are shown on Drawing No. 1: TP-1 Located on Lot 2 at the west end o.o to 1.0ft Topsoil -Silty Sand; dark brown, moist, loose; 1.0 to :J.5ft Silty Sand; light brown, moist, medium dense; 3.5 to 8.oft Sand with gravel; light brown, moist, medium dense; no groundwater encountered; TP-2 Located at south end of Lot 3 o.o to 1.3ft Topsoil -Silty Sand; dark brown, moist, loose; 1.3 to5.oft Sandy Gravel; light brown, moist, medium dense to dense; no groundwater encountered; TP-3 Located on Lot 2 at the east end o,o to 0.9ft. Topsoil -Silty Sand; dark brown, moist, loose; 0.9 to 3.0ft Silty Sand; light brown, moist, medium dense; :3.0 to 7.5ft Sandy Gravel; light brown, moist, dense; no seepage; Robert M. Pride, LLC 13203 Holmes Point Drive NE Page 1 Kirkland, WA 98034 RECEIPT EG00050972 BILLING CONTACT MUNDY JO HOLDINGS LLC 2800 156 Ave SE , Suite 120 Bellevue, WA 98007 REFERENCE NUMBER FEE NAME LUA16-000217 PLAN ~ Modification Technolo~" Fee Printed On: September 28, 2016 Prepared By: Holly Powers --------Renton® 1055 S Grady Way, Renton, WA 98057 TRANSACTION TYPE Fee Payment Fee Pavment Transaction Date: March 18, 2016 PAYMENT METHOD Check ##1356 Check ##1356 SUB TOTAL TOTAL AMOUNT PAID $150.00 $4.50 $154.50 $154.50 Page 1 of 1