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HomeMy WebLinkAboutSWP272171 (2) TRANSMITTAL SHEET A U G 0 = 1995 Ci i OF RENTON DAMES & MOORE, Inc. Engineering Dept. 500 Market Place Tower, 2025 First Avenue, Seattle, WA 98121 Phone (206) 728-0744 FAX (206) 727-3350 Date: 8/3/95 To: City of Renton Planning/Building/Public Your Order No. Works Dept. Municipal Bldg Our Job No. 699-017-016 Renton, WA 98055 Attention: Mr. Scott Woodbury Subject: Revised Geotechnical Report - Wetland Mitigation Banking Sites We are sending you via regular mail the following: 1. Report of Geotechnical Investigation and Consultation - Revision ##1 , dated 8/2/95. (3 copies) 2. Typical specifications for HDPE pond liner. (1 copy) This is for These are for your use. No. of Copies Submitted: (see above) Copies to: Dames & Moore, Inc. W. Martin McCabe, PE Project Manager CITY OF RENTON PLANNING/BUILDING/PUBLIC WORKS MEMORANDUM DATE: October 10, 1995 TO: Lisa Stephens FROM: Scott Woodbury S�,} SUBJECT: DAMES & MOORE CONTRACT AGREEMENT CAG-94-139 NOTICE OF CONTRACT CLOSEOUT AND TRANSMITTAL OF PRODUCTS Attached for your file regarding the above-referenced project is a copy of the Report of Geotechnical Investigation, Revision 1, Wetland Mitigation Banking Sites, Renton, WA by Dames & Moore dated August 2, 1995. Also attached for the file are copies of two faxes dated 9/27/95 and 10/9/95 that provide additional clarification of seepage loss calculations and assumptions used in the report. Also attached for your file is a copy of a letter to Dames & Moore stating that the project is completed. Thank you for your assistance. If you have any questions, please contact me at X-5547. U:65119:95-006:SW attachments cc: Ron Straka y CITY OF RENTON Planning/Building/Public Works Department Earl Clymer,Mayor Gregg Zimmerman P.E.,Administrator October 12, 1995 W. Martin McCabe, P.E., Associate Dames & Moore 500 Market Place Tower 2025 First Avenue Seattle, WA 98121 SUBJECT: CITY OF RENTON CONTRACT CAG-94-139 (DAMES & MOORE JOB NO. 699-017-016) NOTICE OF PROJECT COMPLETION Dear Mr. McCabe: Thank you for your services in completing a geotechnical investigation of the wetland mitigation banking site in Renton and submitting a report of your findings. This letter is your notification that the project has been completed. Final payment for the full contract amount has been processed and the account closed. Thank you for your work and the efforts of others who contributed to the project. If you have any questions, please call me at (206) 277-5547. Sincerely, GJ' 'U' Scott Woodbury, P.E., Pr ect Manager Surface Water Utility H:DOCS:95-870:SW:ps CC: Ron Straka City Clerk file 200 Mill Avenue South - Renton,Washington 98055 ,► SENT BY: 9-27-93 : 8:40AM DAMES & MOORE SEA- 206 235 2.541:t 1/ 4 y-a 7-Y,Y D s & MOORE, INC• To jc� Uc�tq Namc: u.rV _ Company: C�'� Q� I Telephone Number; FAX Number: 235 2541 _ na te;Fmm j 21 5 Mime: Oar�y MCC . Numbu of Place(including cover sheet): Charge Number: `C)1 i Messaec ��� .si 'z�A Q � �. - _Q��s,-r -� Engineering Excellence and Environmental Responsibility Dames S? Moore A serving clients for move than 50 yew-N OUR SERVICES INCLUDE: • Geotedulical Engineering • Remedial Investigations/Feasibility Studies • Environmental Engineering • Lnvironmenlal Studies • Hazardous/Toxic/Kadinacfive Waste Management • Wetlands Evaluation •Water Resouvoes Develupment • Earthquake Engineering •Solid Waste Management • Engineering Dvsib-it Services • rermitdng • Risk Assessment/Toxicology • Regulatory Compliance • Air(Quality Management • Property Transfer Asscssmcnts • Dispersion Mudeling • Industrial Hygiene • Aquatic Ecology/Fishcrics • Asbestos Assessments Dames& Moore-500 Market Place Tower• 2025 First Avenue•Seattle, WA 96121 (206)726-0744• FAX(206)727-3350- Please Note New FAX Number SENT BY: 9-27-95 8:41AM DAMES & MOORE SEAS 206 235 2541:t 2/ 4 + FILE SUBJECT r SHEET OF— X � o r ►- 1 W W Q 4 z > \ Ui ti+ L l � L h'L�R C w.. / /' c fs w c o W r j T ` R) U U I t DAMES &MOORE �e5.1(12i0n1 l'IitNIED IN U.S A. SENT BY: 9-27-95 8:41AM DAMES & MOORE SEA- 206 235 2541:t 3/ 4 FILE SUBJECT_. SHEET ?—OF— I I 0 0 ly 111 � U 0 LL l l W W N / W } Y w m to 7;7f n` r m a W oo Y � z w n Y r n f3 DAMES.� MVUxh: �5.1(12/dfJ I'HJNItD IN 11,$,A. -• .. �� � 1 SENT BY: 9-27-93 8:41AM DAMES & MOORE SEA- 206 233 2541:t 4/ 4 + ' FILE =c/ 7--,,t 6 SUBJECT _ SHEET-S—OF— O 0 ,y 61 O 0 ajj- 3 9� �r W W ► 16. Q I N W N Y v\ OI O m m 4/- 12-0 W 1- - I � mW 00 Y V > w a r = o S E Zv oc DAMES & MOORE 3�5.1 117106J PRINYCU IN U.S.A. � 2-O „ I,-/ 7 SENT BY: 10- 9-95 :12:50PM DAMES & MOORE SEA- 206 235 2541:t 1/ 7 A)—�"y� DAMES & MOORE, INC. To SCzy . �OO��urY (mum an Ct� a� �Z�Y�o`\ No _. _ . p y: - __.._. Telephone Number: PAX Number: 2'3 5 — 25 Ar Dn re: ko - 4— gS From l Name: Number of Pages(including cover sheet): Charge Number. r Engineering Excellence and �--� Environmental Responsibility Dames & Moore servvig clients for more than 50 years OUR SERVICES INCLUDE: • Ccotechnical Ensineering • RomMial Investigations/Feasibility Studies • Envirurtrnenta�Engineering, • Environmental Studies • Hazardous/Toxic/RadiciactivP Waste Management • We.t]Ands Evaluation • Water Resources Development • Earthquake EnKillmring • Solid Waste Management • Engineering design Services • Permitting • Risk Asseaament/'Toxicology • Regulatory Compliance • Air Quality Manageriterit • Property Transfer Assessments • Dispersion Modeling • In Hygiene • Aquatic Ecology/FSsheries, • Asbestos Assessments Damas &Moore•500 Market Place Tower.2025 First Avanue•Saattle, WA 98121 (206)728-0744• FAX(206)727-3350- Please Note New FAX Number SENT BY: 10- 9-93 :12:51FNI DAMES & MOORE SEA- 206 235 2541:t 21 7 DAMES & MOORE MEMORANDLN TO: Scott Woodbury, City of Renton FROM. Martin McCabc {,✓ �,�,y� DATE: 10/6/95 SUBJECT: Seepage Losscs Wetland Mitigation Danking Sitcs Renton, WA Dames & Moore Job # 00699-017-016 After further review of our estimates of seepage losses for tic case of a membrane liner, it appears that two somewhat compensating errors were made on page 2 of our calculations. The first, as you pointed out, is that the thickness of a 20 mil membratu: (the minimum thickness recommended) is .052 cm and not the 0.2 cm used in the analysis. Sruundly, the "permeability" value for the membrane was higher in our calculations than would be cstimated using currently known relationships for vapor and water permeation through this type of material. A more acmirate value is about 5 x 10r"cm/second, assuming that the membrane consists of PVC. This calculation is based on the approach used by R,M. Koemor(Designing With Oeosyiithedcs, 3rd Fitition, 1994). A copy of the method from the book is attached. This conversion is necessary because flow through the membrane is not controlled by Darcy's Law. Our analysis method used a time honored method of calculating the equivalent permeability of two materials in series. Recent research has produced a more accurate method of estimating tic flow rate through either a single membrane or a membrane+soil layer liner system. The attached Table 8.3 from Sharma & Lewis(Waste Contaiment Systems, Waste Stabilization, and Landfills: Design and Evaluation, 19M) gives some estimated leakage rates for various liner systems for various values of hydraulic. head of contained water. Note that the "permeation" value in the table means flow through a membrane with no holes. The table shows that "pernncaLion" through a 40 mil liner when the head is 10 feet is approximately 10 gallons per day per acre of liner. For comparison, the seepage loss rate presented in the Dames & Moore calculation sheet(6 gallons per minute for the entire 31 acre wetland during wet season) amounts to a loss of about 278 gallons per day per acre_ In my opinion, it would be prudent to plan for at least a tew small holes in the liner, SENT BY: 10- 9-95 :12:51PM DAMES & MOORE SEAS 206 235 2541:# 31 7 431) Chap.5:Dcoigning with C60111nurLranea The test is also performed using two different weights forcing tile. extrudate � out of the orifice: for example, one performs a test at 2.16 kg, and then the next one at 5.0 kg. T'hc tusaltillg MI values are then made tote a ratin as follow,: III i where FRR — the flow tatc rtuiu. the melt flow index under 5.0 kg weight, and j M17 = the melt flow indey tinder 2.16 kg weight. High values of FRR indicate broad molecular weight distributions, and various empirical relationship; have been proposed, 1 'c This tcst is very important in the quality control and quality assurance of ' polyethylene resins and gcomcmbrancs. i 3.1.2.4 Mass per Unit Area(Weight) The weight of a geomembranc, actually its mass per unit area but invariably called simply weight, utilizes a unit amn of a representative specimen and accurately weighs it for calculation of ounce per square yard (oz./yd.t) or grams per square meter (gIM2). The conversion between the systems of units 6 1 uz,lyd.' _ 33.9 g/nI The test is straighiforward ro perform and usually follows ASTM D1910 procedures. 5.1.2.5 Water Vapor Transmission Sincc nothing is ahsnlutely impermeable,the assessment of the relative impermeability of gcumcmbranes is an important issue. it 1s placed in thi-category of physical property tests for want of a bettci location. The test itself could use an adapted form of n geotechnical engineering test using water as the permcant; however, this would be impractical. In such a ca;e. the hydranlic heads required would be so great that leaks or failed spccirnuns would invariably result. At lower heads, long test times leading to evaporation problems would become a majtn uUstacic. Instead, a completely ditterent approach is taken whereby water vapor is used as the permcant. In the water vapor transmission (WVT) test, a test specimen is sealed over an aluminum cup with tither water or a desiccant in it, dud a controlled relative humidity difference is maintained. The ASTM test method is covered under E96.With waicr in the cup(i.e., 100%o rclative humidity) and lower relative humidity outside of it, a weight loss over time can be nnoniturcd(sec)~inure 3.1). With a desiccant in the cup(i.e.,0%relative humidity) and higher relative humidity outside of it, a weight Rain over time would he seen and appropriately monitored. The required test time varies, but is usually from 3 to 30 clays. Water vapor transmission, permeance, and permeability are then cal- culated, us shown in the following example. Exarnple: Calculate the WVT, permeanec, and perincability of a 30-mil-thick geontembrane of area 0.003 In', which re;nUed in the test data of Figure 5.1 at 80% rclative humidity diffc,euuc while at a temperature o[90`k'.(The complete problem together with other approaches is given in Lord and Koctuer (1].) SENT BY: 10- 9-95 =12:52PM DAMES & i1100RE SEAS 206 235 2541:t 4/ 7 r� 1, Geomembrone Properties and Test Methods 431 • I Ia��Ce it�, i . j r u I 1 , 4 190.55 190.50 { i 'x� 1fl0.lfi ; ab t 190 l0 n S 10 15 Time(days) I h Figure 5.1 ;Photograph of water vapor transmission test setup and resulting data for 30•mil F thick geomembrano at rolativo humidity difference of 19076 and tempomturo of VF. I Solution:'Calculations in stages using the slope of the curve in Figure S.1. (a).Water vapor transmission wvr = gx24 t .v, a where g - the weight chaugc (in giaulb), r the time interval (in hours), a - the area of specimen (in square meters). WVT = (0.12)(24) 3.08 g/m2-day (13)(24)(0,003) (b) 1'he permeance is given as WVT WVT permcancc — AP S(R, — Hz) where Al'= the vapor Pressure difference across membrane (in millimeters of mercury), S — the saturation vapor pressure at test temperature (ill tili(1ignul.rci of mercury), 'i SENT BY: 10- 9-95 :12:53PM DAMES & MOORE SEAS 206 235 2541:t 5/ 7 432 ChuN,5;Designtng with Geomembram R, — the rclativc humidity within cup, and R,, = the rclativc humidity outside cup (in cnvironnictital chamber), � perm 3.Oli cancc — = 0.120 metric perm 32 (1.00 — 0.20) y (c) Permeability = permeance x thickness = 0.120(30) = 3.6 metric perm-mils Example: �.. Using the information and data trom the prerr..ding example,calculate an equivalent hydraulic conductivity (c immunly called the permeability coefficienr) of the liner as is customarily measured in a geotcchnical engineering type of test on clay soils,, Solution: The parallel theories are Darcy's formula,q — kiA. qr— — (cm Ah lem H3Ol ( tt JJ t J z) Sec. k sec. Al cm soil A cm WVT test: __ ' cm H2O� flow((cm k 2 cm A(cm ) 1sec.� l,tcs.ure�cm-scc.-cm I1=O/cm liner cm IitiCr Thus we must now get the data of Elie Nicceding example into the proper unitc' WVT = 3.08 z9 1 m-day(ltr)(24)(W)(60) I — 3.56 x 10-9— S cmz-scc. WVT _ WVT pcttneeutc — AP S(Rt — Rz) 3.56 x 10' (32)(1.00 — 0,20) = 1.39 x 10 '° 9 cm'-sec.-mm Hg permeahility = perme.ance x liner thickness r, 1.39 x 10-10(0.030 x 2.54) i v t rr i SENT BY: 10- 9-95 :12:53PM DAMES & MOORE SEA- 206 235 2541:t 61 7 met Gooreombrunc Properties and Teat Methods 433 1.06 x 10 " g I cm'-sec.-inm Hg/cm liner i = 10.6 x 10-11 8 cmZ-sec. cni Ng/cm liner I In tcrrns of water pressure: x hydraulic conductivity = 10.6 x 10-11 8 anz-scc.-•cm Hg 13.6 water II cm liner mercury K ut - 0.78 x 10-' cm�-sec. cm Hg/em liner Now wing the density of water: ° I hydraulicconductivlty = 0.78 x 10-" E cm water cm'-sec.- l.11 g cm liner cm' t, Canceling the units out, we get a comparable k for the geomernbrane of k = 0.78 x 10`11 cm/sec. The WVT values for a number of common geomcmbranes of different thicknesses are given in Table 5.2. Of particular interest is the conversion of the 1.0 Ve-day being approximately equal to 1.0 gal./acre-day, which is the leakage r' Table 5.2 Water vapor tram mis:inn valmos after Remo(2) Gromembrone 77acknesr WYT Residu Type mil mm Qlm'-day Peron-cm ' 1'VC 11 0.7R 4.4 1.2 x 10-3 <' 20 0.52 2.9 1.4 x 10-' 30 0.76 119 1.1 x 10-' CPF, 21 0.53 0.64 0.32 y 10-1 31 0.79 0.32 0,24 x 10 = } 38 0.9Y 0.56 O i x I!1-2 CSPE 33 0.89 0.44 0.94 x 10-t FFDM 20 0.51 0.27 0.13 x 10-1 49 I.23 0.31 0.37 x 10 ' HDPt3 31 0.80 0.017 0.013 x 1(J-' 96 2.44 0.006 0 014 x 10-1 Nn)e: 1.0 g/m'-day - 1.07 gaIdure day. i SENT BY: 10- 9-95 :12:54PM DATES & MOORE SEA- 206 235 2541:t 71 7 UnmOSISILMS:UvrI(VIC-W 383 dzb scsnch is still required to understand the flow mechanisms through compncite..liners arld Iv ostirnate Iei,kagc rates. 8,2.2.4 Comparison of Liner 3ysferrr Leakage. Table 6.3 compares flow rates through a clay liner, goomembrunc liner, and a composite liner fur various liquid depths above the liner. in mating these comparisons;, it ir, importunt to renicnibei that fluw through a hole in a geomembrane liner assumes infinite_ permeability materials on both sides of the geomerubtanc, in fie)d situations, a I LC KS above the genmemhntne may be considered infinitely permeublc; howcvcr, it is unlikely that the underlying subgiade would be Infinitely per .neshlr•. The values for leakage through gcomcmbranc holes utay thcrcfure be smaller than estimated by the orifice ennAtion (8.7). Also, due to the overlying LCRS or drainage layer, ills depth of liquid above landfill base and cover liners is generally less than I foot. In t compuring the leakage rates on Table 8.3,the following observations may be made: 3 For all liquid depths above the liner,clay liners and geomernhranr liners have 4 significantly greater leakage than eouhpusile liners. This is especially true for liquid depths below I foot. .5 • For genme.mbrane liners alone, leakage due to permeation through the gwaic- mbrane may be considered negligible at the pressure,applied in most landfill b applications;however,for cunrlAisite liners permeation may form a significant portion of the overall leakage rate due to the low leakage rate through compus- ite liners. TABLE 8.,4 Comparison of Approzhnatc Le-4kage Rates Through various Types or Liners'(gallons/acre/day) Liquid depth Above Liner,h„ 3-foot-thick com L cakaRe _ 3iroud and BOhna• Type of Liner Mechanism 0.01 ft 0.1 ft l ft 10 It 100 ft Clay liltct Flow through 93 96 125 400 1 100 porous media 7t)r Geumembrane liner Permeation U,U0001 0.001 0.1 f0 30 urn leakage We Small hole 10 30 100 300 1,000 "told cundiduttb Large hole W. 1,000 3,000 10.000 30,000 Composite liner t conditions are good held NermeAtinn 0.00001 0.001 0.1 10 30 9 cracks;and that conditions surall hide 0.002 0.015 U,UI 0.9 S soil,The worst Large halt 0.002 0.02 OAS 1 9 j hrfaec, and con- Pan field Permeation 0-0(lUU1 0.01 0.1 10 30 `t nth the underly- conditions Small hole 0.01 0.08 0.6 5 40 I' !st ease and.the Large hole 0.01 0.1 0.7 6 s0 ie Ieaka c tares X 7, ' (,At j g Sourrr.-(rinmid And Bonaparte(1989b).Reproduoed by pertnisaicn of Usevicr. rf is an enormous 'Assumes a 3-it-thick clay liner with a 1 x to-'cm/s creffirirnr of permeability and a 40-mil ADPE itlo'ns results in St-nmombrane.A amsll hole hm m area of o,005 inf and a large 1NItc has su OnA of o.t6 in',One hole )usly, much re- is a>sunied per aerc. -L .f� � c h/s ,�` ►�.. f; 3,'3 ILA 2,,5y N 3>`1rtics, i.3 �� — 3t 33 f�a J G F s „t FOV ..o�o '-fie•Q Pt Gov 13 't � ����- � r^-tv'a �est� •t., i �r y i tt �s �• s � ,- � "r : •i `^ 4 -., ��- �, 1' �' \lam ) ���� - w- avcros.a, .«mrw-rr .u-•--•--�-sa�c�yTy'Fsi� 13 — ��'`��.+`+�'4 •.V� t��A�S�` `l� Dur ed Dedr' k C tos 1 � - v� ,�� _ i[ — f t 7 - REPORT OF GEOTECHNICAL INVESTIGATION REVISION 1 WETLAND MITIGATION BANKING SITES RENTON, WASHINGTON FOR CITY OF RENTON August 2, 1995 DAMES & MOORE JOB NO. 00699-017-016 DAMES & MOORE 500 MARKET PLACE TOWER, 2025 FIRST AVENUE, SEATTLE, WASHINGTON 98121 (206) 728-0744 FAX: (206) 727-3350 August 2, 1995 Mr. Scott Woodbury Planning/Building/Public Works Department City of Renton Municipal Building 200 Mill Avenue South Renton, Washington 98055 Report of a Geotechnical Investigation and Consultation Revision #1 Wetland Mitigation Banking Sites Renton, Washington for City of Renton Job No. 699-017-016 Gentlemen: We submit herewith three copies of our 'Report of Geotechnical Investigation, Revision #1, Wetland Mitigation Banking Sites, Renton, Washington." This investigation was performed according to your contract dated January 17, 1995. An earlier version of this report was submitted on March 27, 1995. City of Renton review comments were subsequently provided to Dames &Moore in your May 4, 1995, letter. Certain of these review comments were then selected by the City of Renton for incorporation into Revision #1 of the report. The recommendations in Revision #1 also reflect the clarifications provided to us regarding the concept of the wetland for Site No. 2. We appreciate the opportunity to assist you on this project. If you have any questions regarding this report, or should need further assistance, please do not hesitate to call us. Nl Yours very truly, DAMES & MOORE, INC. 23499 ; W. Martin McCabe P.E. Associate EXPIRES: Z -28-C-7 01 6\REPORTS\RENTON3.RWP 00699-017-016 TABLE OF CONTENTS Page 1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.0 SCOPE OF SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3.0 SITE CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3.1 SURFACE CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3.2 SUBSURFACE CONDITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2.1 Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2.2 Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.3 GROUNDWATER CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.0 LABORATORY TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.0 IN-SITU INFILTRATION AND LABORATORY PERMEABILITY TEST RESULTS . . . . . . 5 6.0 ENGINEERING ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.1 SEEPAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.0 EVAPORATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.0 CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1 FEASIBILITY OF WETLAND CREATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.2 WETLAND CONSTRUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.3 ONSITE SUITABLE STRUCTURAL FILL MATERIALS . . . . . . . . . . . . . . . . . . . . 8 8.4 PREPARATION OF WETLAND BOTTOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.5 PERMANENT SLOPE ANGLE . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.0 CLOSURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Appendix A - Site Exploration and Laboratory Testing 016\REP0RTS\RENT0N3.R W P 00699-017-016 DABS & MOORE REPORT OF GEOTECHNICAL INVESTIGATION WETLAND MITIGATION BANKING SITES RENTON, WASHINGTON for CITY OF RENTON 1.0 INTRODUCTION The proposed Wetland Mitigation Banking sites are located near the southern boundary of the City of Renton. A vicinity map, Plate 1, is provided at the end of this report. The wetland mitigation banking sites are engineered wetlands to be constructed for the purpose of replacement or enhancement of existing wetlands. The project includes two sites. Site 1 is about 31 acres in size and is located near the northwest corner of SW 34th Street and Oakesdale Avenue SW. Site 2 is about 14 acres and is located near the southeast corner of SW 34th Street and Oakesdale Avenue SW. We understand that the depth of the proposed wetland at Site 1 will be about 6 feet below the existing ground surface, and the depth of the proposed wetland at Site 2 will be about 10 to 12 feet below the existing ground surface. The bottom of the wetland for Site 2 is to be at the same level as the bottom of the adjacent Springbrook Creek. The current plan is to join the Site 2 wetland to Springbrook Creek using an open channel. 2.0 SCOPE OF SERVICES The purpose of this geotechnical investigation is to evaluate the feasibility of creating an engineered wetland on the two sites. Specifically, our service includes the following: 1. Exploration of soil and ground-water conditions underlying the sites by excavating five test pits on Site 1 and five test pits on Site 2. The test pits were excavated with a rubber- tired backhoe to maximum depths of up to 14 feet below current site grades. Representative samples were obtained from each soil stratum encountered in the test pits. 2. Installation of two piezometers on Site 1 and one piezometer on Site 2. The piezometers were used for monitoring of groundwater fluctuation during the exploration program. 3. Performance of three in-situ subsurface infiltration tests on each site. The tests were conducted according to King County Surface Water Design Manual. Test depths were 12 feet or less below site grade as field determined by our field engineer. 4. Laboratory testing to assess the pertinent physical characteristics of the site soils. Tests include moisture content determination (ASTM test procedure D2216), gradation (ASTM D422), compaction (ASTM D 1557), and laboratory permeability. 016\R EPORTS\RENTON3.R W P 00699-017-016 1 DAMES p MOORE 5. Evaluation of the depth, quantity, and permeability of the on-site soils to evaluate the availability and suitability of on-site soils to support wetland creation. Recommendations regarding excavation,stockpiling,placement,compaction, and other construction methods are provided. Recommendations regarding the need for a synthetic impermeable liner, including type, bedding, cover, etc., are also provided. 6. Evaluation of the suitability of the onsite soils for use as on-site or off-site fill materials. 7. Recommendation regarding site dewatering. 8. A written geotechnical report containing a test pit location plan,test pit logs, a description of subsurface conditions, and our findings and recommendations. The site explorations were coordinated by an experienced field engineer from our staff who located the test pits, obtained samples,and maintained a continuous log of each test pit. The engineer also conducted the in-situ subsurface infiltration tests. Recovered soil samples were taken to our Seattle laboratory for further examination and testing. The results of the site exploration and laboratory testing form the basis for our engineering analyses and recommendations commensurate with the scope of services described herein. 3.0 SITE CONDITIONS The sites are located in the eastern portion of Green River valley. The sites are less than 1/2 mile from the river. Most of the areas to the east of the sites are developed for commercial and industrial uses, whereas the areas to the west of the sites are undeveloped. 3.1 SURFACE CONDITIONS Site 1 has a rectangular shape and Site 2 has a triangular shape (see Plates 2 and 3). At the time of this report both sites were covered with sparse trees and patches of grass. The field exploration was conducted during the wet season. Ponded water existed in the eastern and western portions of site 1, and portions of site 2. The surface soils at both sites were wet and soft. A ditch about 5 feet wide exists near the western and northern boundaries of Site 1. The ditch is about 3 feet deep along the eastern boundary and up to 6 feet deep along the northern boundary. The ditch contained about one foot of water during our field exploration program. Ground surface elevations across the reasonably flat site typically ranged from Elevation 17 to 20, except for a local depression in the northeast corner that extended to Elevation 12 and a somewhat shallower depression extending to Elevation 15 just north of the center of the site. The topographic high point of the site at approximately Elevation 20 is located just south of the center of the site, and extends to the southern boundary. 01 6\REPORMIZENTONIR W P ,{ 00699-017-016 2 DAMES & MOORE Springbrook Creek runs parallel to the southeastern boundary of Site 2. Stream gaging information provided to us by the City of Renton indicates that the creek level was at approximately Elevation 7 at the time of our field investigation. The ground surface at the reasonably flat site dips very gently downward from about Elevation 17 in the southwest corner to about Elevation 15 in the northeast corner. The bottom of Springbrook Creek is reported to be at approximately Elevation 5. Please note that all ground surface and water level elevations in this report refer to the 1929 National Geodetic Vertical Datum (NGVD-29). 3.2 SUBSURFACE CONDITION The subsurface conditions at each site were investigated by excavation of five test pits on each site. Short-term monitoring of groundwater level was conducted using temporary piezometers installed in the test pits. Also,the in-situ infiltration rate of subsoils was tested using subsurface infiltration tests. Details of the field exploration program are presented in Appendix A. The following paragraphs present the description of the subsurface conditions at the two sites. 3.2.1 Site 1 Site 1 is covered with fill soils about 2 to 3 feet in thickness. The materials include gravel, silty sand and silt. The fill soils are underlain by alluvial deposits which include interbedded layers of silt, silty sand, and sand. Our test pits were terminated in these soils. In general, the upper 4 to 10 feet of the alluvial deposits is a soft silt, and the silt is underlain by a sand. The exception to this profile was found at the center of the site where the surface fill soil was directly underlain by a sand (see Test Pit TP-3). The different soil conditions at this test pit may be the result of the presence of a previous creek or drainage channel in this vicinity, as suggested in a 1962 topographic map of the site provided by the City of Renton. The location of this old meandering channel is shown on Plate 2 herein. The actual location may differ from that shown due to uncertainties is identifying site borders. 3.2.2 Site 2 Site 2 has a soil profile similar to that of Site 1 except that the surface fill soils at Site 2 are slightly thicker - in the range of 2 to 5 feet. The fill is also underlain by alluvial soils, and the upper 4 to 10 of which is also a silt. The silt at Site 2 differs than that at Site 1 in two ways: (1) The interbedded sand layers at Site 2 are thicker, in the range about 2 to 2.5 feet in thickness, and (2) thin layers of peat are common at Site 2. 01 6\REPORTSTENTONIRWP 00699-017-016 3 DAMES & MOORE 3.3 GROUNDWATER CONDITIONS Groundwater was encountered during test pit excavation and monitored in temporary piezometers installed during the field exploration program. The measurements are presented in TABLE 1. TABLE 1. Observation of Groundwater Level Test Pit No. Time of Observation Groundwater below Approximated Groundwater Ground Surface(ft) Elevation(ft) During Excavation 5 12.5 10:45 am, 2-1-95 TP-1-Site 1 Piezometer Reading 11:15 5.5 12 am, 2-3-95 Piezometer Reading 4.5 13 7:30 am, 2-7-95 TP-3-Site 1 During Excavation 5.8 13 3:40 pm, 2-1-95 During Excavation 2 16 2:30 pm, 2-1-95 Tp-S-Site 1 Piezometer Reading 2.5 15.5 8:57 am, 2-2-95 Piezometer Reading 3.8 14.2 4:25 pm, 2-7-95 During Excavation 8 8 Tp-4-Site 2 10:20,2-7-95 Piezometer Reading 8.1 7.9 7:35, 2-8-95 Note 1. Test Pit TP-5-Site 1 was located about 30 feet from the ditch, the bottom of which was about 2 to 3 feet below the ground surface at the test pit. The ditch had about one foot of water during the excavation of the test pit. Note 2. Test Pit TP-4-Site 2 was located about 90 feet from Springbrook Creek, the bottom of which was at approximately Elevation 5 in this area(per City of Renton). The creek had about 2 to 3 feet of water during the excavation of the test pit. Note 3. All ground surface and water level elevations refer to the 1929 National Geodetic Vertical Datum (NGVD-29). Water level measurements were recorded up to 6 days following excavation of the test pits and installation of the piezometers. In general, water level measurements made on the day of piezometer installation are expected to change as the disturbed soil and ground water conditions stabilize. The water levels may rise or fall during the stabilizing period, depending on the manner in which the piezometer was installed and the nature of soil and water conditions in the vicinity. The reason for the higher ground water elevations in TP-5 -Site 1 compared with other measurements at Site 1 is not clear. Surface water collected in the nearby trench may be exerting an influence on the piezometer measurements. We would expect a more uniform ground water level across the site. Additional measurements may be required over time to clarify this situation. 016\REPORTS\RENTON3.R W P 00699-017-016 4 DAMES & MOORE 4.0 LABORATORY TESTING Representative samples were obtained during the field exploration. The samples were transported to our Seattle laboratory for further examination and testing. The laboratory tests include moisture content determinations, particle size analyses, compaction tests, and permeability tests. The moisture content test results are presented in the test pit logs,the particle size analysis and compaction test results are presented at the end of Appendix A. The permeability test results are presented in the next section. 5.0 IN-SITU INFILTRATION AND LABORATORY PERMEABILITY TEST RESULTS A total of 3 in-situ infiltration tests were conducted on each site. The purpose of the tests is to obtain an estimate of the permeability of the in-situ soils. The tests were conducted according to the method presented in the King County Surface Water Design Manual. Test results are presented in TABLE 2. A constant-head permeability test was conducted in the laboratory. The purpose of this test was to gain an estimate of the permeability of a compacted on-site silt soil. The test sample was prepared at a moisture content of 25.5%, and a dry density of 93 pounds per cubic foot (pcf). The dry density corresponds to about 93% of the maximum dry density based on the ASTM D1557 test method. The permeability test was conducted in a Standard Proctor Mold according to ASTM D2434 test procedures. The test result is also presented in TABLE 2. TABLE 2.In-situ Infiltration and Laboratory Permeability Test Results Sample Location Test Type Sample Depth(ft) Soil Type Permeability(cm/sec) TP-1-Site 1 Infiltration 10 Silt 8.0 x 10' TP-3-Site 1 Infiltration 11.6 Silty Sand 7.5 x 10' TP-5-Site 1 Infiltration 11.6 Silty Sand 1.2 x 10' TP-1-Site 2 Infiltration 5.5 Silt 5.5 x 10` TP-2-Site 2 Infiltration 8.5 Silt 2.2 x 10' TP-2-Site 2 Infiltration 8.5 Silt 6.5 x 10' TP-4-Site 1 Lab Permeability 3 Silt 2.9 x 10' 6.0 ENGINEERING ANALYSES 6.1 SEEPAGE One-dimensional seepage analyses were conducted to estimate the potential seepage loss from the bottom of the proposed engineered wetlands. The analyses assume the presence of a 6-foot-thick silt layer below the bottom of the proposed wetland at Site 1, and 3 feet thick silt layer below the bottom of the proposed wetland at Site 2. Two groundwater levels were considered in the analyses: 1) at the bottom of the 01 RREP0RTS\RENT0N3.R W P 00699-017-016 5 DAMES & MOORE wetlands, and 2) at the bottom of the silt layer. The former would simulate the average groundwater condition during wet seasons and the latter would simulate the possible groundwater condition during dry seasons. For Site 2 the dry season water level assumed for exfiltration calculation purposes is about 3 feet below the level of water typically flowing in Springbrook Creek. The actual dry season ground water levels at Site 2 may be higher. Assumptions about dry season water levels for both sites should be confirmed by measurements. The seepage analyses utilize the permeability of the silt layer estimated from the in-situ infiltration and laboratory permeability tests. The average permeability of the silt was taken as 1 x 10-5 cm/sec. A synthetic flexible membrane liner (FML) having a permeability of 1 x 10' cm/sec was also considered in the seepage analyses. Only the soil or membrane at the bottom of the wetland area was considered in the analysis, and the potential exfiltration losses from the relatively small area constituting the sloping sides of the wetlands was ignored. TABLE 3 presents the results of the seepage analyses. TABLE 3. Results of Seepage Analysis Location Seepage Loss in inchestday(gpm) Seepage Loss in inchesJday (gpm) (Without Membrane) (With Membrane) Dry Seasons Wet Seasons Dry Seasons Wet Seasons Site 1 0.4 (400) 0.2 (200) 0.01 (12) 0.005 (6) Site 2 2.9 (775) 0.9 (250) 0.07 (20) 0.04 (10) Notes: gpm=gallon per minute. Seepage loss estimates above are based on a wetland surface area of 31 acres for Site 1 and 14 acres for Site 2. The exfiltration losses (Q in gallons per minute) were assumed to be governed by Darcy's Law, and were calculated using the equation below: Q = k x i x A where k = permeability of the soil i = hydraulic gradient = hydraulic head/ flow path length A = area of bottom of wetland 7.0 EVAPORATION The evaporation loss was estimated using the published information about the mean annual lake evaporation of 24" in Seattle area (reference: Hydrologic Analysis & Design by Richard H. McCuen). 01 6\REPORTS\RENTON3.RWP 00699-017-016 6 DATES & MOORE We assume that about 80% of the annual evaporation loss occurs in the dry seasons. Based on this assumption, the estimate shows that the evaporation loss in the dry seasons is about 0.1 inches/day for both sites, or 50 gpm for Site 1, and 25 gpm for Site 2. Table 4 shows the combined seepage and evaporation losses for various conditions. TABLE 4. Combined Seepage and Evaporation Losses Location Loss inches/day(gpm) Loss in inches/day (gpm) (Without Membrane) (With Membrane) Dry Seasons Wet Seasons Dry Seasons Wet Seasons Site 1 0.5 (450) 0.2 (200) 0.11 (62) 0.005 (6) Site 2 3.0 (800) 0.9 (250) 0.17 (45) 0.04 (10) Note: gpm =gallon per minute. 8.0 CONCLUSIONS AND RECOMMENDATIONS 8.1 FEASIBILITY OF WETLAND CREATION Based on the results of our study, we are of the opinion that wetland creation at the proposed sites is feasible. However,the water loss through seepage is relatively high for both sites during the dry seasons. The necessary pool level for wetlands can be maintained through water replenishment, or reduction in seepage loss. The former will include both precipitation and hydraulic injection,the latter can be achieved using a synthetic membrane installed at the bottom of the wetlands. If an open channel connects the Site 2 wetland with Springbrook Creek,the wetland water level will be controlled by the creek water level with likely only minor influences from seepage and evaporation losses. In the event that the ground water table at Site 2 drops below the creek level, recharge of the ground water throughout the wetland area will occur by way of flow from the interconnected Springbrook Creek. A detailed hydrogeologic study in the vicinity of the site, and a detailed water budget analysis are not within the scope of this study,but should be performed to assist in the selection of a preferred option. 8.2 WETLAND CONSTRUCTION The wetland construction should be conducted in the dry season when the groundwater table is low. Our field exploration was conducted in the wet period of the year. The observed groundwater table was relatively close to the proposed wetland bottom at Site 1, and was above the proposed wetland bottom at Site 2. We believe that during the dry season the groundwater table will be at least a few feet lower than the observed levels. As such, we do not expect the need for general site dewatering at Site 1. However, dewatering using sumps may be needed at local wet areas or where zones of permeable granular soils must be overexcavated and replaced with low permeability silt and clay. 01 6\REPORTS\RENTON3.RWP 00699-017-016 7 DAMES p MOORE The need for substantial dewatering is much more likely for Site 2. A system of trench sumps will likely prove satisfactory throughout much of the site,but the presence of the nearby creek may require well point dewatering along the creek boundary. The well points should be spaced about 10 to 15 feet, and installed to a depth about 5 feet below the proposed bottom of the wetland. The actual dewatering requirements may change depending on conditions encountered during construction. Consideration should be given to diversion of storm drainage away from creek inflow points during the construction period in order to reduce seepage from the creek. The dewatering system should be designed to drop the water level 2 feet below the working ground surface. Note that seepage from trapped water in pockets of sand and granular fill soils should be expected at both sites. The water can most likely be handled by pumping from sumps. Wet soil conditions will likely present some operational problems for earthwork equipment. Use of lightweight equipment is advised when operating only a few feet above the groundwater level. A small dozer (e.g., John Deere 450) with wide tracks would be appropriate for grading and compaction. If excavating to the ground water level to remove and replace unsuitable soils, placement of a geotextile on the bottom of the excavation for stabilization purposes may be required before replacement soils are compacted. Replacement soils should be compacted as described in Section 8.4. Soils excavated from the wetland area and intended for re-use should be stockpiled in such a way that aeration and moisture content reduction can be achieved in favorable weather conditions. Stockpile surfaces should be loose or scarified to promote drying, and protection during rainfall should be provided using visqueen securely anchored over the soil. 8.3 ONSITE SUITABLE STRUCTURAL FILL MATERIALS In general, the fill soils found in the upper few feet of both sites are suitable structural fill materials, i.e., fill that is compacted to support pavements, slabs or structural members (footings), or to form stable slopes. The sand found below the surficial fill soils, for example in Test Pit TP-3-Site 1, is also suitable for structural fill. However, the sand is usually interlayered with silt. Separation of the sand from the silt will be difficult, and a predominant portion of the excavated soils from both Sites 1 and 2 will likely not be considered useable as structural fill. These soils can be dried and used as nonstructural fill for landscaping and general site grading. 8.4 PREPARATION OF WETLAND BOTTOM The preparation of wetland bottom is critical to optimal performance of the wetland. Note that our previous estimate of seepage loss is based on 6 feet of silt soil at the bottom of the wetland at Site 1 and 3 feet of silt soil at the bottom of the wetland at Site 2. The actual distribution of soils in the vertical and lateral directions cannot be accurately predicted. If a synthetic membrane is not used, the vertical continuity of low-permeability silt layers should be confirmed during construction at random locations throughout the wetland area in order to validate design assumptions. Where bottom conditions are found 01 6\REPORTS\RENTON3.RWP 00699-017-016 8 DAMES ° MOORE to consist primarily of higher permeability sandy soils, removal and replacement with low permeability soils will be required. The following paragraphs present the recommendations for the preparation with or without a synthetic membrane. Bottom with Membrane: The membrane should have a minimum 20 mil thickness and a permeability rating of 1 x 10-'cm/sec or lower. The membrane should be installed at the bottom of the excavation by an experienced contractor. Prior to membrane placement, soils at the bottom of the excavation should be cleared of any sharp or oversized particles (e.g., larger than 1 inch in maximum dimension) and tracked to an even surface. The membrane should be covered by at least one foot of lightly compacted onsite or offsite borrow soil. Gravelly soils or soil consisting of more than about 50 percent peat should not be used for the membrane cover. Details concerning anchorage, seaming and handling should be developed during the design phase. Geosynthetic clay liners (GCL) are also acceptable low permeability alternatives to an FML. The elevation of the membrane and operation water levels in the wetland should be such that unusually high ground water conditions will not cause flotation of the membrane. For Site 1 "typical" and "unusually high" levels would be considered Elevation 13 and Elevation 14,respectively. For Site 2, the typical water level may be assumed at Elevation 8, but unusually high levels could be several feet higher depending on the flow level in Springbrook Creek. Bottom without Membrane: We expect nonuniform soil conditions at the bottom of the wetlands. In order to reduce the seepage loss, any primarily sandy soils exposed at the bottom of the excavation should be overexcavated by at least 2 feet and replaced with compacted onsite silt. The compaction criteria for the silt is presented below. In the event that an insufficient amount of low permeability silt is encountered,the permeability of on-site sandy soils can be substantially reduced by mixing with powdered bentonite clay. The mixing can be performed in-place by dozer-towing of discing equipment. Mixtures of 10% to 20% bentonite would be sufficient, and would also help reduce the moisture content of the native soils. The following criteria should be used for the compaction of the silt: 1. The silt should be moisture conditioned to about 1 to 4% wet of the optimum moisture content. Our laboratory test results indicate that the optimum moisture content of the silt is 17.1% and the moisture content of the insitu silt is at least 29.8%. Hence, drying of the soil will likely be required prior to compaction. 2. The material should be placed in 6 inches lifts and compacted to a dry density that is at least 95% of the maximum dry density as determined by ASTM D1698 test method. 016\REPORTS\RENTON3.R W P 00699-017-016 9 DAMES & MOORE The wet-of-optimum moisture content is suggested so that the compacted soil will have a low permeability. 8.5 PERMANENT SLOPE ANGLE We recommend that the wetland banks be sloped to an angle no steeper than 3 horizontal to 1 vertical. At the side of the wetland that borders Springbrook Creek, the top of the slope should be at least 20 feet away from the creek bank. The purpose in maintaining this horizontal separation is to protect the wetland and liner against potential damage from several sources. One possible mode of damage could be sloughing or slides that might occur along the steep bank of the creek. Damage could also occur from high seepage flows through the soil from the creek to the wetland and accompanying piping (internal erosion of soil) or liner blow-out at highly permeable zones that may exist. The seepage-related concerns are applicable only during construction or other instances where the water level in the creek is significantly higher than that in the wetland. 9.0 CLOSURE The recommendations presented in this report are provided for design purposes and are based on soil conditions disclosed by field observations and subsurface explorations. Subsurface information presented herein does not constitute a direct or implied warranty that the soil conditions between exploration locations can be directly interpolated or extrapolated or that subsurface conditions and soil variations different from those disclosed by the explorations will not be revealed. The recommendations outlined in this report are based on the assumption that the proposed plan is consistent with that shown on Plate 1 and the description provided in this report. If, during construction, subsurface conditions different from those disclosed by the exploration borings are observed, we should be advised at once so that we can review these conditions, and if necessary, reconsider our recommendations 016\REP0RTS\RENT0N3.R W P 00699-017-016 10 DAISES & MOORE �' 11 E 5 CC � . \ ia0 YL 2 --Green . � � \ � Mitigation 2| Banking /! Si! 1 w| m [ c m - ± f . . .. m ". SW 34wS m � / 7777 /mgtn , 0 2- Banking / \ Si! 2 � / \ O ED M N Creek . Not to Scale VICINITY MAP _ Job Noboeme,s@e Wetland Mitigation DAmF-s &MooR Banking Sites PLATE 1 00699_07.CDR r — - -ri��-, T - -- - - - - - - - - - - - — - - - -TP-4 INF-3 I i PIZO-2 • 2 I I TP-3 INF-2 I I 3 TP-6 • TP-2 I � TP-1 P ZO-1 I— — — I— — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — -� LEGEND Previous Channel Location TP-3-i� Dames & Moore test pit from Aerial Survey of 1962 N City of Renton INF Indicates infiltration test performed Kroll Map No. 345 PIZO Indicates piezometer installed 0 200 400 2• Previous test pit by others TEST PIT LOCATION PLAN Scale in Feet SITE 1 _ Job No.00699-017-016 Wetland Mitigation Banking Sites DAMES &MOORE PLATE 2 0 U 0 �I m O 0 O - - - -1 I I - _ _ _ _ - _ _ _ - _ _ 1 TP-2 / INF-2 i TP-1 / I INF-1 t / TP-3 / i U) / QI � I TP-4co / PIZO-1/ as I G{e� O I /ooN- t TP-5 INF-3 / 1 � I / / I � 1 f LEGEND r TP-3-6� Dames& Moore test pit INF Indicates infiltration test performed PIZO Indicates piezometer installed N 0 200 400 TEST PIT LOCATION PLAN Scale in Feet SITE 2 _ Job No.00699-017-016 Wetland Mitigation DAMES &MOORE Banking Sites PLATE 3 A F E �; [: iC A APPENDIX A SITE EXPLORATION AND LABORATORY TESTING FIELD EXPLORATION A field exploration program comprised of six test pits at Site 1 and five test pits at Site 2 was accomplished to help characterize the subsurface conditions at the sites. The locations of these.test pits are shown on the Test Pit Location Plans, Plate 2, and Plate 3. The test pits were excavated with a Case 580, Extended backhoe. Whenever possible the test pits were excavated to the maximum reach of the backhoe at about 14 feet below ground surface. A six-inch diameter PVC pipe was installed in Test Pits 1, 3, and 5 on Site 1, and in Test Pits 1, 2 and 5 on Site 2. The pipes were used to conduct subsurface infiltration tests. A one-inch diameter PVC pipe equipped with a sand pack at the bottom of the pipe was installed in Test Pits 1 and 5 on Site 1, and in Test Pit 4 on Site 2. These pipes (piezometers) were used for the monitoring of groundwater level during the field exploration program. Logs of all test pits are presented on Plates A-1 through A-11. A key to symbols used on the test pit logs is shown on Plate A- 12. All soils have been classified in accordance with the Unified Soil Classification System which is shown on Plate A-13. All ground surface elevations refer to the 1929 National Geodetic Vertical Datum(NGVD- 29). LABORATORY TESTING Soil samples recovered during the field exploration program were visually examined and classified in our laboratory and a testing program was conducted to evaluate pertinent engineering properties. Moisture content tests were performed on selected soil samples. The test results are indicated adjacent to the appropriate sample notations on the test pit logs. The gradation and compaction test results are presented in Plates A-14, and A-15. Results of a rigid permeameter, constant head permeability test are presented in Table 2 in the text of this report. 01 aREPORTS\RENTON3.R W P 00699-017-016 A-1 DAMES & MOORE TP — 1 —Site 1 00 0 Q o�:07 Surface Elevation: t17.5 GW Grayish brown fine to coarse gravel with trace of fines and occasional cobbles (moist) (fill) (medium dense) ML Grayish brown silt with trace to some fine sand (moist) (fill) (soft) 29.5 2.5 ML Gray silt with lenses of black fine to medium sand(wet) (soft) 5 r 7.5 grades very soft and wet 10 SM/SP Black fine to medium sand, trace to some fines 12.5 (wet) (medium dense) rn rn Peat visible at 14 ft 0 N Test Pit TP-1—Site 1 completed at a depth of > 14 feet on 2-1-95. Piezometer installed at a depth of 13 feet. Infiltration pipe installed at p 15 a depth of 10 feet. Groundwater encountered at a depth of 5 feet during excavation. D U) rn rn 17.5 I 0 0 o NOTE: o Groundwater encountered at a depth of 5 feet N during excavation. a D U N U 0 0 J LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-1 TP-2—Site I �v v �Q- cp Surface Elevation: t18 0 SM Yellowish brown silty fine to medium sand (moist) (loose) ML Yellowish brown silt (moist) (medium stiff) 2.5 Seepage at 4 ft 5 SP/SM Reddish brown fine to medium sand with trace to some fines (wet) (loose) Test Pit TP-2—Site 1 abandoned on 2-1-95 due to 7.5 caving at a depth of 7.0 feet. No groundwater encountered during excavation. 10 12.5 rn rn I o , N J 0 15 J N a D o) rn 17.5 i - 00 0 r� 0 0 V) T N - 0 O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-2 TP -3 —Site I Surface Elevation: t18.5 0 ..': GW Reddish brown fine to coarse gravel with trace of fines (moist) medium dense) (fill) SP/SM Gray fine to medium sand with trace to some fines 2.5 (moist) (loose) 5 'N ti•- 7.5 "Z SM Brown silty fine to medium sand 30.6% fines 32.2 (wet) (medium dense) 10 12.5 rn rn i C C%i Test Pit TP-3—Site 1 completed at a depth of 14 feet on 2-1-95. Infiltration pipe installed at a depth of 11.6 feet. 0 15 Groundwater encountered at a depth of 5.8 feet during excavation. a D Ln In O) °i 17.5 I Co 0 I M 0 V N T O O O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-3 TP -4—Site I Arc,° o� Q`� °��P Surface Elevation: t17 0 1 i I I OL Dark brown or anic silt with abundant roots oist) (topsoI (soft) SW Brown fine to coarse sand with trace of fines (moist) (fill) (loose) Q; 2.5 OL Dark brown organic silt with abundant roots 1 i (wet) (soft) (old topsoil) i I 29.8 ML Gray and brown lavers of silt with occasional roots (moist) (soft) 5 Layer (6 in) of brown medium to coarse sand and . 75 fine to coarse gravel, occasional small cobble ML Gray silt with some mottling and occasional fine roots (moist) (medium stiff 10 grades wet and soft 12.5 rn i PT�OL Peat and dark gray organic silt (wet) (soft) 0 cli Test Pit TP-4—Site 1 completed of a depth of > 14 feet on 2-1-95. No groundwater encountered during excavation. U 15 0 Cn N Cn Q' 17.5 1 co O C O Cn T O O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-4 TP-5—Site I h Q 0 Q Q- ���o o� ` Q`"� o�3Q Surface Elevation: t18 0 ML Yellowish brown silt with abundant roots (wet) (topsoil) (very soft) rades with mottling and no roots moist) (medium stiff) ML Brown fine to medium sandy silt (moist) (soft) grades with lenses of brown silty fine to medium sand (moist) (soft) 5 7.5 25.8% fines 41.5 10 SM Dark gray silty fine to medium sand (wet) (loose) Test Pit TP-5—Site 1 abandoned on 2-1-95 due to cavingg at a depth of 11 feet. Piezometer instolled at a depth of 10.5 feet. Infiltration pipe installed at a depth of 11.6 feet. 12 5 Groundwater encountered at a depth of 2 feet during excavation. rn rn I r� C N O 15 J m a N N rn °i 17.5 i a I r7 O 0 V) N 'a v rn U O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-5 _ T- 6—Site I Surface Elevation: t22 C,W Reddish brown sandy fine to coarse gravel with abundant cobbles and trace of fines ;. (moist) (dense) 5.5% fines 6.3 ¢: 2.5 . Test Pit TP-6—Site 1 completed at a depth of 3 feet on 2-1-95. 5 7.5 10 12.5 rn rn i 0 N J 15 0Cx J N N 17.5 I ro 0 I 0 O U1 N T f] O� O O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-6 TP— 1 —Site 2 , a 2� Z Surface Elevation: t16 y SP/SM Yellowish brown fine to medium sand with some fineto coarse gravel and trace of fines (wet) (fill) • ) (medium dense) seepage at 2 feet 2.5 PT Peat and wood debris (wet) ML Reddish brown sandy silt with abundant roots (moist) (medium stiff) ML Gray silt with some roots (wet) (soft) 5 SP/SM Dark gray fine to medium sand with trace to some u: 7,5 fines(wet) (loose) (medium dense) ML/OL Interbedded ray silt and dark gray organic silt (moist) (soft Test Pit TP-1—Site 2 abandoned on 2-7-95 due to 10 caving at a depth of 9.5 feet. Infiltration pipe installed at a depth of 5.5 feet. No groundwater encountered during excavation. 12.5 rn rn i 0 N J O 15 a D U In rn 17.5 Co NOTE: o No groundwater encountered during excavation. T m a O� O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-7 TP-2—Site 2 Surface Elevation: tl 6 SPASM Grayish brown fine to medium sand with roots in the upper 6 inches (wet) (very loose) (fill) ML/SM Layer of gray sandy silt and silty fine sand (moist) (fill) (stiff and medium dense) 2.5 ML Dark gray silt with some roots (wet) (very soft) 5 seepage at 6 ft 7.5 PT/OL Peat and dark grayish brown organic silt 10 (wet) (soft) Sp Black fine to medium sand, trace fines (wet) (loose) Test Pit TP-2—Site 2 abandoned on 2-7-95 at a depth of 11.5 feet due to caving. Infiltration pipe installed at a depth of 8.5 12.5 feet. No groundwater encountered during rn excavation. rn I r� C N 1 0 15 J O V) N CD D1 17.5 I 0 0 T m U O O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-8 TP -3 —Site 2 Po IZ ,D ,p Iz °�P Surface Elevation: t16 SP/SM Yellowish brown fine to medium sand with trace of =: fines and fine to coarse gravel at the surface (moist) (fill) (medium dense) 5.5% fines 14.7 ~' Maximum Dry Density 123 pcf at 10.3% 2.5 PT Wood debris and seepage at 2.5 feet. ML Reddish brown mottled fine sandy silt (moist) (possible fill) (medium stiff) ML Gray silt with some roots (moist) (soft) 5 grades mottled 16.3% fines 39.1 SP/SM Dark gray fine sand with trace to some fines 7.5 (wet) (medium dense) ML Gray silt with seams of peat (wet) (very soft) 10 SP Black fine sand with trace of fines (wet) (loose) Test Pit TP-3—Site 2 abandoned on 2-7-95 at a 12.5 depth of 12 feet due to caving. Q, No groundwater encountered during excavation. rn i M 0 N 0 15 J W a U) 0 L0 rn 17.5 Co 0 I PO 0 V) T a v 0 0 LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-9 TP-4—Site 2 Surface Elevation: t16 0 ML Reddish brown fine sandy silt with abundant roots —(moist) (topsoil) (very soft) SM Grayish brown mottled silty fine to medium sand (moist) (fill) (medium dense) 39.2% fines 33.0 2.5 grades wet ML/PT Gray silt and peat (wet) (soft) 5 Reddish brown staining around abundant root holes 7.5 SP Grayish brown fine to medium sand (moist) (loose) ML Gray silt (wet) (very soft) 10 ML Purplish brown silt with some fine sand (wet) (soft) seam of peat at 11 feet t' SP Black fine to medium sand (wet) (medium dense) 12.5 Test Pit TP-4—Site 2 abandoned on 2-7-95 at a rn depth of 12.5 feet due to caving. Peizometer I installed at a depth of 12 feet. Groundwater encountered at a depth of 8 feet 0 during excavation. N J p 15 J O CL Co O1 rn 17.5 O O V) N U 0 O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-10 TP -5 —Site 2 ka- Surface Elevation: t17 0 ML Dark brown silt with abundant roots et) (topsoil) (very soft) SM Dark brown fine sand with some silt (moist) (loose) (possible fill) 20.9% fines 27.4 2.5 seepage at 3 feet 5 ML Dark ray silt with occasional wood debris (wet) TSOOft) 75 10 grades with lenses of reddish brown silt at 1 feet (moist) (medium stiff) ;« SP Black fine sand, trace fines (moist) (loose) 12.5CT Test Pit TP-5—Site 2 completed at a depth o= 14 feet on 2-7-95. Infiltration pipe installed a depth of 8.5 feet below ground surface. 0 15 No groundwater encountered during excavation a N U) Q 17.5 d 0 O T U O O O LOG OF TEST PIT Dames & Moore Job No. 00699-017-016 PLATE A-11 KEY: Indicates depth of grabbed samples. NOTE: The discussion in this report is necessary for a proper understanding of the nature of the subsurface materials. KEY Dames & Moore Job No. 00699-017-016 PLATE A-12 Major Divisions Graphic Letter Symbol Symbol Typical Descriptions "P``Q Well-Graded Gravels, Q GW Gravel-Sand Mixtures, Gravel and Clean Gravels Little or no Fines Gravelly Soils (little or no fines) 0 O Poorly-Graded Gravels, O 0 GP Gravel-Sand Mixtures, Coarse Grained 0 o Little or no Fines Soils Silty Gravels, GM Gravel-Sand-Silt Mixtures More than 50% of Gravels with Fines Coarse Fraction (appreciable amount Retained on of fines) Clayey Gravels, No. 4 Sieve GC Gravel-Sand-Clay Mixtures a a Well-Graded Sands, 4 , V 4 SW Gravelly Sands, Sand Clean Sand a°v Little or no Fines and (little or no fines) Sandy Soils Poorly-Graded Sands, More than 50% SP Gravelly Sands, of Material is Little or no Fines Larger than No. 200 Sieve Size Silty Sands, More than 50% of , SM SandZIt Mixtures Coarse Fraction Sands with Fines Coarse Passing through (appreciable amount ]it No. 4 Sieve of fines) Clayey Sands, SC Sand-Gay Mixtures Inorganic Silts and Very Fine Sands, M L, Rock Flour, Silty or Clayey Fine Sands or Clayey Silts with Slight Plasticity Fine Grained Silts Liquid Limit Inorganic Gays of Low to Medium Soils and Less than 50 CL Plasticity, Gravelly Clays, Sandy Clays, Clays Silty Gays, Lean Clays. ' I Organic Silts and Organic QL Silty Gays of Low Plasticity Inorganic Silts, Micaceous or MH Diatomaceous Fine Sand or Silty Soils More than 501% of Material is Salts Liquid Limit Inorganic Gays of High Smaller than and Greater than 50 CH Plasticity, Fat Clays No. 200 Sieve Size Clays Organic Clays of Medium to OH High Plasticity, Organic Silts Peat, Humus, Swamp Soils Highly Organic Soil PT with High Organic Contents Note: Dual symbols are used to indicate borderline soil classifications. 0 Unified Soil Classification System Dames & Moore PLATE A-13 GRAVEL SAND COBBLES SILT OR CLAY Coarse Fine Coa. Medium Fine U.S.Standard Sieve Size in Inches U.S.Standard Sieve Numbers I Hydrometer 3 3/4 3/8 4 10 20 40 100 200 100 80 - --- -- — 60 — --- -- PASSING BY WEIGHT 40 20 0 II iiii i ii ii IIii i � 1 00 100 1 1 01 01 GRAIN SIZE (mm) i GRAIN SIZE DISTR113UTIO SYMBOL BORING DEPTH DESCRIPTION % % NO. (ft) GRAVEL SAND FINES 0 TP-6-Site 1 0-3 ft Fine to coarse sandy gravel 62.8 31.6 5.6 TP-3-Site 2 1.5 ft Fine to medium sand 5.0 89.5 5.5 REMARKS: 03-24-1995 Wetlands Mitigation Banking Sites DAMES & MOOR E JOB N0.00699-017-016 PLATE A-14 r COMPACTION TEST 150 140 130 ZERO Al, VOID R TIO 120 DRY DENSITY (Pco 110 100 90 80 70 0 10 20 30 40 MOISTURE CONTENT(%) SYMBOL SAMPLE DEPTH DESCRIPTION TEST OPTIMUM LOCATION (ft) METHOD MOISTURE(%) O TP-4-Site 1 4 Gray and brown silt D1557A 17.1 f TP-6-Site 1 0-3 Reddish brown fine to coarse sandy gravel D1557C 8.1 TP-3-Site 2 1.5 Yellowish brown flne to medium sand D1557A 10.3 REMARKS: 03-09-1995 Wetlands Mitigation Banking Sites DAMES & MOORE JOB NO. 00699-0 1 7-0 1 6 PLATE A-15 s, `% CITY OF RENTON Planning/Building/Public Works Department Earl Clymer, Mayor 6/i?/Fr FAX TRANSMITTAL MEMO Not paaea 3 m�C N t SCOIT woo 06U May 4, 1995 W. Martin McCabe, P.E., Associate r Dames & Moore A7^Vi T44 500 Market Place Tower 2025 First Avenue Seattle, WA 98121 10 P°2 7,a tj:r To ADD 4 TP i,J -rAk SUBJECT: CITY OF RENTON CONTRACT CAG-94-139 C�0CvI>,R6,161C4 gUESr�u►JS (DAMES & MOORE JOB NO. 699-017-016) REVIEW COMMENTS TO MARCH 27, 1995 REPORT A7_ 277 -5. 5Y7, Dear Mr. McCabe: yl4att Following are my review comments regarding the above-referenced report. Other miscellaneous comments are included in the attached pages from the March 27, 1995 report. PG Z, 8 VkC-0-ssARH Faf, iP.f 6(!.r Soil Logs TP-3 on Site 1 was probably located where an old Green River meander is situated. This should be confirmed and discussed in the report. I suspect this is the case because the soii qil profile is so unlike the other test pits on Site 1. The 1962 topographic map that I provided to Dames & Moore prior to start of the work shows the location of the old meander. The N�, depths of the old meander is unclear from the 1962 topo because only 5 foot contours were po►� mapped. Af- Z-CTS PCB 3 The soil logs and report text should note that elevations are approximate and based on gy available topographic maps on the vertical datum NGVD 29 provided by the City. PCB 3 76 r^130C rl�j ©A fl s S g 5 'n CrAAcKt '5vj coN. gyrate Surface Conditions This section should include a discussion of the general site topography. The 1980 Corps of Engineers topo for Site 1 and the 1992 ALTA/ACSM survey for Site 2 provided to Dames & Moore are sufficient for this purpose, except for identifying the location and size of the approximately 4-foot high mound on the southern boundary of Site 1, which is not shown in the Corps topo. N-�- ^"e-cGrlo Groundwater Conditions Based on my discussion with Dames & Moore's C. J. Shin, silty soils can draw water upward in the soil column from the groundwater table by capillary action. Therefore, the ')nn Mill AvannP Cniith - RPntnn Wnchinntnn QR01SS W. Martin McCabe, Dames & Moore Page 2 seepage encountered in silty soil during excavation may not have been the actual groundwater level. Including the location of the observed seepage in silty soil in Table 1, Observation of Groundwater-Level;--as-the approximate groundwater level may. not be appropriate.rreportedto have been particularly t ele a not iceable o during Texcavation P-5 on 't groundwatere 1 were the and several days later was Nr�h measured in the piezometer at elevation 14.2. 10 I Additionally, the data for TP-1 and TP-5 seem to be conflicting in that the water level rose about 1-foot in TP-1 from„2/31 5,Jo Z�7/.95 while the water level dropped about 1-foot in TP-5 from 2/2/95 to 2/7/95. Based on the fact that the gas main was ruptured on 2/2/95 at TP-1 while re-excavating the test pit to install the piezometer, I believe the piezometer was not installed until the morning of 2/3/95 at the earliest. Maybe the water had not had sufficient �.g time to stabilized when the reading was made in TP-1 at 11.15 am on 2/3/95 which may be r'pa why the water level rose about 1-foot by the 2/7/95 reading. More interpretation of the data (f,r° is needed to address these issues. Interpolating between the stream gaging stations at SW 27th Street (about elev. 6) and SW 43rd Street (about elev. 8), the water level adjacent to Site 2 was approximately elevation 7 /vb'f on 2/7/95 when TP-4 on Site 2 was excavated. This is near typical winter baseflow Nv,SS elevation based on interpolation from the continuous water level records from the SW 27th and SW 43rd stations. Seepage The report should include a discussion of the sensitivity of the results to changes in the FIX �kw underlying assumptions, such as the thickness and permeability of the silt layer. Table 2 ��tO Ax shows a two orders of magnitude difference in the permeability of the silt layers tested. The W assumed permeability of the silt in the seepage analysis is not cited. 'Po p�,,o i'„ok able 3 or the text of the report does not include the assumed area used in determining the v Y" seepage loss, whether it is per acre, for the entire site, or something else. I believe it is the entire site area. Listing of the assumed area in the document is needed. N��fSSi k Evaporation fob It is not mentioned whether evaporation loss from soil is comparable to lake evaporation. This should be clarified. Whether or not it is comparable, it is apparent that the seepage Elosses are the predominate factor for the without membrane case, especially for Site 2. Mir Fon f4ro" i WUUI'd L.(GE f/¢Rf.tt Wetland Construction The report states that during the dry season it is believed that the groundwater table will be Not spin' at least a few feet lower than observed levels. However, it is unclear exactly what water �,('0 level below the proposed bottom of excavation is acceptable for operating mechanical FUF equipment, especially if over excavation is needed to install and compact an impermeable �V, soil layer or place a synthetic liner on compacted soil. Also, even if the water table is below the proposed excavation, will the water content of the on-site silts be similar to that U�g.v encountered in the test pits this winter? This should be addressed in the report in addition to what equipment is or is not classified as lightweight. W. Martin McCabe, Dames & Moore Page 3 On-site Suitable Structural Fill Materials /To assist in estimating the cost of soil excavation, placement, and recompaction either on- site or on a separate fill site, it would be helpful if the report discussed anticipated expansion and shrinkage effects and recommended handling and compaction methods for the different 0 �,x soils encountered on the sites. The report should also address if the soil must be dried U�.�L-° before placement and compaction and if so what drying methods are recommended. ✓`�'J� What are the possible uses of the soils that are not usable as structural fill? s �or►'40& Preparation of Wetland Bottom IX If on-site soil is to be used a liner material, how should the material be temporarily OK stockpiled? I assume that the stockpiles should be covered during wet weather. If possible, it would be helpful if the consultant would provide a sample membrane installation and subgrade preparation construction specification. ,,,Permanent Slope Angle �y, Differential water levels between the creek and the wetland will not be significant c�ris considering that the wetland will have an open connection to the creek. It is unclear why the top of the slope at the wetland side of Springbrook Creek should be at least 50 feet away Rip from the creek bank. Please address the above comments and resubmit two original reports with the revisions. I appreciate the quality of work that was done on this project and C. J. Shin's consistent efforts to keep me informed of the project as the work progressed. have received an invoice dated April 28, 1995 in the amount of $3,291.38, bringing the total invoiced to $9,899.69. This is $198.98 over the approved contract amount of $9,700.71. Final payment for that portion of the April 28, 1995 invoice that brings the total payment to $9,700.71 will be processed once the final report is received. Thank you for your assistance. If you have any questions, please call me at 277-5547. Sincerely, Scott Woodbury, P.E., P7r Manager Surface Water Utility H:DOCS:95-389:SW:ps Enclosures CC: Ron Straka ��i{� �= CITY OF RENTON "LL Planning/Building/Public Works Department Earl Clymer, Mayor bA� W/3#,r t)AVE May 4, 1995 /At/o RT/a1 Tv /„jC.0 uoF w/fly W. Martin McCabe, P.E., Associate -7#6 W04-. 7A1 "TC S'Lf&uk0 Dames & Moore /V7 AA,U 500 Market Place Tower 2025 First Avenue Seattle, WA 98121 T/), 7v e��_gr PAUkii4t, SUBJECT: CITY OF RENTON CONTRACT CAG-94-139 T (DAMES 8, MOORE JOB NO. 699-017-016) REVIEW COMMENTS TO MARCH 27, 1995 REPORT /k'AcC ARf A-n.p Dear Mr. McCabe: AvPoS,/ -7 4jr A e_t61­1-T)vA rJa,'gi✓f 4 LZ_0r- rk-- Following are my review comments regarding the above-referenced report. Other 1. c.,rtut, miscellaneous comments are included in the attached pages from the March 27, 1995 X-,t Fa/L }¢ report. ?'G Z/ 8 k<-'-SsA 2H Fars W666 - S v/0YI-4 on . Soil Logs fc,10 TP-3 on Site 1 was probably located where an old Green River meander is situated. This should be confirmed and discussed in the report. I suspect this is the case because the soil qi, profile is so unlike the other test pits on Site 1. The 1962 topographic map that I provided to Yuk corcv G�55 ' Dames & Moore prior to start of the work shows the location of the old meander. The N� depths of the old meander is unclear from the 1962 topo because only 5 foot contours were mapped. af-S P(, 3 51 The soil logs and report text should note that elevations are approximate and based on 5 available topographic maps on the vertical datum NGVD 29 provided by the City. PCB 3 r6 ?�r�L ri 5u#3Slicr)OA. rot-tr Surface Conditions This section should include a discussion of the general site topography. The 1980 Corps of Engineers topo for Site 1 and the 1992 ALTA/ACSM survey for Site 2 provided to Dames & Moore are sufficient for this purpose, except for identifying the location and size of the approximately 4-foot high mound on the southern boundary of Site 1, which is not shown in the Corps topo. N-)- F-� /2-i Groundwater Conditions Based on my discussion with Dames & Moore's C. J. Shin, silty soils can draw water upward in the soil column from the groundwater table by capillary action. Therefore, the W. Martin McCabe, Dames & Moore Page 2 seepage encountered in silty soil during excavation may not have been the actual groundwater level. Including the location of the observed seepage in silty soil in Table 1, Observation of Groundwater Level, as the approximate groundwater level may. not be l�SrggP� appropriate.rreportedto have been at elevatcularly ion not iceable excavationduring 't and se eral groundwater days latere 1 were th r-d' measured in the piezometer at elevation 14.2. ° Additionally, the data for TP-1 and TP-5 seem to be conflicting in that the water level rose about 1-foot in TP-1 from 2/3/95 to 2/7/95 while the water level dropped about 1-foot in TP-5 from 2/2/95 to 2/7/95. Based on the fact that the gas main was ruptured on 2/2/95 at TP-1 while re-excavating the test pit to install the piezometer, I believe the piezometer was not � ^nstalled until the morning of 2/3/95 at the earliest. Maybe the water had not had sufficient f time to stabilized when the reading was made in TP-1 at 11:15 am on 2/3/95 which may be F°h why the water level rose about 1-foot by the 2/7/95 reading. More interpretation of the data (fir° is needed to address these issues. Interpolating between the stream gaging stations at SW 27th Street (about elev. 6) and SW 43rd Street (about elev. 8), the water level adjacent to Site 2 was approximately elevation 7 Nbf on 2/7/95 when TP-4 on Site 2 was excavated. This is near typical winter baseflow N�L�s elevation based on interpolation from the continuous water level records from the SW 27th and SW 43rd stations. Seepage The report should include a discussion of the sensitivity of the results to changes in the WX ��, underlying assumptions, such as the thickness and permeability of the silt layer. Table 2 rt shows a two orders of magnitude difference in the permeability of the silt layers tested. The assumed permeability of the silt in the seepage analysis is not cited. V�pvy able 3 or the text of the report does not include the assumed area used in determining the Vh�hy,. seepage loss, whether it is per acre, for the entire site, or something else. I believe it is the entire site area. Listing of the assumed area in the document is needed. Nt`6SSt ',� Evaporation It is not mentioned whether evaporation loss from soil is comparable to lake evaporation. / This should be clarified. Whether or not it is comparable, it is apparent that the seepage ( losses are the predominate factor for the without membrane case, especially for Site 2. Mr n/�cFg�r, p"n Ajfof� , wovljo Wetland Construction The report states that during the dry season it is believed that the groundwater table will be Noy S�r� at least a few feet lower than observed levels. However, it is unclear exactly what water �k6 level below the proposed bottom of excavation is acceptable for operating mechanical F6t� �o�," equipment, especially if over excavation is needed to install and compact an impermeable (`tf�I/- soil layer or place a synthetic liner on compacted soil. Also, even if the water table is below V(,N� the proposed excavation, will the water content of the on-site silts be similar to that encountered in the test pits this winter? This should be addressed in the report in addition to what equipment is or is not classified as lightweight. J W. Martin McCabe, Dames & Moore Page 3 On-site Suitable Structural Fill Materials o assist in estimating the cost of soil excavation, placement, and recompaction either on- site or on a separate fill site, it would be helpful if the report discussed anticipated expansion and shrinkage effects and recommended handling and compaction methods for the different soils encountered on the sites. The report should also address if the soil must be dried before placement and compaction and if so what drying methods are recommended. ✓ 'P� What are the possible uses of the soils that are not usable as structural fill? Preparation of Wetland Bottom N.,_�If on-site soil is to be used a liner material, how should the material be temporarily 04A". stockpiled? I assume that the stockpiles should be covered during wet weather. If possible, it would be helpful if the consultant would provide a sample membrane installation and subgrade preparation construction specification. Permanent Slope Angle �yd Differential water levels between the creek and the wetland will not be significant q(ss considering that the wetland will have an open connection to the creek. It is unclear why the G Vh/ top of the slope at the wetland side of Springbrook Creek should be at least 50 feet away R0 from the creek bank. Please address the above comments and resubmit two original reports with the revisions. I appreciate the quality of work that was done on this project and C. J. Shin's consistent efforts to keep me informed of the project as the work progressed. I have received an invoice dated April 28, 1995 in the amount of $3,291.38, bringing the total invoiced to $9,899.69. This is $198.98 over the approved contract amount of $9,700.71. Final payment for that portion of the April 28, 1995 invoice that brings the total payment to $9,700.71 will be processed once the final report is received. Thank you for your assistance. If you have any questions, please call me at 277-5547. Sincerely, Scott Woodbury, P.E., Prdject Manager Surface Water Utility KDOCS:95-389:SW:ps Enclosures CC: Ron Straka % - CITY OF RENTON "LL Planning/Building/Public Works Department Earl Clymer, Mayor May 4, 1995 W. Martin McCabe, P.E., Associate Dames & Moore 500 Market Place Tower 2025 First Avenue Seattle, WA 98121 SUBJECT: CITY OF RENTON CONTRACT CAG-94-139 (DAMES & MOORE JOB NO. 699-017-016) REVIEW COMMENTS TO MARCH 27, 1995 REPORT Dear Mr. McCabe: Following are my review comments regarding the above-referenced report. Other miscellaneous comments are included in the attached pages from the March 27, 1995 report. Soil Logs TP-3 on Site 1 was probably located where an old Green River meander is situated. This should be confirmed and discussed in the report. I suspect this is the case because the soil profile is so unlike the other test pits on Site 1. The 1962 topographic map that I provided to Dames & Moore prior to start of the work shows the location of the old meander. The depths of the old meander is unclear from the 1962 topo because only 5 foot contours were mapped. The soil logs and report text should note that elevations are approximate and based on available topographic maps on the vertical datum NGVD 29 provided by the City. Surface Conditions This section should include a discussion of the general site topography. The 1980 Corps of Engineers topo for Site 1 and the 1992 ALTA/ACSM survey for Site 2 provided to Dames & Moore are sufficient for this purpose, except for identifying the location and size of the approximately 4-foot high mound on the southern boundary of Site 1, which is not shown in the Corps topo. Groundwater Conditions Based on my discussion with Dames & Moore's C. J. Shin, silty soils can draw water upward in the soil column from the groundwater table by capillary action. Therefore, the 200 Mill Avenue South - Renton, Washington 98055 r W. Martin McCabe, Dames & Moore Page 2 seepage encountered in silty soil during excavation may not have been the actual groundwater level. Including the location of the observed seepage in silty soil in Table 1, Observation of Groundwater Level, as the approximate groundwater level may not be appropriate. This is particularly noticeable for TP-5 on Site 1 were the groundwater is reported to have been at elevation 16 during excavation and several days later was measured in the piezometer at elevation 14.2. Additionally, the data for TP-1 and TP-5 seem to be conflicting in that the water level rose about 1-foot in TP-1 from 2/3/95 to 2/7/95 while the water level dropped about 1-foot in TP-5 from 2/2/95 to 2/7/95. Based on the fact that the gas main was ruptured on 2/2/95 at TP-1 while re-excavating the test pit to install the piezometer, I believe the piezometer was not installed until the morning of 2/3/95 at the earliest. Maybe the water had not had sufficient time to stabilized when the reading was made in TP-1 at 11:15 am on 2/3/95 which may be why the water level rose about 1-foot by the 2/7/95 reading. More interpretation of the data is needed to address these issues. Interpolating between the stream gaging stations at SW 27th Street (about elev. 6) and SW 43rd Street (about elev. 8), the water level adjacent to Site 2 was approximately elevation 7 on 2/7/95 when TP-4 on Site 2 was excavated. This is near typical winter baseflow elevation based on interpolation from the continuous water level records from the SW 27th and SW 43rd stations. Seepage The report should include a discussion of the sensitivity of the results to changes in the underlying assumptions, such as the thickness and permeability of the silt layer. Table 2 shows a two orders of magnitude difference in the permeability of the silt layers tested. The assumed permeability of the silt in the seepage analysis is not cited. Table 3 or the text of the report does not include the assumed area used in determining the seepage loss, whether it is per acre, for the entire site, or something else. I believe it is the entire site area. Listing of the assumed area in the document is needed. Evaporation It is not mentioned whether evaporation loss from soil is comparable to lake evaporation. This should be clarified. Whether or not it is comparable, it is apparent that the seepage losses are the predominate factor for the without membrane case, especially for Site 2. Wetland Construction The report states that during the dry season it is believed that the groundwater table will be at least a few feet lower than observed levels. However, it is unclear exactly what water level below the proposed bottom of excavation is acceptable for operating mechanical equipment, especially if over excavation is needed to install and compact an impermeable soil layer or place a synthetic liner on compacted soil. Also, even if the water table is below the proposed excavation, will the water content of the on-site silts be similar to that encountered in the test pits this winter? This should be addressed in the report in addition to what equipment is or is not classified as lightweight. W. Martin McCabe, Dames & Moore Page 3 On-site Suitable Structural Fill Materials To assist in estimating the cost of soil excavation, placement, and recompaction either on- site or on a separate fill site, it would be helpful if the report discussed anticipated expansion and shrinkage effects and recommended handling and compaction methods for the different soils encountered on the sites. The report should also address if the soil must be dried before placement and compaction and if so what drying methods are recommended. What are the possible uses of the soils that are not usable as structural fill? Preparation of Wetland Bottom If on-site soil is to be used a liner material, how should the material be temporarily stockpiled? I assume that the stockpiles should be covered during wet weather. If possible, it would be helpful if the consultant would provide a sample membrane installation and subgrade preparation construction specification. Permanent Slope Angle Differential water levels between the creek and the wetland will not be significant considering that the wetland will have an open connection to the creek. It is unclear why the top of the slope at the wetland side of Springbrook Creek should be at least 50 feet away from the creek bank. Please address the above comments and resubmit two original reports with the revisions. I appreciate the quality of work that was done on this project and C. J. Shin's consistent efforts to keep me informed of the project as the work progressed. I have received an invoice dated April 28, 1995 in the amount of $3,291.38, bringing the total invoiced to $9,899.69. This is $198.98 over the approved contract amount of $9,700.71. Final payment for that portion of the April 28, 1995 invoice that brings the total payment to $9,700.71 will be processed once the final report is received. Thank you for your assistance. If you have any questions, please call me at 277-5547. Sincerely, Scott Woodbury, P.E., Prct Manager Surface Water Utility H:D0CS:95-389:SW:ps Enclosures CC: Ron Straka U god s,c,fi, CITY OF RENTON 9 PLANNING/BUILDING/PUBLIC WORKS*�"t MEMORANDUMS DATE: March 30, 1995 TO: File FROM: Scott Woodbury SUBJECT: PRELIMINARY COMMENTS TO DAMES & MOORE'S DRAFT GEOTECHNICAL INVESTIGATION REPORT FOR THE WETLAND MITIGATION BANK SITES Following are preliminary comments to the above-referenced report dated 3/27/95. Other miscellaneous comments are included in the text of the report. Soil Logs I suggest that the logs include identifiers for each sample noted as to whether or not a test was conducted using the sample, and if so, what test(s). TP-3 on Site 1 was probably located where an old Green River meander is situated. This should be confirmed and discussed in the report. I suspect this is the case because the soil profile is so unlike the other test pits on Site 1. The 1962 topographic map that I provided to Dames & Moore prior to start of the work shows the location of the old meander. The depths of the old meander is unclear from the 1962 topo because only 5 foot contours were mapped. The soil logs and report text should note that elevations are approximate and based on available topographic maps on the vertical datum NGVD 29 provided by the City. Surface Conditions This section should include a discussion of the general site topography. The 1980 Corps of Engineers topo for Site 1 and the 1992 ALTA/ACSM survey for Site 2 provided to Dames & Moore are sufficient for this purpose, except for identifying the location and size of the approximately 4-foot high mound on the southern boundary of Site 1, which is not shown in the Corps topo. Groundwater Conditions Based on my discussion with Dames & Moore's C.J. Shin, silty soils can draw water upward in the soil column from the groundwater table by capillary action. Therefore, the seepage encountered in silty soil during excavation may not have been the actual groundwater level. March-5, 1995 Page 2 Including the location of the observed seepage in silty soil in Table 1, Observation of Groundwater Level, as the approximate groundwater level may not be appropriate. This is particularity noticable for TP-5 on Site 1 were the groundwater is reported to have been at elevation 16 during excavation and several days later was measured in the piezometer at elevation 14.2. Additionally, the data for TP-1 and TP-5 seem to be conflicting in that the water level rose about 1-foot in TP-1 from 2/3/95 to 2/7/95 while the water level dropped about 1-foot in TP-5 from 2/2/95 to 2/7/95. Based on the fact that the gas main was ruptured on 2/2/95 at TP-1 while re- excavating the test pit to install the piezometer, I believe the piezometer was not installed until the morning of 2/3/95 at the earliest. Maybe the water had not had sufficient time to stabilized when the reading was made in TP-1 at It:15 am on 2/3/95 which may be why the water level rose about 1-foot by the 2/7/95 reading. More interpretation of the data is needed to address these issues. Interpolating between the stream gaging stations at SW 27th Street (about elev 6) and SW 43rd Street (about elev 8), the water level adjacent to Site 2 was approximately elevation 7 on 2/7/95 when TP-4 on Site 2 was excavated. This is near typical winter baseflow elevation based on interpolation from the continuous water level records from the SW 27th and SW 43rd stations. Seepage The report should include a discussion of the sensitivity of the results to changes in the underlying assumptions, such as the thickness and permeability of the silt layer. Table 2 shows a two orders of magnitude difference in the permeability of the silt layers tested. The assumed permeability of the silt in the seepage analysis is not cited. Table 3 or the text of the report does not include the assumed area used in determining the seepage loss, whether it is per acre, for the entire site, or something else. I believe it is the entire site area. Listing of the assumed area in the document is needed. Evaporation It is not meantioned whether evaporation loss from soil is comparable to lake evaporation. This should be clarified. Whether or not it is comparable, it is apparent that the seepage losses are the predominate factor for the without membrane case, especially for Site 2. Wetland Construction The report states that during the dry season it is believed that the groundwater table will be at least a few feet lower than observed levels. However, it is unclear exactly what water level below the proposed bottom of excavation is acceptable for operating mechanical equipment, especially if overexcavation is needed to install and compact an impermeable soil layer or place a synthetic liner on compacted soil. Also, even if the water table is below the proposed excavation, will the water content of the on-site silts be similar to that encountered in the test pits this winter? This should be addressed in the report in addition to what equipment is or is not classified as lightweight. Onsite Suitable Structural Fill Materials To assist in estimating the cost of soil excavation, placement, and recompaction either on-site or on a separate fill site, it would be helpful if the report discussed anticipated expansion and March, 1995 Page 3 shrinkage effects and recommended handling and compaction methods for the different soils encountered on the sites. The report should also address if the soil must be dried before placement and compaction and if so what drying methods are recommended. What are the possible uses of the soils that are not useable as structural fill? ll Preparation of Wetland Bottom If on-site soil is to be used a liner material, how should the material be temporarily stockpiled? I assume that the stockpiles should be covered during wet weather. If possible, it would be helpful if the consultant would provide a sample membrane installation and subgrade preparation construction specification. Permanent Slope Angle Differential water levels between the creek and the wetland will not be significant considering that the wetland will have an open connection to the creek. It is unclear why the top of the slope at the wetland side of Springbrook Creek should be at least 50 feet away from the creek bank. U:65119:95-001:SW CITY OF RENTON _ Planning/Building/Public Works Department Earl Clymer, Mayor Gregg Zimmerman P.E., Administrator March 16, 1995 Robert C. Guile, Risk Manager Washington Natural Gas Company 815 Mercer Street P.O. Box 1869 Seattle, WA 98111 SUBJECT: LETTER REGARDING CLAIM NO. 55264 GAS FACILITIES AT 3400 OAKESDALE AVENUE SW, RENTON Dear Mr. Guile: On February 20, 1995, 1 received a letter regarding damages done to Washington Natural Gas Company's distribution facilities at the above address. A billing for the expenses incurred during the repair was also included. As I communicated to you in a follow-up phone conversation on February 22, 1995, there was a misunderstanding as to who was responsible for causing the damage. The damage was not caused by the City, as cited in the letter, but by an excavator performing subcontracting work for Dames & Moore of Seattle, WA, an engineering services consulting firm. Therefore, I requested with your concurrence that the claim be submitted to the Dames & Moore project manager at the following address: C.J. Shin, Project Manager Dames & Moore 500 Market Place Tower 2025 First Avenue Seattle, WA 98121 Since the billing will be submitted to Dames & Moore instead of the City, I will disregard the February 20, 1995, claim billing as agreed. Thank you for your assistance in this matter. If you have any questions, please call me at 277-5547. Sincerely, �� ('�Cr J Scott Woodbury, Project Manager Surface Water Utility Engineering H:D0CS:95-230/SSWAf cc: Ron Straka 200 Mill Avenue South - Renton, Washington 98055 1 A M M f� Vw4amns Ma s M� Natural Gas A Washington Energy Company 02/14/95 FEB 2 0 1995 City of Renton CITY OF RENTON 200 Mill Av S Engineering Dept. Renton Wa 98055 RE: Claim Number: 55264 . Gas facilities at 3400 Oaksdale Wy SW, Renton Person Causing Damage: Scott Woodbury, Contact Ladies and Gentlemen: On 02/02/95, damage was done to our distribution facilities at the above address, by your firm. Attached is a bill reflecting the expenses accumulated during repair. According to our information you did not call for locates as required by the One-Call Law (RCW 19 . 122) . The Law is to protect public health and safety from interruption in utility services. Excavators shall request utility locates (1-800-424-5555) not less than two (2) business days or more than ten (10) business days before excavation, except for emergencies. Excavators shall not excavate until all known facilities have been marked. Once marked by the owner of the underground facility, the excavator is responsible for maintaining the markings. An excavator shall use reasonable care to avoid damaging underground facilities. An excavator who, in the course of excavation, contacts or damages an underground facility shall notify the utility owning or operating such facility and the one-call locator service. No damaged underground facility may be buried until it is repaired or relocated. RCW 19 . 122 also indicates that in those cases in which an excavator fails to notify known underground facility owners or the one-call locator service, any damage to the underground facility may be subject to treble damages for costs incurred in repairing or relocating the facility. Should you have any questions regar ing this claim please contact me at 521-5228 . Si , cerely, 2P�o�� � �{ RECEIVED � S � �� FEB 17 "1995 Robert C. Guile, f ur� pp-r- . Risk Manager �G ^� did �I 1�` g + 15 COMMlUNITY SERVICES Washington Natural Gas Company 815 Mercer Street(P.O. Box 1869),Seattle,Washington 98111, (206)464-1999, 1-800-999-4964 M M f� Washington Natural Gas AwashingtonEnergyCompany ZIF Claim Number: 55264 . 0 2/14/9 5 t��B O iggs City of Renton Oc RENTON 200 Mill AV S CIT`f Dept,Renton Wa 98055 Engineering FIRST NOTICE Incident Date: 02/02/95 Address of Incident: 3400 Oaksdale Wy SW, Renton Person Causing Damage: Scott Woodbury, Contact Details of Incident: While digging a test pit with a backhoe, City of Renton crew hit and broke a 4" plastic gas main at the above address. Costs of repairs Labor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 . 00 Crew Truck 3 . 50 Hours * 13 . 70 = 47 . 95 47 . 95 Service Truck 1 . 00 Hours * 3 . 40 = 3 . 40 3 . 40 Co. Backhoe Hours * 39 . 50 = 0 . 00 0 . 00 Contractor: Costs = Cntr. Backhoe 3 . 00 Hours * 46 . 00 = 138 . 00 138 . 00 Overtime Meals # of * 9 . 00 = 0 . 00 0 . 00 Materials = 1. 22 1 . 22 City / County (Permits / Paving) _ Misc. Charges: _ $ 402 . 57 Please detach below line and return with payment to: Washington Natural Gas Company 815 Mercer St, P.O. Box 1869 Seattle, WA 98111 Attn: Claims Department ----------------------------------------------------------------------- City of Renton 200 Mill AV S Renton Wa 98055 Please write claim number 55264 . on check. Amount Due: $ 402 . 57 Amount of Payment: $ Incident Date: 02/02/95 Incident Address: 3400 Oaksdale Wy SW, Renton Any questions contact: Robert C. Guile Ph. 521-5228 00178100 Washington Natural Gas Company 815 Mercer Street(P.O. Box 1869),Seattle, Washington 98111, (206)464-1999, 1-800-999-4964 CITY OF RENTON MEMORANDUM DATE: February 3, 1995 TO: Ron Straka FROM: Scott Woodbury SUBJECT: SUMMARY OF FEBRUARY 2, 1995 GAS LINE RUPTURE AT OAKESDALE AVENUE SW AND SW 33RD STREET Following is a summary of the February 2, 1995 gas line rupture at Oakesdale Avenue SW and SW 33rd Street that occurred during geotechnical investigation work by Dames and Moore (D&M) on wetland mitigation bank (WMB) site 1 (see Figure 1). The City executed CAG-94-139 with D&M of Seattle, WA, on January 17, 1995 for geotechnical investigation of the WMB sites shown on Figure 1 . • Dames & Moore subcontracted with Deeny Construction Company of Seattle, WA, for the excavation of the tests pits on the WMB sites. On February 2, 1995 at about 11 :30 am, I arrived at site 1 to observe the work and ask about the data that was being collected just as D&M and Deeny were breaking for lunch. • C.J. Shin, D&M's manager for the project, arrived during the lunch break and joined in the discussion of the work that had been completed the previous day and that morning. • At about 12:00 noon, D&M directed Deeny to excavate for the installation of a piezometer. Deeny had just started to excavate at the southeast corner of site 1 as shown in Figure 2 when the gas line was ruptured by the backhoe's bucket. • After the rupture, I immediately radioed the City shops to request that Washington Natural Gas (WNG) Company be notified of the break. • Signal shops radioed confirmation that WNG had been notified and would arrive at the site as soon as possible. • 1 radioed signal shops again and asked that WNG be queried whether any evacuations or other safety measures should be taken. Ron Straka r' Summary of February 2, 1995 Gas Line Rupture Page 2 • Signal shops radioed back that WNG had advised that sources of ignition be kept 50-feet clear of the break. No evacuation was said to be necessary. • D&M's field engineer and Deeny relocated to site 2 shown in Figure 1 to start the test pit work on that site. C.J. Shin and I remained behind to wait for WNG to arrive. • At about 12:20 p.m. a fire truck arrived and blocked off Oakesdale Avenue SW north of the SW 34th Street intersection. • At about 12:40 p.m., WNG arrived. WNG indicated that the ruptured line was a 4" line that was stubbed west out of the 4" line in Oakesdale Avenue SW. The stubbed line was installed for future extension when SW 33rd Street was constructed. When WNG asked D&M if an underground utility locate had been requested prior to excavating, C.J. Shin said no. • 1 asked C.J. if the work on site 2 should be delayed until a locate was performed for the proposed excavations. C.J. said that he would go to site 2 and stop the work and that he would try to arrange for a locate early next week. • When I left the site at about 1 :45 pm, WNG had not yet repaired the rupture, but were waiting for a backhoe to arrive. I hope this summary helps identify the information related to the gas line rupture. Earlier today I contacted C.J. Shin of D&M who said that WNG completed the repair of the break yesterday at about 4:30 pm. C.J. has arranged for a locate on site 2 for February 7, 1995. The site 2 excavation work should be completed that day. If you have any questions or wish to have more information, please let me know. 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RENTON, WASH. 98055 V ty Q UTILITY SYSTEMS DIVISION - 235-2631 NT TRANSPORTATION SYSTEMS DIVISION - 235-2620 TO: DATE: JOB NO.: RE: ATTN: GENTLEMEN: WE ARE SENDING YOU ❑ ATTACHED ❑ UNDER SEPARATE COVER VIA THE FOLLOWING ITEMS: ❑ SHOP DRAWINGS ❑ PRINTS ❑ REPRODUCIBLE PLANS ❑ SPECIFICATIONS o COPY OF LETTER ❑ COPIES DATE NUMBER DESCRIPTION AND REMARKS THESE ARE TRANSMITTED AS CHECKED BELOW: ❑ FOR APPROVAL o APPROVED AS SUBMITTED o RESUBMIT COPIES FOR APPROVAL ❑ FOR YOUR USE ❑ APPROVED AS NOTED o SUBMIT COPIES FOR DISTRIBUTION o AS REQUESTED ❑ RETURNED FOR CORRECTIONS ❑ RETURN CORRECTED PRINTS ❑ FOR REVIEW AND COMMENT ❑ ❑ PRINTS RETURNED AFTER LOAN TO US COPIES TO: SIGNED TITLE IF ENCLOSURES ARE NOT AS NOTED, KINDLY NOTIFY US AT ONCE