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HomeMy WebLinkAboutCoal Mine Hazard Report 0864001.CMH Report.042314 Report Geological Engineering Services Coal Mine Hazard Assessment Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 ICE File No. 0864-001 Prepared For: Merlino Land Development Co., Inc. Prepared By: Icicle Creek Engineers, Inc. April 23, 2014 Merlino Land Development Co., Inc. Attn: Gary Merlino 5050 1st Ave S, Suite 102 Seattle, Washington 98134-2400 Report Geological Engineering Services Coal Mine Hazard Assessment Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington ICE File No. 0864-001 1.0 INTRODUCTION This report summarizes the results of Icicle Creek Engineers’ (ICE’s) coal mine hazard assessment for the Merlino Short Plat (referred to as the Merlino Property in this report) 7-Lot Residential Development located southwest of the intersection of South 7th Street and Cedar Avenue South in Renton, Washington. The Merlino Property is shown relative to nearby physical features on the Vicinity Map, Figure 1. The general layout of the Merlino Property is shown on the Site Plan, Figure 2. Our services were completed in general accordance with our Scope of Services and Fee Estimate dated April 22, 2009 and our Proposal dated February 4, 2014; these services were authorized in writing by Gary Merlino on April 24, 2009 and March 17, 2014, respectively. 2.0 BACKGROUND INFORMATION ICE previously completed coal mine hazard assessments of the subject property for a previous property owner, GWC, Inc. (GWC); the results of those assessments are presented in our reports dated January 17 and June 10, 2005. Those reports included the Merlino Property as well as additional property that GWC owned to the east and south of the southerly part of the Merlino Property. ICE also completed a hydrogeologic report for GWC dated March 24, 2006 and a geotechnical report for GWC dated September 30, 2005. The approximate locations of subsurface explorations completed on the Merlino Property for those 2005 studies are shown on Figure 2. In addition, ICE completed a geotechnical critical areas report of the Merlino Property; the results are summarized in our report dated April 23, 2014. We understand that, subsequent to the reports we prepared in 2005 and 2006, GWC sold the portion of the GWC property that lies between Cedar Avenue South (and its southerly extension) and Interstate 405 (I-405) to the Washington State Department of Transportation (WSDOT) because preliminary plans for I-405 widening indicated encroachment into this property depending on final I-405 roadway configuration and the need for slope support measures. Thereafter, as part of the I-405 widening project, WSDOT’s design-build team for the I-405 widening project, I-405 Corridor Design Builders (CDB), Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 2 I c i c l e C r e e k E n g i n e e r s 0864001/042314 placed excess soil that was excavated from an adjacent portion of the I-405 project onto what is now the Merlino Property (property that at the time was owned by WSDOT). The fill was designed as a Reinforced Soil Slope (RSS – the RSS is referred to as the “Engineered Fill” in the remainder of this report) by CDB (with CDB joint venturer CH2M Hill providing the I-405 project’s geotechnical engineering). David Halinen, attorney for MLDC, forwarded to ICE a copy of the CDB report entitled Technical Memorandum, I-405 Renton Stage 2 Design/Build Project, WSDOT Exchange Property Reinforced Soil Slope, Geotechnical Design Recommendations Memorandum, dated August 14, 2009, a technical memorandum that was prepared specifically for that Engineered Fill. That technical memorandum is attached to this report (Attachment A). Page 6 of the CDB Technical Memorandum states an assumption that “structures (e.g., residences) will be constructed on the Engineered Fill in the future” and noted that the factors of safety (FOS) used in the CDB Technical Memorandum were based on that assumption. For that purpose, CDB evaluated the stability of the Engineered Fill for sliding, global stability, compound failure, internal stability, and seismic stability. The final design of the Engineered Fill required a minimum FOS of at least 1.5 for all the factors evaluated. In ICE’s June 2005 coal mine hazard assessment (completed for GWC) that included 12 test pits and three test borings in the Merlino Property area, we concluded that a “High Coal Mine Hazard Area” occurs at the south end of Cedar Avenue South. We reached that conclusion by evaluating historical mine maps and data from borings completed outside of that immediate area. Additional subsurface evaluation completed for this study (2009 ground proofing – seven test borings) targeted the High Coal Mine Hazard Area consistent with Renton Municipal Code (RMC) 4-3-050J.1 (Geologic Hazards - Applicability) and 4-3-050J.2 (Geologic Hazards - Special Studies Required). 3.0 SCOPE OF SERVICES The purpose of our services was to explore subsurface soil and bedrock conditions as a basis for evaluating the High Coal Mine Hazard Area within the Merlino Property. Specifically, our services included the following:  Completion of a detailed geologic reconnaissance along the pre-Engineered Fill embankment slope bordering Cedar Avenue South in order to evaluate surface conditions related to underground mine- related collapse (sinkholes) (a reconnaissance completed in 2009 with a post-Engineered Fill reconnaissance on February 2, 2014).  Evaluation of subsurface soil and bedrock conditions through a ground-proofing program by means of drilling seven test borings to depths ranging from 53 to 84 feet to evaluate the coal seam and location/collapse status of the mine workings that potentially underlie the south end of Cedar Avenue South (an evaluation completed in 2009).  Based on the results of the ground-proofing program, reclassification, if appropriate, of the High Coal Mine Hazard Area as either a Low or Medium Coal Mine Hazard Area.  Evaluation of the potential for regional ground subsidence in Medium Coal Mine Hazard Areas (vertical ground subsidence, ground tilt and ground strain), if appropriate.  Development of mitigation recommendations for future development within High and Medium Coal Mine Hazard Areas, as needed. 4.0 GEOLOGIC SETTING The surficial geology at the site has been mapped by the US Geological Survey (USGS - D. R. Mullineaux, 1965, “Geologic Map of the Renton Quadrangle, King County, Washington,” Geologic Quadrangle Map Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 3 I c i c l e C r e e k E n g i n e e r s 0864001/042314 GQ-405) as “undifferentiated glacial sediments” underlain by “Renton Formation” bedrock. Undifferentiated glacial sediments are described by the USGS as consisting of layers of glacial till (ice deposited silty sand with gravel), glacial outwash (stream-deposited sand and gravel), glaciolacustrine deposits (lake-deposited clay and sand), and nonglacial sand and clay. Renton Formation bedrock is described by the USGS as interbedded (layered) sedimentary rock consisting of sandstone, siltstone, shale, claystone, carbonaceous shale and coal beds. Structurally, the bedrock has been uplifted, folded and faulted over time. This structural deformation of the bedrock has caused the “bedding” of the rock to be tilted about 10 to 14 degrees down to the east in the Merlino Property area. 5.0 SITE CONDITIONS 5.1 SURFACE CONDITIONS Surface reconnaissance of the Merlino Property was performed and completed by Brian Beaman of ICE on April 27, 2009 and February 2, 2014. The Merlino Property is located on a west-facing hillside overlooking the City of Renton and is bordered by Cedar Avenue South to the east, Cedar Crest Condominiums to the north, I-405 to the west and undeveloped WSDOT-owned forest land and a Puget Sound Energy (PSE) transmission line easement to the south. Before placement of the Engineered Fill, the portion of the subject property immediately west of Cedar Avenue South was characterized by a steep (60 percent grade) road embankment long-ago-created for Cedar Avenue South, an embankment that was about 5- to 15-feet high and that transitioned to a natural slope inclined downward to the west at about a 20 to 30 percent grade. The natural slope tended to flatten gradually to the west. Mine Rock Fill (Coal Spoils) consisting of broken rock and coal fines were observed during field reconnaissance and test pits (Test Pits TP-8, TP-14 and TP-16) completed for our previously described 2005 study; these test pit locations are shown on Figure 2. Presently, the Engineered Fill has formed along most of the Merlino Property’s east side abutting the west edge of Cedar Avenue South a nearly-level plateau area that extends west the west edge of the existing Cedar Avenue South right-of-way about 112- to 122-feet to the plateau’s crest. This nearly-level plateau area is where the seven residential lots are planned. From the west edge of the plateau, a slope field measured at about 30 degrees (about 1.75H:1V – horizontal to vertical) extends down to the west toward the I-405 right-of-way. The nearly-level plateau area is vegetated with grass. The slope is vegetated with Douglas fir trees about 8-feet high and with shrubs. No surface water was observed within the Merlino Property at the time of our 2009 and 2014 site reconnaissance efforts. We also did not observe topographic anomalies, such as steep-sided pits (sinkholes), which could indicate underground mine collapse within Merlino Property pre- or post- Engineered Fill. 5.2 ABANDONED UNDERGROUND COAL MINES 5.2.1 Documented Mining The Renton Mine was active in the vicinity of the Merlino Property from about 1874 to 1933 on the No. 3 Coal Seam. Typically, coal was removed from this mine using room-and-pillar mining methods; coal “pillars” were left in place for support of the “rooms” where the coal was removed. Eventually, most, or all, of the coal pillars were removed upon retreat of these production areas to promote collapse of the Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 4 I c i c l e C r e e k E n g i n e e r s 0864001/042314 mined-out areas. A “barrier pillar” of intact coal was usually left in place in the shallowest areas of the coal mine to reduce the risk of causing a collapse of the ground surface. The thickness of coal mined was about 8 feet according to historical records. The total thickness of the No. 3 Coal Seam is about 12 feet. Based on our review of the previously-referenced available information and site observations, the original main slope coal mine entries (referred to as the “Main Entry” and “Fan House” for the Renton Mine) are located about 170 feet south of the central portion of the Merlino Property’s south property line as shown on Figure 2. As the mine expanded, a rock tunnel was driven from the main slope west- northwest to a point along the east side of the current location of Benson Road (a road that lies along the base of the hill adjacent to the current location of Sam’s Club). The rock tunnel provided an easier means for removing coal from the underground mine workings. The rock tunnel crosses under the WSDOT property to the south of the Merlino Property and extends west-northwest under I-405, as shown on Figure 2, to where the backfilled (currently inaccessible) mine entry to the west is located. The location of that mine entry is not shown on Figure 2 as it is west-northwest of the mapped area. The mine workings extend north-northeast and east from the rock tunnel at an approximately 10 degree angle below horizontal with a series of haulageways and production or room areas that were driven at right angles to the main slope. Each haulageway along with its production area was referred to as a “Level.” Underlying a portion of the southeast part of the Merlino Property in the vicinity of the south end of Cedar Avenue South is the 1st Level of the Renton Mine. The Renton Mine ultimately contained 12 levels extending underground a distance of over 1 mile east of the south end of the Merlino Property. 5.2.2 Undocumented Mining The Renton Mine is located in an area where undocumented mining occurred. We observed no evidence of undocumented mining during our field reconnaissance and observation efforts within the Merlino Property or its immediate vicinity. 5.3 2009 GROUND-PROOFING PROGRAM SUMMARY Subsurface conditions in the area of the south end of Cedar Avenue South (High Coal Mine Hazard Area) were explored by drilling seven, three-inch-diameter borings (Borings B-5 through B-11) at the approximate locations shown on Figure 2. Exploration locations were established by measuring from physical features at the site. The number of borings was determined such that the probability of drilling through “support pillars” was reduced to a very low level. The borings were drilled on April 27, 2009 to depths ranging from 53 to 84 feet below the ground surface in the area likely underlain by a portion of the 1st Level of the Renton Mine. The borings were advanced using track-mounted, hydraulic/air- percussion drilling equipment owned and operated by McCallum Rock Drilling, Inc. of Chehalis, Washington. Borings B-5, B-10 and B-11 were drilled at a vertical orientation. Borings B-6 through B-9 were drilled at an angle (varying from 25 to 30 degrees off of vertical) from the surface location of Boring B-5. The purpose of drilling the angle borings was to evaluate the conditions of the Renton Mine and the No. 3 Coal Seam in areas that were otherwise inaccessible. Soil and bedrock samples (drill cuttings) were observed continuously as the borings were advanced. The subsurface explorations were continuously logged by a geological engineer from our firm. Soils were classified in general accordance with ASTM Test Method D 2488 as shown on the Explanation for Boring Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 5 I c i c l e C r e e k E n g i n e e r s 0864001/042314 Logs, Figure 4. Bedrock was classified in general accordance with the WSDOT Geotechnical Design Manual. The boring logs are presented in Figures 5 through 11. The borings for this study were supplemented by three test borings (Borings B-1 through B-3) that were previously completed by ICE for GWC (ICE, June 10, 2005). The locations of these supplemental borings are shown on Figure 2. Boring B-4 (not shown on Figure 2) was completed for GWC on a nearby property and into a different coal seam (No. 2 Coal Seam) not related to this project. The logs of Borings B-1 through B-3 are included in Attachment B. A summary of the subsurface conditions observed in the current and supplemental borings is presented below. Test Boring Number Total Depth (feet) Depth to Bedrock (feet) Depth to Coal Seam/Mine (feet) Uncollapsed (full height mine void) Unmined (intact coal) Thickness Intact Coal (feet) B-1 (2005) 110 7 7 - Yes 12 B-2 (2005) 60 8 8 - Yes 11½ B-3 (2005) 60 10 10 - Yes 13½ B-5 (2009) 71 5 57 - Yes 13 B-6 (2009) 77 6 65 12-foot void No - B-7 (2009) 53 6 39 14-foot void No - B-8 (2009) 83 6 51 - Yes 15 B-9 (2009) 84 6 59 - Yes 14 B-10 (2009) 59 5 36 - Yes 13 B-11 (2009) 59 5 41 - Yes 11 Note: The thickness of void indicated is not corrected for drilling at an angle; the actual thickness of void is likely 2 to 3 feet less than that indicated by the drilling penetration. Borings B-1 through B-3 encountered the top of the No. 3 Coal Seam (intact – not mined) immediately below the overburden soils at a depth ranging from 7 to 10 feet below the ground surface. Borings B-5 through B-11 encountered about 5 to 6 feet of overburden soils. Borings B-5 through B-11 encountered a 3- to 5-foot thick layer of carbonaceous shale overlying the No. 3 Coal Seam or Renton Mine, which is generally overlain by sandstone. Borings B-5 and B-7 through B-11 encountered sandstone underlying the No. 3 Coal Seam. We encountered “intact bedrock” at the base of the Renton Mine void in Borings B-6 and B-7, but were unable to observe drill cuttings because of the loss of air circulation caused by the void. No groundwater was observed in Borings B-1 through B-3 or Borings B-5 through B-11 at the time of drilling. 5.4 GENERAL DESCRIPTION OF HAZARDS ASSOCIATED WITH COAL MINES The principal physical hazards associated with abandoned underground coal mines include the following:  Sinkholes (High Coal Mine Hazard Areas)  Regional ground subsidence (Medium Coal Mine Hazard Areas) Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 6 I c i c l e C r e e k E n g i n e e r s 0864001/042314 5.5 THE CITY OF RENTON’S DEFINITIONS OF THREE CLASSES OF COAL MINE HAZARD AREAS RMC 4-3-050J.1.e defines coal mine hazards as follows: High Coal Mine Hazards - Areas with abandoned and improperly sealed mine openings and areas underlain by mine workings shallower than two hundred feet (200') in depth for steeply dipping seams, or shallower than fifteen (15) times the thickness of the seam or workings for gently dipping seams. These areas may be affected by collapse or other subsidence. Medium Coal Mine Hazards – Areas where the mine workings are deeper than two hundred feet (200’) for steeply dipping seams, or deeper than fifteen (15) times the thickness of the seam for gently dipping seams. These areas may be affected by subsidence. Low Coal Mine Hazards – Areas with no known mine workings and no predicted subsidence. While no mines are known in these areas, undocumented mining is known to have occurred. 6.0 ANALYSIS OF COAL MINE HAZARDS 6.1 HIGH COAL MINE HAZARD AREAS As previously mentioned, the goal of ICE’s 2009 ground-proofing program was to further evaluate the location and coal seam/mine condition within the Merlino Property. Our June 2005 report completed for GWC includes three test borings (Borings B-1, B-2, and B-3) within the Merlino Property; seven additional test borings (Borings B-5 through B-11) within the Merlino Property and within the adjacent south end of the Cedar Avenue South right-of-way were completed in 2009. These boring locations are shown on Figure 2. Based on the results of these explorations, we were able to accurately locate the 1st Level of the Renton Mine (encountered in Borings B-6 and B-7) and also locate intact coal, commonly referred to as a “barrier pillar,” that was left in place to protect the ground surface. It appears that the 1st Level of the Renton Mine is located about 30 feet east and about 25 feet south of the location shown in ICE’s June 2005 report. Our reinterpretation of the High Coal Mine Hazard Area at the Merlino Property, which is based on Borings B-5 through B-11, is shown on the Coal Mine Hazard Map, Figure 3. 6.2 MEDIUM COAL MINE HAZARD AREAS No ground subsidence should occur outside of the High Coal Mine Hazard Area because it appears (based on ground proofing) to be underlain by intact coal (a barrier pillar) that was left in-place to protect the ground surface. No Medium Coal Mine Hazard Areas exist outside of the High Coal Mine Hazard area within the Merlino Property or within adjacent Cedar Avenue South. 6.3 LOW COAL MINE HAZARD AREAS Based on our site observations in 2009 and 2014, and review of the regional mapping of coal mine hazards by the City of Renton, portions of this area are where no known mine workings occur and no predicted subsidence is probable. Although undocumented coal mining could have occurred in this area, no evidence was observed during our reconnaissance efforts completed for this study. The Low Coal Mine Hazard Area within the Merlino Property and within abutting Cedar Avenue South is shown on Figure 3. Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 7 I c i c l e C r e e k E n g i n e e r s 0864001/042314 7.0 CONCLUSIONS Based on our review of available information, site observations, ground proofing and analysis of coal mine hazards within the Merlino Property and Cedar Avenue South, we have developed the following conclusions:  The results of our ground-proofing program (Borings B-5 through B-11) suggest that the 1st Level of the Renton Mine is situated slightly east (about 30 feet) and south (about 25 feet) of the location indicated in ICE’s June 2005 report.  Borings B-6 and B-7 encountered uncollapsed mine workings (1st Level, Renton Mine, No. 3 Coal Seam) at depths of 65 feet and 39 feet, respectively. At these depths, a portion of the Renton Mine is located beneath the southeast corner of the Merlino Property at the south end of Cedar Avenue South.  Borings B-5 and B-8 through B-11 encountered intact coal (unmined No. 3 Coal Seam), indicating a barrier pillar that was left in-place to protect the ground surface from subsidence. The presence of the intact coal (barrier pillar) is consistent with the results of Borings B-1 through B-3 that were completed to the west and north of the south end of Cedar Avenue South (ICE, June 2005).  Based on the results of Borings B-5 through B-11, we conclude that the High Coal Mine Hazard Area should be delineated as shown on Figure 3. Other areas that were previously delineated as a High Coal Mine Hazard Area in ICE’s June 2005 report should be reclassified as a Low Coal Mine Hazard Area.  The Medium Coal Mine Hazard Area is included (subsumed) within the High Coal Mine Hazard Area.  None of the proposed seven lots lie within the High Coal Mine Hazard Area or within the Medium Coal Mine Hazard Area as shown on Figure 3.  Most of the area of Cedar Avenue South proposed to be widened lies outside of the High Coal Mine Hazard Area as shown on Figure 3.  Based on our site observations in 2009 and 2014, and knowledge of the location of the Renton Mine, Low Coal Mine Hazard Areas are shown on Figure 3. 8.0 RECOMMENDATIONS  No structures should be constructed in High Coal Mine Hazard Areas. In our opinion, fill may be placed in High Coal Mine Hazard Areas provided that the fill is not used to support structures. The stormwater vault and underground pipes could be supported by a deep foundation that extends below the underground mine, or structurally designed to span a void of 10 feet in diameter along with the drag forces caused by caving soils around these structures should a sinkhole occur. Manholes would need to be structurally supported on the side of the vault.  Road access, including fill placement for road access (no cuts), may be constructed in the High Coal Mine Hazard Areas. 9.0 USE OF THIS REPORT We have prepared this report for use by Merlino Land Development Co., Inc. The data and report should be used for land use planning, but our report, conclusions and interpretations should not be construed as a warranty of subsurface conditions. There are probable variations in subsurface conditions between the explorations; variation in subsurface conditions may also occur with time. A contingency for unanticipated conditions should be included in the short plat infrastructure construction’s budget and schedule. During construction, sufficient observation, testing and consultation by our firm should be provided to (1) evaluate whether the Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 8 I c i c l e C r e e k E n g i n e e r s 0864001/042314 conditions encountered are consistent with those indicated by the explorations, (2) provide recommendations for design changes if the conditions encountered during construction differ from those anticipated, and (3) evaluate whether earthwork activities comply with contract plans and specifications. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time the report was prepared. No warranty or other conditions, express or implied, should be understood. ******************* We trust this information meets your present needs. If you have any questions or if we can be of further assistance to you, please call. Yours very truly, Icicle Creek Engineers, Inc. Brian R. Beaman, PE, LEG, LHG Principal Engineer/Geologist/Hydrogeologist Kathy S. Killman, LEG Principal Engineering Geologist Document ID: 0864001.CMH.Report Attachments: Vicinity Map – Figure 1 Site Plan – Figure 2 Coal Mine Hazard Map – Figure 3 Explanation for Boring Logs – Figure 4 Boring Logs – Figures 5 through 11 Attachment A – I-405 CDB Technical Memorandum, August 14, 2009 Attachment B – Supplemental Boring Logs Submitted via surface mail (three original copies) cc: David Halinen, Halinen Law (email as pdf, surface mail – one original copy) I c i c l e C r e e k E n g i n e e r s 0864001/042314 FIGURES 0 ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 FigureCHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: As Shown DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON VICINITY MAP 1 0864-001 2,0000 4,000BensonRoadBensonRoadMerlino Property Approximate Scale in Feet ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 Figure 0864-001 CHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: 1 inch - 100 feet DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON Base map provided by Core Design, undated Cedar Avenue SouthSouth 7th StreetProposed Right-of-Way Line Existing Right-of-Way Line Merlino Property WSDOT Property 180 Borings B-5 through B-9 were drilled from the same location; Boring B-5 was vertically oriented and Borings B-6 through B-9 were drilled at an angle varying from 25 to 30 degrees off of vertical. B-2(2005)B-2(2005) TP-5 B-1(2005)TP-6B-3(2005) TP-3 TP-4 TP-13TP-12 TP-2 TP-1 Mine Rock Fill (Coal Spoils) (based on 2005 field reconnaissance) removed or covered during I-405 expansion) EXPLANATION Backfilled Mine Opening Boring Location (2009) TP-1 Test Pit Location (2005) B-5 Boring Location (2005)B-3 B-5 B-6 B-7B-8 B-9 B-10 B-11 B-6 B-9 B-5 B-7B-8 B-10 B-11 Approximate Scale in Feet 0 100 200 TP-16 TP-14TP-14 TP-8 TP-7 TP-15 SITE PLAN Main Entry (backfilled mine opening - Renton Mine) Fan House (backfilled mine opening - Renton Mine) Renton Mine Rock Tunnel Area 2 ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 Figure 0864-001 CHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: 1 inch - 100 feet DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON Base map provided by Core Design, undated Cedar Avenue SouthSouth 7th StreetProposed Right-of-Way Line Existing Right-of-Way Line Merlino Property WSDOT Property EXPLANATION High Coal Mine Hazard Area Areas with abandoned and improperly sealed mine openings and areas underlain by mine workings shallower than 200 feet in depth (RMC 4-3-050J.1.e.iii.). No structures should be planned in this area; fill placement is OK. Low Coal Mine Hazard Area Areas with no known mine workings and no predicted subsidence J.1.e.i.). Building and road development should be allowed; no mitigation recommended. (RMC 4-3-050 COAL MINE HAZARD MAP Approximate Scale in Feet 0 100 200 3 MAJOR DIVISIONS Soil Classification and Generalized Group Description Coarse- Grained Soils More than 50% retained on the No. 200 sieve Fine- Grained Soils More than 50% passing the No. 200 sieve Highly Organic Soils GRAVEL More than 50% of coarse fraction retained on the No. 4 sieve SAND More than 50% of coarse fraction passes the No. 4 sieve SILT AND CLAY Liquid Limit less than 50 SILT AND CLAY Liquid Limit greater than 50 CLEAN GRAVEL GRAVEL WITH FINES CLEAN SAND SAND WITH FINES INORGANIC ORGANIC INORGANIC ORGANIC GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Well-graded gravels Poorly-graded gravels Gravel and silt mixtures Gravel and clay mixtures Well-graded sand Poorly-graded sand Sand and silt mixtures Sand and clay mixtures Low-plasticity silts Low-plasticity clays Low plasicity organic silts and organic clays High-plasticity silts High-plasticity clays High-plasticity organic silts and organic clays PeatPrimarily organic matter with organic odor Unified Soil Classification System Component Size Range Boulders Coarser than 12 inch Cobbles 3 inch to 12 inch Gravel 3 inch to No. 4 (4.78 mm) Coarse 3 inch to 3/4 inch Fine 3/4 inch to No. 4 (4.78 mm) Sand Coarse No. 4 (4.78 mm) to No. 200 (0.074mm) No. 4 (4.78 mm) to No. 10 (2.0 mm) Medium No. 10 (2.0 mm) to No. 40 (0.42 mm) Fine No. 40 (0.42 mm) to No. 200 (0.074 mm) Silt and Clay Finer than No. 200 (0.074 mm) Soil Particle Size Definitions Soil Moisture Description Dry Moist Wet Absence of moisture Damp, but no visible water Visible water Soil Moisture ModifiersNotes: 1) Soil classification based on visual classification of soil is based on ASTM D2488. 2) Soil classification using laboratory tests is based on ASTM D2487. 3) Description of soil density or consistency is based on interpretation of blow count data and/or test data. Sampling Method Boring Log Symbol Description Blows required to drive a 2.4 inch I.D. split-barrel sampler 12-inches or other indicated distance using a 300-pound hammer falling 30 inches. Blows required to drive a 1.5- inch I.D. split barrel sampler (SPT - Standard Penetration Test) 12-inches or other indicated distance using a 140-pound hammer falling 30 inches. 34 12 21 14 30 P Location of relatively undisturbed sample Location of disturbed sample Location of sample attempt with no recovery Location of sample obtained in general accordance with Standard Penetration Test (ASTM D-1586) test procedures. Location of SPT sampling attempt with no recovery. Pushed Sampler Grab Sample Sampler pushed with the weight of the hammer or against weight of the drilling rig. Sample obtained from drill cuttings.G Key to Boring Log Symbols Test Symbol Density Grain Size Percent Fines Atterberg Limits Hydrometer Analysis Consolidation Compaction Permeability Unconfined Compression Consolidated Undrained TX Consolidated Drained TX Chemical Analysis Laboratory Tests DN GS PF AL HA CN CP PM UC CU CD CA Unconsolidated Undrained TX UU Note: The lines separating soil types on the logs represents approximate boundaries only. The actual boundaries may vary or be gradual. Moisture Content MC ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 FigureCHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: N/A DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT DEVELOPMENT RENTON, WASHINGTON EXPLANATION FOR BORING LOGS 4 0864-002 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 5 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB BRB: 04/29/09Rock Rock Rock Rock Rock SM Forest duff and topsoil Rock Bedrock encountered at 5 feet Brown silty fine to medium SAND (completely weathered bedrock) Brown medium-grained SANDSTONE (slightly weathered, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Light brown medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock Boring B-5 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-5 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 5 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB BRB:04/29/09Boring completed at 71 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 57 - 70 feet - not mined) Rock Rock Rock Rock No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 6 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Brown medium-grained SANDSTONE (slightly weathered, very weak) (Renton Formation bedrock) Light brown medium-grained SANDSTONE (fresh, very weak) (Renton formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock SM Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock)Rock Rock Boring B-6 (top hole location at Boring B-5 oriented o oat 25 from vertical at azimuth 090 ) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-6 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 6 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 77 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) RENTON MINE (open mine workings - uncollapsed) Rock Rock Void VoidVoid Void Complete loss of compressed air circulation at 65 feet Drilling resistance indicates intact rock (not mined) at 77 feet RENTON MINE (open from 65 - 77 feet - mined out) No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-7 (top hole location at Boring B-5 oriented o oat 30 from vertical at azimuth 180 Approximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 7 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Void Forest duff and topsoil Void Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock SM Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) RENTON MINE (open from 39 - 53 feet - mined out) Complete loss of compressed air circulation at 39 feetRENTON MINE (open mine workings - uncollapsed) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-7 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 7 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 53 feet on April 27, 2009 Void RENTON MINE (open from 39 - 53 feet - mined out) Drilling resistance indicates intact rock (not mined) at 53 feet RENTON MINE (open mine workings - uncollapsed) No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 8 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) SM Rock Rock RockDark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Boring B-8 (top hole location at Boring B-5 oriented o oat 30 from vertical at azimuth 000 ) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-8 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 8 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 83 feet on April 27, 2009 Rock Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 51 - 66 feet - not mined) Rock Rock Rock Rock Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 9 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock SM Forest duff and topsoil Rock Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Light brown medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (slightly weathered bedrock, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Rock Boring B-9 (top hole location at Boring B-5 oriented o oat 30 from vertical at azimuth 312 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-9 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 9 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 84 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 59 - 73 feet - not mined) Rock Rock Rock Rock Rock Rock Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-10 Approximate Ground Surface Elevation: 186 feet Page 1 of 2 Boring Log - Figure 10 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 5 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock SM Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 36 - 49 feet - not mined) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock)Rock 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-10 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 10 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 59 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-11 Approximate Ground Surface Elevation: 185 feet Page 1 of 2 Boring Log - Figure 11 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 5 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock SM Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 41 - 52 feet - not mined) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-11 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 11 Ground Water Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 59 feet on April 27, 2009 Rock Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 41 - 52 feet - not mined) No groundwater observed I c i c l e C r e e k E n g i n e e r s 0864001/042314 ATTACHMENT A I-405 CORRIDOR DESIGN BUILDERS TECHNICAL MEMORANDUM DATED AUGUST 14, 2009 I-405 RENTON STAGE 2 DESIGN/BUILD PROJECT WSDOT EXCHANGE PROPERTY REINFORCED SOIL SLOPE GEOTECHNICAL DESIGN RECOMMENDATIONS MEMORANDUM REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 2 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Subsurface Conditions Geotechnical conditions for the WSDOT Exchange Property area were established on the basis of existing geotechnical explorations supplemented by 3 new explorations advanced by Icicle Creek Engineers in support of the Renton Stage 2 Project. The new boring logs were used with the existing site soil information to develop geotechnical parameters for analysis and design of RSS slope. Geotechnical Explorations The following exploration locations were used in the evaluation of the site conditions and in the creation of soil profiles beneath the RSS. The boring and test pit logs were also used to develop geotechnical parameters for analysis and design of the RSS. The source of the exploration information is summarized in Table 1. Figure 2 shows the approximate locations of the explorations. Figure 3 shows the interpreted typical subsurface. Copies of the exploration logs are included in Attachment B. TABLE 1: WSDOT EXCHANGE PROPERTY EXPLORATION LOCATIONS Exploration Location Type Source B-1 Boring Icicle Creek Engineers, Inc., 2005 B-2 Boring Icicle Creek Engineers, Inc., 2005 B-3 Boring Icicle Creek Engineers, Inc., 2005 TP-1 Test pit Icicle Creek Engineers, Inc., 2005 TP-2 Test pit Icicle Creek Engineers, Inc., 2005 TP-3 Test pit Icicle Creek Engineers, Inc., 2005 TP-4 Test pit Icicle Creek Engineers, Inc., 2005 TP-5 Test pit Icicle Creek Engineers, Inc., 2005 TP-6 Test pit Icicle Creek Engineers, Inc., 2005 TP-7 Test pit Icicle Creek Engineers, Inc., 2005 TP-8 Test pit Icicle Creek Engineers, Inc., 2005 TP-12 Test pit Icicle Creek Engineers, Inc., 2005 TP-13 Test pit Icicle Creek Engineers, Inc., 2005 TP-14 Test pit Icicle Creek Engineers, Inc., 2005 TP-15 Test pit Icicle Creek Engineers, Inc., 2005 TP-16 Test pit Icicle Creek Engineers, Inc., 2005 515-4-06 Boring Geoengineers, 2007 CDB-6p-08 Boring Geoengineers, 2007 SRX-20-05 Boring Geoengineers, 2007 REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 3 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL TABLE 1: WSDOT EXCHANGE PROPERTY EXPLORATION LOCATIONS Exploration Location Type Source 515-6-06 Boring Geoengineers, 2007 515-7-06 Boring Geoengineers, 2007 B-5 Boring Icicle Creek Engineers, Inc., 2009 B-10 Boring Icicle Creek Engineers, Inc., 2009 B-11 Boring Icicle Creek Engineers, Inc., 2009 Icicle Creek Engineers, Inc., “Report- Coal Mine Hazard Assessment and Preliminary Geotechnical Evaluation, Renton Hill Property, King County Parcel Nos. 2023059085 and 0007200194/196, Renton, Washington,” June 10, 2005. GeoEngineers, 2007, “Geotechnical Baseline Report I-405/1-5 to SR 169 Stage 2 – Widening and SR 515 Interchange, Renton, Washington,” September 7, 2007. Icicle Creek Engineers, Inc., “Report, Geological Engineering Services, Coal Mine Hazard Assessment, WSDOT Property, Renton, Washington,” May 11, 2009. Interpreted Geotechnical Conditions and Groundwater Location The existing WSDOT Exchange property is an undeveloped parcel of land located on the hillside between I-405 and Cedar Avenue. Slopes vary from 5 to over 90 percent, with slope lengths varying from 25 to over 100 feet. The site elevation varies from approximately 140 feet to 230 feet. The general subsurface profile consists of colluvium/fill overlying residual soils weathered from the Renton Formation overlying the Renton Formation. The colluvium/fill/residual soils are difficult to distinguish from each other and are considered as one unit for the analysis. The site is underlain by the Renton Formation sandstone bedrock. In the southwest portion of the site there are deposits of materials consisting of mine tailings and old municipal waste that are associated with the abandoned Renton Civic Dump site. The general characteristics of the predominant geologic units are as follows: • The colluvium/fill/residual soils vary from ~1 foot to 10 feet thick over the site. These soils are generally medium dense and consist primarily of silty sand. • The tailings/municipal waste thickness varies from a thin veneer to over 25 feet thick. These soils are loose to medium dense and contain a wide variety of materials including silt, sand, slag, ashes, glass, metal, debris, and other materials associated with municipal waste disposal. Mine tailings may also be incorporated in this material, either as cover soils, or as a result of previous mining activities that occurred in the same area. • The Renton Formation consists of weak sandstone bedrock with occasional siltstone layers and extends below the depth explored with borings at the site. Boring log information indicates that groundwater was found generally in the Renton Formation, below elevation 100 feet. REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 4 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Seismicity and Ground Motions The Renton Stage 2 Project is being designed in accordance with WSDOT’s current seismic design requirements. These requirements include use of a design earthquake that has a 7 percent probability of exceedance in a 75-year exposure period. The seismic ground motions and liquefaction potential for this design earthquake are summarized below. Seismic Ground Motions Design peak ground acceleration (PGA) of 0.44g is used in analysis. This ground motion was determined using the AASHTO ground motions hazard map and a site coefficient for peak ground acceleration (Fpga) of 1.0 based on Site Class C site classification. Per the WSDOT GDM (2008), a horizontal pseudo-static acceleration coefficient, kh = 0.22 (F*PBA/2) was used in the global stability analysis. Use of this reduced seismic coefficient implies that several inches of permanent slope displacement is acceptable during the design seismic event. Liquefaction Potential Soils at the project site below the water table are the sandstone bedrock; therefore, liquefaction potential of site soils is very low. Surface water will be routed from the RSS and fill to prevent infiltration and possible ponding of water within the compacted fill layers and RSS. Geotechnical Design The design of RSS follows the steps outlined in Chapter 7 of FHWA Publication FHWA- NHI-00-043, “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines,” by Elias, et al. (2001). General Design Considerations The general design considerations for this project are listed below. • Traffic Surcharge assumed equivalent to 2.0 feet of soil surcharge (surcharge unit weight = 125 pcf) = 125 pcf x 2 feet = 250 psf. • Extensible (geosynthetic geogrid) reinforcement is to be used. • A wrapped face is not required because the slope is shallower than 1.2(H):1(V) (GDM, 2008). • Minimum length of reinforcing is 6 feet (GDM, 2008). • Primary reinforcing shall be vertically spaced at 3 feet or less (GDM, 2008). • Minimum long-term allowable strength of primary reinforcing = 1,250 lb/ft. REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 5 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL • Secondary reinforcing between layers of primary reinforcing shall be at a maximum vertical spacing of 1 foot (GDM, 2008). Secondary reinforcing shall not be included in the internal stability analysis of the RSS. • Minimum long-term allowable strength of secondary reinforcing = 115 lb/in. • Backfill within the reinforced zone of the RSS shall consist of Common Borrow, meeting the requirements of WSDOT Standard Specifications Section 9-03.14(3), as modified in the Project Technical Specification drafted for the RSS. As follows: Sieve Size Percent Passing 3-inch 100 No. 4 100 - 20 No. 200 0 - 35 Geotechnical Material Properties The following properties were used in the design of the RSS: New Fill: • Unit weight = 130 pcf • Internal angle of friction = 36 degrees • Cohesion (static case) = 0 psf • Internal angle of friction (seismic case) = 34 degrees • Apparent cohesion (seismic case) = 200 psf Residual soil/colluvium/fill: • Unit weight = 130 pcf • Internal angle of friction = 36 degrees • Cohesion (static case) = 0 psf • Apparent cohesion (seismic case) = 200 psf Renton Formation: • Uniaxial compressive strength = 300 psi (43.2 ksf) • Geologic strength index (GSI) = 40 • Intact rock constant (mi) for sandstone = 17 • Disturbance factor (D) for good quality excavation = 0.0 • Mohr-Coulomb fit (Hoek-Brown Criteria), internal angle of friction = 32 degrees • Mohr-Coulomb fit (Hoek-Brown Criteria), cohesion (seismic and static cases) = 2100 psf Municipal Waste: • Unit weight = 115 pcf • Internal angle of friction = 28 degrees • Cohesion (static case) = 300 psf • Apparent cohesion (seismic case) = 300 psf REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 6 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Reinforcement Length Requirements Analyses were conducted at selected sections along the RSS to evaluate the minimum reinforcement lengths (Lmin) required to satisfy stability requirements. The analytical results were compared to GDM minimum acceptable criteria shown below. • Sliding FS 1.5 • Global Stability (outside of reinforced zone) FS 1.5 • Compound Failure (through face of RSS) FS 1.5 • Internal Slope Stability (through the reinforcing) FS 1.5 • Lateral Squeeze (bearing failure) FS 1.5 • Seismic Stability FS 1.1 The above factors of safety assume that structures (e.g., residences) will be constructed on the RSS fill in the future. For sliding, global stability, compound failure, internal stability, and seismic stability evaluations, the computer program SLIDE (Rocscience, 2008) was used. Lateral squeeze does not apply because the RSS is founded on competent bearing materials. To achieve the required FS, a geogrid with minimum long-term design strength of 1,250 lb/ft, coupled with the reinforcement lengths summarized in Table 2, is required. The length of reinforcing was generally controlled by a combination of static and seismic stability. The approximate station extents for the different Lmin are summarized in Table 2. All stations are based on a construction reference alignment CEDAR RW Line. For a given embankment location, all reinforcing lengths are constant for the entire embankment height. TABLE 2: REINFORCEMENT TABLE Beginning Station Ending Station Minimum Reinforcement Length (Lmin) Bottom Reinforcing Elevation (ft) Top Reinforcing Elevation (ft) 10+35 10+75 25 200 Varies, max 220 10+75 11+50 40 194 220 11+50 11+75 40 182 220 11+75 12+50 50 172 222 12+50 13+00 45 172 222 13+00 13+75 40 176 222 13+75 14+50 40 172 224 14+50 15+45 40 172 226 15+45 15+95 40 172 Varies, max 226 REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 7 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Settlement Due to the granular consistency and/or heavily overconsolidated nature of the existing soils and bedrock, settlement is anticipated to be elastic in nature and is expected to occur during embankment construction. Construction Requirements The construction of the RSS and backfill require careful planning and construction control, including oversight by the project geotechnical engineer, to assure that the slope is constructed in such a manner that short- and long-term stability requirements are met. The following subsection summarizes key construction requirements. Specific requirements for construction of the RSS are included in the technical specification Reinforced Soil Slope, I.5:1 (Horizontal to Vertical) Slopes, included as Attachment C to this memorandum. Subgrade Preparation and Ground Improvement Before placement of fill or backfill for the RSS, all surface vegetation, topsoil, trash, construction debris, or other deleterious materials shall be removed from beneath the reinforced soil zone and properly disposed of offsite. Loose, soft, or wet material should also be removed and replaced with competent backfill. All sharp stone protrusions that could damage the reinforcing should also be removed. The subgrade within the footprint of the reinforced soil volume should be graded level as required for construction, proof rolled, and compacted to 95% of Standard Proctor Density (ASTM D698, AASHTO T99). Fill shall be keyed into the existing slope following Section 2- 03.3(14) “Hillside Terraces” of the Standard Specifications. Because of the variable nature of the site fill, field review and approval of the RSS subgrade and construction site preparation below the RSS by the project geotechnical engineer is required. Overexcavation may be required in areas where actual subgrade conditions do not meet the design recommendations. Depth and extent of overexcavation will be as directed by the geotechnical engineer. Fill and Backfill Requirements Backfill within the reinforced zone of the RSS shall consist of Common Borrow, meeting the requirements the RSS Project Technical Specification. The borrow source is expected to be the Renton Formation that is excavated to construct other project elements. The backfill material must be free of organics and other deleterious materials. The maximum particle size should be 3 inches. If wet-weather construction makes it difficult to achieve the required moisture and compaction density, Select Borrow (Section 9-03.14(2)) or Gravel Borrow (Section 9-03.14(1)) shall be used in lieu of Common Borrow. Backfill in the reinforced zone shall be placed in loose lifts of maximum 12-inch thickness and compacted to 95% of maximum density in accordance with the requirements of Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications and the project-specific technical specification (see Attachment C). REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 8 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Backfill behind the reinforced zone shall be Common Borrow in accordance with the requirements of Section 9-03.14(3) of the Standard Specifications, provided that the material can be compacted in accordance with the requirements of Sections 2-03.3(14)C and 2- 03.3(14)D of the Standard Specifications. If wet-weather construction makes it difficult to achieve the required moisture and compaction density, Select Borrow (Section 9-03.14(2)) or Gravel Borrow (Section 9-03.14(1)) may be used in lieu of Common Borrow. Temporary Excavation Limited excavation may be required in order to construct the reinforced soil slope. Temporary excavations sloped to 1:1 should perform adequately during construction. If the Renton Formation bedrock is encountered in temporary excavations needed to place reinforcing grids, the lengths of the geogrid may be reduced, provided the project geotechnical engineer is notified in advance to verify subsurface conditions. In no case shall the reduced length of reinforcing be keyed into the Renton Formation less than 5 feet. Existing Utilities No known utilities cross beneath the proposed the RSS footprint. If any are encountered during construction, they should be brought to the attention of the project geotechnical engineer. In no case should the arrangement of slope reinforcing by modified to accommodate utilities without the approval of the project geotechnical engineer. Drainage and Erosion Control Temporary construction slopes shall direct water away from the RSS slope face to prevent erosion. The face of the RSS shall be stabilized following project temporary erosion and sediment control procedures and shall be planted with permanent vegetation in accordance with the project landscaping plans. References AASHTO (2002). Standard Specifications for Highway Bridges, 17th Edition (2002) – Allowable Stress Design. American Association of State Highway and Transportation Officials, 2002. AASHTO (2007). AASHTO LRFD Bridge Design Specifications, Fourth Edition. American Association of State Highway and Transportation Officials, 2007. FHWA (2001). Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines. U.S. Department of Transportation, Federal Highway Administration. FHWA-NHI-00-043. March 2001. RocScience (2008). SLIDE Version 5.0 - User’s Manual. WSDOT (2008). Geotechnical Design Manual. Washington State Department of Transportation. WSDOT (2008). Standard Specifications for Road, Bridge, and Municipal Construction. Washington State Department of Transportation. M41-10. 90100100 100 100100100 110110 110 110 110110 120120 120120120120 130 130 13 0 130 130 130 130140140140 140140140 150150 150 150 150 1 5 0 160160160 160 160 160 170 170 170 170 170 170 170180180 180 180 180180 190190 190 190 190 19020 0 200 200 200 200 200210 210 210 210 210210220 220 220 220 220 220230230230 230 230 230 240240240240 ROW CLF CLF 200 NO. Washington State Department of Transportation ISSUE DATE ISSUE RECORD - DESCRIPTION DESIGNED BY ENTERED BY CHECKED BY WASH10 NO. DESIGN MANAGER: DESIGN TASK LEAD: PACKAGE: REGION STATE CONTRACT NO. P.E. STAMP BOX DATE B 07/29/09 K. LORENTSONFINAL DESIGN - 1B M. ROHILAC. HERMOGENES 08/14/09 K. LORENTSON M. ROHILAC. HERMOGENES0RELEASE FOR CONSTRUCTION - 1B WSDOT EXCHANGE PROPI-405 AND SR 515 INTERCHANGE STAGE 2 - WIDENING I-5 TO SR 169 SHEET OF SHEETS 7624_04_CG_1_01.dlv2:48:56 PM8/12/20097624150160 160 170170 170 180 180 180 190 190 190200 200 200210 210 220220 230 230230 1110 12 13 14 15 16 9 100101102103EE R.J NO RTHBOUND I-405 SOUTHBOUND I-405 J. BAUMAN K. LORENTSON SCALE IN FEET 0 30 60 A T. 23N. R. 5E. W.M. CG-0-02 CG-0-02 CEDAR RW LINE A S. FORMAN C. HERMOGENES CEDAR AVE S 1230 1230 B 06/19/09 PRELIMINARY DESIGN NB405 LINE SB405 LINE LEGEND 200 1.5:1CUT LINE CG-0-01 NOTES:2:12:11.5:11.5:12:1FILL LINE1.5:12:1 1.5:1 2:1 1.5:12:1 1 .5 :1 2:11.5:12:1 1.5:1 CEDAR RW 10+91.62, 113.77’ RT ELEV 228.00 CEDAR RW 11+63.35, 113.00’ RT ELEV 230.00 CEDAR RW 12+86.86, 8.00’ LT ELEV 232.00 CEDAR RW 11+89.62, 8.00’ LT ELEV 230.00’ CEDAR RW 13+74.52, 114.82’ RT ELEV 234.00 CEDAR RW 14+69.96, 115.25’ RT ELEV 236.00 CEDAR RW 14+00.63, 8.00’ LT ELEV 234.00 CEDAR RW 15+39.28, 118.95’ RT ELEV 236.00 CEDAR RW 15+99.89, 0.00’ RT ELEV 238.00 CEDAR RW 14+97.08, 8.00’ LT ELEV 236.00 CONTOUR GRADING WSDOT EXCHANGE PROPERTY2:1CEDAR RW 12+60.26, 113.59’ RT ELEV 232.00 CEDAR RW 10+97.21, 10.78’ LT ELEV 228.00’ N1^26’53.75"E 2:1 A. BASTASCH DITCH, SEE DRAINAGE PLANS VARIES 2:1 MAX STREAM BUFFER THUNDER HILLS CREEK EXISTING MAJOR CONTOUR EXISTING MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR STREAM/ WETLAND BUFFER SLOPE ARROW LIMITED ACCESS WSDOT ROW AR LI NE 1. 2. 3. 4. ACCESS SEE CG-0-05 1.5:1 629 CEDAR AVE S CONDOMINIUMS FOR DITCH PROFILES, SEE DRAINAGE PLAN AND PROFILES. FOR SLOPE ROUNDING, SEE DLS-0-02. FOR REINFORCED SOIL SLOPE DETAILS, SEE SHEET CG-0-04. FOR EXISTING UTILITIES, SEE UTILITY PLANS. RFC - 1B E405 L INE LIMITS OF FILL WITHIN WSDOT RIGHT-OF-WAY NOT TO EXCEED SIX (6) FEET IN HEIGHT AND NOT TO ENCROACH OVER FILL LINE SHOWN Dense BrushTreesTreesTreesDense BrushBrushBrushBrushSSSSSSSSRandomSIGN Request 140780TR_SN_OverheadSignTR_SN_OverheadSignUTILITY Request 1TP_MM_UnknownObjectTP_MM_UnknownObjectRD_BR_BarrierFaceRD_BR_BarrierFace31379Copy of GEOTECH Request 1Random"EXIT 4""900 WEST""169 SOUTH"100100110110120120120130130130140140140 150150150160160160170170170180180180190190190200200200210210210220220220230230230240240240250250BL_LN_BreaklineGenericBL_LN_BreaklineGeneric1000Book 1BreaklineWSDOT EXCHANGE PROP!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>CEDAR AVENB I-405B-5B-3B-2B-1B-11B-10TP-8TP-7TP-6TP-5TP-4TP-3TP-2TP-1TP-16TP-15TP-14TP-13TP-12515-7-06515-6-06515-4-06SRX-20-05CDB-6p-08050 100 150 20025Feet³Figure 2: WSDOT Exchange PropertySubsurface Investigation Locations I c i c l e C r e e k E n g i n e e r s 0864001/042314 ATTACHMENT B SUPPLEMENTAL BORING LOGS 0 10 15 20 25 30 35 40 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-1 Approximate Ground Surface Elevation: 190 feet Icicle Creek Engineers Page 1 of 3 Boring Log - Figure A-2 Rock 5 Rock Rock Forest duff, topsoil and roots (drill cuttings) SM ICE File No. 0584-001Rock Rock Penetration Resistance (Blows/foot - ) 4020 60 80 Moisture Content (Percent - ) 20 40 60 80 LaboratoryTesting Installation - Ground Water Data Piezometer Soil-Bentonite BackfillGroupSymbolBlowCountSampleLocation5 Rock Rock RockLogged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property See Figure A-1 for explanation of symbols Bentonite Surface SealBrown fine SAND with silt (loose, moist) (drill cuttings) Black COAL (medium dense, moist) (Renton formation) (INTACT COAL - NO. 3 COAL SEAM - NOT MINED) occasional thin layers of carbonaceous shale grades to very dense Light-gray, fine-grained SANDSTONE (very dense, moist) (Renton formation) Brownish-gray , fine-grained SILTSTONE with thin layers of coal (Renton formation) Gray SILTSTONE (Renton formation) Black COAL (Renton formation) Grey SILTSTONE (Renton formation) SP-SM 20 63 50/6” 55 75 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance (Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-1 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 2 of 3 45 65 See Figure A-1 for explanation of symbols Rock Soil-Bentonite Backfill 40 60 80 50 70 Rock Rock Rock Rock Rock Rock Rock Gray SILTSTONE (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-2 Gray SILTSTONE with thin layers of coal (Renton formation) 95 115 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance (Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-1 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 3 of 3 85 105 See Figure A-1 for explanation of symbols Soil-Bentonite Backfill 80 100 120 90 110 Rock Boring completed at 110 feet on May 4, 2005 Rock Gray SILTSTONE with thin layers of coal (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-2 Gray SILTSTONE (Renton formation) Black COAL (Renton formation) Gray SILTSTONE (Renton formation) 0 10 15 20 25 30 35 40 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-2 Approximate Ground Surface Elevation: 190 feet Icicle Creek Engineers Page 1 of 2 Boring Log - Figure A-3 Rock 5 Rock Rock Forest duff, topsoil and roots (drill cuttings) SM ICE File No. 0584-001Rock Rock Penetration Resistance (Blows/foot - ) 4020 60 80 Moisture Content (Percent - ) 20 40 60 80 LaboratoryTesting Installation - Ground Water Data Piezometer Soil-Bentonite BackfillGroupSymbolBlowCountSampleLocation5 Rock Rock RockLogged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property See Figure A-1 for explanation of symbols Bentonite Surface SealSP-SM 26 34 50/5” Brown fine to medium SAND with silt and gravel (medium dense, moist) Black COAL (medium dense, moist) (Renton formation) (INTACT COAL - NO. 3 COAL SEAM - NOT MINED) occasional thin layers of carbonaceous shale grades to dense Light gray fine-grained SANDSTONE (very dense, moist) (Renton formation) Gray SILTSTONE (Renton formation) 78/9” 55 75 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance (Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-2 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 2 of 2 45 65 See Figure A-1 for explanation of symbols Rock Soil-Bentonite Backfill 40 60 80 50 70 Rock Rock Rock Gray SILTSTONE (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-3 Boring completed at 60 feet on May 5, 2005 Gray SILTSTONE with thin layers of coal (Renton formation) 0 10 15 20 25 30 35 40 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-3 Approximate Ground Surface Elevation: 200 feet Icicle Creek Engineers Page 1 of 2 Boring Log - Figure A-4 Rock 5 Rock Rock Forest duff, topsoil and roots (drill cuttings) SM ICE File No. 0584-001Rock Rock Penetration Resistance (Blows/foot - ) 4020 60 80 Moisture Content (Percent - ) 20 40 60 80 LaboratoryTesting Installation - Ground Water Data Piezometer Soil-Bentonite BackfillGroupSymbolBlowCountSampleLocation5 Rock Rock RockLogged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property See Figure A-1 for explanation of symbols Bentonite Surface SealSM 27 25 19 Brown silty fine SAND (medium dense, moist) Black COAL (medium dense, moist) (Renton formation) (INTACT COAL - NO. 3 COAL SEAM - NOT MINED) occasional thin layers of carbonaceous shale Light gray fine-grained SANDSTONE (very dense, moist) (Renton formation) 51 drill action indicates gravel from 7 to 10 feet Gray SILTSTONE (Renton formation) 55 75 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance (Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-3 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 2 of 2 45 65 See Figure A-1 for explanation of symbols Rock Soil-Bentonite Backfill 40 60 80 50 70 Rock Rock Rock Gray SILTSTONE (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-4 Boring completed at 60 feet on May 6, 2005 Brownish-gray SILTSTONE with thin layers of coal (Renton formation)