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Home My WebLink AboutR-402702r,, I GEOTECHNICAL ENGINEERING NOTES N O THE FOLLOWING IS EXCERPTED FROM SECTION 4.0 OF THE GEOTECHNICAL ENGINEERING REPORT PREPARED BY MIGIZI GROUP, PROJECT P1258—T18, DATED 5/18/18 4.0 CONCLUSIONS AND RECOMMENDATIONS Q IT IS OUR UNDERSTANDING THAT THE PROJECT AREA WILL BE STRIPPED, PAVED, AND CONNECTED w TO THE EXISTING WSADA PARKING AREA TO THE NORTH. THE NEW PARKING LOT WILL BE AT OR NEAR EXISTING GRADE. WE OFFER THESE RECOMMENDATIONS: • FEASIBILITY: BASED ON OUR FIELD EXPLORATIONS, RESEARCH, AND EVALUATIONS, THE PROPOSED PAVEMENTS APPEAR FEASIBLE FROM A GEOTECHNICAL STANDPOINT. • PAVEMENT SECTIONS: WE RECOMMEND A CONVENTIONAL PAVEMENT SECTION COMPRISED OF AN ASPHALT CONCRETE PAVEMENT OVER A CRUSHED ROCK BASE COURSE OVER A PROPERLY PREPARED (COMPACTED) SUBGRADE OR A GRANULAR SUBBASE. ALL SOIL SUBGRADES SHOULD BE THOROUGHLY COMPACTED, THEN PROOF —ROLLED WITH A LOADED DUMP TRUCK OR HEAVY COMPACTOR. ANY LOCALIZED ZONES OF YIELDING O SUBGRADE DISCLOSED DURING THIS PROOF —ROLLING OPERATION SHOULD BE OVER J EXCAVATED TO AN ADDITIONAL MAXIMUM DEPTH OF 12 INCHES AND REPLACED WITH A SUITABLE STRUCTURAL FILL MATERIAL. z THE FOLLOWING SECTIONS OF THIS REPORT PRESENT OUR SPECIFIC GEOTECHNICAL CONCLUSIONS AND RECOMMENDATIONS CONCERNING SITE PREPARATION, SPREAD FOOTINGS, SLAB —ON —GRADE FLOORS, ASPHALT PAVEMENT, AND STRUCTURAL FILL. THE WASHINGTON STATE DEPARTMENT OF TRANSPORTATION (WSDOT) STANDARD SPECIFICATIONS AND STANDARD PLANS CITED HEREIN Q REFER TO WSDOT PUBLICATIONS M41-10, STANDARD SPECIFICATIONS FOR ROAD, BRIDGE, AND n MUNICIPAL CONSTRUCTION, AND M21-01, STANDARD PLANS FOR ROAD, BRIDGE, AND MUNICIPAL CONSTRUCTION, RESPECTIVELY. Q 0 4.1 SITE PREPARATION Q PREPARATION OF THE PROJECT SITE SHOULD INVOLVE EROSION CONTROL, TEMPORARY DRAINAGE, CLEARING, STRIPPING, EXCAVATIONS, CUTTING, SUBGRADE COMPACTION, AND FILLING. EROSION CONTROL: BEFORE NEW CONSTRUCTION BEGINS, AN APPROPRIATE EROSION CONTROL SYSTEM SHOULD BE INSTALLED. THIS SYSTEM SHOULD COLLECT AND FILTER ALL SURFACE WATER RUNOFF THROUGH SILT FENCING. WE ANTICIPATE A SYSTEM OF BERMS AND DRAINAGE DITCHES AROUND CONSTRUCTION AREAS WILL PROVIDE AN ADEQUATE COLLECTION SYSTEM. SILT FENCING FABRIC SHOULD MEET THE REQUIREMENTS OF WSDOT STANDARD SPECIFICATION 9-33.2 TABLE 3. IN ADDITION, SILT FENCING SHOULD EMBED A MINIMUM OF 6 INCHES BELOW EXISTING GRADE. AN EROSION CONTROL SYSTEM REQUIRES OCCASIONAL OBSERVATION AND MAINTENANCE. SPECIFICALLY, HOLES IN THE FILTER AND AREAS WHERE THE FILTER HAS SHIFTED ABOVE GROUND SURFACE SHOULD BE REPLACED OR REPAIRED AS SOON AS THEY ARE IDENTIFIED. TEMPORARY DRAINAGE: WE RECOMMEND INTERCEPTING AND DIVERTING ANY POTENTIAL SOURCES OF SURFACE OR NEAR —SURFACE WATER WITHIN THE CONSTRUCTION ZONES BEFORE STRIPPING BEGINS. BECAUSE THE SELECTION OF AN APPROPRIATE DRAINAGE SYSTEM WILL DEPEND ON THE WATER QUANTITY, SEASON, WEATHER CONDITIONS, CONSTRUCTION SEQUENCE, AND CONTRACTOR'S METHODS, FINAL DECISIONS REGARDING DRAINAGE SYSTEMS ARE BEST MADE IN THE FIELD AT THE TIME OF CONSTRUCTION. BASED ON OUR CURRENT UNDERSTANDING OF THE CONSTRUCTION PLANS, SURFACE AND SUBSURFACE CONDITIONS, WE ANTICIPATE THAT CURBS, BERMS, OR DITCHES PLACED AROUND THE WORK AREAS WILL ADEQUATELY INTERCEPT SURFACE WATER RUNOFF. CLEARING AND STRIPPING: AFTER SURFACE AND NEAR —SURFACE WATER SOURCES HAVE BEEN CONTROLLED, SOD, TOPSOIL, AND ROOT —RICH SOIL SHOULD BE STRIPPED FROM THE SITE. THE PROPOSED WORK AREA IS CURRENTLY PAVED AND NO STRIPPING WILL BE NECESSARY. SITE EXCAVATIONS: BASED ON OUR EXPLORATIONS, WE EXPECT THAT EXCAVATIONS WILL ENCOUNTER LOOSE/SOFT TO MEDIUM DENSE/STIFF SILTY, SANDY ALLUVIAL SOILS WHICH CAN BE EASILY EXCAVATED USING STANDARD EXCAVATION EQUIPMENT. DEWATERING: WE ENCOUNTERED GROUNDWATER SEEPAGE IN TWO OF THREE OF OUR EXPLORATIONS AT A DEPTH OF 4 TO 41% FEET BELOW EXISTING GRADE. GIVEN THE FACT THAT OUR EXPLORATIONS WERE PERFORMED JUST OUTSIDE OF WHAT IS GENERALLY CONSIDERED THE RAINY SEASON (NOVEMBER 1 TO MARCH 31), WE DO NOT ANTICIPATE THAT GROUNDWATER WILL RISE MUCH HIGHER THAN THAT WHICH WE OBSERVED. IF GROUNDWATER IS ENCOUNTERED IN SHALLOWER EXCAVATIONS, WE ANTICIPATE THAT AN INTERNAL SYSTEM OF DITCHES, SUMPHOLES, AND PUMPS WILL BE ADEQUATE TO TEMPORARILY DEWATER MOST EXCAVATIONS. FOR DEEPER EXCAVATIONS WELL BELOW THE WATER TABLE, EXPENSIVE DEWATERING EQUIPMENT, SUCH AS WELL POINTS, MAY NEED TO BE UTILIZED IN ORDER TO ADEQUATELY DEWATER EXCAVATIONS. TEMPORARY CUT SLOPES: ALL TEMPORARY SOIL SLOPES ASSOCIATED WITH SITE CUTTING OR EXCAVATIONS SHOULD BE ADEQUATELY INCLINED TO PREVENT SLOUGHING AND COLLAPSE. TEMPORARY CUT SLOPES IN SITE SOILS SHOULD BE NO STEEPER THAN 11xH:1V, AND SHOULD CONFORM TO WASHINGTON INDUSTRIAL SAFETY AND HEALTH ACT (WISHA) REGULATIONS. SUBGRADE COMPACTION: EXPOSED SUBGRADES FOR THE FOUNDATIONS OF THE PLANNED ADDITIONS SHOULD BE COMPACTED TO A FIRM, UNYIELDING STATE BEFORE NEW CONCRETE OR FILL SOILS ARE PLACED. ANY LOCALIZED ZONES OF LOOSER GRANULAR SOILS OBSERVED WITHIN A SUBGRADE SHOULD BE COMPACTED TO A DENSITY COMMENSURATE WITH THE SURROUNDING SOILS. IN CONTRAST, ANY ORGANIC, SOFT, OR PUMPING SOILS OBSERVED WITHIN A SUBGRADE SHOULD BE OVEREXCAVATED AND REPLACED WITH A SUITABLE STRUCTURAL FILL MATERIAL. SITE FILLING: OUR CONCLUSIONS REGARDING THE REUSE OF ONSITE SOILS AND OUR COMMENTS REGARDING WET —WEATHER FILLING ARE PRESENTED SUBSEQUENTLY. REGARDLESS OF SOIL TYPE, ALL FILL SHOULD BE PLACED AND COMPACTED ACCORDING TO OUR RECOMMENDATIONS PRESENTED IN THE STRUCTURAL FILL SECTION OF THIS REPORT. SPECIFICALLY, BUILDING PAD FILL SOIL SHOULD BE COMPACTED TO A UNIFORM DENSITY OF AT LEAST 95 PERCENT (BASED ON ASTM: D-1557). ONSITE SOILS: WE OFFER THE FOLLOWING EVALUATION OF THESE ONSITE SOILS IN RELATION TO POTENTIAL USE AS STRUCTURAL FILL: • FILL: THE FILL THAT OVERLIES THE SITE CONTAINS CONSTRUCTION DEBRIS AND SOME ORGANIC MATERIAL, SO IS NOT REUSABLE AS STRUCTURAL FILL. IF AREAS OF DEBRIS AND ORGANIC —FREE FILL ARE ENCOUNTERED DURING THE CONSTRUCTION PROCESS AND ARE THOUGHT TO BE REUSABLE, WE RECOMMEND THAT MGI EVALUATE THEIR POTENTIAL FOR REUSE. • ALLUVIAL SILT AND SILTY SAND: THE ALLUVIAL SILTY SAND THAT UNDERLIES THE SITE IS VERY MOISTURE SENSITIVE AND WILL BE DIFFICULT OR IMPOSSIBLE TO REUSE DURING MOST WEATHER CONDITIONS. THE MAJORITY OF THIS SOIL TYPE IS CURRENTLY ABOVE THE OPTIMUM MOISTURE CONTENT AND WILL NOT COMPACT ADEQUATELY UNLESS EXTENSIVELY AERATED. • ALLUVIAL FINE TO MEDIUM SAND WITH GRAVEL: WHERE ENCOUNTERED, AND IF PROPERLY SEGREGATED FROM ITS SILTIER COUNTERPART, THE CLEAN NATIVE FINE SANDS ARE A POSSIBLE SOURCE OF STRUCTURAL FILL. THIS MATERIAL TYPE IS RELATIVELY IMPERVIOUS TO MOISTURE CONTENT VARIATIONS AND CAN BE REUSED IN MOST WEATHER CONDITIONS. PERMANENT SLOPES: ALL PERMANENT CUT SLOPES AND FILL SLOPES SHOULD BE ADEQUATELY INCLINED TO REDUCE LONG—TERM RAVELING, SLOUGHING, AND EROSION. WE GENERALLY RECOMMEND THAT NO PERMANENT SLOPES BE STEEPER THAN 2H:1V. FOR ALL SOIL TYPES, THE USE OF FLATTER SLOPES (SUCH AS 2XH:1V) WOULD FURTHER REDUCE LONG—TERM EROSION AND FACILITATE REVEGETATION. SLOPE PROTECTION: WE RECOMMEND THAT A PERMANENT BERM, SWALE, OR CURB BE CONSTRUCTED ALONG THE TOP EDGE OF ALL PERMANENT SLOPES TO INTERCEPT SURFACE FLOW. ALSO, A HARDY VEGETATIVE GROUNDCOVER SHOULD BE ESTABLISHED AS SOON AS FEASIBLE, TO FURTHER PROTECT THE SLOPES FROM RUNOFF WATER EROSION. ALTERNATIVELY, PERMANENT SLOPES COULD BE ARMORED WITH QUARRY SPALLS OR A GEOSYNTHETIC EROSION MAT. 4.2 ASPHALT PAVEMENT SINCE ASPHALT PAVEMENTS WILL BE USED ACROSS MUCH OF THE PROJECT SITE, WE OFFER THE FOLLOWING COMMENTS AND RECOMMENDATIONS FOR PAVEMENT DESIGN AND CONSTRUCTION. SUBGRADE PREPARATION: WE RECOMMEND A CONVENTIONAL PAVEMENT SECTION COMPRISED OF AN ASPHALT CONCRETE PAVEMENT OVER A CRUSHED ROCK BASE COURSE OVER A PROPERLY PREPARED (COMPACTED) SUBGRADE OR A GRANULAR SUBBASE. ALL SOIL SUBGRADES SHOULD BE THOROUGHLY COMPACTED, THEN PROOF —ROLLED WITH A LOADED DUMP TRUCK OR HEAVY COMPACTOR. ANY LOCALIZED ZONES OF YIELDING SUBGRADE DISCLOSED DURING THIS PROOF —ROLLING OPERATION SHOULD BE OVER EXCAVATED TO AN ADDITIONAL MAXIMUM DEPTH OF 12 INCHES AND REPLACED WITH A SUITABLE STRUCTURAL FILL MATERIAL. ALL STRUCTURAL FILL SHOULD BE COMPACTED ACCORDING TO OUR RECOMMENDATIONS GIVEN IN THE STRUCTURAL FILL SECTION. SPECIFICALLY, THE UPPER 2 FEET OF SOILS UNDERLYING PAVEMENT SECTION SHOULD BE COMPACTED TO AT LEAST 95 PERCENT (BASED ON ASTM D-1557), AND ALL SOILS BELOW 2 FEET SHOULD BE COMPACTED TO AT LEAST 90 PERCENT. PAVEMENT MATERIALS: FOR THE BASE COURSE, WE RECOMMEND USING IMPORTED CRUSHED ROCK, SUCH AS "CRUSHED SURFACING TOP COURSE" PER WSDOT STANDARD SPECIFICATION 9-03.9(3). IF A SUBBASE COURSE IS NEEDED, WE RECOMMEND USING IMPORTED, CLEAN, WELL —GRADED SAND AND GRAVEL SUCH AS "BALLAST"OR "GRAVEL BORROW"PER WSDOT STANDARD SPECIFICATIONS 9-03.9(1) AND 9-03.14, RESPECTIVELY. CONVENTIONAL ASPHALT SECTIONS: A CONVENTIONAL PAVEMENT SECTION TYPICALLY COMPRISES AN ASPHALT CONCRETE PAVEMENT OVER A CRUSHED ROCK BASE COURSE. WE RECOMMEND USING THE FOLLOWING CONVENTIONAL PAVEMENT SECTIONS: IY11101TDPm1.114111M116* DRIVEWAYS AND AREAS SECTION AUTOMOBILE PARKING AREAS SUBJECT TO TRUCK TRAFFIC ASPHALT CONCRETE PAVEMENT 2 INCHES 3 INCHES CRUSHED ROCK BASE 4 INCHES 6 INCHES COMPACTION AND OBSERVATION: ALL SUBBASE AND BASE COURSE MATERIAL SHOULD BE COMPACTED TO AT LEAST 95 PERCENT OF THE MODIFIED PROCTOR MAXIMUM DRY DENSITY (ASTM D-1557), AND ALL ASPHALT CONCRETE SHOULD BE COMPACTED TO AT LEAST 92 PERCENT OF THE RICE VALUE (ASTM D-2041). WE RECOMMEND THAT AN MGI REPRESENTATIVE BE RETAINED TO OBSERVE THE COMPACTION OF EACH COURSE BEFORE ANY OVERLYING LAYER IS PLACED. FOR THE SUBBASE AND PAVEMENT COURSE, COMPACTION IS BEST OBSERVED BY MEANS OF FREQUENT DENSITY TESTING. FOR THE BASE COURSE, METHODOLOGY OBSERVATIONS AND HAND —PROBING ARE MORE APPROPRIATE THAN DENSITY TESTING. PAVEMENT LIFE AND MAINTENANCE: NO ASPHALT PAVEMENT IS MAINTENANCE —FREE. THE ABOVE DESCRIBED PAVEMENT SECTIONS PRESENT OUR MINIMUM RECOMMENDATIONS FOR AN AVERAGE LEVEL OF PERFORMANCE DURING A 20—YEAR DESIGN LIFE, THEREFORE, AN AVERAGE LEVEL OF MAINTENANCE WILL LIKELY BE REQUIRED. FURTHERMORE, A 20—YEAR PAVEMENT LIFE TYPICALLY ASSUMES THAT AN OVERLAY WILL BE PLACED AFTER ABOUT 10 YEARS. THICKER ASPHALT AND/OR THICKER BASE AND SUBBASE COURSES WOULD OFFER BETTER LONG—TERM PERFORMANCE BUT WOULD COST MORE INITIALLY; THINNER COURSES WOULD BE MORE SUSCEPTIBLE TO "ALLIGATOR" CRACKING AND OTHER FAILURE MODES. AS SUCH, PAVEMENT DESIGN CAN BE CONSIDERED A COMPROMISE BETWEEN A HIGH INITIAL COST AND LOW MAINTENANCE COSTS VERSUS A LOW INITIAL COST AND HIGHER MAINTENANCE COSTS. 4.3 STRUCTURAL FILL THE TERM "STRUCTURAL FILL" REFERS TO ANY MATERIAL PLACED UNDER FOUNDATIONS, RETAINING WALLS, SLAB —ON —GRADE FLOORS, SIDEWALKS, PAVEMENTS, AND OTHER STRUCTURES. OUR COMMENTS, CONCLUSIONS, AND RECOMMENDATIONS CONCERNING STRUCTURAL FILL ARE PRESENTED IN THE FOLLOWING PARAGRAPHS. MATERIALS: TYPICAL STRUCTURAL FILL MATERIALS INCLUDE CLEAN SAND, GRAVEL, PEA GRAVEL, WASHED ROCK, CRUSHED ROCK, WELL —GRADED MIXTURES OF SAND AND GRAVEL (COMMONLY CALLED "GRAVEL BORROW" OR "PIT —RUN"), AND MISCELLANEOUS MIXTURES OF SILT, SAND, AND GRAVEL. RECYCLED ASPHALT, CONCRETE, AND GLASS, WHICH ARE DERIVED FROM PULVERIZING THE PARENT MATERIALS, ARE ALSO POTENTIALLY USEFUL AS STRUCTURAL FILL IN CERTAIN APPLICATIONS. SOILS USED FOR STRUCTURAL FILL SHOULD NOT CONTAIN ANY ORGANIC MATTER OR DEBRIS, NOR ANY INDIVIDUAL PARTICLES GREATER THAN ABOUT 6 INCHES IN DIAMETER. FILL PLACEMENT: CLEAN SAND, GRAVEL, CRUSHED ROCK, SOIL MIXTURES, AND RECYCLED MATERIALS SHOULD BE PLACED IN HORIZONTAL LIFTS NOT EXCEEDING 8 INCHES IN LOOSE THICKNESS, AND EACH LIFT SHOULD BE THOROUGHLY COMPACTED WITH A MECHANICAL COMPACTOR. COMPACTION CRITERIA: USING THE MODIFIED PROCTOR TEST (ASTM: D-1557) AS A STANDARD, WE RECOMMEND THAT STRUCTURAL FILL USED FOR VARIOUS ONSITE APPLICATIONS BE COMPACTED TO THE FOLLOWING MINIMUM DENSITIES: FILL APPLICATION MINIMUM COMPACTION ASPHALT PAVEMENT BASE 95 PERCENT ASPHALT PAVEMENT SUBGRADE (UPPER 2 FEET) 95 PERCENT ASPHALT PAVEMENT SUBGRADE (BELOW 2 FEET) 90 PERCENT SUBGRADE OBSERVATION AND COMPACTION TESTING: REGARDLESS OF MATERIAL OR LOCATION, ALL STRUCTURAL FILL SHOULD BE PLACED OVER FIRM, UNYIELDING SUBGRADES PREPARED IN ACCORDANCE WITH THE SITE PREPARATION SECTION OF THIS REPORT. THE CONDITION OF ALL SUBGRADES SHOULD BE OBSERVED BY GEOTECHNICAL PERSONNEL BEFORE FILLING OR CONSTRUCTION BEGINS. ALSO, FILL SOIL COMPACTION SHOULD BE VERIFIED BY MEANS OF IN —PLACE DENSITY TESTS PERFORMED DURING FILL PLACEMENT SO THAT ADEQUACY OF SOIL COMPACTION EFFORTS MAY BE EVALUATED AS EARTHWORK PROGRESSES. SOIL MOISTURE CONSIDERATIONS: THE SUITABILITY OF SOILS USED FOR STRUCTURAL FILL DEPENDS PRIMARILY ON THEIR GRAIN —SIZE DISTRIBUTION AND MOISTURE CONTENT WHEN THEY ARE PLACED. AS THE "FINES" CONTENT (THAT SOIL FRACTION PASSING THE U.S. NO. 200 SIEVE) INCREASES, SOILS BECOME MORE SENSITIVE TO SMALL CHANGES IN MOISTURE CONTENT. SOILS CONTAINING MORE THAN ABOUT 5 PERCENT FINES (BY WEIGHT) CANNOT BE CONSISTENTLY COMPACTED TO A FIRM, UNYIELDING CONDITION WHEN THE MOISTURE CONTENT IS MORE THAN 2 PERCENTAGE POINTS ABOVE OR BELOW OPTIMUM. FOR FILL PLACEMENT DURING WET —WEATHER SITE WORK, WE RECOMMEND USING "CLEAN" FILL, WHICH REFERS TO SOILS THAT HAVE A FINES CONTENT OF 5 PERCENT OR LESS (BY WEIGHT) BASED ON THE SOIL FRACTION PASSING THE U.S. NO. 4 SIEVE. Call 811 • • ® two business days before you dig m REVISION SITTS & HILL ENGINEERS, INC. CIVIL ■ STRUCTURAL ■ SURVEYING 4815 CENTER STREET TACOMA, WA. 98409 PHONE: (253) 474-9449 FAX: (253) 474-0153 hftp://www.sittshill.com/ Project No.: 17668 Project Mgr.: KH Proj. Engineer: MBK Proj. Drafter: JMW R-402702 IN COMPLIANCE WITH CITY OF RENTON STANDARDS DEVELOPMENT ENGINEERING Ar*` bbannwarthIL 11/13/2018 W1 SURVEYED: SCALE: AS NOTED VERTICAL:NAVD 1988 83/1 HORIZONTAL: NAD 193/1991 DATU M • CITY 0E RENTON Nuiv Planning/Building/Public Works Dept. WSADA PARKING LOT GEOTECHNICAL ENGINEERING NOTES DATE: DESIGNED: K H flELDB00K: PAGE: DRAWN: JMW ONE INCH DRAWING NO: CO.O CHECKED: MBK AT FULL SCALE IF NOT ONE INCH SCALE ACCORDINGLY BY DATE APPR APPROVE : KH SHEET: OF:25 O Lid O O 00 T u W CM O O O i 00 T O J 0 z oC LL a r) Q U)