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HomeMy WebLinkAbout04-015 Misc_Bales Self Storage34 (later 35) TOWNHOUSES & 19,360 SQ FT OF COMMERCIAL • The applicant is requesting Environmental (SEPA) Review and Administrative Site Plan approval for the construction of four commercial buildings totaling {19,360 sq. ft.) and 10 multi-family buildings. The commercial component would include retail, restaurant, office and a small espresso building. Thirty four (34) townhouse and semi-attached units, a community building and common space are also proposed. The multi-parcel 4.37 acre site is zoned Center Suburban (CS) and currently contains two structures proposed to be removed. Access would be provided from both NE 4th St. and Duvall Ave. NE. Approximately 152 parking stalls, including surface and garage spaces, would be provided. The project also includes the installation of landscaping, a pedestrian walkway and necessary utility and street improvements. The original site plan approval was issued on 3-30-04. On 10-25-04, an minor administrative amendment to relocate a drive through in the commercial area and to increase the building setback from NE 4th street was approved subsequent to the original approval. On 4-8-05, an second amendment to change the community bldg to a 35th unit was approved as a minor administrative amendment subsequent to the original approval. On 2/10/06 Dev. Svcs. Dir. issued extension new exp: 3/31/08 9-1-06 Schneider Homes purchases the property and requests a 3rd administrative modification for a "minor amendment" to alter only the residential portion of the amended site plan approval in order to increase the on-site parking and revise the residential building elevations. This amendment required 3 additional code modifications: : 1) A modification to have fourteen more parking stalls than are typically allowed by the parking code; 2) a modification to have several landscape areas less than the standard minimum of 5' in width; and 3) a modification to the refuse and recycling standards to have individual rather than communal refuse containers. These code modifcations were approved on November 7, 2006. The 3rd minor amendment to the site plan was approved on November 14, 2006. GEOTECHNICAL ENGINEERING STUDY PROPOSED OFFICE BUILDING NORTHEAST 18™ PLACE AND 138TH AVENUE SOUTHEAST RENTON, WASHINGTON E-7570-1 December 21, 2000 PREPARED FOR BALES SELF STORAGE : ·~•_,,')i.~lt..;.G ":\,TC11-.J Earth Consultants, Inc. • f. \~ "I Jf ... 1 'i / .. 1805 -136th Place Northeast, Suite 201 Bellevue, Washington 98005 (425) 643-3780 Toll Free 1-888-739-6670 :J' -('<A ( '/) December 21, 2000 Bales Self Storage PO Box 3015 \, , 111 Earth Consultants Inc. "') (rl·otl'chnical Fn~irwcrs. (i('Ologists & E1wirrmm('!Hcll S< 11 -11 11~1-.; E-7570-1 Renton, Washington 98056 Attention: Subject: Dear Mr. Bales: Mr. Robin Bales Geotechnical Engineering Study Proposed Office Building Northeast 18"' Place and 138"' Avenue Southeast Renton, Washington At your request, we are pleased to present this geotechnical engineering study for the proposed Bales Self Storage Facility, Northeast 18'h Place and 138'h Avenue Southeast, Renton, Washington. The purpose of our work was to evaluate the subsurface conditions at the subject site and based on the conditions encountered, provide geotechnical recommendations for the proposed development. Project Description The general location of the site is shown on the Vicinity Map, Plate 1 . At the time our study was performed, the subject site, proposed building and our test pit locations were approximately as shown on the Test Pit Location Plan, Plate 2. The site will be developed with an office building. The facility will consist of a two story building supported on columns above at grade parking. We anticipate the building will be of concrete and wood-frame construction. Based on our experience with similar, we estimate column loads will be on the order of 80 to 120 kips. Slab-on-grade floor loads are estimate to be on the order of one hundred fifty (150) pounds per square foot. The building will be surrounded by asphalt paved parking and driveway areas. I 805 · 136th Place NE, S,ite 201, Bellevue. Washington 98005 Believue (425) 643-3780 FAX I 425 I 7 46-0860 Toll Free (888) 739-6670 GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21 , 2000 E-7570-1 Page 2 If any of the above project information is incorrect or changes, we should be consulted to review the recommendations contained in this report. In any case, ECI should be retained to perform a general review of the final design. Site Conditions The subject site is located in the southeast corner of 18'" Avenue Southeast and Northeast 1 38'" Place in Renton (see Plate 1, Vicinity Map). The rectangular-shaped lot is bordered to the north by Northeast 18'" Place and residences, to the east by residences, to the south by a commercial development, and to the west by 138'" Avenue Southeast. The site is nearly level, with less than about three feet of elevation change across the length of the site. Vegetation consists of a thin overgrowth of grass. Subsurface conditions were evaluated by excavating and sampling three test pits extending to a depth of six and one half to eight feet below grade. The approximate locations of the test pits are shown on Plate 2. Logs of the test pits are attached. Please refer to the test pit logs for a detailed description of the subsurface conditions. The following is a generalized description of the conditions encountered. Our test pits indicate the site is immediately underlain by two and one half to four feet of fill. The fill consisted of silty gravel with sand (Unified Soil Classification GM) and was generally loose and was characterized by trace amounts of roots and organic debris. Underlying the fill, we encountered native soils comprised of medium dense to dense silty sand with gravel (SM). No groundwater seepage was observed in our test pits. As such, we do not anticipate groundwater seepage will result in significant construction related issues. However, the contractor should be aware that groundwater seepage levels will fluctuate depending on the season, amount of rainfall, surface water runoff, and other factors. Seepage levels and rates are typically higher in the wetter winter months (typically October through May). Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21 , 2000 DISCUSSION AND RECOMMENDATIONS General E-7570-1 Page 3 Based on the results of our study, it is our opinion the proposed office building can be constructed generally as planned. Building support should be provided using a conventional spread and continuous footing foundation system bearing on the competent native soil or on structural fill after removal and replacement of the loose fill immediately underlying the building area. This report has been prepared for specific application to this site only and in a manner consistent with that level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area for the exclusive use of Bales Self Storage and their representatives. No warranty, expressed or implied, is made. This report, in its entirety, should be included in the project contract documents for the information of the contractor. Site Preparation and General Earthwork The building and pavement areas should be stripped and cleared of surface vegetation, organic matter, and any other deleterious material. Existing utility pipes to be abandoned should be plugged or removed so that they do not provide a conduit for water and cause soil saturation and stability problems. Following the stripping and excavating operation, the ground surface where structural fill, foundations, or slabs are to be placed should be observed by a representative of ECI. Proofrolling may be necessary in order to identify soft or unstable areas. Proofrolling should be performed under the observation of a representative of ECI. Soil in loose or soft areas, if recompacted and still yielding, should be overexcavated and replaced with structural fill to a depth that will provide a stable base beneath the general structural fill. The optional use of a geotextile fabric placed directly on the overexcavated surface may help to bridge unstable areas. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21, 2000 E-7570-1 Page 4 Structural fill is defined as compacted fill placed under buildings, roadways, slabs, pavements, or other load-bearing areas. Structural fill under floor slabs and footings should be placed in horizontal lifts not exceeding twelve (12) inches in loose thickness and compacted to a minimum of 90 percent of its laboratory maximum dry density determined in accordance with ASTM Test Designation D-1557-91 (Modified Proctor). The fill materials should be placed at or near their optimum moisture content. Fill under pavements and walks should also be placed in horizontal lifts and compacted to 90 percent of maximum density except for the top twelve (12) inches, which should be compacted to 95 percent of maximum density. During dry weather, most soils, which are compactible and non-organic, can be used as structural fill. Based on the results of our laboratory tests, the on-site soils at the time of our exploration appear to near their optimum moisture content and should be suitable for use in their present condition as structural fill, provided the grading operations are conducted during dry weather. However, the native soils have more than five percent fines passing the No. 200 sieve. Soil with fines in this range will degrade if exposed to excessive moisture, and compaction and grading will be difficult if the soil moisture increases significantly above its optimum condition. If the native soil is exposed to moisture and cannot be adequately compacted then it may be necessary to import a soil which can be compacted. During dry weather, non-organic compactible soil with a maximum grain size of six inches can be used. Fill for use during wet weather should consist of a fairly well graded granular material having a maximum grain size of six inches and no more than 5 percent fines passing the No. 200 sieve based on the minus 3/4-inch fraction. A contingency in the earthwork budget should be included for this possibility. Conventional Foundations Based on the results of our study, it is our opinion the proposed office building can be supported on a conventional spread and continuous footing foundation system bearing on the competent native soil underlying the existing fill, or on structural fill after the overexcavation of the existing fill. Exterior foundation elements should be placed at a minimum depth of eighteen (18) inches below final exterior grade. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty-four (24) inches, respectively. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21, 2000 E-7570-1 Page 5 With foundation support obtained as described, for design, an allowable soil bearing capacity of two thousand five hundred (2,500) psf for the native soil or structural fill can be used. Loading of this magnitude would be provided with a theoretical factor- of-safety in excess of three against actual shear failure. For short-term dynamic loading conditions, a one-third increase in the above allowable bearing capacities can be used. With structural loading as expected, total settlement in the range of one inch is anticipated with differential movement of about one half inch. Most of the anticipated settlements should occur during construction as the dead loads are applied. Horizontal loads can be resisted by friction between the base of the foundation and the supporting soil and by passive soil pressure acting on the face of the buried portion of the foundation. For the latter, the foundation must be poured "neat" against the competent native soils or backfilled with structural fill. For frictional capacity, a coefficient of .30 can be used. For passive earth pressure, the available resistance can be computed using an equivalent fluid pressure of three hundred (300) pcf. These lateral resistance values are allowable values, a factor-of-safety of 1 . 5 has been included. As movement of the foundation element is required to mobilize full passive resistance, the passive resistance should be neglected if such movement is not acceptable. All footing excavations should be observed by a representative of ECI, prior to placing forms or rebar, to verify that conditions are as anticipated in this report. Slab-on-Grade Floors Slab-on-grade floors may be supported on the existing fill recompacted in-place or on structural fill. Areas of the subgrade disturbed during construction must either be recompacted or replaced with structural fill. Slabs should be provided with a minimum of four inches of free-draining sand or gravel. In areas where slab moisture is undesirable, a vapor barrier such as a 6-mil plastic membrane may be placed beneath the slab. Two inches of damp sand may be placed over the membrane for protection during construction and to aid in curing of the concrete. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21, 2000 Seismic Design Considerations E-7570-1 Page 6 The Puget Lowland is classified as a Seismic Zone 3 in the 1994 Uniform Building Code (UBC). Earthquakes occur in the Puget Lowland with regularity, however, the majority of these events are of such low magnitude they are not detected without instruments. Large earthquakes do occur, as indicated by the 1949, 7.2 magnitude earthquake in the Olympia area and the 1965, 6.5 magnitude earthquake in the Midway area. There are three potential geologic hazards associated with a strong motion seismic event at this site: ground rupture, liquefaction, and ground motion response. Ground Rupture: The strongest earthquakes in the Puget Lowland are widespread, subcrustal events, ranging in depth from thirty (30) to fifty-five (55) miles. Surface faulting from these deep events has not been documented to date. Therefore, it is our opinion, that the risk of ground rupture at this site during a strong motion seismic event is negligible. Liquefaction: Liquefaction is a phenomenon in which soils lose all shear strength for short periods of time during an earthquake. Groundshaking of sufficient duration results in the loss of grain to grain contact and rapid increase in pore water pressure, causing the soil to behave as a fluid. To have a potential for liquefaction, a soil must be cohesionless with a grain size distribution of a specified range (generally sand and silt); it must be loose; it must be below the groundwater table; and it must be subject to sufficient magnitude and duration of groundshaking. The effects of liquefaction may be large total and/or differential settlement for structures founded in the liquefying soils. In our opinion, the potential for liquefaction induced settlement of the medium dense to very dense deposits underlying the site should be negligible. Ground Motion Response: Based on the soil conditions, it is our opinion that a soil profile type of S0 , Stiff Soil Profile, should be used from table 16-J of the 1997 UBC. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21, 2000 Excavations and Slopes E-7570-1 Page 7 The following information is provided solely as a service to our client. Under no circumstances should this information be interpreted to mean that ECI is assuming responsibility for construction site safety or the Contractor's activities; such responsibility is not being implied and should not be inferred. In no case should excavation slopes be greater than the limits specified in local, state and Federal safety regulations. Based on the information obtained from our field exploration and laboratory testing, the existing fill would be classified as Type C by OSHA. Temporary cuts greater than four feet in height in Type C soils should be sloped at an inclination of 1.5H:1V. The medium dense to dense native soils underlying the fill would be classified as Type B and can be cut at a 1 H: 1 V inclination. If slopes of this inclination, or flatter, cannot be constructed, temporary shoring may be necessary. Shoring will help protect against slope or excavation collapse, and will provide protection to workers in the excavation. If temporary shoring is required, we will be available to provide shoring design criteria. Permanent cut and fill slopes should be inclined no steeper than 2H: 1 V. Cut slopes should be observed by ECI during excavation to verify that conditions are as anticipated. Supplementary recommendations can then be developed, if needed, to improve stability, including flattening of slopes or installation of surface or subsurface drains. In any case, water should not be allowed to flow uncontrolled over the top of slopes. Permanently-exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. Site Drainage If seepage is encountered in foundation or grade beam excavations during construction, the bottom of the excavation should be sloped to one or more shallow sump pits. The collected water can then be pumped from these pits to a positive and permanent discharge, such as a nearby storm drain. Depending on the magnitude of such seepage, it may also be necessary to interconnect the sump pits by a system of connector trenches. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21 , 2000 E-7570-1 Page 8 During construction, the site must be graded such that surface water is directed off the site and away from building areas. Water must not be allowed to stand in area where buildings, slabs, or pavements are to be constructed. Loose surfaces should be sealed at night by compacting the surface to reduce the potential for moisture infiltration into the soils. Final site grades must allow for drainage away from the building foundations. The ground should be sloped at a gradient of three percent for a distance of at least ten feet away from the structure, except for paved areas, where the grade can be reduced to two percent. LIMITATIONS Our recommendations and conclusions are based on the site materials observed, selective laboratory testing and engineering analyses, the design information provided us, and our experience and engineering judgment. The conclusions and recommendations are professional opinions derived in a manner consistent with that level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. No warranty is expressed or implied. The recommendations submitted in this report are based upon the data obtained from the test pits. Soil and groundwater conditions between test pits may vary from those encountered. The nature and extent of variations between our exploratory locations may not become evident until construction. If variations do appear, ECI should be requested to reevaluate the recommendations of this report and to modify or verify them in writing prior to proceeding with the construction. Additional Services As the engineer of record, ECI should be retained to perform a general review of the final design and specifications to verify the recommendations presented in this letter have been properly interpreted and implemented in the design and in the construction specifications. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Bales Self Storage December 21 , 2000 E-7570-1 Page 9 ECI should also be retained to provide geotechnical services during construction. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. We do not accept responsibility for the performance of the foundation or earthwork unless we are retained to review the construction drawings and specifications, and to provide construction observation and testing services. We appreciate this opportunity to be of continued service to you. If you have any questions, or if we can be of further assistance, please call. Respectfully submitted, EARTH CONSULTANTS, INC. Robert S. Levin Principal SDD/RSL/jme Attachments: Plate 1 Plate 2 Test Pit Logs Vicinity Map Test Pit Location Plan Earth Consultants, Inc. Reference: Puget Sound Area King County/ Map 626 By Thomas Brothers Maps Dated 2000 NOTE: This plate may contain areas of color. ECI cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. tM ~,~h~i!S.\g~e?~2~~~1h;\~~~::al ~~nS; Vicinity Map Bales Self Storage Renton, Washington Drwn. GLS Date Dec. 2000 Proj. No. 7570-1 Checked RDP Date 12/13/00 Plate 1 - • ----- r--1 I I I I L --.J r-----I I I I r--1 I I --I r--1 I L -J I I --I r--1 I I ,1 I L_ I I I I I L -j I I I I I I I I I I L, ,-I I I I I I _, I ' I I L, ,-L, ,- I _, L a I I -J L' I I I I I I I I I L-----I ____ ) I I I I L-----L_ _____ I rl ~l /i.M{::~ -~--.u-,1-.;_,,,., __ ----, Swale I -•-TP-31 TP-11 I -j--•-TP-21 I Parking Area I ' I I I I I I I I _________ J LEGEND TP-1 -7-Approximate Location of ECI Test Pit, Proj. No. E-7570-1, Dec. 2000 Subject Site D Proposed Building ,----1 I I , 1 Existing Building L----- ,----- 1 I I ~, ' ' '-Parking Area I I I I I I r -1 I I __ I L-~ Not -To -Scale Test Pit Location Plan Bales Self Storage Renton, Washington NOTE: This plate may contain areas of color. ECI cannot be responsible tor any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. Drwn. GLS Date Dec. 2000 Pro]. No. 7570-1 Checked RDP Date 12/13/00 Plate 2 -- . - - . - • I _j TEST PIT TP-1 Depth 0.0 -2.5 2.5 -6.5 TEST PIT TP-2 Depth 0.0 -4.0 4.0 -8.0 uses GM SM uses GM SM TEST PIT LOGS E-7570-1 Description FILL: Dark brown silty GRAVEL with sand, loose, moist • contains trace amounts of roots and other organic debris • 15. 7 percent moisture content at 2 feet Gray silty SAND, medium dense to dense, moist • 9.6 percent moisture content at 5 feet • no groundwater seepage encountered at time of excavation Description FILL: Dark brown silty GRAVEL with sand, loose, moist • contains trace amounts of roots and other organic debris • 13 percent fines at 2 feet • 6.8 percent moisture content at 2 feet • 13.8 percent moisture content at 4 feet Gray silty SAND, medium dense to dense, moist • 10.0 percent moisture content at 7 feet • no groundwater seepage encountered at time of excavation Earth Consultants, Inc. TEST PIT TP-3 Depth 0.0 -4.0 4.0 -6.5 uses GM SM Description FILL: Dark brown silty GRAVEL with sand, loose, moist • contains trace amounts of roots and other organic debris • 28.4 percent moisture content at 3 feet Gray silty SAND, medium dense, moist • no groundwater seepage encountered at time of excavation Earth Consultants, Inc.