Report Geotechnical Engineering Services Lift Station No. 3 Rehabilitation Whitecaps Circle Maitland, Orange County, Florida PSI Project No.

Transcription

1 Report Geotechnical Engineering Services Lift Station No. 3 Rehabilitation Whitecaps Circle Maitland, Orange County, Florida PSI Project No

2 June 10, 2015 Burgess & Niple, Inc Pembrook Drive Suite 265 Orlando, Florida Attention: Mr. Scott D. Perfater, P.E. Vice President RE: Report Geotechnical Engineering Services Maitland Lift Station No. 3 Rehabilitation Whitecaps Circle Maitland, Orange County, Florida PSI Project No Dear Mr. Perfater: PSI has completed a subsurface exploration program at the site of the referenced project. Our services were performed in accordance with PSI Proposal No and your authorization through an agreement dated May 13, The subsurface exploration was conducted to provide geotechnical engineering recommendations for site preparation and wet well design for the rehabilitation of Lift Station No. 3. The following report presents the results of our exploration as well as our recommendations pertaining to the geotechnical aspects of the project. PROJECT INFORMATION The project site is located on Whitecaps Circle, approximately 300 feet south of the intersection of Adams Drive and Whitecaps Circle in Maitland, Orange County, Florida. The existing lift station is located on the east side of Whitecaps Circle, a narrow residential roadway. Overhead power lines are present above the lift station and adjacent roadway. Based on information provided to us, we understand that the City of Maitland plans a rehabilitation of the existing wastewater Lift Station No. 3. We understand a new wet well and associated pump equipment will be installed to replace the existing lift station. The station is anticipated to extend to a maximum depth of 12 to 16 feet below the existing ground surface and the wet well is planned to be a 6 to 8-foot diameter concrete structure. Professional Service Industries, Inc rd Street Orlando FL Phone 407/ Fax 407/ Engineering Certificate of Authorization 3684

3 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 2 of 8 If any of the stated information is incorrect or has been changed, PSI should be notified so appropriate changes to our recommendations can be incorporated in this report. USGS Quadrangle Map REVIEW OF PUBLISHED INFORMATION The topographic survey map published by the (USGS) entitled Orlando East, Florida was reviewed for ground surface features in the vicinity of the project. Based on this review, the project site is located in an urban area containing single-family residential homes. The map indicates the ground surface elevation in the vicinity of the site is approximately +70 feet NGVD. Lake Maitland has a reported normal water level of +66 feet NGVD. No site-specific topographic data was provided to us to compare with the USGS data. An excerpt of the topographic map is provided in the Appendix (Figure 1). Orange County Soil Survey The Soil Survey of Orange County, Florida, published by the USDA SCS, was reviewed for general near-surface soil information within the general project vicinity. This information indicates one soil mapping unit at the project location. The mapped soil unit is summarized in the following table. Soil Series 48 Tavares-Urban land complex, 0 to 5 percent slopes Depth (inches) Unified Classification USDA Seasonal High Groundwater Table Depth (feet) 0 to 80 SP, SP-SM, SM 3.5 to 6.0 Tavares-Urban land complex, 0 to 5 percent slopes (Soil Group No. 48) consists of moderately well drained soil found on low ridges and knolls on the uplands and on the flatwoods. Soil Series 48 generally is in areas that are artificially drained, but in undrained areas, a seasonal high water table is typically at a depth of between 3.5 to 6 feet during more than half of the year. An excerpt of the SCS Orange County Soil Survey map (Figure 2) showing the approximate site location is included in the Appendix.

4 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 3 of 8 General FIELD EXPLORATION Due to energized overhead power lines and numerous existing underground utilities at and around the site, PSI was limited to performing one (1) hand auger boring to a depth of 7 feet below existing grade. The approximate location of our boring is shown on Sheet 1 in the Appendix. The boring was performed in general accordance with the procedures of ASTM D The soil types encountered at the specific boring location are presented in the form of a soil profile on Sheet 2 in the Appendix. Included with the boring profile is a legend describing the encountered soils in USCS format and the measured groundwater level. The results of laboratory testing are provided adjacent to the boring log at the depth interval from which the sample was obtained. The soil stratification presented is based on visual observation of the recovered soil samples and interpretation of the field log by a geotechnical engineer. It should be noted that variations in the subsurface conditions are expected and may be encountered away from the boring location. Also, whereas the boring log indicates distinct strata breaks, the actual transition between the soil layers may be more gradual than shown on the soil profile. Soil Conditions The boring revealed alternating deposits of fine sands grading from relatively clean to slightly silty fine sands (i.e. SP and SP-SM materials) and highly organic soil (Peat material) to the boring termination depth of 7 feet. The peat layer was encountered between approximately 3 and 4 feet below the existing ground surface. Groundwater Conditions At the time of our fieldwork (May 18, 2015), groundwater was encountered at a depth of approximately 3 feet below the existing ground surface. Groundwater conditions vary with environmental changes and seasonal conditions, such as the frequency and magnitude of rainfall patterns, and man-made influences such as swales, drainage ponds, underdrains and areas of covered soil (paved parking lots, sidewalks, etc.). The estimated normal seasonal high groundwater levels presented herein are based on the observed soil stratigraphy, measured groundwater levels in the borings, USDA Soil Survey information, and our past experience in the project vicinity. In this regard, we estimate the normal seasonal high groundwater level will be at or slightly higher than the high water level in Lake Maitland. In general, the normal seasonal high groundwater level is not intended to define a limit or ensure that future seasonal fluctuations in groundwater levels will not exceed the estimated levels. Postdevelopment groundwater levels could exceed the normal seasonal high groundwater level estimate as a result of a series of rainfall events, changed conditions at the site that alter surface water drainage characteristics, or variations in the duration, intensity, or total volume of rainfall.

5 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 4 of 8 General SITE PREPARATION CONSIDERATIONS The following recommendations have been developed on the basis of the previously described project characteristics and subsurface conditions encountered. If there is any change in the project criteria, a review must be made by PSI to determine if additional fieldwork and/or any modifications to our recommendations will be required. Once final design plans and specifications are available, a general review by PSI is strongly recommended as a means to check that the evaluations made in preparation of this report are correct and that earthwork and foundation recommendations are properly interpreted and implemented. Site Clearing/Stripping At the outset of construction, removal or rerouting of existing utilities, clearing and grubbing (including removal of any organic-laden soil), and performing any required excavations should be completed. This normally includes removing the surface vegetation, stripping topsoil, grubbing major root systems, and removing any miscellaneous debris, organic soils (i.e. Stratum 2) and/or other deleterious materials. It should be noted that unsuitable organic soils may be present at depths below the termination of PSI s boring. Material generated during stripping operations should be disposed of off-site in a proper manner as directed by the Owner. Initial site clearing and preparation work should be carried out under the observation of a representative of the geotechnical engineer. Fill Placement and Subgrade Preparation Following excavation for the new lift station, the subgrade area should be inspected to confirm no unsuitable soils are present. The exposed subgrade should be evaluated as directed by representatives of PSI to confirm that all unsuitable materials have been removed. Due to the small size of the area, this may consist of probing the area using a static-cone penetrometer. It may be necessary to use a light, jumping jack or vibratory plate compactor in confined areas to avoid damaging in-place utilities or structures. Careful observations should be made prior to fill placement to help identify any areas of soft/yielding soils that may require over-excavation and replacement filling. Engineered Fill Any off site fill imported for the project should consist of clean fine sand with less than 12 percent by dry weight passing the U.S. Standard No. 200 sieve and be free of rubble, organics, clay, debris and other deleterious material. Fill should be tested and approved prior to import and placement. Each lift should have a loose thickness not exceeding 12 inches. Density tests should be performed to confirm the required compaction is being achieved prior to placing the next lift.

6 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 5 of 8 Prior to beginning compaction, soil moisture conditioning may be required. Soil moisture contents should be controlled in order to facilitate proper compaction. A moisture content within two percentage points of the material s optimum indicated by the modified Proctor test (ASTM D-1557) is recommended prior to compaction of the natural ground and fill. Any fill placed in structural areas should be compacted to at least 95 percent of the material s modified Proctor (ASTM D-1557) maximum dry density. FOUNDATION DESIGN CONSIDERATIONS Based on our evaluations and analyses, the soil conditions encountered in the borings performed for the project are considered capable of supporting the proposed structure on a shallow foundation system following satisfactory completion of the subgrade preparation recommendations noted herein, particularly the removal of unsuitable materials (i.e. organic soils including Stratum 2, roots, debris, etc.) are removed from foundation areas. Based on the anticipated construction and recommended site preparation, foundations may be designed for a net allowable bearing pressure of 2,000 pounds per square foot (psf). The foundations should bear on properly placed and compacted cohesionless (sand) fills and/or densified native sandy soils as discussed previously. All foundation excavations should be observed by the Geotechnical Engineer or his representative to explore the extent of any fill, excessively loose, soft, or otherwise undesirable materials. If the foundation excavations appear suitable for support, the bottom of foundation excavations should be compacted after excavation. The subgrade soils should be compacted to a minimum density requirement of 95 percent of the material s modified Proctor (ASTM D-1557) maximum dry density for a minimum depth of two feet below the bottom of footings, as determined by field density compaction tests. If soft, loose or unsuitable materials are encountered in the foundation excavations, then such materials should be removed and the subgrade re-established by backfilling. This backfilling may be done with a well-compacted, suitable fill such as engineered fill, a lean concrete, or crushed FDOT No. 57 or FDOT No. 67 stone. Sand backfill should be compacted to at least 95 percent of the material s modified Proctor maximum dry density (ASTM D-1557), as previously described. Crushed stone should be compacted to a firm and unyielding condition. If the recommended subgrade preparation operations presented herein are properly performed, total foundation settlement should be less than one inch. Differential settlements should be approximately 50 percent of the total movements. The settlement of shallow foundations supported on sandy soils should occur relatively quickly after initial loading. Thus, the majority of expected settlement should occur during construction as dead loads are imposed.

7 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 6 of 8 Earth Pressures on Walls OTHER CONSIDERATIONS The wet well for the project should be designed to resist pressures exerted by the adjacent soils and hydrostatic head. For walls that are not restrained during backfilling but are free to rotate at the top, active earth pressure should be used in design. Walls that are restrained should be designed assuming at-rest pressures. Recommended soil parameters for the near-surface granular soils encountered at the site are presented in the following. Total Unit Weight, b = 120 lb/ft 3 Angle of Internal Friction, = 30 Coeff. of Sliding Friction = 0.40 Active Soil Pressure coeff., Ka = 0.33 At-rest Soil Pressure coeff., Ko = 0.50 Passive Soil Pressure coeff., Kp = 3.00 Design should incorporate hydrostatic effects. In order to avoid wall damage due to excessive compaction, hand operated mechanical tampers should be used to densify backfill soils; heavy compaction equipment should not be allowed within five feet of walls. The soils behind walls should consist of clean sands as described in the Engineered Fill section of this report and should be compacted to approximately 95 percent of the material s modified Proctor (ASTM D-1557) maximum dry density. Site Dewatering Based on the anticipated excavation depth, dewatering will likely be necessary. Excavations that are only a few feet below the water table can typically be dewatered with a sump pump. Deeper excavations will most likely require well pointing to achieve adequate drawdown. In either case, the dewatering system should be designed and operated to lower the groundwater table to a depth at least 2 feet below the bottom of surfaces to be compacted in any given area. The dewatering process may have an effect on nearby structures, as lowering the groundwater table will cause an increase of effective stress in the soils. A qualified dewatering contractor should be used to develop a dewatering plan that will minimize the impact on nearby structures. The discharge from the dewatering system should be handled in accordance with current regulatory criteria. Excavations In Federal Register, Volume 54, No. 209 (October 1989) the United States Department of Labor, Occupational Safety and Health Administration (OSHA) amended its Construction Standards for Excavations, 29 CFR, part 1926, Subpart P. This document was issued to better insure the safety of workmen entering trenches or excavations. It is mandated by this federal regulation that excavations, whether they be utility trenches, general construction excavations or footing excavations, be constructed in accordance with the new OSHA guidelines. It is our understanding that these regulations are being strictly enforced and if they are not closely followed the Owner and the contractor could be liable for substantial penalties.

8 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 7 of 8 The contractor is solely responsible for designing and constructing stable, temporary excavations and should shore, slope, or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom. The contractor s responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor s safety procedures. In no case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in local, state, and federal safety regulations. PSI is providing this information solely as a service to our client. PSI does not assume responsibility for construction site safety or the contractor s or other parties compliance with local, state, and federal safety or other regulations. REPORT LIMITATIONS Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. This company is not responsible for the conclusions, opinions or recommendations made by others based on these data. The scope of PSI s geotechnical study was intended to evaluate soil conditions within the influence of the proposed lift station and does not include an evaluation of potential deep soil problems such as sinkholes. The analysis and recommendations submitted in this report are based upon the data obtained from the soil boring performed at the location indicated. If any subsoil variations become evident during the course of this project, a re-evaluation of the recommendations contained in this report will be necessary after we have had an opportunity to observe the characteristics of the conditions encountered. The applicability of the report should also be reviewed in the event significant changes occur in the design, nature or location of the proposed construction. The scope of our services does not include any environmental assessment or investigation for the presence or absence of hazardous or toxic materials in the soil, groundwater, or surface water within or beyond the site studied. Any statements in this report regarding odors, staining of soils, or other unusual conditions observed are strictly for the information of our client.

9 Burgess & Niple, Inc. June 10, 2015 PSI Project No Page 8 of 8 CLOSURE PSI appreciates the opportunity to provide our services to Burgess & Niple, Inc. on this project and we trust the information presented herein is sufficient for your needs at this time. If you have any questions regarding the contents of this report, or if we may be of further service, please contact the undersigned. Sincerely, PROFESSIONAL SERVICE INDUSTRIES, INC. Certificate of Authorization No Max S. McGahan, E.I. Staff Engineer Jonathan K. Thrasher, P.E. Project Engineer Florida License No Robert A. Trompke, P.E. Principal Consultant/Department Manager Florida License No (Maitland Lift Station No. 3 Rehab).doc Attachments Figure 1 USGS Vicinity Map Figure 2 USDA Soils Map Sheet 1 Boring Location Plan Sheet 2 Boring Profile

10 APPENDIX

11 APPROXIMATE SITE LOCATION REFERENCE: U.S.G.S SECTION: TOWNSHIP: RANGE: SOUTH 30 EAST "ORLANDO EAST, FLORIDA" QUADRANGLE MAP ISSUED: PHOTOREVISED: SCALE: "=2000' LIFT STATION No. 3 REHABILITATION WHITECAPS CIRCLE

12 APPROXIMATE SITE LOCATION 48 REFERENCE: U.S.D.A.-S.C.S. "ORANGE COUNTY, FLORIDA" SOILS MAP SECTION: TOWNSHIP: RANGE: SOUTH 30 EAST ISSUED: SCALE: AUGUST "=500' SOILS LEGEND LIFT STATION No. 3 REHABILITATION WHITECAPS CIRCLE

13 AB-1 LOCATION PLAN SCALE: 1"=100' LEGEND APPROXIMATE LOCATION OF AUGER BORING LIFT STATION No. 3 REHABILITATION WHITECAPS CIRCLE

14 AB-1 SOIL PROFILE SCALE: 1"=5' LEGEND LIGHT BROWN TO GRAY-BROWN FINE SAND TO SLIGHTLY SILTY FINE SAND, (SP), (SP-SM) DARK BROWN PEAT, (PT) (SP) UNIFIED SOIL CLASSIFICATION GROUP SYMBOL DEPTH TO GROUNDWATER LEVEL IN FEET WITH DATE OF READING W -200 OC NATURAL MOISTURE CONTENT IN PERCENT FINES PASSING #200 SIEVE IN PERCENT ORGANIC CONTENT IN PERCENT LIFT STATION No. 3 REHABILITATION WHITECAPS CIRCLE