Loading...
HomeMy WebLinkAbout940677-008; Poinsiettia Shores Planning Area C; Poinsiettia Shores Planning Area C; 1998-01-27HI m LEIGHTON AND ASSOCIATES, INC. Geotechnicol and Environmental Engineering Consultants GEOTECHNICAL REPORT FOR TENTATIVE MAP PURPOSES, POINSETTIA SHORES, PLANNING AREA C, CARLSBAD, CALIFORNIA January 27, 1998 Project No. 940677-008 Prepared For: COLRICH COMMUNITIES 4141 Jutland Drive, Suite 200 San Diego, California 92117 3934 MURPHY CANYON ROAD, SUITE B205, SAN DIEGO, CA 92123 (619) 292-8030 • (800) 447-2626 FAX (619) 292-0771 m LEIGHTON AND ASSOCIATES, INC. Geotechnicol and Environmental Engineering Consultants ^^i m m m m January 27,1998 ProjectNo. 4940677-008 To: ColRich Communities 4141 Jutland Drive, Suite 200 San Diego, California 92117 Attention: Mr. John Sherritt Subject: Geotechnical Report for Tentative Map Purposes, Poinsettia Shores Planning Area C, Carlsbad, California References: Geocon, Inc., 1994, Geotechnical Investigation for Poinsettia Shores, Carlsbad, California, Project No. 05318-12-01, dated June 3,1994. International Conference of Building Officials (ICBO), 1994, Uniform Building Code, Volume I-Administrative, Fire- and Life-Safety, and Field Inspection Provisions; Volume II-Structural engineering Design Provisions; and Volume III - Material, Testing and Installation,Provisions: ICBO. Leighton and Associates, Inc. 1995, Final As-Graded Report of Rough Grading, Lots 1 through 8, Lot 79, and Unit II, Poinsettia Shores, Carlsbad Tract 94-01, Carlsbad, California, dated October 20 1995. O'Day Consultants, 1998, Poinsettia Shores Planning Area 'C' Tentative Map, Scale 1 "=40,2 Sheets, dated January 26,1998. Introduction In response to your request, this report has been prepared for tentative map purposes to update the geotechnical conditions and provide preliminary geotechnical recommendations relative to planned development of Poinsettia Shores Planning Area C located in Carlsbad, California (see Site Location Map, Figure 1). The purpose of our geotechnical evaluation for tentative map purposes is to review the existing site conditions and the project geotechnical reports relative to the geotechnical conditions of the site and to provide preliminary geotechnical recommendations (including foundation design considerations) for the planned development. 3934 MURPHY CANYON ROAD, SUITE B205, SAN DIEGO, CA 92123 (619) 292-8030 • (800) 447-2626 FAX (619) 292-0771 ** 940677-008 *** Accompanying Tables. Figures. Plate and Appendix m Table 1 - Minimum Foundation and Slab Design Recommendations- 7 '* Table 2 - Post-Tensioned Foundation Design Recommendations - Page 8 •m Table 3 - Minimum Presaturation Recommendations for Conventional Foundation Subgrade Soils-Page 10 Table 4 - Minimum Foundation Setback from Slope Faces - Page 10 f Table 5 - Lateral Earth Pressures - Page 11 ^jj Figure 1 - Site Location Map - Page 3 Figure 2 - Retaining Wall Drainage Detail - Page 12 m Plates 1 and 2 - GeotechnicalMap - In Pocket ^ Appendix A - General Earthwork and Grading Specifications for Rough Grading- Rear of Text m Proposed Development pi Based on the site development plans prepared by O'Day Consultants (O'Day, 1998), the proposed development of Planning Area C will consist of the construction of 56 attached residential single-family structures and associated improvements. Site improvements are anticipated to include the installation of underground utilities and construction of the private and common street pavement sections. Fine grading is also anticipated to include the placement of approximately 60,000-cubic yards of fill. *• Existing Site Conditions On January 15, 1998, a geologist from Leightonand Associates performed a site reconnaissance to observe ** the existing geotechnical conditions of the Poinsettia Shores, Planning Areas C project. In addition, the Hi project geotechnical reports (Geocon, 1994, and Leighton, 1995) were reviewed. Based on our site reconnaissance and review of the project reports, the site was rough-graded creating three relatively flat, *" sheet-graded pads and associated slopes. « The rough-grading operations were performed between October 8, 1994 and October 20, 1995 under the *• testing and observation of Leighton and Associates (Leighton, 1995). The grading operations included 1) M the removal of potentially compressible documented and undocumented artificial fill, topsoil, and weathered formational material; 2) construction of fill slope keys; 3) the placement of compacted fill; and •» 4) the excavation of formational material in cut areas. In addition, four desilting basin and associated buried ^ storm drain pipes were constructed on the site. IP As-Graded Geotechnical Conditions m Based on the project as-graded report (Leighton, 1995), the geologic units encountered during site rough- grading were generally similar to those described in the project geotechnical investigation report (Geocon, 1994). The geologic units mapped within the site boundaries of Planning Area C currently include previously placed documented fill soils and Quaternary-aged Terrace Deposits. The documented fill is present at grade predominantly in the north corner and southern portions of the site and generally consists of ** silty to slightly silty sands derived from the Terrace Deposits and Santiago Formation. Terrace Deposits were encountered at grade in the central portion of the site and extend below the fill material placed during the rough-grading procedures. The Tertiary-aged Santiago Formation underlies the entire site at depth, but -2- LEIGHTOHAHD ASSOCIATES, INC. BASE MAP: Thomas Bros. GeoFinder for Windows, San Diego County, 1995, Page 1126 2000 4000 APPROXIMATE SCALE IN FEET Poinsettia Shores Planning Area C Carlsbad, California SITE LOCATION MAP PROJECT No. 4940677-008 DATE January 1998 LnJ FIGURE No. 1 m 940677-008 * is not anticipated to be exposed at finish grade on the Planning Area C site. The approximate location of the HI geologic units are indicated on the Geotechnical Maps (Plates 1 and 2). « gg Ground Water ip Ground water was not encountered or anticipated during the rough-grading operations at the site (Leighton, ^ 1995) nor observed during our recent site reconnaissance. Perched groundwater or seepage may occur over time in response to increased irrigation, rainfall, changes in surface drainage or as of the result of future m grading or improvements. m Findings and Conclusions g^Based on our site reconnaissance and review of the appropriate project geotechnical reports, the subject site has not significantly changed since the completion of rough grading. Observations of the site during our reconnaissance indicated the following geotechnical conditions and/or concerns are present on the site: • Minor to moderate erosion and rilling has occurred to most of the slopes on the site. The erosion ** gullies/rills are generally less than approximately 1 foot. • A moderate growth of weeds and small shrubs are present across the surface of the site.*•» m In conclusion, it is our professional opinion that Planning Area C is suitable for the intended residential use provided the geotechnical recommendations presented herein are incorporated into the fine-grading and <" residential construction phases of the proj ect. a *» Recommendations Recommendations presented herein should be followed during the future grading and residential m construction phases of the project. However, it should be noted that the recommendations presented herein are preliminary and may be subject to change based on the actual as-graded geotechnical conditions of the site (after the building pads and private drives are graded to the planned design). gm *" Earthwork We anticipate that earthwork at the site will consist of site preparation, fill placement, and trench excavation 911 and backfill. We recommend that earthwork on site be performed in accordance with the following recommendations, the City of Carlsbad grading requirements, and the General Earthwork and Grading Specifications for Rough Grading (GEGS) included in Appendix A. In case of conflict, the following ** recommendations shall supersede those included as part of Appendix A. -4- LEIGHTON AND ASSOCIATES, INC. 940677-008 Site Preparation Prior to the grading of areas to receive structural fill or engineered structures, the area should be cleared of surface obstructions, any existing debris, potentially compressible material (such as desiccated fill soils, etc.) and stripped of vegetation. Vegetation and debris should be removed and properly disposed of offsite. Holes resulting from the removal of buried obstructions and/or erosion gullies which extend below finished site grades should be cleaned out to competent material and replaced with suitable compacted fill material. Due to the length of time since the construction and placement of the fill soils on the site and the moderate amount of erosion of the site, the surficial soils of the site have become desiccated. As a result, we recommend that areas of planned grading be overexcavated and/or reprocessed a minimum of 1 to 2 feet, moisture-conditionedto a near-optimum moisture-content and compacted to a minimum 90 percent relative compaction (based on American Standard of Testing and Materials [ASTM] Test Method Dl 557-96). Construction of Fill Slopes Keys Prior to the construction of fill slopes and/or fill-over-cut slopes, a key should be constructed at the base of the fill (as indicated in Appendix A). The key should be constructed a minimum of 2 feet below the toe-of-slope,a minimum of 15 feet wide with the key bottom angled a minimum of 2 percent into-the- slope. The 2-foot depth requirement is not needed for a fill-over-cut slope key.m m • Cut/Fill Transition Pads The cut/fill transition condition on the planned building pads were not mitigated during the rough- grading operations. Once the actual site development plans are prepared and the locations of the cut/fill transitions are known, the cut portion of the building pads should be overexcavated a minimum of 3 feet below the finish pad grade (at least 5 feet outside the building footprint) and replaced with compacted fill. Cut/fill transition conditions should be determined in the field during the planned fine-grading operations. Storn Drain Pipe Desilting Basin Removals We recommend that the loose silt that has accumulated in the onsite desilting basins and any saturated and soft fill soils at the base and along the sides of the basin be completely removed to competent material prior to the placement of additional fill. We estimate the removals in the bottom of the desilting basin will be on the order of 2 to 5+ feet in depth. If the storm drain pipes are to be abandoned, we recommend the storm drain pipe be removed and the excavation filled in with compacted fill (minimum 90 percent relative compaction based on ASTM Test Method D1557-96). Storm drain pipe not removed should be completely filled with a sand-cement slurry.•I ** • Fill Placement and Compaction The on-site soils are generally suitable for use as compacted fill provided they are free of organic material, trash or debris, and rock fragments larger than 8 inches in maximum dimension. All fill soils should be brought to near-optimum moisture conditions and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method -5- LEIOHTOHAHO ASSOCIATES, INC. •» 940677-008 ** D1557-96). The optimum lift thickness required to produce a uniformly compacted fill will depend on H the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general * accordance with the current City of Carlsbad grading ordinances, sound construction practices, and the M General Earthwork and Grading Specifications of Rough Grading presented in Appendix A. m • Excavations •Excavations of the on-site materials may generally be accomplished with conventional heavy-duty m earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of ^ oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during grading. If oversized rock is encountered, it should be placed as fill in accordance with the details pi presented in Appendix A. H Due to the relatively high density characteristics and coarse nature of the on-site soils, temporary m excavations such as utility trenches with vertical sides in the on-site soils should remain stable for the period required to construct the utility, provided they are free of adverse geologic conditions. However, in accordance with OSHA requirements, excavations between 5 and 15 feet in depth should be shored or laid back to inclinations of 1:1 (horizontal to vertical) if workers are to enter such excavations. For excavations deeper than 15 feet, specific recommendations can be made on a case-by-case basis.m • Foundation Design Considerations4H <* The proposed residential foundations should be designed in accordance with structural considerations and the recommendations presented herein. Specific recommendations will be made after site regrading m has been completed. Generally, we assume that the finish grade soils of the site will posses a very low • to low expansion potential and therefore, the residential structures may be constructed with either conventional or post-tensioned foundations. m H The conventional or post-tensioned foundations should be designed and constructed in accordance with the design parameters presented in the following sections. 91 gj • Conventionallv-ReinforcedFoundation Design (all lots) <•» Conventionally-reinforced foundations should be designed and constructed in accordance with the recommendations contained in Table 1 and the expansion potential of each lot. The actual lot specific expansion potential is expected to range from very low to low (per U.B.C. 18-2) and will be determined jp following site regrading. llg The vapor barrier should be sealed at all penetrations and laps. Moisture vapor transmission may be additionally reduced by the use of concrete additives. Moisture barriers can retard but not eliminate moisture vapor movement from the underlying soils up through the slabs. We recommend that the floor ** coverings installer test the moisture vapor flux rate prior to attempting applications of the flooring. "Breathable" floor coverings should be considered if the vapor flux rates are high. A slipsheet or equivalent should be utilized above the concrete slab if crack-sensitive floor coverings (such as ceramic " tiles, etc.) are to be placed directly on the concrete slab. -6- LEIGHTOH AND ASSOCIATES, IHC. 940677-008 Table 1 Minimum Foundation and Slab Design Recommendations U.B.C. Expansion Index 0-20 Very Low Expansion U.B.C. Expansion Index 21-50 Low Expansion 1-Story Footings (See Note 1) All footings 12" deep. Reinforcementfor continuous footings: one No. 4 bar top and bottom. All footings 12" deep. Reinforcementfor continuous footings: one No. 4 bar top and bottom. 2-Story Footings (See Note 1) All footings 18" deep. Reinforcementfor continuous footings: one No. 4 bar top and bottom. All footings 18" deep. Reinforcementfor continuous footings: one No. 4 bar top and bottom. Minimum Footing Width Continuous: 12" for 1-story Continuous: 15" for 2-story Isolated column: 24" (18" deep minimum) Continuous: 12" for 1-story Continuous: 15" for 2-story Isolated column: 24" (18" deep minimum) Garage Door Grade Beam (See Note 2) A grade beam 12" wide x 12" deep (18" deep for 2-story) should be provided across the garage entrance. A grade beam 12" wide x 12" deep (18" deep for 2-story) should be provided across the garage entrance. Living Area Floor Slabs (See Notes 3,4 and 6) Minimum4" thick slab (6x6-10/1OWWF, No. 3 bars @ 18" or No. 4 rebars @ 24" on center each way at mid-height. 2" clean sand over 6 mil moisture barrier on pad. Minimum4" thick slab. 6x6-10/10WWF, No. 3 bars @ 18", or No. 4 bars @ 24" on center, each way at midheight. 2" clean sand over 6 mil moisture barrier over 2" clean sand. Garage Floor Slabs (See Notes 4,5 and 6) Minimum 4" thick concrete slab on 2" sand base over moisture barrier on pad 6x6-10/10 WWF, No. 3 bars @ 18", or No. 4 rebars @24" on center each way at midheight. Slab should be quarter-sawn. Minimum 4" thick on 2" sand base over moisture barrier on pad. 6x6-10/10 WWF, No. 3 bars @ 18", or No. 4 bars @ 24" on center, each way at midheight. Slab should be quarter-sawn. Presoaking of Living Area and Garage Slabs Normal slab subgrade wetting to a depth of 6 inches. 1.2 times the optimum moisture content to a depth of 12". Allowable Bearing Capacity 2,000 pounds per square foot (one-third increase for short term loading) 2,000 pounds per square foot (one-third increase for short term loading) Notes: (1) (2) (3) (4) (5) (6) Depth of interior or exterior footing to be measured from lowest adjacent finish grade or drainage swale flowline elevation. The base of the grade beam should be at the same elevation as that of the adjoining footings. Living area slabs should be tied to the footings as directed by the structural engineer. 6-mil Visqueen sheeting is acceptable. Equivalents are acceptable. All laps and penetrations should be sealed. Garage slabs should be isolated from stem wall footings with a minimum 3/8" felt expansion joint. Sand base should have a Sand Equivalent of 30 or greater (e.g. washed concrete sand). Our experience generally indicates that use of reinforcement in slabs and foundations will generally reduce the potential for drying and shrinkage cracking. However, some cracking should be expected as -7- LEIGHTONAHO ASSOCIATES, /JVC. m m m a 940677-008 the concrete cures. In addition, all reinforcement(especially welded wire mesh) should be placed at slab midheight. Chairs or other methods should be used for mesh and rebars to insure mid-slab placement. Minor concrete slab cracking is considered normal, however, it is often aggravated by a high water/cement ratio, high concrete temperature at the time of placement, small nominal aggregate size, and rapid moisture due to hot, dry and/or windy weather conditions during placement and curing. Cracking due to temperature and moisture fluctuations can also be expected. The use of low slump concrete (not exceeding 4 to 5 inches at the time of placement) can reduce the potential for shrinkage cracking. The bearing capacity values presented in Table 1 are based on a short- term total and differential settlement of 3/4 inches and 1/2 inches, respectively. Short-term settlement is anticipated to occur upon application of the footing load or shortly thereafter. The slab subgrade soils underlying the conventional foundation systems should be presoaked as indicated in the section entitled "Slab Subgrade Moisture Conditioning" (on page 9) prior to placement of the moisture barrier and slab concrete. Post-TensionedFoundation System Design (all Lots) We recommend that the post-tensioned slabs be designed in accordance with the following design parameters presented in Table 2 and the criteria of the 1994 edition of the Uniform Building Code (ICBO, 1994). In lieu of the following design, the spanability method of foundation and slab design may be utilized on lots having a very low expansion potential (i.e. soils having an expansion index less than20(perUBC18-I-B). Table 2 Post-Tensioned Foundation Design Recommendations Design Criteria Edge Moisture Variation, em Differential Swell, ym Center Lift: Edge Lift: Center Lift: Edge Lift: Short-Term Differential Settlement: Allowable Bearing Capacity: Expansion Index (UBC18-2) Very Low to Low (0-50) 5.5 Feet 2.5 Feet 0.8 inches 0.2 inches 3/4 inch 2,000 psf The post-tensioned foundations and slabs should be designed in accordance with structural considerations. Continuous footings (ribs or thickened edges) with a minimum width of 12 inches and a minimum depth of 12 inches below adjacent grade may be designed for a maximum allowable bearing pressure of 2,000 pounds per square foot if founded into competent formational soils or properly -8- LEIGHTOHAHD ASSOCIATES, UK. 940677-008 compacted fill soils. Where the foundation is within 3 feet (horizontally) of adjacent drainage swales, the adjacent footing (thickened edge or rib) should be embedded a minimum depth of 12 inches below the swale flow line. The allowable pressures may be increase by one-third when considering loads of short duration such as wind or seismic forces. Slabs should be underlain by a minimum of 2 inches of clean sand (sand equivalent greater than 30) which is in turn underlain by a vapor barrier. The vapor barrier should be sealed at all penetrations and laps. Moisture vapor transmission may be additionally reduced by use of concrete additives. Moisture barriers can retard, but not eliminate moisture vapor movement from the underlying soils up through the slabs. We recommend that the floor covering installer test the moisture vapor flux rate prior to attempting applications of the flooring. "Breathable" floor coverings should be considered if the vapor flux rates are high. A slipsheet or equivalent should be utilized above the concrete slab if crack- sensitive floor coverings (such as ceramic tiles, etc.) are to be placed directly on the concrete slab. Our experience indicates that use of reinforcement in slabs and foundations will generally reduce the potential for drying and shrinkage cracking. However, some cracking should be expected as the concrete cures. Minor cracking is considered normal; however, it is often aggravated by a high water/cement ratio, high concrete temperature at the time of placement, small nominal aggregate size, and rapid moisture loss due to hot, dry and/or windy weather conditions during placement and curing. Cracking due to temperature and moisture fluctuations can also be expected. The use of low slump concrete (not exceeding 4 to 5 inches at the time of placement) can reduce the potential for shrinkage cracking and the action of tensioning the tendons can close small shrinkage cracks. In addition to the careful control of water/cement ratios and slump of concrete, application of 50 percent of the design post-tensioning load within three to four days of slab pour may be an effective method of reducing the cracking potential. Presaturation of the slab subgrade soils underlying post-tensioned foundation systems may be omitted provided the slab subgrade soils have a very low to low expansion potential (per U.B.C. 18-I-B). Slab Subgrade Moisture Conditioning The slab subgrade soils underlying the conventional foundation systems should be presoaked in accordance with the recommendations presented in Table 3 prior to placement of the moisture barrier and slab concrete. If a post-tensioned foundation system is utilized on the lots, the post-tensioned slab subgrade soils should be wetted to a depth of 6 inches prior to the placement of the moisture barrier. The subgrade soil moisture content should be checked by a representative of Leighton and Associates prior to slab construction. -9- LEIGHTOHAHO ASSOCIATES, OK. 940677-008 TableS Minimum Presaturation Recommendations for Conventional Foundation Subgrade Soils Expansion Potential (UBC18-I-B) Very Low Low Presoaking Recommendations Near-optimum moisture content to a depth of 6 inches Minimum of 1 .2 times the optimum moisture content to a minimum depth of 12 inches below slab subgrade Presoaking or moisture conditioning may be achieved in a number of ways. But based on our professional experience, we have found that minimizing the moisture loss on pads that have been completed (by periodic wetting to keep the upper portion of the pad from drying out) and/or berming the lot and flooding for a short period of time (days to a few weeks) are some of the more efficient ways to meet the presoaking recommendations. If flooding is performed, a couple of days to let the upper portion of the pad dry out and form a crust so equipment can be utilized should be anticipated. Foundation Setback from Slope Face We recommend a minimum horizontal setback distance from the face of slopes for all structural foundations, footings, and other settlement-sensitive structures as indicated on Table 4. This distance is measured from the outside bottom edge of the footing, horizontally to the slope face and is based on the slope height and type of soil. However, the foundation setback distance may be revised by the geotechnical consultant on a case-by-case basis if the geotechnical conditions are different than anticipated. Table 4 Minimum Foundation Setback from Slope Faces Slope Height less than 5 feet 5 to 15 feet greater than 15 feet Minimum Recommended Foundation Setback 5 feet 7 feet H/2, where H is slope height; not to exceed 10 feet Please note that the soils within the structural setback area possess poor lateral stability, and improvements (such as retaining walls, sidewalks, fences, pavements, etc.) constructed within this setback area may be subject to lateral movement and/or differential settlement. Potential distress to such - 10- LEIGHTOHAHD ASSOCIATES, OK. **• m 940677-008 improvements may be mitigated by providing a deepened footing or a pier and grade beam foundation system to support the improvement. The deepened footing should meet the setback as described above. Lateral Earth Pressures and Retaining Wall Design Considerations The recommended lateral pressures for the site soil (expansion index less than 50 per U.B.C. 18-I-B) and level or sloping backfill are presented on Table 5. Table 5 Lateral Earth Pressures Conditions Active At-Rest Passive Equivalent Fluid Weight (pcf) Level Backfill Onsite Soils 35 55 350 2:1 Sloping Backfill Onsite Soils 60 65 350 Embedded structural walls should be designed for lateral earth pressures exerted on them. The magnitude of these pressures depends on the amount of deformation that the wall can yield under load. If the wall can yield enough to mobilize the full shear strength of the soil, it can be designed for "active" pressure. If the wall cannot yield under the applied load, the shear strength of the soil cannot be mobilized and the earth pressure will be higher. Such walls should be designed for "at-rest" conditions. If a structure moves toward the soils, the resulting resistance developed by the soil is the "passive" resistance. The passive earth pressure values assumes sufficient slope setback (see previous section). For design purposes, the recommended equivalent fluid pressure for each case for walls founded above the static ground water and backfilled with import soils of very low to low expansion potential or onsite (moderately expansive soils) is provided in Table 5. The equivalent fluid pressure values assume free- draining conditions. If conditions other than those assumed above are anticipated, the equivalent fluid pressure values should be provided on an individual-case basis by the geotechnical engineer. Surcharge loading effects from the adjacent structures should be evaluated by the geotechnical and structural engineer. All retaining wall structures should be provided with appropriate drainage and appropriately waterproofed. The outlet pipe should be sloped to drain to a suitable outlet. Typical wall drainage design is illustrated in Figure 2. - 11- LEIGHTOHAHD ASSOCIATES, IHC. r \ SOIL BACKFILL. COMPACTED TO 90 PERCENT RELATIVE COMPACTION* RETAINING WALL WALL WATERPROOFING PER ARCHITECT'S SPECIFICATIONS FINISH GRADE S ^ZZ^Z^-Z^Z^^gZ^^z^Zz^ X r—^=-^=.— o ° OU*0 A* ^0 06* MIN. o OVERLAP 0 « 0 / .*- •:1' MIN. ' V/T 0 K=S SS-rS—r-^—— •=ur~" —3- J"?"tYP.~S--- i^£== — FILTER FABRIC E i^iif (MIRAFI 140N OF fs|l EQUIVALENT)** ^ — 3/4'-1-1/2' CLEAf iil^, 4* (MIN.) DIAMET 5^ PVC PIPE (8CHE -==>!-: EQUIVALENT) Wl -££=•=. ORIENTED DOWN qji^i MINIMUM 1 PERCI ~sj~ 'O SUITABLE OU" WALL FOOTING— Hi| ^ 3* MIN. NOT TO SCALE SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL U.S. Standard Steve Size 1" 3/4" 3/8" No. No. No. No. No. 4 8 30 50 200 % Passing 100 90-100 40-100 25-40 18-33 5-15 0-7 0-3 Sand Equivalent>75 COMPETENT BEDROCK OR MATERIAL AS EVALUATED BY THE GEOTECHNICAL CONSULTANT * BASED ON A3TM D1657 * * IF CALTRANS CLASS 2 PERMEABLE MATERIAL (SEE GRADATION TO LEFT) IS USED IN PLACE OF 3/4'-1-1/2* GRAVEL. FILTER FABRIC MAY BE DELETED. CALTRANS CLASS 2 PERMEABLE MATERIAL SHOULD BE COMPACTED TO 00 PERCENT RELATIVE COMPACTION * NOT&COMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR J-ORAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR CLASS 2. INSTALLATION SHOULD BE PERFORKCD IN ACCORDANCE WITH MANUFACTURER'S SPECIFICATIONS. RETAINING WALL DRAINAGE DETAIL Project No. Scale Engr./Geol. Drafted By 4940677-008 Not to scale JQF/RKW orb LJU 1042 889 Figure No. 2 "" 940677-008 *• For sliding resistance, the friction coefficient of 0.37 may be used at the concrete and soil interface. In combining the total lateral resistance, the passive pressure or the frictional resistance should be reduced * by 50 percent. Wall footings should be designed in accordance with structural considerations. The iH passive resistance value may be increased by one-third when considering loads of short duration such as wind or seismic loads. The horizontal distance between foundation elements providing passive W resistance should be a minimum of three times the depth of the elements to allow full development of m these passive pressure. The total depth of retained earth for design of cantilever walls should be the vertical distance below the ground surface measured at the wall face for stem design or measured at the (• heel of the footing for overturning and sliding. •Wall back-cut excavations less than 5 feet in height can be made near vertical. For back cuts greater *» than 5 feet in height, but less than 15 feet in height, the back cut should be flattened to a gradient of not gg steeper than 1:1 (horizontal to vertical) slope inclination. For back cuts in excess of 15 feet in excess of 15 feet in height, specific recommendations should be requested from the geotechnical consultant. The w backfill soils (having an expansion index less than 50 per UBC 18-I-B) should be compacted to at least 90 percent relative compaction (based on ASTM Test Method D1557-91). The walls should be constructed and backfilled as soon as possible after back-cut excavation. Prolonged exposure of back- — cut slopes may result in some localized slope instability. "* Foundations for retaining walls in competent formational soils or properly compacted fill should be ^ embedded at least 18 inches below lowest adjacent grade. At this depth, an allowable bearing capacity of 2,000 psf may be assumed. M • Cement Type for Construction *• * Concrete in contact with earth materials should be designed in accordance with the appropriate category of Table 19-A-4 of the Uniform Building Code (UBC, 1977). Based on our experience with similar ^ soils on other planning areas of the Poinsettia Shores project, we assume that the finish grade soils on Hi the lots will have a negligible soluble sulfate content based on 1994 Uniform Building Code criteria. Therefore, we expect that concrete in contact with the on-site soils (e.g. foundation, slab, and exterior » flatwork) may utilize Type II cement (or equivalent). However, the soluble sulfate content of the finish IB grade soils on the site should be determined from representative samples taken by a representative of Leighton prior to slab construction. *• — • Graded Slopes M It is recommended that any regraded slope within the development be planted with ground cover vegetation as soon as practical to protect against erosion by reducing runoff velocity. Deep-rooted vegetation should also be established to protect against surficial slumping. Oversteepening of existing p, slopes should be avoided during post-grading and construction unless supported by appropriately designed retaining structures. m • Control of Surface Water and Drainage Control * Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings. Positive drainage may be accomplished by providing drainage away from buildings at a gradient of at least 2 percent for a distance of at least 5 feet, and further maintained by a m -13- LEIGHTONAHO ASSOCIATES, IHC. «• 940677-008 ** swale or drainage path at a gradient of least 1 percent. Where limited by 5-foot side yards, drainage •I should be directed away from foundations for a minimum of 3 feet and into a collective swale or pipe system. Where necessary, drainage paths may be shortened by use of area drains and collector pipes. • Eave gutters are recommended and reduce water infiltration into the subgrade soils if the downspouts KM are properly connected to appropriate outlets. •I Planters with open bottoms adjacent to buildings should be avoided, if possible. Planters should not be M designed adjacent to buildings unless provisions for drainage, such as catch basins and pipe drains, are made. Overwateringof lots should be avoided. ^ • Preliminary Pavement Design pn Final pavement recommendations should be provided based on R-value testing of the private m drives/street subgrade soils once final grades are achieved. However, based on our professional experience in the Carlsbad area and assuming a Traffic Index of 5.0 and a R-Value of 3 0, a preliminary p, pavement section of 4-inches of Asphalt Concrete (A.C.) over 4-inches of Class 2 Aggregate Base material (A.B.) may be assumed. The upper 12 inches of subgrade soils should be scarified, moisture conditioned and compacted to a minimum of 95 percent relative compaction based on ASTM Test Method D1557-96. If fill is required ** to reach subgrade design grade, fill placement should be performed in accordance with the recommendations presented in the recommendation section on earthwork. The aggregate base material should be compacted to a minimum of 95 percent relative compaction. m If Portland Cement Concrete (P.C.C.) pavement is planned, we recommend a minimum of 6 inches of ** P.C.C. on native soils. The P.C.C. pavement should be provided with appropriate steel reinforcement • and crack-control joints as designed by the project structural engineer. Minimum reinforcement should consist of No. 3 rebars at 18 inches (on center) at slab midheight which continues through all crack- W control joints but not through expansion joints. If saw-cuts are used, they should be a minimum depth of H 1 /4 of the slab thickness and made within 24 hours of concrete placement. We recommend that sections be as nearly square as possible. A 3,250 psi concrete mix should be utilized. m ^ Asphalt Concrete, Portland Cement Concrete, and Class 2 Aggregate Base materials should conform to and be placed in accordance with Carlsbad requirements and the latest revision of the California m* Department of Transportation Standard Specifications (Caltrans) and American Concrete Institute (ACI) codes. „. If pavement areas are adjacent to landscape areas, we recommend steps be taken to prevent the subgrade soils from becoming saturated. Concrete swales should be designed in roadway or parking areas subject to concentrated surface runoff. Regular maintenance (such as seal coats and crack m infilling) is an important part of extending pavement life. ^ • Construction Observation and Testing Construction observation and testing should be performed by the geotechnical consultant during future • grading, excavations, and foundation or retaining wall construction at the site. Grading and foundation design plans should also be reviewed by the geotechnical consultant prior to construction. to -14'- m LEIGHTON AND ASSOCIATES, UK. 940677-008 If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service. Respectfully submitted, LEIGHTON AND ASSOCIATES, INC. Randall K. Wagner, CEG/1612 (Exp. 3/31/98) Project Geologist CERTIFIED ENGINEERING KBC/RKW/JGF Distribution: (6) Addressee (4) O'Day Consultants Attention: Mr. Tim Carroll '•dfc ,RCEFranzone,RCE 39552 of Engineering -15- LEIGHTOHAHD ASSOCIATES, INC. Leighton and Associates, Inc. GENERAL EARTHWORK AND GRADING SPECIFICATIONS Page 1 of6 LEIGHTON AND ASSOCIATES, INC. GENERAL EARTHWORK AND GRADING SPECIFICATIONS FOR ROUGH GRADING 1.0 General 1.1 Intent These General Earthwork and Grading Specifications are for the grading and earthwork shown on the approved grading plan(s) and/or indicated in the geotechnical report(s). These Specifications are a part of the recommendations contained in the geotechnical report(s). In case of conflict, the specific recommendations in the geotechnical report shall supersede these more general Specifications. Observations of the earthwork by the project Geotechnical Consultant during the course of grading may result in new or revised recommendations that could supersede these specifications or the recommendations in the geotechnical report(s). 1.2 The Geotechnical Consultant of Record: Prior to commencement of work, the owner shall employ the Geotechnical Consultant of Record (Geotechnical Consultant). The Geotechnical Consultants shall be responsible for reviewing the approved geotechnical report(s)and accepting the adequacy of the preliminary geotechnical findings, conclusions, and recommendations prior to the commencement of the grading. Prior to commencement of grading, the Geotechnical Consultant shall review the "work plan" prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel to perform the appropriate level of observation, mapping, and compaction testing. During the grading and earthwork operations, the Geotechnical Consultant shall observe, map, and document the subsurface exposures to verify the geotechnical design assumptions. If the observed conditions are found to be significantly different than the interpreted assumptions during the design phase, the Geotechnical Consultant shall inform the owner, recommend appropriate changes in design to accommodate the observed conditions, and notify the review agency where required. Subsurface areas to be geotechnically observed, mapped, elevations recorded, and/or tested include natural ground after it has been cleared for receiving fill but before fill is placed, bottoms of all "remedial removal" areas, all key bottoms, and benches made on sloping ground to receive fill. The Geotechnical Consultant shall observe the moisture-conditioningand processing of the subgrade and fill materials and perform relative compaction testing of fill to determine the attained level of compaction. The Geotechnical Consultant shall provide the test results to the owner and the Contractor on a routine and frequent basis. 3030.1094 Leighton and Associates, Inc. GENERAL EARTHWORK AND GRADING SPECIFICATIONS Page 2 of 6° 1.3 The Earthwork Contractor The Earthwork Contractor (Contractor) shall be qualified, experienced, and knowledgeable in earthwork logistics, preparation and processing of ground to receive fill, moisture-conditioning and processing of fill, and compacting fill. The Contractor shall review and accept the plans, geotechnical report(s), and these Specifications prior to commencement of grading. The Contractor shall be solely responsible for performing the grading in accordance with the plans and specifications. The Contractor shall prepare and submit to the owner and the Geotechnical Consultant a work plan that indicates the sequence of earthwork grading, the number of "spreads" of work and the estimated quantities of daily earthwork contemplated for the site prior to commencement of grading. The Contractor shall inform the owner and the Geotechnical Consultant of changes in work schedules and updates to the work plan at least 24 hours in advance of such changes so that appropriate observations and tests can be planned and accomplished. The Contractor shall not assume that the Geotechnical Consultant is aware of all grading operations. The Contractor shall have the sole responsibility to provide adequate equipment and methods to accomplish the earthwork in accordance with the applicable grading codes and agency ordinances, these Specifications, and the recommendations in the approved geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory conditions, such as unsuitable soil, improper moisture condition, inadequate compaction, insufficient buttress key size, adverse weather, etc., are resulting in a quality of work less than required in these specifications, the Geotechnical Consultant shall reject the work and may recommend to the owner that construction be stopped until the conditions are rectified. 2.0 Preparation of Areas to be Filled 2.1 Clearing and Grubbing Vegetation, such as brush, grass, roots, and other deleterious material shall be sufficiently removed and properly disposed of in a method acceptable to the owner, governing agencies, and the Geotechnical Consultant. The Geotechnical Consultant shall evaluate the extent of these removals depending on specific site conditions. Earth fill material shall not contain more than 1 percent of organic materials (by volume). No fill lift shall contain more than 5 percent of organic matter. Nesting of the organic materials shall not be allowed. If potentially hazardous materials are encountered, the Contractor shall stop work in the affected area, and a hazardous material specialist shall be informed immediately for proper evaluation and handling of these materials prior to continuingto work in that area. As presently defined by the State of California, most refined petroleum products (gasoline, diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered to be hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the ground may constitute a misdemeanor, punishable by fines and/or imprisonment, and shall not be allowed. 3030.1094 m 4* Leighton and Associates, Inc. GENERAL EARTHWORK AND GRADING SPECIFICATIONS Page 3 of6 2.2 Processing Existing ground that has been declared satisfactory for support of fill by the Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing ground that is not satisfactory shall be overexcavated as specified in the following section. Scarification shall continue until soils are broken down and free of large clay lumps or clods and the working surface is reasonably uniform, flat, and free of uneven features that would inhibit uniform compaction. 2.3 Overexcavation In addition to removals and overexcavations recommended in the approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich, highly fractured or otherwise unsuitable ground shall be overexcavated to competent ground as evaluated by the Geotechnical Consultant during grading. 2.4 Benching Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical units), the ground shall be stepped or benched. Please see the Standard Details for a graphic illustration. The lowest bench or key shall be a minimum of 15 feet wide and at least 2 feet deep, into competent material as evaluated by the Geotechnical Consultant. Other benches shall be excavated a minimum height of 4 feet into competent material or as otherwise recommended by the Geotechnical Consultant. Fill placed on ground sloping flatter than 5:1 shall also be benched or otherwise overexcavated to provide a flat subgrade for the fill. 2.5 Evaluation/Acceptance of Fill Areas: All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide the survey control for determining elevations of processed areas, keys, and benches. 3.0 Fill Material 3.1 General: Material to be used as fill shall be essentially free of organic matter and other deleterious substances evaluated and accepted by the Geotechnical Consultant prior to placement. Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill material. 3.2 Oversize: Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 8 inches, shall not be buried or placed in fill unless location, materials, and placement methods are specifically accepted by the Geotechnical Consultant. Placement operations shall be such that nesting of oversized material does not occur and such that oversize material is completely surrounded by compacted or densified fill. Oversize material shall not be placed within 10 vertical feet of finish grade or within 2 feet of future utilities or underground construction. 3.3 Import If importing of fill material is required for grading, proposed import material shall meet the requirements of Section 3.1. The potential import source shall be given to the 3030.1094 Leighton and Associates, Inc. GENERAL EARTHWORK AND GRADING SPECIFICATIONS Page 4 of6 Geotechnical Consultant at least 48 hours (2 working days) before importing begins so that 1 its suitability can be determined and appropriate tests performed. i " 4.0 Fill Placement and Compaction t 4.1 Fill Layers: Approved fill material shall be placed in areas prepared to receive fill (per «• Section3.0) in near-horizontal layers not exceeding 8 inches in loose thickness. The Geotechnical Consultant may accept thicker layers if testing indicates the grading procedures can adequately compact the thicker layers. Each layer shall be spread evenly *, and mixed thoroughly to attain relative uniformity of material and moisture throughout. 4.2 Fill Moisture Conditioning Fill soils shall be watered, dried back, blended, and/or mixed, ^ as necessary to attain a relatively uniform moisture content at or slightly over optimum. Maximum density and optimum soil moisture content tests shall be performed in m accordance with the American Society of Testing and Materials (ASTM Test Method D1557-91). * 4.3 Compaction of Fill: After each layer has been moisture-conditioned, mixed, and evenly spread, it shall be uniformly compacted to not less than 90 percent of maximum dry density ** (ASTM Test Method D15 5 7-91). Compaction equipment shall be adequately sized and be «• either specifically designed for soil compaction or of proven reliability to efficiently achieve the specified level of compaction with uniformity. <m 4.4 Compaction of Fill Slopes: In addition to normal compaction procedures specified above, compaction of slopes shall be accomplished by backrolling of slopes with sheepsfoot •"* rollers at increments of 3 to 4 feet in fill elevation, or by other methods producing ^ satisfactory results acceptable to the Geotechnical Consultant. Upon completion of grading, relative compaction of the fill, out to the slope face, shall be at least 90 percent of — maximum density per ASTM Test Method Dl 557-91. mm 4.5 Compaction Testing: Field tests for moisture content and relative compaction of the fill „ soils shall be performed by the Geotechnical Consultant. Location and frequency of tests shall be at the Consultant's discretion based on field conditions encountered. Compaction *"" test locations will not necessarily be selected on a random basis. Test locations shall be ^, selected to verify adequacy of compaction levels in areas that are judged to be prone to inadequate compaction (such as close to slope faces and at the fill/bedrock benches). tm 4.6 Frequency of Compaction Testing: Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition, as a <m guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope face and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill construction is such that the testing schedule can be accomplished by the Geotechnical ** Consultant. The Contractor shall stop or slow down the earthwork construction if these minimum standards are not met. 3030.1094 Leighton and Associates, Inc. GENERAL EARTHWORK AND GRADING SPECIFICATIONS Page 5 of6 4.7 Compaction Test Locations The Geotechnical Consultant shall document the approximate elevation and horizontal coordinates of each test location. The Contractor shall coordinate with the project surveyor to assure that sufficient grade stakes are established so that the Geotechnical Consultant can determine the test locations with sufficient accuracy. At a minimum, two grade stakes within a horizontal distance of 100 feet and vertically less than 5 feet apart from potential test locations shall be provided. 5.0 Subdrain Installation Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line and grade after installation and prior to burial. Sufficient time should be allowed by the Contractor for these surveys. 6.0 Excavation Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only. The actual extent of removal shall be determined by the Geotechnical Consultant based on the field evaluation of exposed conditions during grading. Where fill-over-cut slopes are to be graded, the cut portion of the slope shall be made, evaluated, and accepted by the Geotechnical Consultant prior to placement of materials for construction of the fill portion of the slope, unless otherwise recommended by the Geotechnical Consultant. 7.0 Trench Backfills 7.1 The Contractor shall follow all OHSA and Cal/OSHA requirements for safety of trench excavations. 7.2 All bedding and backfill of utility trenches shall be done in accordance with the applicable provisions of Standard Specifications of Public Works Construction. Bedding material shall have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot over the top of the conduit and densified by jetting. Backfill shall be placed and densified to a minimum of 90 percent of maximum from 1 foot above the top of the conduit to the surface. 7.3 The jetting of the bedding around the conduits shall be observed by the Geotechnical Consultant. 7.4 The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one test should be made for every 300 feet of trench and 2 feet of fill. 3030.1094 Leighton and Associates, Inc. GENERAL EARTHWORK AND GRADING SPECIFICATIONS Page 6 of6 7.5 Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications of Public Works Construction unless the Contractor can demonstrate to the Geotechnical Consultant that the fill lift can be compacted to the minimum relative compaction by his alternative equipment and method. 3030.1094 ~™ ^™ —• •""•^— —.^^ — ^^^^— «— "^ ^™ ^™ ^— —~ — ^~ ^m*—* ^— ^^^^^^^^^^^^^PROJECTED PLANE 1 TO 1 MAXIMUM FROM TOE OF SLOPE TO APPROVED GROUND NATURAL GROUND FILL SLOPE . REMOVE UNSUITABLE MATERIAL BENCH HEIGHT 2'MIN. KEY DEPTH —15' MIN. LOWEST BENCH (KEY) FILL^VER-CUT SLOPE NATURAL GROUND FI LOW 1PMIN.—-ILOWEST BENCH' r TYPICAL k l—BENCH HEIGHT REMOVE UNSUITABLE MATERIAL — V MIN. KEY DEPTH CUT FACE SHALL BE CONSTRUCTED PRIOR TO FILL PLACEMENT TO ASSURE ADEQUATE GEOLOGIC CONDmONS CUT FACE TO BE CONSTRUCTED PRIOR TO FLL PLACEMENTv NATURAL GROUND OVERBUILT AND TRIM BACK PROJECTED PLANE 1TO1 MAXIMUM FROM TOE OF SLOPE TO APPROVED GROUNO DESIGN SLOPE REMOVE NSUITABLE MATERIAL CUT-OVER-FILL SLOPE For Subdrains See Standard Detail C BENCH HEIGHT 2' MIN.—' KEY DEPTH LOWEST BENCH (KEY) BENCHMQ SHALL BE DONE WHEN SLOPES ANGLE IS EQUAL TO OR GREATER THAN 5:1 MNMUM BENCH HEIGHT SHALL BE 4 FEET MINIMUM FILL WIDTH SHALL BE 9 FEET KEYING AND BENCHING GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAILS A n_JU REV. 4/11/98 FINISH GRADE SLOPE FACE — — -| V-^HB^1 «• — — JETTED OR FLOODED GRANULAR MATERIAL • Oversize rock is larger than 8 inches in largest dimension. • Excavate a trench in the compacted fill deep enough to bury all the rock. • Backfill with granular soil jetted or flooded in place to fill all the voids. • Do not bury rock within 10 feet of finish grade. • Windrow of buried rock Shan be parallel to the finished slope fill.ELEVATION PROFILE ALONG WINDROW A-Af JETTED OR FLOODED GRANULAR MATERIAL OVERSIZE ROCK DISPOSAL GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAILS B LJU 4/95 NATURAL GROUND BENCHING REMOVE UNSUITABLE MATERIAL - COMPACTED FILL 1 2" MIN. OVERLAP FROM THE TOP HOG RING TIED EVERY 6 FEET CALTRANS CLASS II PERMEABLE OR #2 ROCK' (9FT.3/FT.) WRAPPED IN FILTER FABRIC FILTER FABRIC (MIRAF1140 OR APPROVED EQUIVALENT) CANYON SUBDRAIN OUTLET DETAIL DESIGN FINISHED GRADE PERFORATED PIPE 6"<j> MIN. ^COLLECTOR PIPE SHALL BE MINIMUM 6* DIAMETER SCHEDULE 40 PVC PERFORATED PIPE. SEE STANDARD DETAIL D FOR PIPE SPECIFICATION 20' MIN- FILTER FABRIC (MIRAFI 140 OR APPROVED EQUIVALENT) .NON-PERFORATED MIN. V,5' MIN \ *2 ROCK WRAPPED IN FILTER TABRIC OR CALTRANS CLASS II PERMEABLE. CANYON SUBDRAINS GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAILS C OUTLET PIPES 4'<|> NON-PERFORATED PIPE, 100' MAX. O.C. HORIZONTALLY, 30' MAX. O.C. VERTICALLY BACKCUT1:! OR FLATTER 2' MIN. POSITIVE SEAL SHOULD BE PROVIDED AT THE JOI 12- MIN. OVERLAP FROM THE TOP HOG RING TIED EVERY 6 FEET VI OUTLET PIPE (NON-PERFORATED) CALTRANS CLASS II PERMEABLE OR #2 ROCK (3FT.3/FT.) WRAPPED IN FILTER FABRIC FILTER FABRIC (MIRAF1 140 OR APPROVED EQUIVALENT) ECTIONT-CONNECTION FOR COLLECTOR PIPE TO OUTLET PIPE SUBDRAIN INSTALLATION - Subdrain collector pipe shall be installed with perforations down or, unless otherwise designated by the geotechnical consultant Outlet pipes shall be non-perforated pipe. The subdrain pipe shall have at least 8 perforations uniformly spaced per foot. Perforation shad be W to %' if drilled holes are used. All subdrain pipes shall have a gradient at least 2% towards the outlet SUBDRAIN PIPE - Subdrain pipe shall be ASTM D2751, SDR 23.5 or ASTM D1527, Schedule 40, or ASTM D3034, SDR 23.5, Schedule 40 Pol/vinyl Chloride Plastic (PVC) pipe. All outlet pipe shall be placed in a trench no wider than twice the subdrain pipe. Pipe shall be in soil of SE>30 jetted or flooded in place except for the outside 5 feet which shall be native soil backfill. BUTTRESS OR REPLACEMENT FILL SUBDRAINS GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAILS D va-j» uu 4/95