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HomeMy WebLinkAboutCT 72-9; Liddle Condominium; Soils Report; 1972-06-09REPORT to Mr. L. E. Liddle on SOIL INVESTIGATION for LIDDLE CONDOMINIUM Carlsbad, California E. Brian Smith Engineers Civil Engineers GEOCON, INCORPORATED 6675 Convoy Court San Diego, California 92111 Project No. D2-O&7-Sl 9 June, 1972 ENGINEERS AND GEOLOGISTS * CONSULTANTS IN THE APPLIED EARTH SCIENCES INCORPORATED - File No. D2-0047-Sl 9 June, 1972 - Mr. L. E. Liddle c/o E. Brian Smith Engineers 2656 State Street - Carlsbad, California 92008 Subject: - - Dear Sir: Proposed Liddle Condominium Jefferson Street Carlsbad, California SOIL INVESTIGATION - - - - - - - - -~ In compliance with your authorization, we have conducted a soil in- vestigation of the site of a proposed condominium, planned for con- struction on Jefferson Street, adjacent to Buena Vista Lagoon, in Carlsbad, California. We submit herewith a report of that investi- gation. We have found that all of the soils at this site are very suitable for use as load-bearing soils, provided the recormnendations contained in this report are carefully followed. This report will present our findings based on the field investigation and the results of the ~laboratory testing, and also our conclusions and recommendations. Very truly yours, GEOCON, INWOBATED E. Likins, P.E. &d Distr.: (3) Addressee (2) E. Brian Smith engineers - q 6675 CONVOY COURT * SAN DIEGO, CALIFORNIA 92111 * PHONE (714) 292-5100 - - - - - - - - - - - - -- - - File No. D2-0047-Sl 9 June, 1972 SOIL INVESTIGATION Introduction This is to present the results of a soils investigation conducted at the site of a proposed condominium building. The site is located on Jefferson Street, adjacent to Buena Vista Lagoon, in Carlsbad, Cali- fornia. Much of the site is fairly level, but the northwesterly por- tion slopes steeply to the lagoon. It is our understanding that a retaining wall is to be constructed to retain the fill soils necessary to raise this portion of the site to design finish grade, and that other retaining walls will be needed to effect an elevation change in the central portion of the site. The maximum wall height will be about 20 feet. It is also understood that the condominium is to be a two-story wood-frame structure with some depressed parking areas. Footing loads are not yet known, but column loads on the order of 25 kips and wall loads on the order of 3 to 5 kips per linear foot are assumed. The objectives of this investigation were to determine the existing soil conditions at this site, and to determine some of the major physical properties of those soils, so that recommendations could be presented for the safe support of the building and for the design of the retaining walls. In order to accomplish these objectives, five - 1 File NO. D2-0047-Sl 9 June, 1972 - - - - - - - - - - - - -~ - borings were drilled and representative soil samples were obtained from the borings for laboratory testing. Field Investigation All of the borings were drilled with a 6 inch diameter continuous flight auger, at the approximate locations shown on Drawing No. 1, entitled "Site Plan and Location of Test Borings." The borings were drilled to depths of 15.0 to 25.0 feet. A continuous log of the soils encountered in the borings was recorded at the time of drilling, and is shown in detail on Drawing Nos. 2 to 6, inclusive, each entitled "Summary Sheet." The soils were visually classified by the field identification pro- cedures of the Unified Soil Classification Chart. A simplified des- cription of this classification system is presented in the attached Appendix A at the end of this report. Undisturbed samples were obtained at frequent intervals in the soils ahead of the drilling. The drop weight used for driving the sampling tube into the soils weighs 140 pounds, and the average drop was 30 inches. The general procedures used in field sampling are described under "Sampling" in Appendix B. - - File No. D2-0047-Sl - 9 June, 1972 Laboratory Tests Laboratory tests were performed on undisturbed soil samples in order - to determine the dry density and moisture content of the soils. The results of these tests are shown on Drawing Nos. 2 to 6, inclusive. Consolidation tests were performed on representative samples of the - probable foundation soils in order to determine the load-settlement characteristics of the soils. The results of these tests are shown on Drawing Nos. 7 and 8, each entitled "Consolidation Curves." - - r - - - In order to better classify the fine-grained soils found to a depth of 10.0 feet at Boring 4, Atterberg Limits tests were performed on a sample of these soils. The results of these tests indicate that the soil has a Liquid Limit of 19 percent and a Plasticity Index of 3; the soil is classified as a very fine sandy silt with a slight clay content. The moisture-density relationship of the same soil, was determined in accordance with A.S.T.M. Designation D 1557-70; this test indicates that the soil, classified as a very fine sandy silt, has a maximum dry density of 123.5 pounds per cubic foot and an optimum moisture content of 12.7 percent. The general procedures used for the laboratory tests are described - - - - - - - . . .-- - - - - - - - - - File No. DZ-0047-Sl 9 June, 1972 briefly in Appendix B. Soil Conditions The soils encountered in the borings consisted of firm to very firm clayey or slightly clayey sands, and very fine sandy silt; occasional gravel and some cementation was found below depths of 7.0 to 10.0 feet at some of the boring locations. No ground water was encountered in any of the borings. - - - File No. D2-0047-Sl 9 June, 1972 CONCLUSIONS AND RECOMMENDATIONS Conclusions It is concluded from the field investigation and the results of the laboratory testing that: 1. The firm to very firm clayey sands found at all of the boring locations will provide very suitable support for the proposed condo- minium structures and retaining walls. 2. The soils that are to be excavated, other than a layer of fine sandy clay (mudstone) found between the depths of 5.5 and 7.2 feet at Boring 2, may be used as compacted fill material and, when properly compacted to at least 90 percent of maximum dry density, these soils will also provide satisfactory support for structural loads. - Recommendations 1. Grading Operations - It is recommended that all grading operations be accomplished, under - continuous engineering inspection, in accordance with the attached Appendix C, entitled "Standard Specifications for Placement of Com- pacted Filled Ground." It is also recommended that, wherever the fine sandy clay or "mudstone" previously described is encountered, - this type of soil be stockpiled separately from the sands and clayey - sands, and used as fill material only at depths of 3.0 feet or more - 5 - - - - - - - - - - - - - - - - File No. D2-0047-Sl 9 June, 1972 below finish grade. The maximum dry densities and optimum moisture contents of soils that are to be used as fill materials can be deter- mined during the grading operations, if these include any soil types other than those already reported under "Laboratory Tests." 2. Footings It is recommended that all footings be located at least one foot below the lowest adjacent final ground surface. One foot wide continuous footings so located in firm natural ground may be designed for an allow- able bearing value up to 3,000 pounds per square foot, and square column footings that are 3.0 feet wide may be designed for an allow- able bearing value up to 3,900 pounds per square foot. One foot wide continuous footings located at a depth of one foot in properly compacted filled ground may be designed for an allowable bearing value of 1,425 pounds per square foot; this value may be increased at a rate of 550 pounds per square foot for each foot of depth in excess of one foot, and at an additional rate of 185 pounds per square foot for each foot of width in excess of one foot, to a recommended maximum value of 2,500 pounds per square foot. Column footings that are 3.0 feet wide and one foot deep may be designed for an allowable bearing value of 1,900 pounds per square foot; this value may be increased at a rate of 550 pounds per square foot for each foot of depth in excess of one foot, and at an additional rate of - - - - - - - - - - - - - - File No. D2-0047-Sl 9 June, 1972 150 pounds per square foot for each foot of width in excess of 3.0 feet, to a recommended maximum value of 3,000 pounds per square foot. All of the above bearing values are for dead plus live loads only, and may be increased one third for combined dead, live and seismic loads. 3. Retaining Walls It is recommended that retaining walls be designed to resist lateral earth forces equivalent to those of a fluid having a unit weight of 40 pounds per cubic foot. This recommendation assumes that no hydro- static pressures will be allowed to build up in the soils being retained. It is also important to ensure that retaining walls are adequately braced during backfilling operations, to resist the tem- porary additional lateral forces caused by the compacting of the backfill. 4. Lateral Forces In calculating the resistance of natural soils to lateral forces exerted by subsurface structural elements, anallowable pressure of 300 pounds per square foot at a depth of one foot may be used; this value may be increased at a rate of 140 pounds per square foot for each foot of depth in excess of one foot. A friction factor of 0.4 times applied dead loads may also be used. - - - - - - - - - - - - - - - - File No. D2-0047-Sl 9 June, 1972 5. Slab Support The previously-described firm to very firm clayey sands and/or approved fill soils that have been properly compacted will provide adequate support for concrete slabs. Wherever concrete slabs are to be supported partly by undisturbed natural soils and partly by com- pacted filled ground, it is suggested that the portions of the slabs on compacted fill be separated from the balance of the slab by construction felt, in order to minimize any cracking that might otherwise be caused by minor differential settlements. Settlements Based on the results of the load-consolidation tests, the total settlement of a one foot wide continuous footing located as recom- mended in sandy silt soils and loaded to 3,000 pounds per square foot is estimated to be on the order of l/4 inch. Similar footings located in firm or very firm clayey coarse sands may be expected to settle less than l/8 inch. Square footings that are 3.0 feet wide and loaded to 3,000 pounds per square foot may be expected to settle approximately l/2 inch in very fine sandy silt, and approximately l/8 inch in firm to very firm clayey sands. Drainage Downdrains and splashblocks should be utilised on this tract. Lot - - - File No. D2-0047-Sl - 9 June, 1972 - pad grading should provide positive drainage relief for at least - 6 feet away from buildings into swales which deposit water into - streets or drainage easements. If top soil is placed on the lots it should not alter the drainage patterns formed in the building - pad during grading. - - - - - - - - - - -. - - - - - - - File No. D2-0047-Sl 9 June, 1972 LIMITATIONS AND UNIFORMITY OF CONDITIONS 1. The recommendations of this report are based upon the assumption that the soil conditions do not deviate from those disclosed in the borings. If any variations or undesirable conditions are encountered during construction, or if the proposed construction will differ from that planned at the present time, Geocon, Incorporated should be notified so that supplemental recormnendations can be given. 2. This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recormnendations contained herein are brought to the attention of the Architect and Engineer for the project and incorporated into the plans, and that the necessary steps are taken to see that the'contractor and Subcontractors carry out such recom- mendations in the field. - - - - - - - 10 - - - - - - - - - - ! - - ! - 1 - - .~ - - ..-~ _uI ~~~I~~~~ ~~~~~~ ,,__~ ~_, n- +Indi:1:1"appro: si- SCALE location of tes \ I l"=Lbfl' boring “;-- .I1 )--_c, -1 ‘\ ,,\ \ ,‘=?gyq ‘- 1’ ’ ,\ di$&;- \“-\ \\ q’, \\\‘; ?l ce ‘\ -<‘A’ ’ \L 6-43 \ \ 1’ \ --,\,\ 3 I;r\ \ ‘. t ‘\‘$ rl--. /---” *A ‘Lo - ri/, ‘-4 I\ \ f ,/-- /c)---- -(rt -m-\ // 9 / +” I I / --a--- l f /’ / T / SITE PLAN AND LOCATION OF TEST BORINGS Liddle Condominium Jefferson Street Carlsbad, California PROJECT NO. D2-0047-Sl GEOCON, INCORPORATED DRAWING NO. 1 - - - - - - - - - - - - - is - SUMMARYSHEET BORING NO. l ELEVATION 22.4' * Light gray, Slightly moist, Firm - A~--- Less clay content, Very firm, Cemented Clayey Coarse SAND '. " Indicates undisturbed drive sample *t 3 r 2; z i . : G t3.t 7.f 7.1 7 .: - 3.2 1' . , 0.: 2.; - Fy AL n ?ji 2‘ 2l.i .15 .20 ,14 17 - '.80 .i .i .5 * The elevations shown on these Summary Sheets were obtained bv internolatine between contours on a grading plan prepared by-E. Brian Smith Engineers, dat,ed 6-l-72. PROJECT NO. D2-0047-Sl GEOCON, INC. - - - - - - - - - - - - - - - - - - - SUMMARYSHEET BORING NO. 2 ELEVATION 32.6' Gray-white, Slightly moist, Very firm, Sotie rock particle Clayey Coarse cementation SAND ellow,Moist,Ver Firm (Mudstone) bay-white, Moi;;&Very Fine Sandy CLAY Clayey Coarse SAND " i2.1 5.8 SC PROJECT NO. D2-0047-Sl GEOCON, INC. - - - - - - - - - - - - - - SUMMARY SHEET BORING NO. 3 ELEVATION 58.0' Red-brown, Slightly moist, Firm Light yellow, Slightly moist, Compact, Occa- sional gravel Clayey Fine to Coarse SAND Fine SAND Light gray, Mojst, Firm Clayey Coarse SAND _s- * t ?C : u ; t . % 2 E- 2.5 5.c 7.5 SC SP PROJECT NO. D2-0Q47-Sl I GEOCON, INC. I DRAWING NO. 4 - - - - - - - - - - - : - - - - - - - SUMMARYSHEET c BORING NO. 4 ELEVATION 58.4' 3 4 5 6 7 8 9 10 11 12 13 14 15 $...-t--- ‘1 Light brown4 Very Fine Sandy SILT Slightly Clayey Coarse SAND 3l Indicates no sampl 4 recovery 1 R, Indicates loose ba g sample .O - .5 2:5 .O 6.8 102 PROJECT NO. / D2-0047-Sl I GiOCON, INC. - - - - - - - - - - - - - - - - - - ‘----~ .~- ~~-__-~..- SUMMARYSHEET BORING NO. 5 ELEVATION 62.6' led-brown, Moist, Firm Slightly Clayey ' Fine SAND .ed-brown, Moist, Firm Slightly Clayey I C0aix.G SAND Light yellow Slightly moist, Fine ompact, Occasion- al gravel SAND Poorly graded, Few fines GRAVEL 123 I- 03 I SP ~ GP PROJECT NO. D2-0047-Sl GEOCON, INC. - - - - - _- - - - - - - - - - - - - CONSOL1DA-I”1ON CURVES CONSOL1DA-I”1ON CURVES LOA’D IN i(l F’S PEi? SQUARE FOOT LOA’D IN Kl F’S PEi? SQUARE FOOT 6 6 Boring 1, Sample 2 0 Indicates percent consolidation at field moisture l Indicates percent consolidation after saturation PROJECT NO. D2-0047-Sl GEOCON, INCORPORATED DRAWING NO. ~~~I-- - _- - - - - - - - - _- -. - - - - - - CONSOLIDATION CURVES ~ I LOAD IN #I!PS P&ii S,QUARe FOO-T Boring 4, Sample 2 L .,, ’ 0 Indicates percent consolidation at field moisture 0 Indicates percent consolidation after saturation GEOCON. INCORPORATED DRAW;NG NO. - - - - - - Appendix A Unified Soil Classification Chart - - - - - I - ,- - - - - - - 3' GiUWN , INC. 6675 Convoy Court 'San Diego, CaLifornia ;,, ,I i ,' ,,,,' '. : ,I APPENDIX A Unified Soil ,Ciassification Chart* SOIL DESCRIPTION ’ GROUP SYMBOL 1. COARSE GRAINED, More than half sf - material is % than No. 200 sieve size.** GRAVELS ” CLEAN GRAVELS I’,,. More half of coarse fraction is larger than No. 4 sieve size but SmallerGRAVELS WITH FIN’ES than 3 inches (Appreciable amouni of fines) GW GP .GM GC SANDS CLEAN SANDS man half of coarse fraction is smaller than No. 4. sieve size SANDS WITH FINES (Appreciable amount of fitis) Il. FINE GRAINED, More than half of material is smaller than No. 200 sieve sire.“* SILTS AND CLAYS Liquid Limit Leu,than 50 SILTS AND CLAYS Liquid Limit Greoter than 50 Ill. HIGHLY ORGANIC SOILS SW SP SM SC ML CL OL MH CH OH PT TYPICAL I NAMES Well graded gravels, gravel-sand mixtures, little oc no fines. Pearl y graded gravels, gravel-sand mixtures, little or no fines. Silty gravels, poorly graded gravel- sand-silt mixtures. Clayey gravels, poorly graded gravel- sand-clay mixtures. Well graded sand, gravelly sands, little or no Fines. ‘Poorly graded sands, gravelly sands, little or no fines. Silty sands, poorly graded sand-silt mixtures., ‘, Clayey sands, poorly graded sand-clay mixtures. Inorganic silts and very Fine sands, rock flour, sandy silt or clayey-siltsand mixtures with slight plasticity. Inorganic clays of low to medium plas- ticity, gravelly clays, sandy clays, silty clays, lean clays. Organic silts and organic silty-clays of low plasticity. Inorganic silts, micaceous OT diatcma- ceaus fine sandy ar silty soils, elastic silts. inorganic cloys of high plasticity, fat cloys. Organic clays of medium to high plasticity. Peat and other highly organic soils. * Adcpted by the Corps of Enginoors and Bureau of Reclamdtion in Januaw. 1952. - - - - - - - - - - - Appendix B Sampling Procedures Laboratory Testing Procedures . - _- - - - - - - - - - - - - - - - - - .. ,*y , QN INCORPORATED ENGINEERS AND GEOLOGISTS * CONSULTANTS IN THE APPLIED EARTH SCIENCES APPENDIX B Sampling Undisturbed samples are obtained by forcing a special sampling tube into undisturbed soil at specified intervals as the boring penetrates the soil. Ordinarily samples are obtained from each of the various soil strata encountered; sometimes samples are obtained at regular intervals, such as at every 3.0 feet or 5.0 feet. The sampling tube consists of a steel barrel with a special cutting tip at the forward end and lined with thin one inch high brass rings. The sampler, containing the brass ring liner, is forced into the soils, either by pushing or driving. Conventionally the driving is done by dropping a known weight, such as the "Kelly" bar of the drill rig, a specified vertical distance into the sampler; sometimes a known weight is raised by hand and then allowed to fall on the sampler. After the sampler has been pushed or driven into the soil, it is withdrawn and the soil sample confined within the rings is removed from the sample and placed in sealed cylindrical containers for laboratory testing. The "drive energy" is that energy required to force the sampling tube one foot into the soil; it is calculated in foot kips per foot. Shear Tests Shear tests are performed with a direct shear apparatus which utilizes a gear box to apply shearing stresses to one-half of a shear box through a calibrated proving ring. Normal or axial loads are applied to the soil specimen through a counterbalanced hanger assembly. Measurements of applied loads and deformations are made by means of three dial indicators. The proving ring dial is sensitive to 0.001 inch. Ordinarily the applied normal load is that to which the soil sample is subjected in the field; in some instances samples are sheared under varying normal loads, in order to determine the cohesion and the angle of internal friction of the soil. When considered, appropriate, the sample is saturated and drained prior to shearing, in order to simulate extreme field moisture conditions. Consolidation Tests The apparatus used for the consolidation tests is designed to receive one of the one inch high rings of soil as it comes from the field. Loads are applied in several increments to the upper surface of the test specimen and the resulting deformations are recorded at selected time intervals - q 6675 CONVOYCOURT * SAN DIEGO, CALIFORNIA 92111 * PHONE (714) 292-5100 APPENDIX B - for each increment. Generally, each increment of load is maintained on the sample until the rate of deformation is equal to or less than - l/l0000 inch per hour. Porous stones are placed in contact with the top and bottom of each specimen to permit the ready addition or release of water. - Expansion Tests One inch high samples confined in the brass rings are permitted to - air dry at 105°F for at least 48 hours prior to placing into the ex- pansion apparatus. A unit load of 500 pounds per square foot is then applied to the upper porous stone in contact with the top of each - sample. Water is permitted to contact both the top and bottom of each sample through porous stones. Continuous observations are made until downward movement stops. The dial reading is recorded and expansion - is recorded until the rate of upward movement is less than l/10000 inch per hour. Other Tests - Other soil tests, as required, are performed in accordance with applicable accepted specifications, such as A.S.T.M., A.A.S.H.O., County and City - Specifications, etc. - - - - - - - - - - - - - Appendix C Recommended Grading Specifications - - - - - - - - - - - - - - _- - - - GEOCON ENGINEERS AND GEOLOGISTS * CONSULTANTS IN THE APPLIED EARTH SCIENCES INCORPORATED STANDARD SPECIFICATIONS FOR PLACEMENT OF COMPACTED FILLED GROUND 1. General Description. The objective of these specifications is to obtain uniformity and adequate internal strength in filled ground by proven engineering procedures and to check the results by tests, so that the proposed structures may be safely supported. The proce- dures include clearing and grubbing, removal of existing structures, preparation of land to be filled, filling of the land, and spread- ing, and compacting the fill materials to conform with the lines, grades, and slopes as shown on the accepted plans. The owner shall employ a qualified soils engineer to inspect and test the filled ground as placed to verify the uniformity of com- paction of filled ground to the specified percent of maximum dry density. The soils engineer shall advise the owner and grading contractor immediately if any unsatisfactory conditions are observed to exist, and shall have the authority to reject any unsatisfactory filled ground until such time as corrective measures are taken necessary to comply with the specifications. It shall be the sole responsibility of the grading contractor to achieve the specified degree of compaction. 2. Clearing, Grubbinp and Preparing Areas to be Filled. (a> (b) (4 All brush, vegetation and rubbish shall be removed, piled, and burned or otherwise disposed of so as to leave the area to be filled free of vegatation and debris. Any soft, swampy or otherwise unsuitable areas shall be corrected by draining or removal, or both. The natural ground which is determined to be satisfactory for the support of the filled ground shall then be scarified to a depth of at least six inches (6 ,,ply;: gtil the surface is free from ruts, hunnnocks, or othe; uneven features which would tend to prevent uniform compaction by the equipment to be used. Where fills are made on hillsides or exposed slope areas, greater than 10 percent, horizontal benches shall be cut into firm undisturbed natural ground in order to provide both lateral and vertical stability. This is to provide a horizontal base so that each layer is placed and compacted on a horizontal plane. - q 6675 CONVOY COURT * SAN DIEGO, CALIFORNIA 92111 - PHONE (714) 292-5100 - - 3. - The initial bench at the toe of the fill shall be at least 10 feet in width on firm undisturbed natural ground at the elevation of the toe stake placed at the natural angle of repose or design slope. The soils engineer shall determine the width and frequency of all succeeding benches which will vary with the soil conditions and the steepness of slope. (d) After the natural ground has been prepared, it shall then be brought to the proper moisture content and compacted to not less than ninety percent of maximum censity in accordance with A.S.T.M. D-1557-66T method that uses 25 blows of a 10 pound hammer falling from a height of 18 inches on each of 5 layers in a 4" diameter cylindrical mold of a 1/30th cubic foot volume. Materials and Special Requirements. The fill soils shall consist ok select materials so graded that at least 40 percent of the material passes a No. 4 sieve. This may be obtained from the excavation of banks, borrow pits or any other approved sources and by mixing soils from one or more sources. The material used shall be free from vegetable matter and other deleterious substances, and shall not contain rocks or lumps greater than 6 inches in diameter. If excessive vegetation, rocks, or soils with inadequate strength or other unac- ceptable physical characteristics are encountered, these shall be disposed of in waste areas as shown on the plans or as directed by the soils engineer. If during grading operations, soils not encountered and tested in the preliminary investigation are found, tests on these soils shall be performed to determine their physical characteristics. Any special treatment recommended in the preliminary or subsequent soil reports not covered herein shall become an addendum to these specifications. The testing and specifications for the compaction of subgrade, sub- base, and base materials for roads, streets, highways, or other public property or rights-of-way shall be in accordance with those of the governmental agency having jurisdiction. Placing, Spreading, and Compacting Fill Materials. (a) Suitable fill material shall b 1 d in layers which, when compacted, shall not exceed siz !n%zs (6"). Each layer shall be spread evenly and shall be thoroughly mixed during the spreading to insure uniformity of material and moisture in each layer. (b) When the moisture content of the fill material is below that specified by the soils engineer, water shall be added until the moisture content is near optimum as specified by the soils engineer, to assure thorough bonding during the compacting process. - - I - - - - - - - - - - (c) When the moisture content of the fill material is above that specified by the soils engineer, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is near optimum as specified by the soils engineer. (d) After each layer has been placed, mixed and spread evenly, it shall be thoroughly compacted to not less than ninety percent of maximum density in accordance with A.S.T.M. D-1557-66T. Compaction shall be accomplished with sheepsfoot rollers, multiple- wheel pneumatic-tired rollers, or other approved types of com- paction equipment, such as vibratory equipment that is specially designed for certain soil types. Rollers shall be of such design that they will be able to compact the fill material to the specified density. Rolling shall be accomplished while the fill material is at the specified moisture content. Rolling of each layer shall be continuous over its entire area and the roller shall make sufficient trips to insure that the desired density has been obtained. The entire areas to be filled shall be compacted. (e) Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compacting operations shall be continued until the slopes are stable but not too dense for planting and-until there is no appreciable amount of loose soil on the slopes. Compacting of the slopes shall be accomplished by backrolling the slopes in increments of 3 to 5 feet in ele- vation gain or by other methods producing satisfactory results. (f) Field density tests shall be taken by the soils engineer for approximately each foot in elevation gain after compaction, but not to exceed two feet in vertical height between tests. Field density tests may be taken at intervals of 6 inches in elevation gain if required by the soils engineer. The location of the tests in plan shall be so spaced to give the best possible coveragz and shall be taken no farther apart than 100 feet. Tests shall be taken on corner and terrace lots for each two feet in elevation gain. The soils engineer may take additional tests as considered necessary to check on the uniformity of compaction. Where sheepsfoot rollers are used, the tests shall be taken in the compacted material below the disturbed surface. No additional layers of fill shall be spread until the field density tests indicate that the specified density has been obtained. (g) The fill operation shall be continued in six inch (6") com- pacted layers, as specified above, until the fill has been brought to the finished slopes and grades as shown on the accepted plans. - ..- 5. Inspection. Sufficient inspection by the soils engineer shall be maintained during the filling and compacting operations so that he can certify that the fill was constructed in accordance with the accepted specifications. - 6. Seasonal Limits. No fill material shall be placed, spread, or rolled if weather conditions increase the moisture content above -- permissible limits. When the work is interrupted by rain, fill operations shall not be resumed until field tests by the soils engineer indicate that the moisture content and density of the fill are as previously specified. 7. Limitim Values on Nonexpansive Soils. 2;5 Those soils that expand ry to saturation under a unit load -~ of 500 pounds per square foot are considered to be nonexpansive. - - - - - -