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HomeMy WebLinkAbout; Plaza Camino Real Shopping Ctr; Soils Report Settlement; 1968-10-02- - - - - - - - - - - - - - - -. - FINAL REPORT SETTLEMENT Ol? SURCR.&GED AREA ,~ROPOSED SHOPPING CENTER EL CAMIA'O P&L NEAP, THE VISTA FREEWAY cAmsr4r), C~L~F'ORXA RECEIVED OCT 4 1968 CITY OF CARLSBAD Building Department - - - - - - - - - - - - - - - LEROY CRANDALL AND ASSOCIATES October 2, 1968 Plaza Camino Real c/o The May Department Stores Company 10738 West Pica Boulevard Los Angeles, California 90064 Attention: Mr. Kelly Tamer Gentlemen: (Our Job No. B-66171) Final Report Settlement of Surcharged Area Proposed Shopping Cater El Camino Real near the Vista Freeway Carlsbad, California for P&Z? Camino Real SCOPE This report presents the results of our inspection of surcharge fills and observations of settlement markers at the location of the subject shopping center in Carlsbad, California. The building areas of the site were surcharged to reduce future settlements of the proposed buildings and to permit the use of spread footings for foundation support. Our report dated August 12, 1966, presented the results of our foundation investigation of the site, and recommendations for the surcharging. The purpose of our present work was to (1) maintain records of set- tlement readings on the monuments, and compare these records of settlement with our predicted settlement; (2) recommend any changes in the amount of L. kROY CRANDALL. c. E. RUSSELL c. WEBER, c, c, SEYMOUR s. CHIU. c. E FREDRlCK A. BARNES J. D, K,RKGARD, c. E. Pi A~ NAilIAN. c, E. 7^nr, ” I,^“^, 1~~1 ^I _ ^ _ - ^ _ ROBERT CHIERUZZI, c. E. JAMES L. “AN SEVEREN. c. E. - - October 2, 1968 (Our Job No. B-66171) - - - - - surcharge fill required at various parts of the building areas, and (3) advise you as to when the site was adequately preconsolidated and ready for construction. BACKGROUND CONSIDERATIONS The site is located in a valley and on the south flank of Marron Canyon just to the east of the Buena Vista Lagoon and the adjacent marshy ground. While the hillside area is underlain by firm to vary firm geologi- - - tally older deposits, the valley or low areas are underlain by recent allu- vial deposits ranging up to 100 feet or more in depth. The recent alluvial - - - deposits consist of clay, silt, silty sand, clayey sand, and sand; they are ~generally soft to moderately firm and are compressible to varying degrees. The planned development called for cutting the hillside and filling the lowlands; compacted fill on the order of 20 feet in thickness was planned within the building areas. It was computed that, under the planned fill, area1 settlements on the order of three feet would result and that the set- - tlement would take place over a period of several years. To provide adequate - - - - - support to the proposed buildings on spread footings, the area1 settlement would have to be complete prior to the construction of the buildings. Alternatively, the buildings could be supported on driven friction piling, but in view of the depth of the planned fill and the underlying soft soils, the pile foundations would be very costly. Furthermore, the area1 settle- ments would create problems with floor slabs, walkways, and utilities even though the structures were supported on piling. - - Plaza Camino Real October 2, 1968 Page 3 (Our Job No. B-66171) - - -- - - - - - - - In order to permit the use of conventional spread footings without waiting several years, it was decided to surcharge the site to accelerate the settlement. The time required for surcharging would depend on the thickness of the surcharge fill and the settlement rate. of the slowest consolidating layer of the natural soils at a given location. Accordingly, a surcharge requirement chart was prepared showing the required time of sur- charging for various depths of surcharge fill. After discussing the matter with the parties concerned, it was decided to surcharge the main building areas by placing approximately 30 feet of temporary surcharge fill for a period of 18 months. In order to check the actual magnitude and rate of settlement, monuments were set throughout the major building areas and the elevations of the monuments were periodically checked during the placing of fill and after completion of the surcharge fill. In addition to the major building areas, both the May Company and the J. C. Penney building areas were surcharged with approximately 17 and 14 feet of fill, respectively. SETTLEMENT MONUMENTS - The grading operation at the site began in mid-July, 1966; the - placing of about 20 feet of permanent compacted fill and about 30 feet of - - - surcharge fill within the main building areas was completed in late August, 1966. Sixteen settlement monuments were installed on the natural ground surface prior to placing any fill; these monuments are designated as Type A monuments. After the permanent fill was placed, 19 additional monuments were placed on top of the permanent fill prior to the placing of the sur- charge fill; these monuments are designated as Type B monuments. October 2, 1968 (Our Job No. B-66171) - - - - - - - - - - .- - - The placing of the permanent fill throughout the proposed shopping center was completed in October, 1966. The location of the proposed TEA buildings were finalized at a later date and these areas were surcharged in May of 1967. Four Type B monuments were installed at each of the TBA build- ing areas. The extent of the surcharging of the s'ite was defined on the Grading and Drainage Plan dated 6-13-66 (Revised 7-l-66) by Shuirman, Rogoway and Associates. The locations of all the settlement monuments are shown on Plate 1, Plot Plan, Settlement Monument Locations. Because of the large area within the main building areas, the dis- tance between the Type A and Type B monuments ranged up to about 170 feet. To provide information on the settlement occurring at intermediate locations, some 150 supplementary monuments (Type C) were placed at the top of the SW- charge fill on a 50-foot grid over the main building areas in May, 1967. SETTLFCIENT OBSERVATIONS The anticipated settlement was computed at the locations of 15 of the Type A monuments to compare our predictions with the observed field set- tlements. The elevations of the settlement monuments were determined at frequent intervals by Psomas & Young, Surveyors, and a plot of the readings for each monument was maintained by US. Plots of the settlement of the Type A and Type B monuments were submitted periodically to all parties concerned during the course of the project. The results of all of the settlement data for these monuments are presented on Plates 2-A through 2-Z, Rate of Settle- ment. Although not presented herein, the rate of settlement of the monuments within the TBA building areas and of Type C monuments within the main building - - - - - - - - - Plaza Camino Real October 2, 1968 Page 5 (Our Job No. B-66171) areas were observed and the data analyzed. The detailed records of these monuments will be retained in our files. REMOVAL OF SURCHARGE FILL As previously discussed, it was initially estimated that the sur- charge fill within the main building areas would be maintained for a period of 18 months; the scheduled date for the removal of the surcharge fill was March of 1968. In October of 1967, we were asked to review the settlement - - data and determine if it would be possible to remove the surcharge in January, 1968, instead of March. On the basis of the settlement observa- tions and from comparison with our previous calculations, we concluded that the surcharge fill could be removed in January, 1968. HOWaVer, the measured settlement at Monument A-l within the Penney's store area was less than pre- dicated. To assure that the settlement in that area was complete, we re- quested that selected monuments within the Penney's area be maintained for further readings after the removal of the surcharge. This was considered - reasonable as construction of the Penney's store was not scheduled to start until several months after the remainder of the shopping canter. The surcharge over the entire site (including the TBA building areas) was removed in January of 1968, and construction of the May Company store and adjacent shop buildings is currently under way. During the removal of the surcharge fill, the monuments within the Penney's store area which were to be preserved, were destroyed. A few of these monuments, namely A-l, A-2, B-l, and B-3, were restored and settlement readings of these monuments were continued. - - Plaza Camino Real Page 6 October 2, 1968 (Our Job No. B-66171) CONCLUSIONS The total settlement under the permanent fill and the surcharge fill, as indicated by the Type A monuments, ranged from 24 inches to 40 inches. In almost all cases, the curves of the measured settlements com- pare vary well with the curves of the predicted settlements. In all cases, the rate of settlement decreased to a vary nominal amount at the time the surcharge was removed. Only negligible amounts of rebound were observed after the removal of the surcharge. The results of the settlement observations indicate that the soils have been adequately preconsolidated to permit construction of the proposed buildings on conventional spread footings. As stated earlier, most of the buildings are currently under construction. The future settlement of the structures should be nominal and as predicted in our foundation report. Yours very truly, LeROY CRANDALL AND ASSOCIATES LC-PM:lb Attachmnts (27) (3 copies submitted) cc: (1) Krumm & Sorenson (1) Welton Becket and Associates (1) Brandow & Johnston Associates (1) Stacy & Meadville, Inc. (1) Shuirman, Rogoway & Associates (1) Carlsbad Building Department