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Home My WebLink AboutCMWD 99-101; Agua Hedionda Pump Station Containment Basin; Agua Hedionda Pump Station Containment Basin; 1994-12-20GEOTECHNICAL EVALUATION A6UA HEDIONDA PUMP STATION CONTAINMENT BASIN CARLSBAD, CALIFORNIA DECEMBER 20, 1994 PREPARED FOR: CITY OF VISTA/SANITATION ATTN: MR. PETER NIEBLAS P.O. BOX 1988 VISTA, CALIFORNIA 92085 JOB #94-246-E VINJE & MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102 Escondido, California 920294229 Phone (619) 743-1214 Fax (619) 739-0343 Job #94-246-E December 20, 1994 City of Vista/Sanitation Attn: Mr. Peter Nieblas P.O. Box 1988 Vista, California 92085 Geotechnical Evaluation - Agua Hedionda Pump Station Containment Basin, Carlsbad, California Pursuant to your request, Vinje & Middleton Engineering, Inc. has completed the attached evaluation of geotechnical conditions at the above referenced site. The following report summarizes the results of our field investi- gation, including laboratory analyses and conclusions, and provides recommendations for repairs of the concrete containment basin. From a geotechnical engineering standpoint, it is our opinion that the repairs of the indicated unfavorable geotechnical conditions are feasible provided the recommendations presented in this report are incorporated into the final repair plans and implemented during the construction phase. The conclusions and recommendations provided in this study are consistent with the site geotechnical conditions and are intended to aid in preparation of final repair plans and allow more accurate estimates of the associated costs. Thank you for choosing Vinje & Middleton Engineering, Inc. If you have any questions concerning this report, please do not hesitate to call us. Reference to our Job #94-246-E will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. Ralph M. Vinje GE #863 RMV/kmh TABLE OF CONTENTS Page I. INTRODUCTION 1 II. SITE DESCRIPTION/DEVELOPMENT 2 III. FIELD INVESTIGATION 3 IV. FINDINGS 3 A. Earth Materials 3 B. Laboratory Testing/Results 4 1. Maximum Dry Density and Optimum Moisture 4 2. In-Place Dry Density and - Moisture Content 4 V. CONCLUSIONS 5 VI. RECOMMENDATIONS 6 VII. LIMITATIONS 9 ATTACHMENTS: Plate Site Plan 1 Test Trench Logs 2 Cross-Sections .... 3 Photograph 4 Reconstruction Map 5 Key and Benching Details 6&7 New Slab at Existing Slab Detail 8 GEOTECHNICAL EVALUATION AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN CARLSBAD, CALIFORNIA I. INTRODUCTION The property investigated in this work chiefly includes a graded embankment for a sewage containment basin located near the south margin of the Agua Hedionda Lagoon approximately as shown on the vicinity map below. VICINITY MAP The containment structure is a graded cut/fill earth structure provided with concrete paved interior surfaces. Numerous cracks affect the concrete, and we understand that a previous overflow condition resulted in erosion of ground surfaces along the north perimeter of the basin. The purpose of our investigation was to evaluate existing subsur- face conditions at the site and determine their influence upon the noted distress and possible impact upon the future performance of the structure. The specific areas investigated are depicted on a Site Plan attached to this report as Plate 1. VINJE ff MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOIL TESTINQ PERC TEST SOIL INVESTIGATIONS GEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 2 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 II. SITE DESCRIPTION/DEVELOPMENT The containment structure is a graded basin which was developed in 1989 by cut/fill grading. The grading created lh:l (horizontal to vertical) graded slopes on each of four sides of the structure which reach a maximum vertical height of 23 feet within the northern embankment. Subsequent paving of the interior surface created the existing liner which is also provided with interior drain pipes. Interior concrete surfaces of the basin are affected by continuous cracks. The cracks are chiefly longitudinal features which seem to proliferate in the northern portion. The most notable feature is a continuous crack which trends around the northwest portion approximately parallel with the indicated cut/fill transition line shown on Plate 1. Outside the structure, ground surface areas of the northern embank- ment are locally eroded. A paved brow ditch along the top of the slope is locally undercut, and rip-rap shown around an overflow pipe on Plate 1 is largely missing. Original ground surface contours (shown on Plate 1) indicate that the area prior to grading was characterized by a canyon which drained southward into the nearby lagoon. Existing grades are the result of cutting throughout the southeast portion and placing generated soils as fill beneath the north and west perimeter. An approximately cut/fill transition line is depicted on Plate 1. Grading compaction records for the work were not available for review. VINJE 6? MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOILTESTINQ PERC TEST SOIL INVESTIGATIONS "tjEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 3 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20, 1994 III. FIELD INVESTIGATION Geotechnical conditions' in the area of the project basin were determined from a review of the project grading plans (reproduced on Plate 1) and physical inspections of the site conducted by the undersigned. Subsurface conditions were determined by the excavation of two test trenches excavated with a tractor-mounted backhoe. The trenches were logged by our project engineer and representative soil samples retained for laboratory testing. In addition, in-place density tests of exposed fill soils were recorded by field technicians under the supervision of the engineer. Trench locations are shown on Plate 1. Logs of the trenches are attached with this report as Plate 2, and soil testing results are summarized in a following section. IV. FINDINGS A. Earth Materials; The studied containment basin is a cut/fill graded structure created by excavations into natural hillside terrain and placing fill beneath the north and west perimeter in order to create the existing embankments. Natural earth materials beneath cut areas of the structure include red-brown colored terrace deposit materials (chiefly beneath the west perimeter fill) and light colored bedrock units beneath the cut areas of the southeast portion. Exposures of these materials were noted in graded outcrops along the east and west margins of the project site. Both terrace and bedrock units at the project site consist of cemented, stable units which are expected to perform well beneath the structure. Minor amounts of natural alluvial soil may be present beneath the interior lowest areas of the basin. VINJE <Sf MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOIL TESTINQ PERCTEST SOIL INVESTIGATIONS -_<JEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 4 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 Fill soils derived from the excavation of natural deposits at the site underlie fi.ll areas of the project. The fill includes fine sandy soils as indicated on the attached Plate 2. Field observations indicate that the fill occurs in a relatively dry and loose condition and is inclined over a graded surface in Test Trench T-l. The indicated subsurface configuration of site earth materials is depicted on cross-sections included with this report as Plate 3. B. Laboratory Testing/Results; Excavation of on-site earth materials generated soils which have been grouped into the following soil types: Soil Type Description 1 brown silty fine sand with sandstone fragments and AC chunks 2 red-brown silty sand 3 off-white fine to medium grained sandstone The following tests were conducted in support of this study: 1. Maximum Dry Density and Optimum Moisture Content: The maxi- mum dry density and optimum moisture content of Soil Types 1 and 2 were determined in accordance with ASTM D-1557-91. The results are tabulated below. Maximum Dry Optimum Density Moisture Location Soil Type fpcf) Content (%) T-l @ 3' 1 124.4 12.4 T-2 @ 6' 2 126.0 ' 11.3 2. In-Place Dry Density and Moisture Content; In-place dry density and moisture content of representative soil deposits VINJE 6fMIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOIL TESTINQ PERC TEST SOIL INVESTIGATIONS -jfJEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN PAGE 5 DECEMBER 20. 1994 beneath the site were determined from in-place sand cone tests in accordance with ASTM D-1556-90. Results are pre- sented below and on the attached trench logs. Relative CompactionSoil Location Tvoe T-l T-l T-l T-2 T-2 T-2 @ @ @ @ @ @ 3 6 9 2 6 9 1 1 2 1 2 2 Dry Density (pcf) 90. 90. 93. 87. 93. 93. 5 4 3 2 3 0 Moisture Content m 8.4 8 8 6 6 5 .5 .2 .4 .8 .3 73 73 74 70 74 74 V. CONCLUSIONS Based upon the foregoing investigation, the subject containment structure is a graded cut/fill structure which is underlain by stable bedrock and terrace deposit soils throughout the southeast portion. Fill soils generated from original cut excavations under- lie fill areas of the structure (see Plate 1). Test excavations and laboratory test data indicate the following defects in the fill soils at the site: * Site fill occurs in a loose and uncompacted condition. Moisture levels are well below optimum levels indicated for site soils. * Site fill in original hillside areas was not properly keyed or benched into underlying natural units in accordance with proper grading techniques. Inclined fill/natural contacts were exposed in - Test Trench 1 (T-l) . This condition is indicated on Plate 2 and depicted on the attached Plates 3 and 4. VINJE & MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOIL TESTING PERC TEST SOIL INVESTIGATIONS GEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 6 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 Many of the noted cracks within the concrete shell are thought to reflect normal concrete .shrinkage and stresses which relate to the interior liner configurations; however, prominent features, parti- cularly along the indicated cut/fill transition line, likely reflect local fill movement relative to the more stable areas beneath the cut areas. Based upon the condition of fill noted and tested in the test trenches, additional ground movement at the site can be expected in the future which will likely result in advanced distress. VI. RECOMMENDATIONS Based upon the indicated site geotechnical conditions, the most cost effective method of controlling future basin distress and the potential for major failure is to reconstruct the front (north) fill portion of the basin structure. This should be accomplished by regrading the structure as a properly compacted fill embankment which is keyed and benched into stable underlying units in accor- dance with current grading standards. The portion of the structure recommended for regrading and slab reconstruction is depicted on a Reconstruction Map attached to this report as Plate 5. Visual observations indicated non-expansive sandy soil deposits at the site. An expansion test may be required by the project geotechni- cal engineer at finish grade levels to confirm slab recommenda- tions. The following recommendations are presented: A. Sawcut and remove surface concrete structures in areas shown on Plate 5. Concrete debris may be crushed and reused in recom- pacted fill. The debris should not exceed six to eight inches in diameter and should be evenly dispersed 'throughout site fill soils. B. Remove fill soils to underlying bedrock/terrace deposit materials throughout areas indicated on Plate 5. The removal soils are suitable for reuse in properly recompacted^fill. VINJE # MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOILTESTINQ PERC TEST SOIL INVESTIGATIONS GEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 7 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 * C. Moisture condition site soils to slightly higher than optimum moisture levels and.mechanically recompact the fill in thin horizontal layers to 95% of the laboratory maximum density. • Removal (bottom areas) should be inspected and approved by the project geotechnical engineer prior to placing fill. Field density tests should be taken in the recompacted fill in order % to assist the contractor with moisture conditioning and compac- tion procedures. D. Due to previous soil loss resulted from overflow washouts and • anticipated soil shrinkage at the time of recompaction, import soils will be necessary to complete grading. The import soils should consist of non-expansive, granular deposits. The soils should be inspected, tested, and approved by the project • geotechnical engineer prior to importing to the site. Existing fill materials are expected to shrink nearly 20 to 25% on volume basis when compacted to 95% of the maximum density. ^ E. New fill should be placed to create pre-remedial grading con- figurations. All graded slopes should be compacted to 95% out to the slope face. Slopes should be overbuilt and cut back to the design configuration or backrolled at minimum three-foot • vertical increments and "track-walked" at the completion of grading. All slope constructions should be completed in general accordance with the attached Key and Benching Details (Plates 6 and 7) and as directed in the field by the project geotechnical • engineer. F. The new slab for the containment basin should be a minimum of four inches thick, reinforced with 6x6/10x10 welded wire mesh, • placed mid-height in the slab. The new slab may be constructed over the indicated 1^:1 embankment using "shotcreting" techni- gues. The bottom slab however may be four inches thick, poured VINJE <Sf MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 '9 SOIL TESTING PERCTEST SOIL INVESTIGATIONS GEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 8 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 in-place concrete slab-on-grade. All concrete should develop a minimum compressive strength of 3250 psi per Green Book specification 560 C-3250. G. It is customary to undercut the cut portions of transition pads in order to mitigate adverse affect of cut/fill daylight line of the overlaying improvements and structures. In this case, however, the new slab at the existing slab should be constructed in general accordance with the attached Plate 8 to mitigate this condition. Periodic resealing of joints still may be necessary and should be anticipated. H. Original construction details also provided to us should be used for reconstruction except where superseded in this report. Construction joints around the perimeter should confirm to detail A1/C2. Troweled three-quarter inches deep maximum control joints should also be provided as specified in the plans except the maximum spacing between control joints should be 12 feet. I. The damaged rip-rap structure at the overflow pipe discharge location and the concrete berm on top of slope should be reconstructed as specified on the original plans or by the civil engineer. J. A number of utility pipes cross the project site at the proposed repair areas. All pipes should be identified, removed, and reinstalled as necessary. Pipes may remain in place if approved by the project geotechnical engineer based upon the actual exposures developed during grading operations. Added care will be necessary in order not to damage any pipes or utility lines during the earthworks. VINJE # MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 * SOIL TESTINQ PERCTEST SOIL INVESTIGATIONS -jfJEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 9 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 K. Upon completion of grading works, the northern side of the slope should be provided yith approved ground cover vegetation in accordance with the Green Book or City of Carlsbad requirements. Unprotected slopes will be subject to excessive erosion and are not allowed. L. All utility trench backfill should be compacted to 95% of the maximum dry density. M. Grading operations should be continuously inspected, tested, and approved by the project geotechnical engineer. Testing of fill will assist the contractor to achieve proper moisture and compaction levels. Particular attention should be given to removal operations and keyway construction. N. All slab subgrade soils and steel reinforcement should be tested, inspected, and approved by the project geotechnical engineer. 0. A preconstruction meeting between representatives of this office, the project planner, as well as the project civil engineer, grading contractor, and city representative is recommended to discuss grading and construction details. VII. LIMITATIONS The conclusions and recommendations provided herein have been based on all available data obtained from our field investigation and laboratory analyses, as well as our experience with the soils and formational materials located in the general area. The materials encountered on the project site and utilized in our laboratory testing are believed representative of the total area; however, earth materials may vary in characteristics between excavations. VINJE 6f MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOILTESTINQ PERCTEST SOIL INVESTIGATIONS -§EOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION PAGE 10 AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN DECEMBER 20. 1994 Of necessity we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be verified during the grading operation. In the event discre- pancies are noted, we should be contacted immediately so that an inspection can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to insure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of VINJE & MIDDLETON ENGINEERING, INC. shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our inspection or control. This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made to your tentative development plan, especially with respect to the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. Vinje & Middleton Engineering, Inc. warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. VINJE & MIDDLETON ENGINEERING, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOILTESTINQ PERC TEST SOIL INVESTIGATIONS -sSEOTECHNICAL INVESTIGATIONS GEOTECHNICAL EVALUATION AGUA HEDIONDA PUMP STATION CONTAINMENT BASIN PAGE 11 DECEMBER 20. 1994 No other warranty or representation, either expressed or implied, is included or intended. Once again, should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Job #94-246-E will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, I Ralph M. Vinje GE #863 Dennis Middleton CEG #980 Mehdi Shariat RCE #46174 RMV/DM/kmh Attachments: Plates 1-8 a:94-246-E.GE CERTIRED ENGINEERING WWMA VINJE & MIDDLETON ENQINEERINQ, INC. 2450 Vineyard Avenue, #102, Escondido, California 92029-1229 • Phone (619) 743-1214 • Fax (619) 739-0343 SOIL TESTING PERC TEST SOIL INVESTIGATIONS -j@EOTECHNICAL INVESTIGATIONS SITE PLAN PLATE 1 Agua Hedionda Pump Station, Carlsbad LEGEND: •/ V! LOCATION OF TEST TRENCH ORIGINAL SURFACE CONTOUR ,—@>—* [ I EXISTING SURFACE CONTOUR I / • r| CROSS-SECTION LINE I Scale: 1"=20' 94-246-E Site Plan is reproduced from project grading plan prepared by Wilson Engineering, 4-3-89. Date December 13, 1994 Logged by DM x _ Li. [^ °,: 0 _ — - - -5- — . — - — — — 1O — 15 LU a. CO Vi T "V ' < T-1 DESCRIPTION FILL: Silty fine sand. Poorly mixed with pockets of pale green sandstone fragments and AC chunks. Very loose, slightly moist. SOIL TYPE 1 From 8', includes some rocks. From 9', red-brown silty sand. SOIL TYPE 2 BEDROCK: (upper contact is inclined down slope) Sandstone. Off-white color. Fine to medium grained. Fractured and blocky on the upper exposures. At 12' becomes more uniform, dense. Massive. SOIL TYPE 3 , . , 0 , LUcr to o^ S. 8.4 8.5 8.2 DC W 0 Q Z Q- Q 90.5 90.4 93.3 zU O 3gs? (COO 73 73 74 Dote December 13, 1994 Logged by SMS fp-LLJ "• Q — — - 5 - — — -10- — - -15- LU_J Q.5< CO T • T • T s^^^^s^» T-2 DESCRIPTION FILL: Silty sand. Light brown. Includes sandstone fragments. Loose, slightly moist. SOIL TYPE 1 Silty sand with occasional cobbles. Fine to medium grained. Loose, dry. At 9' becomes uniform and porous (may be natural topsoil) . SOIL TYPE 2 ALLUVIUM (?): Silty sand. Red-brown. Porous. Moderately firm, moist. end trench at I/,' SOIL TYPE 2 LU QLe-«co;s;b^ 6.4 6.8 5.3 >->_t \LC co o;=; z Q.u UJ ^ 0 87.2 93.3 93.0 z111 O - P-s idl- (EOO 70 74 74 Vinje <§? Middleton ENGINEERING, INC TEST TRENCH LOGS AGUA HEDIONDA PUMP STATION Project No. 94-246-E Plate 2 T Sand cone test • Bulk sample D Chunk sample Q Driven rings ORIGINAL SURFACE ' Scale: 1 "=20' i 20- 10- CROSS-SECTIONS PLATE 3 PROJECT PHOTOGRAPHS BEST ORK '/:.-.'- i; # •.ty'-'i-si'j^ it^t.. f/t 'ri*B:*SM:« VIEW INSIDE TEST TRENCH T-1. NOTE LOOSE FILL SOIL ABOVE AND INCLINED FILL-NATURAL CONTACT BELOW. Plate 4 \JPROJECT AGUA HEDIONDA PUMP STATION - CARLSBAD DATE 12-13-94 RECONSTRUCTION MAP PLATE 5 Agua Hedionda Pump Station, Carlsbad RIP RAP-*; LEGEND: *r J APPROX. AREA RECOMMENDED FOR — ' REMOVAL AND RECONSTRUCTION, ACTUAL SAW-CUT LINE TO BE LOCATED IN FIELD BY GEOTECHNICAL ENGINEER Scale: 1"=20' KEY AND BENCHING DETAILS (Typical - no scale) finish slope finish pad. existing ground surface remove unsuitable materials equipment width min. 15'minT key width cut slope (to be excavated prior to fill placement) bench competent bedrock or firm native ground per- project geotechnical consultant Fill-Over-Cut Slope existing ground surface finish pad project 1:1 line from toe of slope to competent materials remove unsuitable materials cut slope (to be excavated prior to fill placement) bench per project geotechnical engineer in the field - also, see geotechnical report competent bedrock or firm native ground per project geotechnical consultant key depth key width Cut-Over-Fill Slope Note: Key and benching details shown herein are subject to revision by the project geotechnical engineer based upon actual site conditions. Back drains may also be necessary as determined by the project geotechnical consultant. Plate #6" KEY AND BENCHING DETAILS (Typical - no scale) project 1:1 line from top of slope to outside edge of key Insuitable V^| materials/T^ existing ground. surface one equipment width min. pad overexcavation and recompaction per project geotechnical engineer 15' min. ,mins key widthdepth J competent bedrock or fi native ground per project geotechnical engineer irjt/ Side Hill Stability Fill Slope finish slope existing ground surface one equipment width minimum/as. \ /—"'bench remove unsuitable materials 2' min. key depth 15' min." key width Fill Slope competent bedrock or firm native ground per project geotechnical engineer Note: Key and benching details shown herein are subject to revisions by the project geotechnical engineer based upon actual site conditions, Back drains may also be necessary as determined by the project geotechnical consultant. Plate # 7 oo o UJ LU Qcall co i-1 521XLU CO <_J CO LU < g 3S ae 5°- 8m •z.UJUJtrocc 01 ^ <Qi uj w>I!IS 1 S* „°-o 1 1 I 11 11 eI si s i =j ^§5 8' 31 5- iu