“UNITED STATES OF AMERICAOCCUPATIONAL SAFETY AND HEALTH REVIEW COMMISSION \u00a0 SECRETARY OF LABOR, \u00a0 ???????????????????????????????????????????? Complainant, \u00a0 ???????????????????????? v. OSHRC DOCKET NO. 76-910 ELECTRICAL CONSTRUCTORS OF AMERICA, INC., \u00a0 ????????????????????????????????????????????? Respondent. \u00a0 \u00a0September30, 1980DECISIONBefore CLEARY, Chairman; BARNAKO and COTTINE,Commissioners.BY THE COMMISSION:??????????? Adecision of Administrative Law Judge James D. Burroughs is before theCommission for review pursuant to section 12(j)[1] of the Occupational Safetyand Health Act of 1970, 29 U.S.C. ?? 651?678 (?the Act?). Judge Burroughsaffirmed a serious citation alleging that Respondent, Electrical Constructorsof America, Inc., (?Elcon? or ?the company?) violated section 5(a)(2)[2] of the Act in that Elconfailed to shore or slope the sides of a trench as required by 29 C.F.R. ?1926.652(c).[3]The judge assessed a penalty of $250. We reduce the penalty to $150, butotherwise affirm the judge?s decision.I??????????? AtHartsfield International Airport in Atlanta, Georgia, Elcon was engaged inrelocating communications cable. This involved making a bore 125 to 140 feetlong under an existing runway. To provide a place for the boring machineadjacent to and below the runway, Elcon excavated a trench approximately 48feet long; six feet, four inches wide; and six to eight feet deep. The trenchwas in hard and compact soil. The excavation was performed using a John Deere400 backhoe, an intermediate size backhoe having a downward reach ofapproximately thirteen feet, six inches. Elcon operated the backhoe at thetrench edge.??????????? Thebore under the runway was required to be exact within a narrow range for error.Therefore, the trench depth and the level nature of the grade within the trenchhad to be as exact as possible. When the backhoe operator and the other Elconemployees at the worksite though the requisite depth and grade had beenachieved, the employees and an engineer employed by the Federal AviationAdministration attempted to make accurate measurements of depth and grade fromthe ground surface, but found they could not do so. They entered the trench andwere in the process of making the measurements when two compliance officersemployed by the Secretary of Labor (?the Secretary?) inspected the trenchingworksite. The depth of the trench where the employees were working was at leastsix feet, and the trench sides were not shored or sloped above the five-footlevel. Accordingly, a citation alleging that Elcon failed to comply withsection 1926.652(c) was issued by the Secretary. The violation wascharacterized by the Secretary as serious.[4] The characterization,according to the testimony of one of the compliance officers, was based on hisown and other compliance officers? experience which indicates that when aportion of a bank of dirt caves in on an employee, ?he is usually seriouslyhurt.? The Secretary proposed a penalty of $500.??????????? Elcondid not contend before the judge that the trench complied with section1926.652(c) but argued, instead, that shoring and sloping could not have beendone until after the company had determined that the correct depth and gradehad been reached. The company argued that if the sides were sloped back beforethe trench was completed, the backhoe could not reach the trench bottom to doany additional digging. The company further asserted that the degree to whichthe trench had to be sloped remained an unknown until the correct depth hadbeen reached. Elcon also contended that the violation, if any, was notestablished as serious on the basis of the compliance officer?s unsupportedopinion. The company additionally argued before the judge that no penalty waswarranted in view of the low gravity of the violation, Elcon?s small size andprecarious financial condition, and Elcon?s good faith as evidenced bycompliance with the sloping requirements immediately after the inspection.??????????? JudgeBurroughs found that Elcon failed to comply with section 1926.652(c) and thatthe company?s defense of impossibility of performance was not established. Herejected Elcon?s contention that the backhoe could not reach the trench bottomif the sides were sloped. The judge noted that the six-to eight-foot sides inhard or compact soil were required to be sloped only at a rate of one-foot riseto each one-half-foot horizontal and only above the five-foot level. In lightof the relatively small degree of sloping required and the fact that the reachof the backhoe was thirteen feet, six inches, which was considerably greaterthan the depth of the trench, Judge Burroughs concluded that the backhoe couldhave reached the bottom of the trench even if the walls had been properlysloped. The judge also found that the measurements of depth and grade couldhave been made with shoring in the trench. He accordingly rejected Elcon?scontention that shoring could not have been installed until after the correctdepth and grade had been reached.??????????? Thejudge further concluded that the violation was serious. He found that if atrench side measuring six feet high collapsed on an employee while the employeewas bending over, ?the chances are great that he would be completely covered,?and that ?the weight of the soil could possibly cause serious physical harm toan individual trapped by a collapse.? The judge, however, assessed a penalty of$250, rather than the $500 proposed by the Secretary, because he concluded thatthe gravity of the violation was low in view of the small likelihood of acollapse of the hard and compact soil composing the trench walls.II??????????? Onreview, Elcon renews its arguments that a defense of impossibility ofperformance was established, that the violation was not serious, and that nopenalty should be assessed.[5] Elcon further argues thatthe judge?s factual findings on seriousness are not supported by the record andthat the judge applied an incorrect legal test to determine that the violationwas serious. Elcon notes that the judge considered whether a collapse of thetrench sides ?could possibly cause serious physical harm? rather than whetherthere was ?a substantial probability that death or serious physical harm couldresult,? as set forth in section 17(k) of the Act.[6] The Secretary did not filea brief on review.??????????? Wereject Elcon?s defense of impossibility of performance on the basis of thejudge?s reasoning. We have examined the record and conclude that the judgeproperly considered the evidence and correctly rejected Elcon?s argument thatthe backhoe could not be used to excavate the trench further if the walls hadbeen sloped to the extent required by the standard prior to the time theemployees entered the trench. Accordingly, we adopt the judge?s findings andconclusions with respect to this issue. Gulf Oil Co., 77 OSAHRC 216\/B10,6 BNA OSHC 1240, 1978 CCH OSHD ? 22,737 (No. 14281, 1977). The remainingportion of Elcon?s defense?that the company could not know what slope wasrequired until it had determined that the correct depth had been achieved?isplainly without merit, particularly since the record shows that the backhoecould have been used to correct the depth even after the sides had been slopedto the extent required for the depth existing at the time the employees wereobserved in the trench.[7] Accordingly, Elcon has notestablished that compliance with the requirements of section 1926.652(c) forsloping was impossible because it would have precluded performance of therequired work. See M. J. Lee Construction Co., 79 OSAHRC 12\/A2, 7 BNAOSHC 1140, 1979 CCH OSHD ?23, 330 (No. 15094, 1979).[8]??????????? Wealso reject Elcon?s arguments that the violation was improperly characterizedas serious. A violation is deemed serious within the meaning of section 17(k)of the Act if there is a substantial probability that death of serious physicalharm could result from an accident.[9] The probability that anaccident will occur is irrelevant. Boonville Division of Ethan Allen, Inc., 78OSAHRC 105\/B4, 6 BNA OSHC 2169, 1979 CCH OSHD ? 23,219 (No. 76?2419, 1978). Wefind that a collapse of the trench would have resulted in a substantialprobability that the employees in the trench could have suffered death orserious physical harm. See Andy Anderson d\/b\/a Andy Anderson Irrigation andConstruction, 78 OSAHRC 34\/A2, 6 BNA OSHC 1595 (No. 76?4082, 1978).Therefore, the violation of section 1926.652(c) was serious.??????????? Thereremains the penalty to be assessed. Because the gravity of the violation waslow, Elcon has no prior history of violation of the Act, nothing appears tocall into question Elcon?s good faith toward compliance, and the company issmall in size, we assess a penalty of $150.??????????? Accordingly,the judge?s decision is modified to assess a penalty of $150 and, as somodified, is affirmed. SO ORDERED.?FORTHE COMMISSION:?RAYH. DARLING, JR.EXECUTIVESECRETARYDATED:SEP 30, 1980?CLEARY,Chairman, concurring:??????????? I would affirm the administrativelaw judge?s decision for the reasons assigned by him.\u00a0\u00a0UNITED STATES OF AMERICAOCCUPATIONAL SAFETY AND HEALTH REVIEW COMMISSION \u00a0 SECRETARY OF LABOR, \u00a0 ???????????????????????????????????????????? Complainant, \u00a0 ???????????????????????? v. OSHRC DOCKET NO. 76-910 ELECTRICAL CONSTRUCTORS OF AMERICA, INC., \u00a0 ????????????????????????????????????????????? Respondent. \u00a0 December 28, 1976DECISION AND ORDERAPPEARANCES:Thomas P. Brown, IV, Esquire, Office ofthe Department of Labor, Atlanta, Georgia, on behalf of complainant.\u00a0John D. Sours, Esquire, Smith, Currie andHancock, Attorneys at Law, Atlanta, Georgia, on behalf of respondent.\u00a0STATEMENT OF CASEBurroughs, Judge:??????????? Thisis proceeding initiated pursuant to section 10(c) of the Occupational Safetyand Health Act of 1970, 29 U.S.C. 651 et seq. (?Act?). Respondent, by letterdated February 16, 1976, timely contested a serious citation issued to it,pursuant to section 9(a) of the Act, on February 4, 1976. Review is also soughtof the penalty proposed for the alleged violation.??????????? Respondentis a corporation having a place of business and doing business in Skyland,North Carolina. It is engaged in business as an electrical contractor. Thecitation resulted from an inspection conducted on January 30, 1976, at theHartsfield International Airport, Atlanta, Georgia. Respondent was engaged inrelocating a communications cable under a runway at the time of the inspection.??????????? Theserious citation alleges that respondent violated section 5(a)(2) of the Act byfailing to comply with the safety standard promulgated at 29 C.F.R. ?1926.652(c). The alleged violation was described as follows:Failed to shore or otherwise support thesides of trenches in hard or compact soil, more than five feet in depth andeight feet or more in length in which employees were exposed to the hazards ofcave-ins in an open trench on the southside of runway #27R near fire station atHartsfield International Airport.\u00a0??????????? Apenalty of $500 was proposed for the alleged violation.??????????? Ahearing was held in this matter on July 6, 1976, in Decatur, Georgia. Noadditional parties desired to intervene in the proceedings.JURISDICTION AND ISSUES??????????? Respondent?sanswer denied that the Commission has jurisdiction of this matter or that it isengaged in a business affecting commerce within the meaning of the Act. Thedenial was based on the contention that the allegations were legal conclusions.??????????? Respondentadmits in the Request for Admissions served upon it by complainant that it usesmachinery, equipment and tools in its business that were manufactured in wholeor part outside the State of Georgia (RA[10] paras. 4, 5).Respondent?s president testified that respondent?s home office is in NorthCarolina and that it does business in North Carolina, Georgia and Tennessee(Tr. 54). These facts are sufficient to conclude that respondent is engaged ina business affecting commerce and that the Commission has jurisdiction of theparties and the subject matter. See Secretary v. Accu-Namics, Inc., 8OSAHRC 890 (1974), aff?d 515 F.2d 828 (5th Cir. 1975), cert. den.96 S.Ct. 1492 (1976).??????????? Thefollowing issues are presented for determination:??????????? 1.Did respondent violate section 5(a)(2) of the Act by failing to comply with 29C.F.R. ?\u00a01926.652(c)???????????? 2.Was the violation, if it occurred, a serious violation within the meaning ofsection 17(k) of the Act???????????? 3.What penalty, if any, should be assessed in the event a violation isdetermined?FINDINGS OF FACT??????????? Thefollowing facts are specifically determined in resolving the issues in dispute:??????????? 1.Respondent is a corporation with its home office located in Skyland, NorthCarolina. It currently operates in Georgia, Tennessee and North Carolina (Tr.54).??????????? 2.Complainant, through a duly authorized compliance officer, conducted aninspection at the Hartsfield International Airport, Atlanta, Georgia, onJanuary 30, 1976 (Tr. 5, 12).??????????? 3. Atthe time of the inspection, respondent was in the process of completing theexcavation of a trench. Approximately 90 percent of the trench had beencompleted the previous day (Tr. 5, 58).??????????? 4.Respondent had 17 employees at the airport at the time of inspection (Tr. 24).Some of the employees were working at another excavation site at the airport(Tr. 24?25).??????????? 5.Respondent had a contract with the Federal Aviation Administration atHartsfield Airport to relocate all communications cables from existingfacilities to a new tower location (Tr. 56).??????????? 6. Atrench had been excavated at the southside runway of the airport. The trenchwas approximately 48 feet long and six feet and four inches wide. The depth ofthe trench varied between six and eight feet. It was seven feet deep in thecenter, eight feet deep at the runway and six feet deep at the opposite end (RAparas. 6?9, Tr. 6, 35).??????????? 7.The trench was excavated in hard and compact soil. The sides of the trench werenot shored, sheeted, braced or otherwise supported (RA paras. 10, 12; Exs. 1,2; Tr. 11).??????????? 8.The trench was not sloped (Exs. 1, 2). Respondent had intended to slope thetrench after the proper grade and depth had been reached (Tr. 63).??????????? 9.Three[11] employees of respondentwere in the trench at the time of the inspection (Ex. 1; Tr. 7, 9, 40). Theywere in the area of the trench that was six feet deep (Exs. 1, 2; Tr. 46?47).??????????? 10.The grade of the trench had to be checked. Three employees entered the trenchto perform this task. The equipment operator was in the trench assisting inchecking the grade and depth at the time of the inspection (Ex. 1; Tr. 39?40,42). Two laborers were also in the trench. One laborer spread the dirt so agood measurement could be taken (Tr. 50, 52?53). An engineer for the FederalAviation Administration was in the trench checking the grade and depth (Tr.42?43, 73?74, 76).??????????? 11.The employees had been in the trench approximately one to two minutes when thecompliance officer arrived (Tr. 43?44, 74).??????????? 12.The trench was excavated in order to place a boring machine in it to bore underthe runway. Communications cables had to be place under the runway (Tr. 18?19,37, 41).??????????? 13.The boring machine was to be placed in the trench after the proper grade hadbeen established (Tr. 56).??????????? 14.The boring machine was to be placed on a track similar to a railroad track. Thetrack had to be level and at the right pitch (Tr. 56?57, 59).??????????? 15.The length of the bore under the runway was to be between 125 and 140 feet. Thebore had to be made in an exact and precise direction (Tr. 57).??????????? 16.The depth of the trench had to be checked at the place where the boring machinewas to be placed. In order to get an accurate measurement, the engineer for FAAand respondent?s employees thought it necessary to go into the trench (Tr. 75).??????????? 17.Respondent does not generally slope excavations in which boring machines are tobe placed until the excavation has been completed. This procedure is followedbecause the slope further limits the reach of the backhoe into the excavation(Tr. 60?61, 63).??????????? 18.Respondent was using a John Deere 400 backhoe to excavate the trench. It had areach of 13 feet and six inches (Tr. 62).??????????? 19.Shoring of the trench would not have interfered with obtaining an accuratemeasurement of the grade and level of the trench (Tr. 78).OPINION??????????? As aresult of an inspection conducted on January 30, 1976, at respondent?s job siteat Hartsfield International Airport, Atlanta, Georgia, respondent was issued aserious citation on February 4, 1976. Complainant alleges that respondentviolated 29 C.F.R. ? 1926.652(c)[12] by failing to shore orotherwise support the sides of a trench excavated in hard or compact soil.??????????? Theundisputed evidence establishes that three employees of respondent were in atrench that was 48 feet long and six feet and four inches wide. The depth ofthe trench varied between six and eight feet. The soil was hard and compact.The trench was not sloped, shored, sheeted, braced or otherwise supported. Itis clear that the requirements of 29 C.F.R. ? 1926.652(c) were violated.??????????? Respondentcontends that the inspection was improper and unwarranted. It is pointed outthat the job site was at a remote area of the airport and was not frequented bythe public or open to ready public view. Under the rationale expressed in Brennanv. Gibson?s Products, Inc., 407 F.Supp. 154 (E.D. Tex. 1976), and Secretaryof Labor v. Rupp Forge Company, ?? F.Supp. ?? (N.D. Iowa 1976), it isargued that complainant could not properly conduct the inspection without firstobtaining a search warrant.??????????? In GibsonProducts, Inc., the compliance officer attempted to inspect the nonpublicportion of a store operated by respondent. It refused to permit the inspection.The court concluded that the Fourth Amendment of the United States Constitutionmandated that a search warrant be obtained for resisted inspections. Thedecision in Rupp Forge Co. followed the rationale as expressed in GibsonProducts, Inc.??????????? Respondent?sreliance on the rationale of the court in Gibson Products, Inc. ismisplaced. There has been no showing that the inspection conducted by thecompliance officer was resisted by respondent. On the contrary, the evidenceclearly shows that employees of respondent consented to the inspection. Inaddition, the inspection was not conducted on respondent?s premises. In Accu-Namics,Inc. v. OSAHRC and Secretary of Labor, 515 F.2d 828 (5th Cir. 1975), cert.den. 96 S.Ct. 1492 (1976), the court concluded that there was no fourthamendment right where the inspection was not conducted on the employer?spremises. In that case, the job site was a public street. In the present casethe inspection was conducted on the premises of the airport which is owned andoperated by the City of Atlanta.??????????? Respondentalso argues that literal compliance with ? 1926.652(c) would have made itimpossible to perform the required task of checking the grade and depth of thetrench. There is no dispute that the grade and level of the trench had to bechecked prior to the boring machine being placed in the trench. The engineerfor the FAA testified that he attempted to perform the measurement at groundlevel but that the measurement had to be made in the middle of the trench wherethe boring machine would be placed (Tr. 75). In order to obtain an accuratemeasurement, he thought it necessary to enter the trench.??????????? It iscontended that the trench could not be sloped until the correct grade and levelhad been achieved. This argument is based on the limited reach of the backhoe.A slope means the backhoe must operate further from the center of the trench(Tr. 60?61). The backhoe being used had a reach of 136? (Tr. 62). The trenchdepth varied from six to eight feet. Since the soil was hard and compact, theslope would not have had to commence until the five foot level. The evidencedoes not establish that the backhoe could not reach the center of the trench ifa proper slope had been made prior to the employees entering the trench[13]. This is especially truesince respondent usually operates its equipment right at the edge of the slope(Tr. 62).??????????? TheFAA engineer testified that the shoring of the trench would not have interferedwith the accuracy of the measurement (Tr. 78). Shoring would have caused someinconvenience but it certainly would not have made it impossible to perform thegrade and level measurements. The defense of impossibility of performance iswithout merit. The violation has been established.NATURE OF VIOLATION??????????? Complainantalleges that the violation of 29 C.F.R. ? 1926.652(c) was a serious violationwithin the meaning of section 17(k) of the Act.[14] The Commission has heldthat the occurrence of an accident because of an existing hazard in violationof the Act need not be substantially probable in order for a violation to beserious. An accident must simply be possible. Serious and non-seriousviolations ?are distinguished on the basis of the seriousness of injuries whichexperience has shown reasonably likely to occur.? Secretary v. Natkin andCompany, 2 OSAHRC 1472 (1973). The probability of an accident occurring isrelevant only to the gravity of the violation. See Secretary v. Emory H.Mixon, 5 OSAHRC 579 (1973).??????????? Respondentwas aware of the fact that employees usually entered the trench in making thegrade and level measurements. Respondent either knew of the violation or couldhave known of it by the exercise of reasonable diligence. Respondent does notcontend that the violation was unknown to it or that the presence of theemployees in the trench was contrary to its instructions. The issue must bedecided on the basis of the type of injuries employees were likely to haveincurred in the event a collapse of the trench walls had occurred.??????????? Thetrench varied in depth from six to eight feet. The evidence does not establishthe exact depth at the portions of the trench where employees performed thegrade and level measurements. The likelihood of employees being fully coveredat the six foot level in an upright position is considered remote. However, acollapse at the six foot level would certainly cover a great portion of thebody of anyone caught in an upright position. If the employee were in a bendingposition, the chances are great that he would be completely covered. In eitherevent, the weight of the soil could possibly cause serious physical harm to anindividual trapped by a collapse. The violation is deemed to be serious withinthe meaning of section 17(k) of the Act.PENALTY DETERMINATION??????????? TheCommission is the final arbiter of penalties in all contested cases.Secretary v. Occupational Safety and Health Review Commission and InterstateGlass Co., 487 F.2d 438 (8th Cir. 1973). Under section 17(j) of the Act theCommission is required to find and give ?due consideration? to the size of theemployer?s business, the gravity of the violation, the good faith of theemployer and the history of previous violations in determining the assessmentof an appropriate penalty. The gravity of the offense is the principal factorto be considered. Secretary v. Nacirema Operating Company, Inc., 1OSAHRC 33 (1972).??????????? Threeemployees of respondent were in the trench. They were present in the trench foronly a brief period of time. The soil was hard and compact. The depth was onlysix to eight feet. The possibilities of a collapse in hard and compact soil atthat level is considered remote. This is especially true since there is noevidence, such as water in the trench or other indicia of a weakening in thewalls, to indicate there was any cause for real concern by the respondent forthe safety of its employees. A penalty of $250 is assessed.CONCLUSIONS OF LAW??????????? 1.Respondent, at all times material hereto, was engaged in a business affectingcommerce within the meaning of section 3 (5) of the Act.??????????? 2.Respondent was subject to the requirements of the Act and the standardspromulgated thereunder. The Commission has jurisdiction of the parties and ofthe subject matter herein.??????????? 3. OnJanuary 30, 1976, three employees of respondent were in a trench which variedin depth from six to eight feet. The soil was hard and compact.??????????? 4.The trench was not sloped, shored, braced or otherwise supported in violationof 29 C.F.R. ? 1926.652(c).??????????? 5. Theviolation was serious. A penalty of $250 is assessed for the serious violation.ORDER??????????? Uponthe basis of the foregoing findings of fact and conclusions of law, it is??????????? ORDERED:??????????? (1)That the serious citation issued to respondent on February 4, 1976, is affirmed;and??????????? ?(2) That the notification of proposed penaltyissued to respondent on February 4, 1976, is modified to assess a penalty of$250 for the serious violation.?Dated this 28th day of December, 1976.?JAMES D. BURROUGHSJudge[1] 29 U.S.C. ?661(i).[2] 29 U.S.C. ?654(a)(2).[3] 29 C.F.R. ?1926.652(c) provides the following:?1926.652 Specific trenching requirements.(c)Sides of trenches in hard or compact soil, including embankments, shall beshored or otherwise supported when the trench is more than 5 feet in depth and8 feet or more in length. In lieu of shoring, the sides of the trench above the5-foot level may be sloped to preclude collapse, but shall not be steeper thana 1-foot rise to each ?-foot horizontal. When the outside diameter of a pipe isgreater than 6 feet, a bench of 4-foot minimum shall be provided at the toe ofthe sloped portion.[4] A serious violationis defined in ? 17(k) of the Act, 29 U.S.C. ? 666(j), which states thefollowing:Forpurposes of this section, a serious violation shall be deemed to exist in aplace of employment if there is a substantial probability that death or seriousphysical harm could result from a condition which exists, or from one or morepractices, means, methods, operations, or processes which have been adopted orare in use, in such place of employment unless the employer did not, and couldnot with the exercise of reasonable diligence, know of the presence of theviolation.[5] Chairman Clearygranted Elcon?s petition for review, which raised these issues. Additionally,former Commission Member Moran directed review of the judge?s decision ?forerror.? In a letter submitted in lieu of a brief on review, Elcon referred theCommission to its post-hearing brief, in which the company additionally hadargued that the inspection was improperly conducted. It is clear, however, thatElcon does not seek modification or reversal of the judge?s decision rejectingthis contention. In its letter filed subsequent to the directions for review,Elcon asserted that the company?s petition and post-hearing brief providedadequate support for ?Respondent?s position in this matter, and fully demonstratethat Respondent has made good the defense of impossibility, that any violation,if found, is to be classed as non-serious, and that, in any event, no penaltyshould be assessed against Respondent. . . .? Elcon did not direct attention tothe inspection issue. Accordingly, the issue of whether the inspection wasproper is not before the Commission for review. See Water Works InstallationCorp., 76 OSAHRC 61\/B8, 4 BNA OSHC 1339, 1976?77 CCH OSHD ? 20,780 (No.4136, 1976); Abbott-Sommer, Inc., 76 OSAHRC 21\/A2, 3 BNA OSHC 2032,1975?76 CCH OSHD ? 20, 428 (No. 9507, 1976). Such unreviewed dispositions of aCommission judge are not precedent binding on the Commission. See LeoneConstr. Co., 76 OSAHRC 12\/E6, 3 BNA OSHC 1979, 1975?76 CCH OSHD ? 20,387(No. 4090, 1979).[6] Note 4 supra.[7] The twocompliance officers testified that they could and did measure the depth of thetrench from the ground surface and described in some detail how thismeasurement should be made to assure substantial accuracy.Elcon did not argue that slopingthe sides of the trench before the employees went into it would prevent themfrom making a sufficiently precise measurement of the depth for the purpose ofsuccessfully completing the bore. Moreover, the Federal Aviation Administrationengineer, who testified on behalf of Elcon, admitted that the necessarymeasurement could be made with the trench sides sloped, although he stated thatmaking the measurement would be more difficult.[8] In addition torequiring an initial showing of impossibility, either of compliance orperformance, we also have required that the employer show that alternativemeans of protection were in use or were unavailable in order to sustain thedefense of impossibility. See Bill C. Carroll Co., 79 OSAHRC 87\/C13, 7BNA OSHC 1806, 1979 CCH OSHD ?23,940 (No. 76?2748, 1979); M. J. Lee Constr.Co., supra. However, we need not consider this aspect of the defensebecause, as we have indicated, Elcon failed to show that compliance would haveprecluded performance of the required work.As has been indicated, Elcon alsoargued and continues to argue that the use of shoring would have precludedperformance of the required work. Because the record shows that Elcon couldhave complied with ? 1926.652(c) by sloping the sides of the trench, we neednot consider whether Elcon has established an impossibility defense as toshoring.[9] That the employereither knew or could have known, with the exercise of reasonable diligence, ofthe presence of the violation is the remaining element of a serious violation.However, Commissioner Cottine does not reach the question of employer knowledgein this case because Elcon has not argued, either before the judge or beforethe Commission, that the violation was not established as serious because itlacked the requisite knowledge of the violation. See Brown-McKee, Inc.,80 OSAHRC ___, 8 BNA OSHC 1247, 1251 n. 8, 1980 CCH OSHD ? 24,409 at 29,738 n.8 (No. 76?982, 1980).Commissioner Barnako, on the otherhand, believes that the element of knowledge must be addressed here because itis an element of the Secretary?s proof of a violation. Brown-McKee, Inc.,supra; Scheel Constr., Inc., 76 OSAHRC 138\/B6, 4 BNA OSHC 1825, 1976?77CCH OSHD ? 21,263 (No. 8687, 1976). He would find that knowledge has been establishedin view of the evidence that Elcon?s crew superintendent was at the unprotectedtrench when the company?s employees went into it to make the depth and grademeasurements.[10] RA refers tocomplainant?s Request for Admissions served upon respondent on June 14, 1976,and respondent?s answers which were served upon complainant on June 29, 1976.[11] Exhibit one showsfour persons in the trench. The compliance officer testified that one of themwas not an employee of respondent (Tr. 9).[12] 29 C.F.R. ? 1926.652(c)provides:(c)Sides of trenches in hard or compact soil, including embankments, shall beshored or otherwise supported when the trench is more than 5 feet in depth and8 feet or more in length. In lieu of shoring, the sides of the trench above the5-foot level may be sloped to preclude collapse, but shall not be steeper thana 1-foot rise to each 1\/2-foot horizontal. When the outside diameter of a pipeis greater than 6 feet, a bench of 4-foot minimum shall be provided at the toeof the sloped portion.[13] Section1926.652(c) requires that the slope ?shall not be steeper than a 1-foot rise toeach 1\/2-foot horizontal.?[14] Section 17(k) ofthe Act provides:(k)For purposes of this section, a serious violation shall be deemed to exist in aplace of employment if there is a substantial probability that death or seriousphysical harm could result from a condition which exists, or from one or morepractices, means, methods, operations, or processes which have been adopted orare in use, in such place of employment unless the employer did not, and couldnot with the exercise of reasonable diligence, know of the presence of theviolation.”