J.—Plaintiffs appeal from a judgment of non-suit in their action to recover damages to their real property allegedly caused by seismic vibrations activated by a static firing rocket motor test conducted by defendant on adjoining lands pursuant to a contract with the United States. The complaint was framed on theories of negligence and strict liability.
In accordance with the well settled rule governing review of a judgment of nonsuit, the evidence will be viewed in the light most favorable to plaintiffs.
(Kopfinger
v.
Grand Central Public Market,
*777 Since 1957, plaintiffs had'been the owners of approximately 160 acres of.land in Potrero Valley near Beaumont in Riverside County. For the first few years following acquisition of the ranch, plaintiffs used it as an adult camp, but they thereafter had undertaken a program of improvements designed for its ultimate use as a boys’ camp. One of the, principal attributes of the property was a well which over the years had consistently produced high quality water.
' In 1961, defendant acquired approximately 9,100 acres in Potrero Valley, one-half' of it from its predecessor, Grand Central Rocket Company, for the purpose of testing rocket motors. A portion of the land bordered plaintiffs’ property on three sides. In early 1962, defendant unsuccessfully sought to acquire plaintiffs’ ranch, at which time defendant’s counsel told plaintiff, “We have to have your land before we can test. ”
On April 25, 1962, the Beaumont News carried a press release issued by defendant announcing a scheduled test firing on May 12, 1962, and stating, “The firing is not expected to produce ground vibrations outside the Potrero1 Valley itself.” Plaintiffs were apprehensive and communicated to defendant their concern for the safety of their well,' structures, and horses. Defendant’s counsel told plaintiffs not to worry and assured them that defendant would take care of any damage caused by the test. Being still concerned, plaintiffs, through their attorney, transmitted a letter, to. defendant again informing it of their anxiety and requested defendant to, desist from proceeding with the test. Defendant’s counsel responded to the communication by informing plaintiffs, “We can’t stop the tests. It wouldn’t be practical,” and reassured them that defendant would take care of any damage.
On May 12, defendant proceeded with the scheduled test firing of a “120 inch solid fuel applied research rocket motor” of three segments, reputedly the largest solid fuel rocket motor to be test fired to that date. The item was manufactured by defendant for the United States Air Force and at the .time of the test the United States was its legal owner. The motor was mounted nose-down on three “thrust collectors” which were affixed to a concrete base imbedded in the ground. The test stand was located approximately 7,800'feet from the boundary of plaintiffs’ property. The firing lasted 132 seconds and created up to a maximum of 350,000 pounds of thrust.
Plaintiff, who was on the sundeck of one of"his buildings at *778 the time of the test, felt a very strong vibration. A witness who was- on plaintiffs’ property testified that there was a rumbling, “similar to an earthquake taking place,” which lasted five or six minutes. Another witness who was in Beaumont recalled that the earth tremor was similar to that which one would sense when a heavy truck passed by.
Immediately following the test, plaintiff inspected his property but found no damage to any structures. Water which was being pumped from the well into the swimming pool was clear throughout the period of the test but at test plus 80 minutes it became muddy. The changed water condition was called to the attention of defendant’s counsel who appeared at the ranch a few hours following the test. Defendant’s counsel stated, “I don’t know how we could have done it, but I can’t argue with 80 minutes.”
Defendant thereafter supplied plaintiffs with bottled water and engaged a contractor to attempt to repair the well. The contractor, however, determined that the casing had been sheared at the 95-foot level and reported that the well was beyond repair. Defendant then engaged a well-digger who drilled a new well within a few yards of the old one but despite extensive tests it failed to produce any consistently potable water.
Plaintiffs’ witness, Dr. Alford, an expert on seismology and structural vibrations, testified that in his opinion the test firing was the “probable cause” of the damage to the well. He found no reported seismic disturbances in Potrero Valley for a period of at least two months before and after the test. In his opinion, despite the low level vibrations at the ranch, the duration of the test increased the amplitude of the vibrations sufficient to cause the damage. He testified that the soil structure in Potrero Valley was porous and that the vibrations probably caused the underground water-filled soil to collapse at some point and that this additional weight on adjoining soil set off an “underground avalanche.” In his opinion, an increase in the mass of the test stand would have decreased the vibrations.
A civil engineer specializing in waterworks testified that the interval of 80 minutes between the test and the time when the .well water became muddy was consistent with the theory that the well damage was caused by a seismic disturbance. He explained the time-lag as “the same phenomena you see in a fresh road-cut, that the dirt continues to ravel after the disturbance occurs.” -
*779 A real estate appraiser testified that the fair market value of the ranch on May 12,1962, with the old well in production, was $206,000 but that absent the water supply, the fair market value would be $60,000.
In addition to the claimed devaluation of the property resulting from the loss of water supply, plaintiffs, in separate causes of action, sought damages for injuries to certain specific items of property caused by the contractors engaged by the defendant to restore the water supply. There was evidence that the contractors damaged a cement block wall, shrubbery, paving, and a skip loader.
At the close of plaintiffs’ case, defendant moved for a non-suit on the following grounds: (1) Plaintiffs’ only remedy was an action in inverse condemnation against the United States; (2) Absence of evidence of negligence or other “breach of duty” by defendant; (3) The inapplicability of the doctrine of strict liability; and (4) Absence of evidence that plaintiffs’ damages were the proximate result of defendant’s act. The court granted the nonsuit primarily because, in its view, there was “insufficient evidence of negligence.” It concluded that it was unnecessary to determine whether defendant’s activity was ultrahazardous, apparently on the ground that the evidence failed to establish a causal relationship between the activity and the injury. 1
Plaintiffs contend that on the evidence presented, the ease should have been submitted to the jury on both theories— negligence and strict liability. If the evidence would support a jury verdict in plaintiffs’ favor on either theory, the judgment must be reversed. This necessarily follows from the rule that a nonsuit may be granted “ '. . . “only when, disregarding conflicting evidence and giving to plaintiffs’ evidence all the value to which it is legally entitled, herein indulging in every legitimate inference which may be drawn from that evidence, the result is a determination that there is no evidence of sufficient substantiality to support a verdict in favor of the plaintiff if such a verdict were given”. . . .’ ”
*780
(Meyer
v.
Blackman, supra,
Before we reach the question whether the case should have been submitted to the jury on either theory of liability, we must determine whether there was sufficient evidence from which the jury could have properly found that the test firing was the cause in fact of the damage to the well. It is axiomatic that an essential element of a plaintiff’s cause of action, whether based on negligence or strict liability, is the existence of a causal connection between defendant’s act and the injury which plaintiff suffered. (Prosser, Law of Torts, (2d ed. 1955) p. 218 et seq.).
Cause in fact, as well as proximate cause, is ordinarily a fact question for the jury.
(Basin Oil Co.
v.
Baash-Ross Tool Co.,
Viewed in the light of those well-established rules, the evidence heretofore summarized was sufficient to entitle plaintiffs to have the issue of causation submitted to the jury. The subject of causation in the circumstances here presented was a proper one for expert opinion.
(Bowen
v.
Sierra Lumber Co.,
Defendant contends that the testimony of Dr. Alford was discredited on cross-examination when he admittedly had difficulty in explaining the time-lag between the test and when the water from the well ran muddy. In reviewing a judgment of nonsuit, however, it is not the function of the reviewing court to pass on the credibility of a witness or determine whether he has been impeached by his own contradictory statements or by the testimony of other witnesses. (See
Michael Distributing Co.
v.
Tobin,
Turning to the issue of negligence, we are in accord with the trial court’s conclusion that there was no evidence from which the jury could have validly found that defendant failed to exercise due care in the selection of the test site, construction of the test stand, or in the manner in which the test was
*782
conducted. Although it might he inferred from Dr. Alford’s testimony that a test stand of a greater mass, or one which was further removed, would have reduced vibrations at plaintiffs’ ranch, there was no evidence to show that reasonably prudent engineering practices for the activity would have required additional precautions or the nature or extent thereof. Since rocket testing is not within the common experience of ordinary persons, the jury could not have been expected to apply a standard of reasonable care drawn from experience. (Prosser, Law of Torts, (2d ed. 1955) p. 135). In short, there was no evidence from which the jury could have determined that the manner in which the test was conducted was not consistent with reasonably prudent engineering practices for the activity in question (cf.
Inouye
v.
Black,
Plaintiffs are, in effect, contending that the jury should have been permitted to draw an inference of negligence from the fact that the test firing caused damage to plaintiffs’ adjoining property; in other words, to apply the doctrine of res ipsa loquitur. In our opinion, res ipsa is inapplicable to the factual setting of this case. “The doctrine of res ipsa loquitur is applicable where the accident is of such a nature that it can be said, in the light of past experiences, that it probably was the result of negligence by someone and that the defendant is probably the one responsible.”
(Di Mare
v.
Cresci,
Defendant's attempt to repair the well and the payment of the cost of drilling the new well did not constitute admissions of negligence. An offer to pay, or actual payment, in aid of one who has been injured is not an admission of liability.
(Oldenburg
v.
Sears Roebuck & Co.,
*783 Plaintiffs complain that the court erroneously precluded their expert from testifying to facts from which the jury might have found negligence. Plaintiffs offered to prove through Dr. Alford that prudent engineering practices would have required the test stand to be placed equidistant from the boundaries of defendant’s property. Objection to the offer was sustained, the court stating that “this was a matter the jury could determine and not a matter of expert testimony. ’ ' 2 Plaintiffs, with some justification, question how the court, after rejecting the offered testimony on the ground that the jury could draw its own conclusion as to whether defendant was negligent in placing the test stand where it did, could, consistent with that ruling, grant a nonsuit for lack of evidence of negligence.
The fact that an expert’s opinion is on an ultimate issue to be determined by a jury is not a ground for its exclusion.
People
v.
Cole,
The crucial consideration in determining whether expert testimony should be received is whether “. . . the subject of the inquiry is one of such common knowledge that men of ordinary education could reach a conclusion as intelligently as the witness or whether, on the other hand, the matter is sufficiently beyond common experience that the opinion of an expert would assist the trier of fact.’’
(People
v.
Cole, supra,
Although we have determined that the evidence on the present state of the record was insufficient to entitle plaintiffs, to have their case submitted to the jury on the negligence theory, since, for reasons hereafter stated, the judgment must otherwise be reversed, plaintiffs should be accorded a new trial as well on the negligence issue in view of the court’s ruling excluding the offered testimony of Dr. Alford.
On the issue of strict liability, plaintiffs urge that defendant was engaged in an ultrahazardous activity and hence, was liable without regard to fault.
*784
California makes no distinction between trespass by forcible injury and trespass committed by consequential and indirect injury.
(Coley
v.
Hecker,
The law in this state respecting liability for trespass is in accord with the view expressed in the Restatement of Torts: “ [T]here is no liability for a trespass unless the trespass is intentional, the result of recklessness or negligence, or the result of injuries in an extra-hazardous activity. ’ ’
(Gallin
v.
Poulou, supra,
140 Cal.App.2d. 638, 645; Rest.2d Torts, §§158, 165, 166; Prosser, Law of Torts, (2d ed. 1955) p. 55;
Dufour
v.
H. J. Kaiser Co.,
As heretofore indicated, the evidence in the instant case was insufficient to show negligence. Nor can defendant’s conduct be deemed an intentional trespass or one resulting from recklessness. The crucial issue, therefore, is whether defendant’s activity may be classified as ultrahazardous.
In
Green
v.
General Petroleum Corp.,
Section 520 of the Restatement of Torts defines ultra-hazardous activity as follows: “An activity is ultrahazardous if it (a) necessarily involves a risk of serious harm to the person, land or chattels of others which cannot be eliminated by the exercise of the utmost care, and (b) is not a matter of common usage.” California has apparently accepted the Restatement definition.
(Luthringer
v.
Moore, supra,
Whether an ativity is ultrahazardous is a question of law to be determined by the court. (Luthringer v. Moore, supra, at page 496; Beck v. Bel Air Properties, Inc., supra, at page 842; Rest., Torts, § 520, com. h).
In our opinion, defendant’s activity must be classed as ultrahazardous. The solid fuel rocket motor was the largest ever tested to that date. Test firing such a device is not a matter of common occurrence. The fact that defendant found it necessary to acquire 9,100 acres for its purposes, and at one time told plaintiffs it needed their property in order to conduct the test, is evidence of its recognition of the risk inherent in the undertaking despite the exercise of due care. In these circumstances, public policy calls for strict liability.
(Luthringer
v.
Moore, supra,
The precise issue before us—whether rocket motor testing constitutes an ultrahazardous activity — was squarely con
*786
sidered and answered affirmatively in
Berg
v.
Reaction Motors Div.
(1962)
Defendant contends that it should not be subjected to strict liability because the testing was conducted in an area remote from civilized influences. It is true that classification of an activity as ultrahazardous does not automatically subject one engaged in it to strict liability without regard to place or circumstances. Thus, while blasting in a developed area calls for strict liability,
(Colton
v.
Onderdonk, supra,
Finally, we reach the contention that since the test was being performed pursuant to a government contract, defendant, in the absence of negligence, is entitled to share the immunity of the government. We shall assume for the purpose of this ease that the United States could not be sued under the Federal Tort Claims Act (28 U.S.C.A. §§1346, 2671-2680) since the act has been held not to extend to cases where liability without fault is the only basis for the asserted liability.
(Dalehite
v.
United States
(1953)
Defendant relies upon the general rule that in the absence of negligence or unauthorized departure from plans and specifications, a contractor engaged in the construction of a public improvement under a contract with a public body is not liable for consequential injury to adjacent property that may result as a necessary incident from the prosecution of the work in accordance with the terms of the contract and the plans and specifications, citing
Yearsley
v.
W. A. Ross Constr. Co.
(1940)
The cases above-mentioned which were cited by defendant are not controlling in the instant ease. They, and others like them which have invoked the general rule, did not involve ultrahazardous activity. Moreover, although some of the cases speak in terms of immunity, thus presupposing an otherwise valid cause of action, the contractor in those eases would not have been liable under accepted legal principles relating to liability for trespass without regard to the question of immunity.
(Gallin
v.
Poulou, supra,
The only ease cited by defendant applying the general rule to a contractor engaged in an ultrahazardous activity is
Pumphrey
v.
J. A. Jones Constr. Co.
(1959)
Other cases, however, have refused to extend immunity to a contractor engaged in the performance of a contract for the construction of a public improvement where damage to adjoining property resulted from the use of explosives. In
Asheville
v.
Southern Ry. Co.
(1927)
In
Berg
v.
Reaction Motors Div., supra
(1962)
The court distinguished
Pumphrey
v.
J. A. Jones Constr. Co., supra,
on the ground that the parties had there stipulated that the blasting was performed under the supervision of government inspectors and in strict accordance with the specifications whereas in
Berg
there was no evidence “. . . to indicate that the Government had prescribed the site of the tests, or the location of the test stands, or the manner of conducting the tests.”
(Berg
v.
Reaction Motors Div., supra,
It is our conclusion that immunity should not be extended to the contractor in the instant case.
Pumphrey
may be distinguished, as it was in
Berg,
because in the present state of the record there is no evidence that the Government selected the test site, prescribed the specifications for the construction of the test stand or its location, or specified the manner of conducting the test. This is a valid ground of distinction. (See
McGrath
v.
Basich Bros. Constr. Co., supra,
We believe that a valid distinction exists in this regard as between one engaged in an ultrahazardous activity and one performing activities not so classed. (See
Rector
v.
Tobin Constr. Co.
(1964, Mo.)
In
Pumphrey
v.
J. A. Jones Constr. Co., supra
(1959)
In
Pumphrey, supra
(1959)
For the foregoing reasons we conclude that the judgment must be reversed with respect to plaintiffs' causes of action (on the theory of negligence and strict liability) for the devaluation of their ranch resulting from the injury to or destruction of their water well.
With respect to the causes of action for damages caused by the contractors engaged by defendant to restore the water supply—damage to the cement block wall, shrubbery, paving, and a skip loader-—the judgment of nonsuit must be affirmed. There is no evidence that the contractors were trespassers or that they were other than independent contractors. Thus a verdict against the defendant for damages to the items mentioned could not be upheld.
(McDonald
v.
Shell Oil Co.,
For the foregoing reasons the judgment of nonsuit is affirmed as to the 5th, 6th and 7th causes of action but reversed as to the remaining causes of action.
McCabe, P. J., and Kerrigan, J., concurred.
A petition for a rehearing was denied February 9, 1967, and respondent’s petition for a hearing by the Supreme Court was denied March 15, 1967.
Notes
In response to an inquiry by plaintiffs ’ counsel whether the court was determining that defendant's act was not ultrahazardous, the court stated, “No. I am not certain that I agree with that statement, because I find no proximate causal relationship between the alleged damages here and the activity involved here, even if it were to be characterized as ultrahazardous. So, I will not rule specifically with respect to that point. I find it unnecessary to determine whether or not this activity was ultrahazardous, because I find no evidence that whatever the character of that activity may have been that there was a causal relationship between that activity and the claimed damage,”
Defendant asserts that the objection was sustained for lack of a foundation. The record, however, does not support this contention.
“One must so use his own rights as not to infringe upon the rights of another. ’ ’ (Civil Code, § 3514)
The jury returned a verdict for both compensatory and exemplary damages. On appeal, the court affirmed the judgment as to compensatory damages but reversed as to exemplary damages on the ground that there was insufficient evidence to support a punitive award.
The question whether the contractor shares the immunity of the United States probably presents a federal question, (cf.
Howard
v.
Lyons
(1959)
