Opinion by

The construction of sewers, in municipalities, for the drainage of surface water, is a matter resting in the discretion of the municipal authorities, and their power in the premises is to be exercised with reference to the existing conditions and the means at their command. The municipality is not liable for damages resulting from an error of judgment on their part, with respect to the location or direction of the sewer, or its sufficiency for the purpose designed. Its liability is confined to injuries due to interference with the natural flow of water, faulty construction, and failure to maintain the sewer in proper condition, and free from obstructions that materially affect its use; and the rule is the same whether a natural water course is adopted for drainage purposes, or an artificial channel is built: Cooper v. Scranton, 21 Pa. Superior Ct. 17; Boehm v. Bethlehem, 4 Pa. Superior Ct. 385; Carr v. Northern Liberties, 35 Pa. 324; Fair v. Philadelphia, 88 Pa. 309; Collins v. Philadelphia, 93 Pa. 272; Blizzard v. Boro, of Danville, 175 Pa. 479; Owens v. City of Lancaster, 182 Pa. 257.

In the case before us, the damage to the plaintiff was caused ,by an overflow of surface water upon his premises. The decía*461ration avers that this was by reason of the defendant’s negligence in allowing a closed culvert, crossing Wyandotte street in front of his property, through which the water should have been discharged, to become clogged with rubbish, sand, stones, brush, etc., and an amendment charges the loss as due to the defendant’s negligence in allowing the opening of a culvert on Broad street to become clogged in like manner, and two inlets leading from the street to the sewer, in front of the plaintiff’s property, to become clogged with ice and debris. The defendant, besides denying the alleged negligence, offered evidence to show that the overflow was caused by an extraordinary flood, resulting from an unusually heavy rainfall. This was objected to by the plaintiff as inadmissible under the pleadings, and its admission forms the subject of the second and third assignments of error.

The declaration contains four paragraphs; the second and third setting forth the character of the alleged negligence, and the fourth laying the damages. On the part of the defendant, its chief burgess filed an answer meeting each paragraph specifically; the second by the averment “ That he denies the allegations set forth in the second paragraph of plaintiff’s statement,” and the like answer to the third and fourth paragraphs, followed by a charge of contributory negligence on the part of the plaintiff, but with no reference to the act of God, in an extraordinary flood, as the cause of the overflow. There was no answer to the amendment, nor was any formal plea entered. The plaintiff contends that, under the answer, the defendant could only give evidence to controvert the charge of negligence and of contributory negligence by the plaintiff, and that thé admission of evidence respecting the extraordinary character of the flood was error.

This contention cannot be sustained. The only plea in trespass, under the procedure act of 1887, is “ not guilty.” The answer here is, in legal effect, this plea. It meets the allegations in each of the three paragraphs of the declaration referred to with a common traverse, omitting the tender of issue. In substance and meaning, its denial of the cause of action is identical with that embodied in the common-law form of the plea, “ That he is not guilty of the said trespasses laid to his charge, or any part thereof, in manner and form as the plaintiff *462hath complained.” The amendment, subsequently filed, not being a new assignment, requires no further plea or answer; and if a tender of issue is not implied in the defendant’s denial, it was waived by going to trial on the pleadings as' they stood. Even aside from the act of 1887, the allegation, in the plea, of contributory negligence by the plaintiff, or of the act of God as the cause of the injury complained of, is unnecessary. These are entirely matters of evidence. The plea of not guilty is sustained by proof that the damage complained of is due to some other cause than the defendant’s act or omission, or that the plaintiff’s negligence contributed to it; and these need not be specified, or even alluded to, in the plea.

The only error alleged in the portion of the charge that forms the subject of the first' assignment is the withdrawal of the condition of the inlets to the sewer in front of the plaintiff’s premises, — or “ sumpts,” as they are styled in the declaration, — from consideration by the jury as a cause of the overflow. . In this, the trial judge was entirely justified. The rain began on Saturday night. The evidence was uncontradicted, — and part of it came from the plaintiff’s witnesses,— that these inlets had been cleaned out by the borough authorities on the preceding Monday, and several witnesses who had observed them meantime testified that they remained' clear. The testimony of one witness, that on Friday their openings were partly closed by ice, does not indicate definitely to whát extent this would interfere with the drainage ; and even if it had been a material obstruction the borough authorities appear to have had no knowledge of it, and the circumstances were not such as to charge them with constructive notice of it two days later. Thus there was no evidence from which tlie jury could have found negligence by the defendant at this point.

There is no merit in the assignment relating to the general character of the charge. It dealt fairly with both sides of the case, and as fully with the evidence for the plaintiff as its nature required. Nearly all of this evidence, bearing on the condition of the inlets and sewer, related to a date subsequent to the rain, when they had become clogged with obstructions carried into' them by the flood, and since it was conceded that the question of their sufficiency for the discharge of the water *463and accompanying obstructions did not enter into the case, no reference to the evidence on this point was necessary, and none would have been pertinent. The trial judge called attention to the condition of the culvert with respect to obstructions, at the time of the rain, as presenting “ the serious, the important, and the pivotal question in the case,” and, without reviewing the evidence on either side, referred it to the jury who had heard it, for their careful consideration. The instructions relative to the flood were clear and accurate. To give a stream or body of water the character of an extraordinary flood, it is not necessary that it should be the greatest flood within memory ; its character in this respect is to be tested by comparison with the usual volume of floods ordinarily occurring. And even if, with an extraordinary flood, there is concurring negligence, the party chargeable with it will be relieved from liability if the flood is so overwhelming in character that it would of itself have produced the injury complained of independently of such negligence : B. & O. R. R. Co. v. School District, 96 Pa. 65; Helbling v. Cemetery Co., 201 Pa. 171. Whether, in the present case, the flood was of this description, was a question of fact, to be determined by the jury from the evidence, and this was submitted to them with adequate instructions.

Nothing in the assignments of error requires further discussion. They are overruled, and the judgment is affirmed.