Parol evidence rule and Deeds

Generally Deeds operate under contract law.

Consider the following case:
Beginning at the northwest corner of Section 11, thence from said point of beginning east along the north line of said Section 200.00 feet; thence leaving said North line south 200.00 feet; thence west 200.00 feet to the west line of said Section 11; thence north 200.00 feet to the point of beginning.

Now assume the Section corner is not in dispute, everyone agrees on the monument there being original. There are pipes at the other three corners. We wouldn't have a dispute if they measured at least close to 200.00 feet, right? Let us just say the pipes are materially at variance with the Deed dimensions and someone is pissed.

Normally the parol evidence rule would not allow testimony to add a statement to the contract terms which calls for a parcel 200.00 feet square and makes no mention of pipes. It's not too hard to find California cases to this effect.

So usually the Courts handle this in several different ways:
1) mutual recognition and acquiescence which I think is a new contract (the consideration being settling the dispute)
2) parol evidence can be admitted if there was a mutual mistake and the contract doesn't reflect the intentions of the parties. For example the seller set the pipes, assumed they marked a square 200' square and showed them to the buyer. This, I think is part of the rationale behind the practical location doctrines which operate where the two parties derive title from a common source.
3) agreed boundary (expressed or implied) which is a contract to settle the boundaries.

California is unique in that we have Justice Traynor's controversial opinion in Pacific Gas & E. Co. v. G. W. Thomas Drayage etc. Co., 69 Cal. 2d 33 (1968); 442 P.2d 641; 69 Cal. Rptr. 561; 1968 Cal. LEXIS 225; 40 A.L.R.3d 1373 in which evidence is held to be admissible to figure out if the contract is ambiguous although patently unambiguous: "A rule that would limit the determination of the meaning of a written instrument to its four-corners merely because it seems to the court to be clear and unambiguous, would either deny the relevance of the intention of the parties or presuppose a degree of verbal precision and stability our language has not attained."

This Is all very interesting to me, anyway.