Let’s say that your neighbor has excavated on their land, and you subsequently find some evidence of subsidence on your property: growing cracks in walls or foundation, for instance. Your neighbor’s excavation might have affected the “lateral support” for your land. As a Colorado landowner, you are entitled to have your land remain in its natural state, and the soil in neighboring property helps to support that state. You could pursue a claim against the next-door excavator based on one of two legal theories: strict liability or negligence.
Strict liability is available to an owner whose property was in a natural and unimproved condition. Even if improvements have been made, strict liability might apply if the weight of additions to the property cannot be found to have “materially increased the lateral pressure” on the land, thereby acting as the proximate cause of damage. The rationale is that “a landowner cannot, by placing improvements on its land, increase its neighbor’s duty to support the land laterally.” To claim strict liability for loss of lateral support, therefore, one must compare the support required by the land in its original, unaltered state with the support required by the same land with its improvements.
If the weight of improvements has materially contributed to the subsidence on the plaintiff’s property, any liability must be based on the theory of negligence. For an excavator to be found liable for negligent withdrawal of lateral support, four elements must be present: (1) the withdrawal of lateral support; (2) the negligent character of the withdrawal; (3) resulting harm to land or to artificial additions thereon; and (4) absence of any action by the landowner that would undermine the claim.
No Colorado decisions have directly addressed what constitutes a negligent withdrawal under requirement 2, but, fortunately, both the Restatement and case law from other jurisdictions fills in the gaps. In order to avoid negligence, an excavator must take “reasonable precautions to minimize the risk of causing subsidence,” and provide notice to an adjacent landowner of “excavations which certainly will harm his structures.” To minimize risk, an excavator must thoroughly investigate soil conditions and exercise reasonable care in all operations. As to the notice requirement, a failure altogether to notify an adjoining landowner of excavations has been regularly held to constitute negligence, while what constitutes “adequate” notice depends on the facts of the case.
Here’s an interesting differentiation between strict liability and negligence theories of lateral support removal: In a strict liability proceeding, “the kind of lateral support withdrawn is material, but the quality of the actor’s conduct is immaterial.” No matter how cautious the excavator, if the property suffers, he is strictly liable. Contrarily, in a proceeding based upon negligence, “the kind of lateral support withdrawn is immaterial, and the quality of the actor’s conduct is material.” No matter the type of support required, the excavator has a duty to use reasonable care.
 Colo. Jury Instr., Civil 12:14.
 Gladin v. Von Engeln, 575 P.2d 418, 420 (Colo. 1978).
 Vikell Investors Pacific, Inc. v. Hampden, Ltd., 946 P.2d 589, 594 (Colo. App. 1997).
 Colo. Jury Instr., Civil 12:14.
 Id. at (e).
 See St. Joseph Light & Power Co. v. Kaw Valley Tunneling 589 S.W. 29 260, 267-68 (Mo. 1979); New York Central R.R. v. Marinucci Bros., 149 N.E.2d 680, 682 (Mass. 1958).
 See Waters v. Biesecker, 298 S.E.2d 746, 748-49 (N.C. Ct. App. 1983) aff’d, 305 S.E.2d 539 (N.C. 1983); Hermanson v. Morrell, 252 N.W.2d 884, 892 (N.D. 1977)
 See XI Properties, Inc. v. RaceTrac Petroleum, Inc., 151 S.W.3d 443, 449 (Tenn. 2004) (thirty days was a reasonable notice for planned excavation of sloped embankment); Smith v. Roberts, 370 N.E.2d 271, 274 (Ill. App. Ct. 1977) (notice that did not give the depth of the planned excavation was inadequate under Illinois’s Protection of Adjacent Landowner’s Act).
 Restatement (Second) of Torts § 819.