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7.5.7: Grading Ordinances and Regulation of Building Sites

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    Building codes deal with the safety of buildings, but how about the site on which the building is constructed? A good example of a poor building site is the Leaning Tower of Pisa. The tower itself is in good shape, but the soils beneath the building are unable to hold it up, and it has settled differentially, causing it to lean.


    A perfectly sound building is unsafe if it’s built on a landslide, on a sea cliff subject to wave erosion, on soils subject to liquefaction, or on an active fault. As part of its public safety obligation, a city or county may take responsibility for evaluation of the safety of a building site, just as it takes responsibility for the structural integrity of a building. Ordinances passed for this purpose are called grading ordinances. Grading, which is one of the first steps in virtually any building project, can include excavation by a bulldozer or backhoe or it might involve placement of fill material to provide a flat surface for building. In either case, the natural landscape is altered, and regulation is required to ensure that the alteration of the landscape will not harm residents of other sites—particularly those downhill, in addition to the potential residents or workers in buildings on the site in question.


    Grading ordinances call into question the fundamental right of individuals to do with their land whatever they want. This differs from building codes, which might require a better-engineered and better-designed structure to be built for safety reasons but would not prevent some sort of structure from being built on a site. It’s difficult for a landowner to accept the fact that the property might contain hidden geological fatal flaws such as active faults or landslides that could prevent it from being developed at all. A site with a beautiful view over a steep hillslope should not be developed if the steep hillslope providing the view is the scarp of an active fault or a landslide. The site could become unstable because of the actions of the builder or owner, such as heavy use of irrigation sprinklers.


    In 1952, the City of Los Angeles adopted the first grading ordinance in the United States and set up a grading section within the Department of Building and Safety. The city was growing out of the lowlands and up into the surrounding hills, and building sites there were found to be subject to major landslides, with extensive property losses.


    The grading ordinance was upgraded in 1963 to require both engineering and geologic reports to be submitted and to require that grading operations be supervised by both a soils engineer and an engineering geologist. Although responsibilities overlap, the soils engineer or geotechnical engineer deals directly with the strength and bearing capacity of earth materials on which a structure is to be built and on the tendency of a hillslope to slide, and an engineering geologist takes more account of the past geologic history of a building site, including old landslides, evidence of faulting, and the inclination of bedding and fracturing of rock formations on site. Geotechnical engineers and geologists must be licensed to practice in all three west coast states.


    The standard reference for grading was Chapter 70 of the Uniform Building Code (UBC), written in the form of an ordinance that can be modified to fit the situation in the city or county where it is adopted. In the 1997 edition of the Code, the Grading Code appears in Chapter A-33. In the 2010 edition, soil and grading information is contained in chapters 18and 18a. Other jurisdictions may have different chapters for grading.


    The local building official decides which sites pose a potential threat to life and public safety, requiring an evaluation of the site and supervision of grading. For commercial developments, Chapter A-33 provides for reports by both geotechnical and geological consultants employed by the developer and a review of the findings by soils engineers and geologists employed by the city or county for that purpose. The cost of a plan review, like the cost of a building inspection, is borne by the developer in the form of permit fees. A plan reviewer might ask questions such as: Is provision for drainage of the property adequate so that other property owners are not affected? Are cut slopes gentle enough that they would not be expected to fail by landslides? Is the bearing strength of the soil sufficient to hold up the building? Do potentially active faults cross the property? This last is covered by Chapter 16 of the Code, which also contains sample regulations that cover geotechnical tests for liquefaction and ground shaking.


    California passed an addition to its Health and Safety Code requires that all cities and counties adopt the UBC Grading Code or its equivalent. Unfortunately, many cities and counties lack the professional expertise to regulate grading effectively. In addition, implementation of the Grading Code in some communities has been opposed by developers and building contractors as well as a few politically well-connected landowners. However, where the Grading Code has been used, including review by consultants for the city or county, losses related to geologic conditions have dropped by 90 to 95 percent. The law works!


    Accompanying the increase in standards for grading is an increase in the number of lawsuits. If the development is approved, but a landslide subsequently destroys homes on the property, the landowner, the contractor, the engineering and geological firm, the city or county approving the plans, even the bank lending the money for the development may be sued. Were any of the parties negligent in approving the development? As the standards of practice are raised, so, then, are the conditions under which someone could be found negligent.


    Oregon and Washington are far behind California in establishing grading ordinances. The ones that exist are largely in the metropolitan areas of Portland and Seattle. Some cities require engineering and geologic reports subject to city review, more do not. This may change after the floods of February and December 1996, when many homes, including some worth hundreds of thousands of dollars, were destroyed by active landslides. According to Scott Burns of Portland State University, the Portland, Oregon, metropolitan area suffered more than seven hundred landslides, resulting in seventeen houses being red-tagged (meaning that they would have to be demolished) and sixty-four houses yellow-tagged (meaning that the occupants could not return until certain repairs had been made). In most cases, these landslides could have been identified by a geologist prior to the development. This led to a flurry of lawsuits, including some against cities and counties. The plaintiff, who may have lost his million-dollar home to a landslide, argues that the city should have known that the site was unsafe since establishing that fact is standard practice in other parts of the country. Many cities are (or should be) watching these lawsuits with interest and perhaps trepidation.


    The Oso landslide in Snohomish County in western Washington on March 22, 2014, was not caused by an earthquake. The area had been studied by a geologist with the USGS who identified the potential for landslides. Nonetheless, the County did not require geotechnical or geological work to be done on the site prior to the construction of homes. The landslide took 43 lives and was widely publicized nationally. Lawsuits resulting from this landslide may force local governments in the Northwest to adopt legally enforceable grading ordinances.


    A problem faced in the Northwest is the difference between what can be done—“state of the art”—and what is the standard level of practice in the area. Clearly the standard level of practice is much higher in the Los Angeles and San Francisco metropolitan regions than it is for most of Oregon or Washington, although the “state of the art” is the same in all those areas. For example, it is quite straightforward to evaluate a building site for liquefaction and ground-shaking potential, and Chapter 16 of the Uniform Building Code presents sample ordinances to do this. But it is not standard practice for most of the Pacific Northwest, and it is not carried out, despite the existence of maps of metropolitan Seattle, Portland, Salem, and Victoria that point to areas of potential hazard from liquefaction, ground shaking, and earthquake-induced landslides, and the success of maps of Olympia and parts of Seattle showing liquefaction and lateral-spread potential in predicting those areas that actually underwent damage in the 2001 Nisqually Earthquake.


    Jim Slosson, an engineering-geology consultant and former state geologist of California, is the source of what has come to be called Slosson’s Law, a corollary to Parkinson’s Law: “The quality of professional work will sink to the lowest level that government will accept.” This applies to the building codes as well as grading ordinances.


    California requires property owners or their agents to disclose to prospective buyers the fact that a property is in a seismic hazard zone or an Alquist-Priolo fault zone. Effective March 1, 1998, an amendment requires disclosure when one of two conditions is met:

    1. The seller has actual knowledge that the property is within a seismic hazard zone; or
    2. A map that includes the property has been provided to city and county officials by the state geologist, and a notice has been posted at the offices of the county recorder, county assessor, and county planning agency.

    Disclosure laws are much weaker in Oregon and Washington.

    This page titled 7.5.7: Grading Ordinances and Regulation of Building Sites is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Robert S. Yeats (Open Oregon State) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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