Chapter 12.04
CITY ELEVATION PLANE
Sections:
12.04.010 Mean sea level datum adopted.
12.04.020 Bench marks with adjusted elevations.
12.04.030 Number and location of bench marks.
12.04.040 Criterion of accuracy.
12.04.050 Bench mark specifications.
12.04.060 Reference to official datum in maps and plans.
12.04.010 Mean sea level datum adopted.
Consistent with modern accurate engineering practices and in order to obtain a more uniform system of elevation control for future construction projects in the city, the city, upon passage of the ordinance codified in this chapter, adopts the mean sea level datum as established and maintained by the United States Coast and Geodetic Survey as the official city datum plane of the city. (Ord. 486 § 1, 1945. Prior code § 8.06.010)
12.04.020 Bench marks with adjusted elevations.
It being understood that the United States Coast and Geodetic Survey at unspecified intervals adjusts and brings up to date the elevations of its various benchmarks, the city engineer or the city surveyor is directed to maintain a system of workable bench mark monuments with elevations adjusted to the current operating adjustment of the United States Coast and Geodetic Survey. (Ord. 486 § 2, 1945. Prior code § 8.06.020)
12.04.030 Number and location of bench marks.
The city engineer or city surveyor is instructed to establish and maintain a system of official city bench marks. The number of such bench mark monuments shall not be less than 10 for each square mile of area within the corporate limits of the city, and shall be located at intervals facilitating rapid accessibility from any point in the city. Upon suggestion of the city engineer or city surveyor, and approval of the city council, additional bench mark monuments may be set outside the corporate limits of the city as control for city construction. Elevations of these monuments shall be checked by level circuits at least once each 10 years. (Ord. 486 § 3, 1945. Prior code § 8.06.030)
12.04.040 Criterion of accuracy.
Criterion of accuracy of differential level circuits establishing elevations on these bench marks shall be as follows: All level circuits must be run in closed loops. All bench mark monuments must be incorporated as “turning points” in the level loop. The allowable error for level circuits of one mile or less distance shall be 0.02 feet. For circuits over one mile in length the allowable error shall be not to exceed 0.05 times the square root of the forward progress in miles. (Ord. 486 § 4, 1945. Prior code § 8.06.040)
12.04.050 Bench mark specifications.
Bench mark monuments established by the city engineer or city surveyor shall bear a bronze cap not less than three inches in diameter and, stamped or cased thereon, shall be sufficient information to positively identify that station. These markings shall give the station an identifying number or letter and shall show the calendar year number when set. The bronze caps shall be set in an existing substantial concrete structure or, if in an open area, shall be set in a concrete base not less than 24 inches in depth and not less than two cubic feet in volume. (Ord. 486 § 5, 1945. Prior code § 8.06.050)
12.04.060 Reference to official datum in maps and plans.
Following passage of this chapter all city sponsored construction, or construction subject to city control, shall be referred to the official datum of the city. All plans, specifications and engineering drawings prepared by the city, and all plans, specifications and engineering drawings accepted from outside agencies who seek to connect with, or enlarge on city utilities, shall clearly show that the basic datum of such plans or designs are referred to the city official datum as established by this chapter. (Ord. 486 § 6, 1945. Prior code § 8.06.060)