HomeMy WebLinkAbout02/06_1/2001, 3 - AMENDMENTS TO BENCH MARK SYSTEM DATUM PLANE council `Tegruary 6, 2001
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CITY OF SAN LU I S OBISPO
FROM: Michael D. McCluskey, Director of Public Works
Prepared By: Bridget Fraser, Associate Engineer
SUBJECT: AMENDMENTS TO BENCH MARK SYSTEM DATUM PLANE
CAO RECOMMENDATION
Introduce an ordinance to print amending section 12.40.050 of the Municipal Code directing the
City Engineer to establish the City's Bench Mark System from datum established by the National
Geodetic Survey.
DISCUSSION
In 1985, Council passed an ordinance directing the City Engineer to establish, as he deemed necessary,
a bench mark system throughout the City based upon a particular elevation datum. This bench mark
system is used for determining all elevations for sidewalks, streets, bridges, etc. and all work and
construction within the City. The use of a benchmark system allows individual plans and projects to be
related to each other through a common datum plane. This system of bench marks was established on
the National Geodetic Vertical Datum of 1929 (NGVD29) which in 1985 was the official federal
vertical datum.
Over time, according to the National Geodetic Survey (NGS), the NGVD29 became outdated and
pieced together due to thousands of leveling lines being added and thousands of points having been
destroyed or affected by earth movements and subsidence. As a result, in 1991, NGS established the
new vertical control datum known as NAVD 88 and adopted it as its official vertical datum.
NGS is no longer supporting and publishing its benchmarks in the 1929 datum. Today's surveying and
Global Positioning System (GPS) equipment and supporting software are compatible with the 1988
datum and not with the older datums. For this reason staff wants to adopt the new and widely used
NAVD 88 datum. To facilitate this transition and any future datum revisions which may result from
new technology and better means of measuring vertical elevation, staff recommends amending Section
12.40.050 of the Municipal Code to allow the City Engineer authority to revise the City's datum plane
and bench marks based on a federally adopted datum.
FISCAL IlVIPACT
There is no fiscal impact anticipated.
Attachments
Ordinance
Legislative Draft
A copy of the revised Bench Mark System is available in the Council Office for review.
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ORDINANCE NO. (2001 Series)
AN ORDINANCE OF THE COUNCIL OF THE CITY OF SAN
LUIS OBISPO AMENDING SECTION 13.40 OF THE SAN LUIS
OBISPO MUNICIPAL CODE TO AUTHORIZE THE CITY
ENGINEER TO ADOPT THE DATUM PLANE FOR THE CITY'S
BENCH MARK SYSTEM.
WHEREAS, the, National.Geodetic Survey (NGS), formerly U.S. Coast and Geodetic
Survey(USCGS), revises its official vertical datum from time to time, and
WHEREAS, the City Council finds that it is important that the City's Bench Mark
System be based on a federally adopted datum;
BE IT ORDAINED by the Council of the City of San Luis Obispo as follows:
SECTION 1. That Section 12.40.050, paragraph A,be modified as follows:
"A. The City Engineer shall establish bench marks throughout the City as he deems
necessary. The City Engineer shall be given the authority to revise the datum plane for the
Bench Mark System based on a datum established and supported by the National Geodetic
Survey."
SECTION 2. A summary of this ordinance, approved by the City Attorney, together
with the names of the Council members voting for and against it, shall be published at least five
days prior to its final passage, in the Tribune, a newspaper published and circulated in this City.
This ordinance will go into effect at the expiration of thirty (30) days after its final passage.
INTRODUCED on the day of 2001 AND
FINALLY ADOPTED by the Council of the City of San Luis Obispo on the day of
2001, on the following roll call vote:
AYES:
NOES:
ABSENT:
Mayor Allen Settle
ATTEST:
Lee Price, City Clerk
APPROVED AS TO FORM:
ffr G.34f se , City Attorney
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LEGISALATIVE DRAFT
12.40.050 Datum plane.
A. The city engineer shall establish benchmarks throughout the city as he deems
necessary. . City Engineer shall be
given the authority to revise the datum plane for the Bench Mark System based on a datum
established and supported by the National Geodetic Survey.
B. The benchmarks shall be used in determining all elevations, streets, pavements,
sidewalks, curbs, sewers;bridges, structures, lot grades and all other work in the city.
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