EASTERN PORTION OF THE COUNTY
Between the years 2000 and 2005 Arapahoe County established a primary Vertical Control Network in the eastern portion of the
County. The network consists of 5 separate phases with one phase completed per year. As shown on the index map the primary
Vertical Control Network extends from Watkins Road to the Town of Deer Trail.
The purpose of the Network is to establish a series of benchmarks that can be used for mapping, surveying, engineering design,
drainage studies and construction purposes.
There was difficulty establishing phasing lines in the first two projects. In the end it was decided to call the first project
Phase I and the second project Phase II. It should be noted that Phase I has been revised. The purpose of the revision is
noted on the cover sheet.
For all 5 projects all elevations are referenced to the North American Vertical Datum of 1988 (NAVD88) and were established
by differential leveling. All field and office procedures followed FGCC 1st order Class II Specifications. However, the controlling
benchmarks for the surveys used to establish the network are classified as Second Order, Class 0. Therefore the surveys used
to establish the network are classified as Second Order, Class 0 as defined by NGS.
Please read the notes on the cover sheet of each project for more information on the methodology used to establish the elevations.
Full survey reports for each individual project are on file in the offices of the Mapping Section.
Due to road construction some of the benchmarks in Phase I were reset in 2006.
In 2010 the County conducted a benchmark recovery project to verify the existence and condition of the benchmarks in the Primary
Vertical Control Network. It should be noted that the County only verified the existence and condition of the benchmarks
and did not check or verify the elevation on individual benchmarks and did not check or verify the difference in elevations
between the benchmarks.
URBAN AREA
In 2010 the County began establishing a Vertical Control Network in the urban area. Since the City of Aurora has established
its own Vertical Control Network the County's network will extend from the western boundary of the City of Aurora to the western
boundary of the County. The first phase was completed in 2011.
The primary purpose of the first phase was to extend existing NGS vertical control along E. Hampden Avenue in the City and
County of Denver into Arapahoe County. As shown on the index map this phase also established a series of benchmarks in the area between S. Monaco Street and S. Havana Street north of E.
Arapahoe Road.
The elevations established by this project are referenced to the North American Vertical Datum of 1988 (NAVD88) and were established
by differential leveling. All field and office procedures followed FGCC 1st order Class II Specifications. However, based
on field verification, the existing NGS benchmarks used to control the Phase I survey can only be classified as Second Order,
Class I. Therefore the Phase I survey is classified as a Second Order, Class I survey as defined by NGS.
Please read the notes on the cover sheet for more information on the methodology used to establish the elevations. A full
survey report for the project is on file in the offices of the Mapping Section.
The County has recently completed the second phase of the network by establishing two benchmark loops off of the primary loop
established in Phase I.
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