Deep Drilled Braced Monument

Back to comparison table	Mount Commonly Used	Stability	Cost	Install Time	Labor	Substrate	Site Impact
	SCIGN mount	high	VARIES	2-4 d	3-4	BR, U	high

The deep drilled braced monument (UNAVCO DDBM*) provides for a high degree of stability and longevity and can be anchored in bedrock or unconsolidated material. It is in the form of a tripod, each leg extending into the ground up to about 40 feet and welded at the top with gusset reinforcements. If site access is an issue and bedrock is available, the short drilled braced monument is the next best alternative to this type. The UNAVCO DDBM is used throughout the PBO network.  It is based on the SCIGN design used at older installations in the SCIGN, BARGEN, PBO and PANGA networks.

* Modified from the original SCIGN DDBM design of Duncan Agnew and Frank Wyatt.

Site ASHM of the BARGEN network, Nevada, Utah, and California.

Pros

• high stability

• longevity

• can be installed in either bedrock or unconsolidated materials

Cons

• labor and tool intensive (requires a drilling rig and crew)

• expensive (depending on drilling company)

• time intensive (requires 2-4 days)

• may not be able to install in some remote locations... depends upon ease of site access

• large construction disturbance footprint

Design and Construction

A drilling contractor is required to install this monument. The cost of installation depends upon factors such as the type of drilling rig used, distance the drill rig and crew need to travel to site (mobilization/de-mobilization), foundation material (ground) being drilled, etc.

• Driller’s Instructions (.pdf)

Documents

• Deep Drilled Braced Monument Technical Drawings in .pdf format:

  • Full

  • Above Surface

  • Top

  • Construction

  • Site Layout

  • Sub-surface

• Deep Drilled Braced Monument Alignment Tool Diagrams in .pdf format:

  • sign-01-01-010.pdf

  • sign-01-01-020.pdf

  • sign-01-01-030.pdf

  • sign-01-02-010.pdf

  • sign-01-02-020.pdf

  • sign-01-02-030.pdf

Installation Photos

• Construction Photos

Approximate Cost

Depends principally on drilling (substrate, distance drill rig needs to travel to and from the site)

This cost is for the monumentation only; the antenna mount (e.g. SCIGN mount) is not included.

Materials

• 21-foot 1.25" diameter schedule 40 stainless steel pipe, threaded (5 per site)

• 10-foot 1.25" diameter schedule 40 stainless steel pipe, threaded (5 per site)

• 1.25" schedule 40 stainless steel threaded adapters (5 per site)

• 3 weld gussets

• threaded adapter (if using the SCIGN antenna mount; see below)

• 2.5" diameter schedule 40 PVC (for each leg and for center post)

• foam wrapper (for each leg and for center post)

• rebar (for each leg and for center post)

• duct tape (for foam)

• concrete (provided by drillers)

• water (provided by drillers)

• welding rod

• gas for the generator (if there is no AC hookup)

• string, paint, nails, and wood stakes (for marking legs)

Tools

• generator (if there is no AC hookup)

• compass

• reel measuring tape (30m/100ft)

• leg alignment tool

• mallet

• large vice grips (2 or more)

• grinder

• vertical and angle level(s)

• welder

• file, pick, brush, gloves, helmet, long-sleeved shirt, hat (for welding)

Mount Commonly Used

The SCIGN mount is the antenna mount most commonly used with the deep drilled braced monument, although it is only required when using the SCIGN radome. Otherwise, any other leveling mount, such as the SECO 2072-series antenna mount, is acceptable.

Send questions or comments to Support (supportunavco.org).