Shallow Braced (non-drilled,hand augered) Monument

Back to comparison table	Mount Commonly Used	Stability	Cost	Install Time	Labor	Substrate	Site Impact
	SCIGN mount	med	$800	1 d	2-3	U	med

The shallow braced (non-drilled, hand augured or pounnded) monument consists of 4-5 1"-diameter stainless steel legs in a tripod configuration pounded into the substrate up to depths of about 5-6 feet. The legs are welded together at the top. The short braced monument is nearly identical to the shallow drilled braced monument, with the exception that the legs are either pounded into unconsolidated ground or a hand auger is used to create the holes for the legs.

Rather than epoxied into holes drilled in bedrock. Use the SBM (Short Braced Monument) at locations where there is no bedrock available.

l
Site P492 of EarthScope’s Plate Boundary Observatory (PBO) (left); test site NWOT on Niwot Ridge (middle) and ,Costa Rica (right).

Pros

installable in unconsolidated substrate
materials relatively inexpensive
drill bits will not get stuck (as in short drilled braced monument)
materials and equipment can be flown to remote locations by helicopter
can be installed in environmentally sensitive sites
relatively quick deployment
site permitting potentially easier than for the deep drilled braced monument

Cons

labor and tool intensive
is probably less stable than the deep drilled braced monument
initial cost to purchase required tools potentially expensive

Design and Construction

A heavy duty hammer drill with a special chuck is required for installation.

Documents

Installation Photos

Ed Arnitz of UNAVCO drives the central rod into the ground with a Hilti drill.

The rods can also be pounded into the ground with a sledgehammer.

You first need to make the ends pointed.

Victor Gonzales (OVSICORI) using the hand auger to dig out the holes for the legs.

Approximate Cost

$800

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

Materials

4 12-foot stainless steel rods (1" diameter) with grooves
3 weld gussets
threaded adapter (if using the SCIGN antenna mount; see below)
welding rod
gas for the generator (if there is no AC hookup)
water (for fire safety while welding)

The materials specific to construction of the SBM are available as a kit which can be purchased from:

McRoberts Machine, Inc. (Judy or Doug McRoberts)
402 Martin St
Longmont, CO 80501
Phone: (303) - 776 - 2397
Fax: (303) - 776 - 0704

When ordering please refer to Part #1090.

Tools

AC-powered heavy-duty hammer drill (e.g. Hilti) with bit
generator (if there is no AC hookup)
chop saw or dry cut saw
grinder
vertical and angle level(s)
leg alignment tool
welder
file, pick, brush, gloves, helmet, long-sleeved shirt, hat (for welding)
compass

Mount Commonly Used

The SCIGN mount is the antenna mount most commonly used with the shallow 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.

Shallow Braced (non-drilled, hand augered or pounded) Monument Overview