FLOOD09801

• County: Arapahoe
• Community: Greenwood Village
• Stream Name: Goldsmith Gulch
• Basin: South Platte
• Title: Contract Documents and Specifications for Goldsmith Gulch and Tributary Channel Improvements
• Date: 6/1/1987
• Prepared For: Goldsmith Metro District
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Project

Subsurface
conditions,
approximate

Conditions: To evaluate
three test borings were
locations shown on Figure 1.

the subsurface
advanced at the

The subsoils encountered at the site were variable and
generally consisted of sand and clay fill overlying natural
sands and clays. Claystone bedrock was encountered beneath
the natural sands and clays at a depth ranging from 10 1/2
to 16 feet.

The fill material consisted of clay and sand and was low to
moderately plastic, loose, moist, brown to black with pieces
of wood and organic materials. The natural clays were
mOderately plastic, slightly saney to very sandy with
occasional sand layers, soft to stiff, very moist to wet,
brown and calcareous. Interbedded sand and clay layers were
also encountered and were fine to medium grained, nil to
moderately plastic, medium dense, moist to wet and brown.
The claystone bedrock encountered was slightly sandy to
sandy, medium hard to very hard, moderately to highly
plastic, moist, brown and iron-oxide stained. Graphic logs
of the test holes are shown on Figures 2 and 3.

Swell consolidation tests run on the natural sands and clays
indicate that these materials exhibit nil to low swell
potential when wetted and loaded. Test results are ~hown on
Figures 4 and 5 and are summarized on Table 1.

Free groundwater was encountered at depths ranging from 3
1/2 to 5 feet below the existing ground surface.

Drop Structures: Considering the subsurface conditions
encountered in the test borings and the nature of the
proposed construction, we recommend the proposed drop
structure be founded on spread footings placed on the
natural undisturbed sand and clays.

The design and construction criteria presented below should
be observed for a spread footing foundation system.

(1)

Footings placed
may be designed
of 2,000 psf.

on undisturbed natural sands and clays
for an allowable soil bearing pressure

(2) The lateral resistance of spread footing foundations
placed on undisturbed natural soils will be a result of
the sliding resistance of the footing on the foundation
materials. Sliding friction at the bottom of the
footings can be taken as 0.4 times the vertical dead
load.

~

(3) Continuous foundation walls should be reinforced top
and bottom to span an unsupported length of at least 10
feet.

2