Although hydroseeding can often be an effective treatment for surficial slope instabilities, steep slopes and landslide prone terrain call for an altogether different approach.

The first step in analyzing a particular site is to determine the primary source of instability. Most frequently this can be attributed to high soil saturation and poor drainage. When combined with weak soils, joints or fissures in the slope material, contrasting material permeability, and steep slopes, the result is often catastrophic.

Estimated landslide susceptibility based on rock strength and slope steepness. Areas along the coast are among the most susceptible to deep landsliding. [California Geological Survey/USGS, 2011]

Developing a Solution

Once the primary sources of instability have been identified and the soil properties analyzed, a mitigation plan can be developed for each area of concern:

• Surface and ground water drainage
• Failure planes/zones
• Soil mass support
• Rockfall hazard
• Vegetative establishment

Common mitigation techniques include percussion driven earth anchors, structural repair with compacted soil lifts, surface and subsurface drains, soil nails, gabions, and gravity systems. Effectively integrating these methods is the key to long-term slope stability.

Thunder Mountain Enterprises offers design-build services for slope stabilization and landslide repair. For more information, please call 916.381.3400

What is a Conical Frustum?

A conical frustum is an essential part of earth anchor mechanics. A basic definition of a “conical frustum” is a cone with the top sliced off.

After an earth anchor is driven to depth, tension is applied to “lock” it in place. The locking process turns the anchor 90 degrees into a horizontal orientation, and creates a frustum of compacted soil above it. This frustum is proportionally much larger than the anchor, giving the anchor its full load bearing capacity.

In some cases, the shear strength of the soil is exceeded during tensioning, causing it to fail. The solution to such failure may be using a larger anchor, which increases the volume of the frustum and thus its bearing capacity.

• conventional: slope repair methods including construction of retaining walls, slope excavation and reconstruction, and rip rap placement
• deadman: buried object (typically concrete with reinforcing steel) used as an anchor
• failure plane: the surface between two layers of soil where mechanical failure occurs
• gabion: steel wire basket filled with rock or concrete; used in slope stabilization, channel linings, revetments, and other earth retention applications
• geocell: honeycomb-like structure made of HDPE and filled with soil, rock, or other materials; used in slope and road base stabilization
• gravity wall: retaining wall typically constructed of stone or concrete, which relies on its mass (“gravity”) to resist the pressure bearing on it
• GRS: geosynthetic reinforced soil
• MSE: mechanically stabilized earth
• percussion anchor: earth anchoring device driven and load-locked into place; forms a frustum cone of compressed soil above anchor
• rotational failure: slope failure occurring on a circular (concave upward) slip surface
• RSP: rock slope protection
• sheet pile: thin, interlocking steel panels driven into the ground to form retaining walls and cofferdams
• shotcrete: pneumatically applied concrete, typically sprayed on reinforcing mesh to form a sculpted wall facing
• soil friction angle: shear strength parameter of soil
• soil nail: reinforcing element such as rebar or a hollow bar drilled and grouted into place; used (often in conjunction with shotcrete facing) in slope stabilization, oversteepened embankments
• soldier pile: wide flange “H” steel piles driven at intervals along a planned excavation perimeter; used in conjunction with lagging to create retaining walls
• tie back: wire, rod, or helical anchor used to secure retaining walls
• uniaxial geogrid: grid-like structure made of HDPE, commonly used in slope reinforcement and retaining wall applications (as opposed to biaxial or triaxial geogrid, commonly used for base reinforcement)

Keeping a pond healthy is not an easy task. The overall health of a pond depends on dozens of factors, including water temperature, pH, nutrient levels, oxygen, and ecological balance, to name a few. When one of these factors is out of balance, the whole pond suffers.

Starting off with the right design is key in determining the ultimate success of a pond. Steep, benched (stepped) sides help regulate water temperature and provide a place for plants to grow. Trees near the pond lend shade, but may also drop their leaves into the water. Location is important – a pond in the bottom of a valley will collect run-off and whatever chemicals or excess nutrients that may contain.

Wildlife provide another challenge. Ducks can introduce water weeds and will fill ponds up with muck. Racoons and other predators can decimate fish, frog, and turtle populations. It’s best to discourage these creatures from taking up residence in or near a pond.

Another important consideration is maintaining a healthy oxygen level. Usually this is accomplished by aerating the pond with a water fountain, waterfall, or aeration device.

Annual storm water reports for the period of July 1, 2011 through June 30, 2012 were due September 1st, and the State has threatened fines for late filings. If you have not yet filed a report, please call Thunder Mountain as soon as possible to avoid any penalties:

916-381-3400

Healthy pond ecosystems help conserve water, reduce carbon dioxide, produce oxygen, provide enjoyment and raise property value.

Three living groups form the basis of every ecosystem: producers (autotrophs), consumers (heterotrophs), and decomposers (saprotrophs). Producers include phytoplankton, plants (such as algae), bacteria and protozoa. These organisms convert carbon dioxide and sunlight into organic compounds that consumers can utilize. Consumers, which include zooplankton, insects, worms, snails, amphibians and fish, survive by feeding on consumers and the nutrients they produce. Bacteria and fungi form the third and final link of the cycle, recycling waste produced by consumers into components that producers can use.

Habitat (a combination of many physical factors and conditions) determines the success or failure of an ecosystem. A properly constructed pond will include habitat features designed to encourage a healthy ecosystem. The result is a lower maintenance, more natural pond.

At Thunder Mountain we apply our environmental expertise and industrial liner know-how to every pond or liner that we design and install. Whether you are looking for a three acre industrial wastewater pond or a 1,000 square foot ranch pond, a Thunder Mountain expert can help.

Call for a free consultation: 916.381.3400