Friday, July 15, 2011

Beyond the scope

A client used one of our reports for application of work beyond the scope of the report, and the County used one line in the report as defense of a project, which it could not support. The client wants us to withdraw the restriction. Now what do we do?

First the report covered a building foundation and a slope stability of a critical portion of creek slope, but the no water features applied to the entire creek length through the property. The client build a storm water management facility, a holding pond, too close to the creek. It does not comply with Alberta Environment Guidelines in a number of areas.

We have not conducted analysis of the bank at that location. The client did not conduct any testing on the roadways; hence, they are not a good client.

So here is the essentials of the letter I provided.

As requested, we has reviewed geotechnical investigation at the above noted site.  The purpose was to examine our recommendations to disallow water features within 30 metres from the top of bank along the creek, for the purpose of allowing a storm water management facility (SWMF)  (storm water pond) at the top of bank at the south end.

First, any storm water pond must comply with Alberta Environment Guidelines for SWMFs. The proposed development is short in a number of ways, assuming the plan provided is the complete plan.

The report was conducted before any SWMF was proposed on any of the plans provided, and as a result, the SWMF was not considered. It is beyond the scope of the report, and the SWMF was designed and partly constructed without any geotechnical or enginnering input from us.

The water feature setbacks, for small slopes, are normally based on a soil dependent factor multiplied by the depth of the slope, and expressed as a distance from the top of the slope. For typical clay till, 6 to 8 times the depth of slope would be typical, in this case about 3 metres, producing a typical setback of 18 to 24 metres from the bottom of the toe. However, no testholes were conducted, and we are unsure if clay, clay till, of sand lenses are present at this location. No analysis has been conducted, and the required information has not been obtained. There is also a question of the point to measure from on the SWMF.

We expect that at this location, the 30 metre water feature restriction can be reduced, but without testholes, testing, and analysis, we are unable to logically provide an exact number at this location. In addition, there are inside pond slope issues and erosion issues that are not addressed in the plans provided to us.  A specific geotechnical investigation would be required to address the SWMF and the setback, along with redesign to comply with the current Alberta Environment guidelines. 

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