Model Generated Economic

SITE 1: Lee’s Tire, Former Phillips 66, Socorro, NM

A large plume spread across 75% of the property towards the roadway at the former gas station site. The site lithology was described as variable ranging from expansive clays, highly angular coarse sands, and large well sorted well rounded gravel. The consultant designed an air sparge and soil vapor extraction system to address the contamination including 12 Vertebrae air sparge well segments and 6 Vertebrae soil vapor extraction well segments. The Vertebrae design was able to address the entire plume with the desired flow rates. With a 4:1 vertical well to Vertebrae well ratio generated by the model, the Vertebrae system is comparable to installing 72 vertical wells. Savings realized were $210,000.

SITE 2: Former D&A Produce, Chipley, FL

Located in a parking lot of a large retail pharmacy, a BTEX plume of approximately 1,600 square feet spanned both shallow and intermediate zones. Recent soil data showed sandy clay with both soil and groundwater samples exceeding target levels in the shallow zone. Three Vertebrae wells with a total of 10 well segments used for in situ injections were designed to address the shallow plume contaminants. The model generated a 2:1 vertical well to Vertebrae well ratio, allowing the installed Vertebrae system provides a coverage comparable to 20 vertical wells. Savings realized were $88,000.

SITE 2: Paramount Heights 66, Denver, CO

Given a slow-moving plume moving towards a no access area, the client wanted to design a barrier treatment wall to prevent the plume from traveling further. Twenty-five years of soil boring logs described a lithology with a mix of sandy claystone and bedrock at the desired well installation depth. Based on the site data, the model generated a 3:1 vertical well to Vertebrae well ratio. The Vertebrae well system was selected and designed to cover the adjacent property border with 11 well segments with spacing for a total of 160’ at depth, which is a coverage comparable to 33 vertical wells. Savings realized were $151,000.

The top portion of Table 1 below summarizes the Vertebrae well system designs for the three sites and breakdown of their installation costs.

Table 1

The EN Rx economic cost model calculates the vertical to horizontal well ratio using equations developed by W. Richard Laton, Ph.D., P.G. as presented in the paper New perspectives on horizontal to vertical well ratios of site cleanup (Remediation. 2019; 30:27-31).  The model generated vertical to horizontal ratios based on site conditions and Vertebrae design are presented in the second column of Table 2 below.

The number of vertical wells needed to provide the same performance (i.e., zone of influence) as the planned Vertebrae systems is calculated by multiplying the number of horizontal well segments by the vertical to horizontal ratios.  These numbers are presented in the third column of Table 2.  It is relevant to note that this is not to suggest that the number of vertical wells presented in Table 2 would actually be installed.  Rather this number represents how many vertical wells would be required to achieve the same performance as the planned Vertebrae system.

The mean cost of the equivalent vertical well system is estimated using a Monte Carlo process that accounts for cost uncertainties related to factors such as design, well installation, trenching, piping, and surface cover.  The Vertebrae savings (or performance value) is calculated by subtracting the Vertebrae system cost from vertical well system mean cost.

Table 2

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