Assessing Risk
SITE
Former Elegance Dry Cleaner – Orlando, Florida
CONTAMINATION
Dissolved solvent constituents (mostly perchloroethylene and trichloroethylene) were estimated to impact approximately 185,000 sf (deep zone, approximately 25 ft bls). The surficial shallow plume (41,000 sf) begins on-site under the building and travels down under the adjacent roadway and property. The below figures show the shallow zone groundwater sampling impacts before and after Vertebrae™ Well Systems (VWS) installations.
OBJECTIVE
The design involved three shallow and four deep VWSs utilizing 84 independent well segments to provide targeted in-situ chemical oxidation to the two layered plume. This case study illustrates how Vertebrae can be efficiently utilized for High Resolution Containment Distribution (HRCD), regardless of the city roadway, site structures and utilities. The deep zone is not shown by this case study for brevity.
BACKGROUND
The Elegance Cleaners operated from 1989 to 1994. During a recent property transaction (2016) a site exploration and sampling event found apparent contamination. This was investigated and delineated in 2016 and 2017.
INSTALLATION DETAILS
The shallow VWS were installed under the building
and parking lot and the deep VWS were installed
under the building parking lot, highway and
adjacent property.
The VWS were installed at the rear of the site and
in the right of way which eliminated business
disruption while allowing complete coverage of the
700 ft long dissolved plume. Installation of the
VWS were completed over two and half weeks
including development activities. The 84 well
segments were 20 ft in length constructed with 1-
inch nominal HDPE screens and geotextile with
half inch riser tubing to the surface.
SAMPLING RESULTS
Prior to the installation of VWS the impact was
characterized by Geo-probe® groundwater
sampling and a limited number of vertical wells
(Figure 1). Sampling of the VWS revealed
significant source area, previously unidentified.
The estimated mass was 8 times more than the
initial contaminant site model (CSM). The data
provided HRCD iso-contours pinpointing the mass
directly under the building where treatment and data collection was unattainable by other tools.
TYPICAL FINDINGS – GAP TYPES
The VWS results from this site are similar tomany other sites. We have collected data thatindicates often gaps are impacted to a greaterextent than estimated. This may be the resultof averaging or optimistic consulting, but it isconsistent with most of the sites where VWShave helped characterize.
It is important to note that some of these sites
did not have perceived gaps. For the Pensacola, Milton, and subject (Elegance) sites, data was collected where monitoring wells were at ‘normal spacing’ yet mass was greater than estimated in between. Therefore, we need to address two data types:
- Obstacle Gaps (Where data is inaccessible, known)
- Spacing Gaps (unknown mass between data points)
COST DISCUSSION
Failure to properly characterize the mass is a big issue in the environmental industry. We all fight the need to keep cost down during assessment and try our best to find all the mass, but to say it is elusive is an understatement. Plus, it is always problematic that a host of obstacles exist to impede our ideal layouts. This is where Vertebrae offer a significant advantage and always saves costs! At sites examined, Vertebrae appears to always save cost. For instance, a site (also in Orlando) was used for analysis of cost comparison for a data gap of 80 x 100 ft under a building and treatment. Three cases were examined; 1) trying to over treat and guess the area was moderately contaminated, 2) treating only what was known, 3) installing the Vertebrae to find out and treat it as precisely as possible. The cost comparison indicated vertebrae saves cost over both alternatives.
RISK RECEPTORS (ALL OF US)
We see that the value in the data helps everyone!Each party has some risk when an area of the siteis left unexplored and when normal spacing failsus. Our biggest problem is the unknown andcompleting HRCD sampling provides a solution tolimit the risk, whether it is perceived or not!
CONCLUSIONS
Vertebrae is an excellent tool for exploringunknown areas of the site. It is also an excellenttool to provide better coverage in open areas ofthe site and then transitions the well(s) to remedial treatment. Utilizing VWS in both situations reduces cost and helps protect all of us from the risk of inadequate and inaccurate CSMs.
