Easier Groundwater Remediation

Environmental consultants agree that the price to remediate contaminated groundwater can be financially ruinous. But there are exceptions. ESA has successfully used a groundwater remediation strategy that saves vast amounts of time and money – when the conditions are right.

ESA first employed this groundwater remediation strategy – which relies more on ingenuity than technology or engineering – in 1990. In our first application, a client had an underground storage tank (UST) that released a large volume of heating oil. The oil was found to be floating on the shallow groundwater. With the client’s approval, ESA circumvented the conventional solution and instead applied our alternative approach, obviating what could have been a long-term groundwater cleanup. Consequently, the client spent far less time and money when compared to the conventional method.  And, this client remains a loyal ESA customer 29 years later.

Three criteria govern the feasibility of this strategy. First, there must be an organic contaminant that floats on water (i.e., light, non-aqueous phase liquid (LNAPL)). Typically, we are talking about gasoline or heating oil, although this technique can also work with certain non-chlorinated organic solvents. If a chlorinated solvent (which is denser than water) has discharged, this strategy will not work. The second variable is soil particle size. Typically, it is preferable to have fine-grained soil particles around the tank because small particle sizes tend to retard groundwater flow, thereby keeping the product close to the tank. The third variable is time. The less time the product has been on the groundwater, the more likely it is that this technique will work.

Let’s examine a typical scenario: upon removing a leaking UST, unleaded gasoline (LNAPL) is found to be floating on the groundwater. The traditional remedial steps in this instance would be:

1. The consultant either skims the product or uses sorbent pads to absorb the product. This waste material is then containerized for disposal.
2. Some readily accessible impacted soil that lies above the water table may be excavated and disposed.
3. Then, at least one groundwater monitor well is installed directly in the former excavation, and ground water sampling begins (if the consultant has followed these steps to this point, it is probable that three or more wells will have been installed).
4. After groundwater impacts have been delineated, one of two things will happen; either some form of active groundwater remediation will begin, or the consultant will apply for a Classification Exception Area (CEA). Active remediation is expensive and takes many years to complete. For budgetary purposes, assume that remedial costs will range from $150,000 – $500,000, and the remediation will last five years or more. However, if the water quality data lends itself to going the CEA route, your costs should come in below $100,000 and you may finish in 2-3 years.

The above series of steps are commonly used. They conform with standard practices within the environmental industry, and they are consistent with the prescriptive guidance contained within New Jersey’s Technical Requirements for Site Remediation (N.J.A.C. 7:26E).  In fact, the regulatory timeframes outlined by the NJDEP for LNAPL are as follows:

60 days from LNAPL discovery:

• Report the presence of LNAPL on the required LNAPL Reporting Form (see N.J.A.C. 7:26E-1.10(b)1);
• Conduct initial LNAPL recovery, when practicable, and report the status of the actions taken within this timeframe using the required LNAPL Reporting Form (see N.J.A.C. 7:26E-1.10(b)2).

1 year from LNAPL discovery:

• Complete the delineation of the LNAPL (see N.J.A.C 7:26E-1.10(c)1);
• Initiate a LNAPL IRM to prevent migration and reduce contaminant mass to the extent practicable and initiate operational monitoring. The IRM should consider all known human and ecological exposure risks (see N.J.A.C. 7:26E-1.10(c)2);
• Document the delineation of the LNAPL, the LNAPL recovery efforts conducted to date, and implementation of the LNAPL IRM through submittal of an LNAPL interim remedial measures report with an updated LNAPL Reporting Form (see N.J.A.C. 7:26E1.10(c)3).

But ESA may be able to employ a less costly, less time-consuming solution:

1. With the client’s full consent and understanding, ESA uses a vacuum truck to pump all accumulated water and free product from the excavation. Groundwater is then allowed to re-enter the excavation, bringing with it more product. This new volume of water and product is again pumped into the vacuum truck.
2. This procedure is repeated 3-5 times. Pumping ceases when the reinfiltrating groundwater no longer conveys appreciable free product.
3. ESA then excavates and properly disposes impacted soil that lies above the water table (in a layer known as the “smear zone”). These efforts (#1-3) immediately remove as much of the free product as possible. This is critical.
4. The excavation is then backfilled with stone. Optionally, ESA may also install a collection sump within the stone backfill to facilitate additional product collection.
5. At least one monitor well must be installed within the area occupied by the former UST. However (and this is key), ESA will delay the installation of this well for as long as practical. Simultaneously, while waiting to install this well, subsurface water quality will naturally improve because the source material has been removed. Consequently, when the well is finally installed and sampled, the ensuing laboratory result will be better than had you installed the well immediately.
6. Normally, full compliance will take approximately 2-3 years and the result will confer a dramatic savings in both money and time.

This method works because wells that are installed immediately following the tank removal always have higher contaminant concentrations. Conversely, wells that are installed after waiting several months normally have much lower contaminant concentrations. This means that groundwater sample results are more likely to favor the best interests of ESA’s client, tipping the odds of a desirable outcome in the client’s favor.

ESA has performed this strategy many times with great success and it has saved each client enormous sums of money and time. It may work for you as well. Contact ESA at 732.469.8888 if you think you may have an issue with groundwater contamination.[/vc_column_text][/vc_column][/vc_row]