| A. Characterization (Geophysical, Physical and Chemical) |
| 1. What technologies have you used for characterization? |
| Technology |
Percent Responding 'Yes' |
|---|
|
| borehole geophysics (single point, resistance) |
68% |
| borehole televiewer/television |
71% |
| fluid loggings (temperature, conductivity) |
55% |
| flow meter (heat pulse, EM) |
65% |
| surface seismic surveys (refraction, reflection) |
45% |
| vertical head profiling (packer isolation, cluster wells, sampling port) |
90% |
| fracture trace analyses |
68% |
| surface EM conductivity surveys |
52% |
| surface GPR surveys |
52% |
| coring |
94% |
| tracer studies |
42% |
| downhole seismic surveys |
6% |
| measurement of hydraulic head |
74% |
| hydraulic testing (injection tests, pumping tests) |
90% |
| PITT tests |
3% |
| outcrop or geologic testing |
45% |
| borehole radar surveys |
16% |
| 2D resistivity surveys |
16% |
| modeling (water or solute transport) |
58% |
| time series sampling |
39% |
| FLUTe with NAPL ribbon |
6% |
| other |
23% |
- subsurface tunneling - combined sewer overflow abatement tunnel projects have been implemented for many major metropolitan areas in NE USA. These provide great subsurface information.
- Micro-Sampling
- VLF
- geo maps + literature review
- Soil Gas Surveys in Overburden
- Caliper Log
- Neutran Density log very useful for porosity information sonic usefl for porosity and fracture dtdction
|
| 2. What was the outcome of the application, i.e. did it tell you what you wanted to know? |
- Packer testing and coring were successful in characterizing fracture zones, but modeling was not. Fracture trace analyses were useful for regional trends only.
- —Submitted on November 08, 2000 at 21:41 UTC
- Using various techniques, I was able to find a combination of tools to characterize the system.
- —Submitted on November 09, 2000 at 15:34 UTC
- Downhole techniques have been quite useful and informative, but have come at the expense of additional wells. That's an unavoidable tradeoff in the world of budget limits, but an annoyance none the less. Simple black-and-white video inspection, combined with caliper logging, was a highly cost-effective way to choose monitoring intervals for nested wells.
Surface-based techniques (GPR, VLF) have been far more limited in success.
Time series sampling proved extremely valuable at one site near a disappearing stream, where we demonstrated that VOC levels increased dramatically during short-duration, high water events, and concluded that much of the remaining contaminant mass is actually located in the vadose zone. Given the site history and geology, this was quite unexpected.
- —Submitted on November 10, 2000 at 19:42 UTC
- Packer injection testing has been an effective way to identify conductive zones in bedrock, and target well completions, at the borehole scale. Very long-term pump testing (28 days!!) has been critical in determining if the flow system can be reasonably represented as a porous medium for hydraulic purposes, at a larger scale (500-1000 foot).
- —Submitted on November 13, 2000 at 16:21 UTC
- A) Borehole geophysics: The outcome was good in that it confirmed the geological drilling logs. However, it did not yield sufficient data to indicate hydraulic and/or flow transport parameters. B) Fluid loggings and flow meter surveys worked very well to indicate areas of primary groundwater transport enabling focus of the remediation system. C) Coring: Coring of the site was very useful in determining the focus areas of groundwater transport and associated remediation areas. Coring was a definite requirement in a minimum number of well locations. D) Hydraulic Testing: Packer testing across select fractures zones was useful in the support of groundwater extraction and injection zones. E) Modeling was only useful to convey information. A significant portion of the modeling was adjusted to represent current conditions, and therefore the predictions capabilities of the model were marginal. Micro-fracture analysis: This technology was very useful to determine the extent of matrix diffusion and potential for the remediation system to be diffusion limited. The data yielded significant matrix diffusion and resulted in selection of a bioremediation remedy versus a chemical oxidation remedy.
- —Submitted on November 13, 2000 at 19:19 UTC
- Most were oriented toward defining bedrock topography and predicting shallow groundwater influences, as well as the presence of fracture zones. The applications that are in the geologic characterization class (fracture trace analysis, outcrop mapping, coring and hydraulic head mapping) are very important to the development of the conceptual model for the site. I missed more emphasis of geologic characterization and conceptual model development in your fractured bedrock seminar.
The other technologies for characterization have been hit or miss. Many are appropriate for smaller-scale studies, which require more effort than typically is considered warranted on the projects I have been involved with.
- —Submitted on November 14, 2000 at 5:45 UTC
- Although this kind of work can improve the general understanding of the flow field that contaminants are moving through they do so only at a broad scale. I have yet to encounter a site where a truly detailed understanding of contaminant flow through fractured bedrock has been achieved.
- —Submitted on November 14, 2000 at 16:19 UTC
- Generally yes. In some case the issue was where to locate a well. In others the outcome was placement of GW sampling devices. Seismic was especially useful for delineating bedrock and bedrock valleys.
- —Submitted on November 15, 2000 at 18:32 UTC
- Basically, we were able to delineate the topography of the base of the fractured rock unit and, combined with that, also the contaminant plume. Even major uncertainties still remain, which are related to budget restrictions to the use of more drilling and/or other characterization
- —Submitted on November 27, 2000 at 20:35 UTC
- Yes; we have had 2 very successful programs of using borehole geographics.
- —Submitted on December 06, 2000 at 16:05 UTC
- In most cases. Modeling in bedrock gave general conditioner but essentially was useless on specifics.
- —Submitted on December 06, 2000 at 19:30 UTC
- In most cases, fracture intervals/zones were identified. Contaminant migration pathways and geology were well described.
- —Submitted on December 06, 2000 at 20:00 UTC
- In most cases, yes.
- —Submitted on December 06, 2000 at 20:59 UTC
- Provided useful data, but not always definitive.
- —Submitted on December 06, 2000 at 21:09 UTC
- Yes, although methods are needed that are cost effective for refined understanding of features.
- —Submitted on December 06, 2000 at 21:20 UTC
- Use of individual applications was limited, but use of multiple characterization technologies gave a much clearer picture of what was going on.
- —Submitted on December 06, 2000 at 21:35 UTC
- For basic characterization, most useful tools have been: ATV, flow meter, and careful logging during---not discussed at conference---recognition of oxidized zone, driller report of fracture ,etc.
- —Submitted on December 08, 2000 at 15:05 UTC
- Borehole geographics is essential for proper characterization. Need good standard operating procedure for QA/QC of logging techniques. Work with vendor to get good log quality.
- —Submitted on December 08, 2000 at 15:40 UTC
- Limited. Fractured flow is very complex.
- —Submitted on December 08, 2000 at 15:51 UTC
- - Very interesting, very expensive.
- We answered questions we had not asked.
- We are able to select a technology for control but not removal.
- —Submitted on December 08, 2000 at 15:56 UTC
- MLS-derived data on microbiology of a borehole are not consistent with microbial obtained from cores/groundwater.
- —Submitted on December 08, 2000 at 16:19 UTC
- Borehole geographics extremely useful. Should we utilize more porosity tools (neutron/density, sonic)? Surface geophysical surveys have been of more limited use good well placement both horizontally and vertical incorporated with good working geological model are the key. Not mention above is the use of drilling and sample logs. the quality of these logs is poor.
- —Submitted on December 08, 2000 at 17:20 UTC
- For the most part. In many instances, we have limited data due to the expense of monitoring wells an boring in rock compared to unconsolidated. materials. From the available data, we often are limited to making a best educated guess about some parameters simply because many times there are no 'Darcy' type empirical relationships in the fractured media.
- —Submitted on December 08, 2000 at 18:05 UTC
- It depended on the application and the site. Each site may have different applications that work. Source applications may work on the majority of the sites (such as borehole flow meter) but all applications don't work on all sites.
- —Submitted on December 08, 2000 at 18:16 UTC
- Yes---each technology yields good results. Integrating the results of everything has not been as successful.
- —Submitted on December 08, 2000 at 18:26 UTC
- The aquifers were adequately characterized for the intended purpose.
- —Submitted on December 08, 2000 at 18:31 UTC
- Integrated methods yield a better conceptual site model.
- —Submitted on December 08, 2000 at 18:39 UTC
|
| 3. If you used any technologies listed above, what technical problems limited their use? |
- Cost of coring was high; also took a long time to obtain core.
- —Submitted on November 08, 2000 at 21:41 UTC
- No one technique works in all environments. A combination of techniques must be applied before it can be determined what works best.
- —Submitted on November 09, 2000 at 15:34 UTC
- Many of the surficial geophysical techniques have proved ineffective due to cultural interference problems--in particular, buried steel junk and overhead power lines. Vendors have greatly oversold their abilities to overcome these problems.
I have also attempted borehole televiewer and acoustic televiewer inspections at MGP sites, but have had to back off because of decontamination issues. MGP tars are extremely difficult to remove, and the tools are expensive.
In 15 years in the industry, both as a consultant and regulator, I have yet to see a fracture trace analysis that incorporated enough geologic reasoning to be worthwhile. Virtually all have been "find some lines and circles" exercises in which the analyst made no attempt to determine what the origin of each feature might be. Properly done, this can be a valuable and cost-effective tool for understanding the subsurface. It isn't properly done very often.
- —Submitted on November 10, 2000 at 19:42 UTC
- The electromagnetic survey had to be completed in the open fields adjacent to our site to get away from the piping, fences, underground services, storage tanks and buildings that cause interference.
Coring without downhole logs was interesting for runs of less than 100% recovery because we were never sure what zone was responsible for the lack of core recovery.
After drilling, it has been a challenge to decide when the water levels and water samples were representative of the local aquifer and not an artifact from the drilling process (due to drilling water losses).
- —Submitted on November 12, 2000 at 20:20 UTC
- Effectiveness of seismic was hindered by resolution, due to limited velocity contrast at the scale of the problem. Packer injection tests are generally OK, but they impact subsequent water-quality testing. Long-term pump tests are difficult logistically, especially on the water management end, and can be resource-intensive, but generally are worth the effort. Flow modeling has been useful, despite some difficulty assigning recharge values at highly industrialized sites, where lots of infiltrating and exfiltrating utilities are present.
- —Submitted on November 13, 2000 at 16:21 UTC
- The primary difficulties of coring are overall cost and longer time periods for drilling. The primary difficulty for conducting temperature analysis is equipment availability.
- —Submitted on November 13, 2000 at 19:19 UTC
- Sometimes the geology doesn't lend itself to the application, or cultural influences cause unacceptable levels of interference.
- —Submitted on November 14, 2000 at 5:45 UTC
- Geophysical tools are often limited by interference.
- —Submitted on November 14, 2000 at 16:19 UTC
- Reports took too long to generate. Problems: fences and utilities. Data interpretation: geophysicists typically want to see a geologic interpretation of the subsurface before providing their own assessment of the subsurface.
- —Submitted on November 15, 2000 at 18:32 UTC
- Site access; GPR has problems with overburden which distorts readings and results.
- —Submitted on November 27, 2000 at 20:35 UTC
- Equipment and software problems. Vendors shipped equipment that did not work, software with viruses, or software that did not work.
- —Submitted on December 06, 2000 at 16:05 UTC
- Agency approval for tracers.
- —Submitted on December 06, 2000 at 19:30 UTC
- (1) Contractor performing work not qualified to do work and misinterpretation of data occurs or data not collected properly. (2) Reluctance to use downhole geophysical equipment at creosote/coal tar sites. (3) Subject to individual's expertise in interpreting the data.
- —Submitted on December 06, 2000 at 20:00 UTC
- Limitations to their use were primarily cost-, availability-, or time-related.
- —Submitted on December 06, 2000 at 20:59 UTC
- Cost of providing access (i.e.: boreholes) for application of in situ technologies.
- —Submitted on December 06, 2000 at 21:09 UTC
- Test equipment is geared toward large intervals. Equipment suppliers. are few and are not providing reliable equipment.
- —Submitted on December 06, 2000 at 21:20 UTC
- All of the technologies had problems that limited their use. Listing them to get adequate resolution with geophysical technique leakage of packers when doing vertical head profiling, etc.
- —Submitted on December 06, 2000 at 21:35 UTC
- The fundamental problem that the geophysical technologies have not solved, and aren't designed to solve, is the problem of having to extrapolate over great distances at a typical commercial site (not a research site). Still stuck with making significant simplifications and assumptions (e.g.., equivalent transmissivity method unable to define interconnectivity, continuity of specific features) in order to construct numerical model in rock. Typical 10-acre site might afford 6-10 deep holes will full-suite logging ($300-$500k) if you're lucky. ultimately, you're still talking a guess at predicting receptors, and concentrations.
- —Submitted on December 08, 2000 at 15:05 UTC
- EM conductivity surveys
Surface GPR Surveys * need finer resolutions for all
Surface Seismic surveys these methods
Borehole geographics- well log quality and repeatability.
"Training vendors" for QA/QC on well quality.
Big problem (See comment #2).
- —Submitted on December 08, 2000 at 15:40 UTC
- Trying to definitely connect to data points to get bigger picture.
- —Submitted on December 08, 2000 at 15:51 UTC
- - 10 cm packing is very expensive.
- —Submitted on December 08, 2000 at 15:56 UTC
- Site access! It's not a technical, but an administrative issue (see A4*)
- —Submitted on December 08, 2000 at 16:19 UTC
- Poor survey design. Use of seismics under the wrong conditions leads to failure. Coring is expensive, usually with little data used. Scale and resolution of fracture trace not good enough for well placement. Modeling very difficult and inaccurate.
- —Submitted on December 08, 2000 at 17:20 UTC
- As above, technical problems most often relate to lack of data points, and the occasional low level of confidence in interpolation of parameters between these points. This is a recognized problem with porous unconsolidated. materials, which is exaggerated with fractured work.
- —Submitted on December 08, 2000 at 18:05 UTC
- - Surface soils/rocks may prevent surface geophysics and/or outcrop test and/or fracture trace analysis.
- Low permeabilities may prevent and/or limit hydraulic testing and/or measuring hydraulic heads prior to installation of monitoring wells.
- What to do with contaminated water during some times of hydraulic testing.
- —Submitted on December 08, 2000 at 18:16 UTC
- Tracer study---borehole dilution problems, now doing borehole dilution.
modeling- using modflow (EPM) on fractured rock.
- —Submitted on December 08, 2000 at 18:26 UTC
- Packers tend to be cumbersome and slow to deploy and recover.
- —Submitted on December 08, 2000 at 18:31 UTC
- - Expertise in data integration is limited in the consultant community.
- Expertise in geophysical methods is extremely limited in the consultant community.
- —Submitted on December 08, 2000 at 18:39 UTC
|
| 4. What factors about site conditions or the technology were most important in making decisions to use it? |
- cost and familiarity to the project officer, then speed of acquisition.
- —Submitted on November 08, 2000 at 21:41 UTC
- Rock properties, particularly rock electrical properties and degree of fracturing.
- —Submitted on November 09, 2000 at 15:34 UTC
- Cultural interference issues are foremost---most of my sites are in heavily urbanized areas with lots of interference sources. My experience with geophysical contractors makes me very reluctant to accept assurances about their capabilities.
Another serious problem is my limited understanding of geophysics. I come from a background as a geochemist and as an exploration geologist (both in petroleum and metals exploration). As such, I am comfortable with my understanding of geologic and geochemical techniques, but not at all confident that I can critically review reports from geophysical contractors. Nobody else at my agency is well versed in this field either, so this is a serious limitation on the use of geophysics.
- —Submitted on November 10, 2000 at 19:42 UTC
- Coring, packer testing, and head measurements provide valuable information during the investigation phase and are routinely available and cost effective. Pump testing and flow modeling provide an important means of "up-scaling" and extrapolating from borehole-scale information provided by the other technologies. Since hydraulic containment is a common remedial objective, pump testing provides critical information at a relevant scale.
- —Submitted on November 13, 2000 at 16:21 UTC
- Containment and degree of fractured environment. In fractured rock environments that are covered by saturated overburden, the temperature/depth evaluation was critical in establishing the primary containment flow pathways. Additionally, in an environment that contain stacked zones of fractured and un-fractured rock, with lenses of cemented sandstone, coring was an important aspect to installation of both remediation and monitoring wells.
- —Submitted on November 13, 2000 at 19:19 UTC
- The need for geologic characterization of the site is the most elemental, and happens to be one of the least expensive tasks to perform properly. Which brings up cost: Cost, without a doubt, is the most important factor in the free market where a consultant must survive. Specifically, drilling costs and specialized geophysical or hydraulic testing seem to drive the cost up because of the field time in addition to the subsequent analysis time required to interpret the data. Thus, we rely heavily on using good geologic mapping techniques including field mapping and fracture trace analysis to optimize our drilling and subsequent testing programs.
- —Submitted on November 14, 2000 at 5:45 UTC
- 1. Bedrock topography.
2. fracture/water bearing intervals in the rock.
3. Availability and cost of technology.
- —Submitted on November 15, 2000 at 18:32 UTC
- Geology (basalt), thickness of fractured aquifer (<15m from ground surface), depth of groundwater (3-4 m below ground level), price and combined use of boreholes for site characterization and plume and contaminants delineation and monitoring.
- —Submitted on November 27, 2000 at 20:35 UTC
- Rock type- Different borehole logs are more/less useful depending upon the geology.
- —Submitted on December 06, 2000 at 16:05 UTC
- Cost.
- —Submitted on December 06, 2000 at 19:30 UTC
- Ability to use USGS expertise to do the work.
- —Submitted on December 06, 2000 at 20:00 UTC
- Cost/benefit (compare to other approaches); availability; access; evaluation Methods/Confidence (i.e., results/interpretations).
- —Submitted on December 06, 2000 at 20:59 UTC
- Distribution and availability of data gathering locations (for in situ work) such as boreholes.
- —Submitted on December 06, 2000 at 21:09 UTC
- Knew that plume orientation was dictated by vertical or near vertical joint systems.
- —Submitted on December 06, 2000 at 21:20 UTC
- Cost. Most of us work in a highly competitive commercial environment. While many of our customers understand the advantage of detailed characterization, we can't win jobs proposing sampling techniques that take 12-hours per well, as I just heard in the flute talk.
- —Submitted on December 08, 2000 at 15:05 UTC
- Factors regarding the usefulness of the overall site concept model and drilling operation/characterization are important. If the technique allows the project manager to optimize the program, then the technology would be cost-effective to use, and allow the risk-to-reward ratio to favor the technology use.
- —Submitted on December 08, 2000 at 15:40 UTC
- Trying to determine more, location and migration of contaminants (mostly VOCs).
- —Submitted on December 08, 2000 at 15:51 UTC
- Fracture distribution, predictability. Depth, expanse of the plume!
* Also, administrative aspects of inside-the-peace DOE work.
Dynamic between regulator (DEQ, EPA), DOE, and contractor impedes research/applications.
- —Submitted on December 08, 2000 at 16:19 UTC
- Rock type, structural geology, known containment distribution, time and cost constraints.
- —Submitted on December 08, 2000 at 17:20 UTC
- At most fractured bedrock sites, technology applications decisions are made much easier if it's highly fractured, or can be pneumatically fractured to the point where the media behaves more like unconsolidated material and the predictability of fluid flow approaches Darcy's Law.
- —Submitted on December 08, 2000 at 18:05 UTC
- Interference of underground and aboveground utilities limited open space in mixed industrial/residential areas.
- —Submitted on December 08, 2000 at 18:26 UTC
- The technologies were available at these sites and also served the intended purpose.
- —Submitted on December 08, 2000 at 18:31 UTC
|
| 5. In retrospect, were your sites characterized sufficiently for the application of a remediation technology and for assessing failure or success? |
- There's always a feeling that more data is needed. If we can find major fractures or water entry zones, then we usually quit, owing to time constraints.
- —Submitted on November 08, 2000 at 21:41 UTC
- Generally yes; however, at times the "client" is unwilling or unable to spend what is needed to complete the characterization in an ideal fashion.
- —Submitted on November 09, 2000 at 15:34 UTC
- Almost never, for either criterion. Nobody wants to do the homework necessary before hand.
Once the remedial system is in place, NOBODY wants to collect data on its effectiveness. The results might be too scary.
- —Submitted on November 10, 2000 at 19:42 UTC
- Yes. Hydraulic containment has been one of our primary remedial objectives and it is usually achievable.
- —Submitted on November 13, 2000 at 16:21 UTC
- Primarily no, the initial characterization typically was not sufficient to complete the design of an effective remediation system. Either wells were not properly installed or logged in sufficient detail to evaluate characterization of contaminant flow.
- —Submitted on November 13, 2000 at 19:19 UTC
- One of the problems we have is that we have difficulty linking the source originating near the surface with the entry zone into fractured bedrock. Normally, the bedrock surface is obscured by overburden, limiting direct to drill holes. Hydraulic containment is beneficial in most cases, as some of the details of entry become moot as risk is managed, but the long-term situation of cleanup still is outstanding.
I think we have an important opportunity to advance the bedrock mapping effort, which was initiated by the USGS prior to the 1980s. This is especially true in New England where the bedrock outcrops, borings, and fracture trace indicators are very powerful and economical means to assist in the development of conceptual models.
- —Submitted on November 14, 2000 at 5:45 UTC
- They were characterized sufficiently to implement remedies that address highly contaminated source areas and to set up capture zones for broad areas. They have not characterized sites well enough to allow smaller more focused remedies more closely focused on the path that contaminated groundwater is actually following.
- —Submitted on November 14, 2000 at 16:19 UTC
- 1. Retrospectives are too seldom done.
2. Once a screened interval is completed, it is difficult to tell whether another interval would have been better.
- —Submitted on November 15, 2000 at 18:32 UTC
- Site investigation still ongoing, so not enough done yet, but tendency is to go for MNA or MENA.
- —Submitted on November 27, 2000 at 20:35 UTC
- Yes.
- —Submitted on December 06, 2000 at 16:05 UTC
- In most cases. Agencies required so much data that more than enough was available.
- —Submitted on December 06, 2000 at 19:30 UTC
- No. Clearly in the last decade the use of downhole geophysics has been much more prevalent and has greatly imparted better site characterization. Fractured rock has been traditionally approached in the same manner as unconsolidated material, and it has only been in the last 5-8 years that the above techniques were being used. So it has been hard to go back and do the proper site characterization to modify/move the remediation. Agencies and PRPs have been reluctant to spend the money.
- —Submitted on December 06, 2000 at 20:00 UTC
- Generally yes.
- —Submitted on December 06, 2000 at 20:59 UTC
- Rarely.
- —Submitted on December 06, 2000 at 21:09 UTC
- Yes.
- —Submitted on December 06, 2000 at 21:20 UTC
- Are they ever? For us consultants, we walk a fine line. Practically speaking, our job is to tell the most compelling story possible with the least amount of data our credibility often hinges upon the relationship we establish with the regulators.
- —Submitted on December 08, 2000 at 15:05 UTC
- Yes.
- —Submitted on December 08, 2000 at 15:40 UTC
- Jury still out on this one.
- —Submitted on December 08, 2000 at 15:51 UTC
- Yes, where plume is concentrated (near injection well, control wells); no, where plume is diffuse, extended.
- —Submitted on December 08, 2000 at 16:19 UTC
- Yes. Site characterization can always be made better. The question is what is sufficient to make a good *decision (*not perfect). Cost (time and money).
- —Submitted on December 08, 2000 at 17:20 UTC
- Marginally, due to numerous questions that are regarding contaminant distribution, conceptual model, and hydrogeological conceptual model.
- —Submitted on December 08, 2000 at 18:05 UTC
- No---a lot of unknowns still exist.
- —Submitted on December 08, 2000 at 18:26 UTC
- Probably not, but remediation was not the goal.
- —Submitted on December 08, 2000 at 18:31 UTC
|
| B. Remediation |
| 1. What technologies have you used for remedial trials, pilot tests or larger scale remediation efforts? |
| Technology |
Percent Responding 'Yes' |
|---|
|
| fracturing |
42% |
| in-situ oxidation |
19% |
| removal by pumping |
58% |
| vacuum vapor extraction |
32% |
| bioremediation |
29% |
| flushing technologies, and/or inject-extraction |
13% |
| thermal |
0% |
| other |
10% |
- MNA
- high vacuum multiphase extraction
- plume mgmt. with pumping.
|
| 2. What was the outcome of the use, i.e. did it meet your expectations? |
- fracturing did increase the porosity (and permeability) as expected, but only in a small area. Pumping was slow but did keep the source contaminants on site.
- —Submitted on November 08, 2000 at 21:41 UTC
- Fracturing is 1 for 2 on my projects: one limited success (TCE in rock), limited by the fact that the consultant underestimated how far down the NAPL plume had sunk. One total failure, in a massive sandstone. Haven't figured out yet what happened there.
- —Submitted on November 10, 2000 at 19:42 UTC
- Fracturing using controlled blasting has been very effective in insuring hydraulic connection for hydraulic containment. Hydrofracturing has also been effective. Vapor extraction has been limited by high water table.
- —Submitted on November 13, 2000 at 16:21 UTC
- The fracturing, to this point, has yielded a significant amount of greater injection flow of nutrients then expected. Removal by pumping has yielded similar results as typical groundwater extraction and treatment systems. Vapor extraction has yielded marginal results.
- —Submitted on November 13, 2000 at 19:19 UTC
- Geological conceptual models were known to be inadequate in some cases, but regulatory agencies and abutters often force an active measure before more cost-effective solutions are agreed upon.
- —Submitted on November 14, 2000 at 5:45 UTC
- 1. We do not optimize/do a retrospective analysis that is meaningful.
- —Submitted on November 15, 2000 at 18:32 UTC
- Vacuum-yes
Fracturing-yes
Pumping for containment-yes
In-situ oxidation - ongoing
Pumping for removal - no
- —Submitted on December 06, 2000 at 19:30 UTC
- Does do a good job of plume control.
- —Submitted on December 06, 2000 at 20:00 UTC
- Sometimes yes, sometimes no.
- —Submitted on December 06, 2000 at 20:59 UTC
- Results were always positive. Expectations are a function of time and money!
- —Submitted on December 06, 2000 at 21:09 UTC
- Yes, until we understood the effects of matrix diffusion.
- —Submitted on December 06, 2000 at 21:20 UTC
- Pump-and-treat plus vapor extraction are successful at most sites where permeability or hydraulic conductivity are sufficient to allow for mass removal. Source areas- with low conductivity/permeability are still a problem.
- —Submitted on December 08, 2000 at 15:40 UTC
- Bioslurping is limited, probably due to limited LNAPC and the connectivity of fractures.
- —Submitted on December 08, 2000 at 15:51 UTC
- Reference Sorenson's work at Idaho Nat'l Engineering and Environment Labs Test area North hotspot. (Addition to accelerate reductive dechlorination).
- —Submitted on December 08, 2000 at 16:19 UTC
- 1. Pump-and-treat remediation speed dependant on geology. Very effective at controlling hydraulics.
2. Will be testing oxidation and bioremediation in near future.
- —Submitted on December 08, 2000 at 17:20 UTC
- Data met expectations or exceeded them, but too many questions reminded regarding scale-up and overall effectiveness over long term.
- —Submitted on December 08, 2000 at 18:05 UTC
- Still trying to get an inward gradient.
- —Submitted on December 08, 2000 at 18:26 UTC
|
| 3. What technical problems limited their use? |
- Disposal of contaminated groundwater; bioremediation vendors were sometimes not very reputable or experienced.
- —Submitted on November 08, 2000 at 21:41 UTC
- Fracturing by blasting has obvious practical and public acceptance problems in settled areas.
- —Submitted on November 10, 2000 at 19:42 UTC
- Vapor extraction has not much value in saturated conditions. It also is burdened with administrative issues (air permits etc.) that can delay implementation until it is a bit late. Controlled blasting raises vibration-energy concerns (residents, manufacturing equipment), but they can be addressed by good monitoring and test blasting. Hydrofracturing is limited by an inability to predict how the fracturing will propagate, especially at shallow depths.
- —Submitted on November 13, 2000 at 16:21 UTC
- Chemical oxidation was limited by sites with significant amount of matrix diffusion. The life of the oxidant was not sufficient to match the limitations of diffusion in a low permeability matrix. Therefore, bioremediation enhancement was selected.
- —Submitted on November 13, 2000 at 19:19 UTC
- The site characterization did not adequately delineate the extent of the plume, partially due to the presence of surface water resources that limited access to drilling and sampling sites. I think horizontal drilling or inclined drilling would be beneficial in this case, but was not available at the time of this particular project.
- —Submitted on November 14, 2000 at 5:45 UTC
- Assuming "we" made a reasonable pick of the technology, the issue became convincing others (in house staff AND the people on the outside with whom we negotiated) that we should use the technology.
- —Submitted on November 15, 2000 at 18:32 UTC
- Access for long-term pumping wells and piping on privately owned off-site properties could not be obtained.
- —Submitted on December 06, 2000 at 20:00 UTC
- Access to portions of impacted aquifer Hydrogen conditions.
- —Submitted on December 06, 2000 at 20:59 UTC
- Gathering verifications data.
- —Submitted on December 06, 2000 at 21:09 UTC
- Matrix diffusion is now limiting recovery.
- —Submitted on December 06, 2000 at 21:20 UTC
- Low-conductivity sediments and lack of connectivity limits source/mass removal.
- —Submitted on December 08, 2000 at 15:40 UTC
- Connectivity of fractures => Contact!!
- —Submitted on December 08, 2000 at 15:51 UTC
- 1. Accessibility of best well location.
2. Inexperience in calculating volume injection rates of oxidants and ORC/HRC.
- —Submitted on December 08, 2000 at 17:20 UTC
- Insufficient geologic data, hydrologic data, lack of inexpensive methods for monitoring & characterization.
- —Submitted on December 08, 2000 at 18:05 UTC
- Spatial influence of pumping, correct placement of wells. # of wells needed ($).
- —Submitted on December 08, 2000 at 18:26 UTC
|
| 4. What factors about the site conditions or the technology were most important in making the decision to use it? |
- LNAPL or DNAPL; Superfund site or corner gas station; time available; familiarity of the project manager with the technology.
- —Submitted on November 08, 2000 at 21:41 UTC
- The fracturing technologies ensure a robust containment system at a scale relevant to the problem. Up-front cost is somewhat higher than conventional well systems, but it is more of a sure thing, so reducing the uncertainty is often attractive to responsible parties. Operations and maintenance (O&M) costs are also generally lower, so in the long-term they may be cheaper, in addition to being effective and relatively reliable.
- —Submitted on November 13, 2000 at 16:21 UTC
- Matrix diffusion, quality of fracture flow understanding, and contaminant type.
- —Submitted on November 13, 2000 at 19:19 UTC
- At one site, high-yield bedrock fractures seemed to be responsible for movement of dissolved chlorinated up-gradient toward a gravel pack municipal well. The link between overburden and bedrock was not sufficiently understood to implement a hydraulic containment source in overburden near the release area and along property boundaries. The importance of bedrock fractures allowing both lateral and upward movement induced by a high yield overburden well was not appreciated. Geology often seems to be undervalued in these remedial assessments, yet controls the design basis for the project. This fact should be given important consideration within your program.
- —Submitted on November 14, 2000 at 5:45 UTC
- Cost
++++COMMENT: Presenters in Providence and Toronto will need to present data on cost of the technologies; retrospective analyses with data; and data on measured matrix diffusion in the field.
- —Submitted on November 15, 2000 at 18:32 UTC
- Cost.
- —Submitted on December 06, 2000 at 19:30 UTC
- The surroundings areas utilize groundwater as the water supply, and it was paramount to control the plume(s) from continued migration.
- —Submitted on December 06, 2000 at 20:00 UTC
- Hydrogeologic setting; contaminant characteristics; remedial goals.
- —Submitted on December 06, 2000 at 20:59 UTC
- 1. Application & treatment costs.
2. Project time frame
3. Target treatment concentrations
- —Submitted on December 06, 2000 at 21:09 UTC
- Pump-and-treat (P&T) is needed to prevent further mass transport of containment
- site conditions- tight, low-k zones are difficult to P&T
- Attempting to use "blast fracturing" with explosives to create fractures to enhance flow rates in P&T wells.
- —Submitted on December 08, 2000 at 15:40 UTC
- Compatibility with contaminants
- —Submitted on December 08, 2000 at 15:51 UTC
- 1 A key factor is the relative depth of the site: ~210 ft. to groundwater. 2 the lack of success when using pump-and-treat.
- —Submitted on December 08, 2000 at 16:19 UTC
- Hydraulic control by pumping to limit uncertainties of fracture network. Need good well data; drill logs, geographics, pump tests.
- —Submitted on December 08, 2000 at 17:20 UTC
- Type of Bedrock: Needs to be reasonably well fractured to begin with (this prerequisite is often a contributing factor to the contamination. problem). size of plume; small source areas possible. Large diffuse plumes---contain them rather than attempt to remediiate. Adsorption and trapped contamination in dead-end or inaccessible fractures---a source area can be aggressively remediated, concentrations reduced by 10 times, but slow bleeding of trapped residuals often makes achieving MCLs impossible. Not a technical problem specific to fractured. media, but harder to address in fractured. Media.
- —Submitted on December 08, 2000 at 18:05 UTC
- Need to capture the plume so that it doesn't reach receptor --- an international water body.
- —Submitted on December 08, 2000 at 18:26 UTC
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| C. Summary |
| 1. Of these barriers towards the use of innovative technologies to remediate contaminated ground water in fractured bedrock, please rank them as (1) very significant, (2) significant, (3) minor significance, or (4) not significant: |
| Barrier |
Average Response Value |
|---|
|
| regulator acceptance |
2
|
| client acceptance |
2
|
| high costs of application |
2
|
| unknown costs |
2
|
| lack of adequate performance information |
2
|
| limited vendors |
2
|
| flow paths and/or plume not characterized well enough |
2
|
| flow paths and/or plume not characterized well enough |
2
|
- lack of contingency plans
- see comment above
- Issue mentioned in A4 is the largest factor for us.
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