HANDBOOK OF COMPLEX ENVIRONMENTAL REMEDIATION PROBLEMS

Source: HANDBOOK OF COMPLEX ENVIRONMENTAL REMEDIATION PROBLEMS CHAPTER GROUNDWATER Kevin John Phillips* FPM Group, Ltd 1.1 INTRODUCTION “A yawn is a silent shout.” GILBERT KEITH CHESTERTON, 1874–1936 1.1.1 Why Is Groundwater Contamination So Important? Demand for groundwater as a resource has been increasing as population growth continues to build and opportunities to develop surface water supplies continue to diminish Groundwater accounts for approximately two-thirds of all the freshwater resources of the world (Nace, 1971) If we subtract out the ice caps and glaciers, it accounts for over 99 percent of all the freshwater available to the planet (Nace, 1971) Clearly, with 99 percent of the available resources, it behooves environmental professionals to try and protect it and, should it become polluted, to treat it However, one aspect of its nature is its long residence time While typical turnover times in river systems average around two weeks, groundwater systems move much slower Indeed, groundwater in certain zones of the Lloyd Aquifer in Long Island, N.Y., has been around since the birth of Christ Hence, in the past, the general viewpoint held by many groundwater professionals and policy makers was that once an aquifer had been polluted, its water usage must be curtailed or possibly eliminated because of the difficulty and time in cleaning up that aquifer.This viewpoint is changing, however, as a result of new methodologies for aquifer cleanup However, as we enter a new century, aquifer cleanup is still a very difficult and a costly endeavor that takes a significant amount of time, often yields less than desirable results, and frequently relies more on risk assessments rather than groundwater standards for cleanup levels simply because it is not yet practical * Dedicated to Sue, Al, and Chris 1.1 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.2 CHAPTER ONE 1.1.2 What Are the Sources of Pollution of Groundwater? Pollution of groundwater can result from many activities, including leaching from municipal and chemical landfills, abandoned dumpsites, accidental spills of chemical or waste materials, improper underground injection of liquid wastes, surface impoundments, placement of septic tank systems in hydrological and geological unsuitable locations, and improper chemical application of fertilizers and pesticides for agricultural and domestic vegetative processes The pollution from solid waste left on the ground surface needs to first be solubilized before it causes a problem Rain or melting snow will solubilize some of the waste that has been disposed of on the land and then carry that dissolved constituent down through the unsaturated zone into the saturated groundwater Some wastes in liquid form are only slightly soluble in water This class of compounds are called nonaqueous-phase liquids (NAPLs) and pose a significant threat to the groundwater system Such waste becomes trapped in the pore spaces of the aquifer and remains there in groundwater, slowly dissolving and yielding a continuous source of pollution There are two kinds of NAPLs—dense NAPLs (DNAPLs) and light NAPLs (LNAPLs) DNAPLs are compounds whose density exceeds that of water (e.g., chlorinated solvents), and LNAPLs are compounds whose density is less than that of water (e.g., oils and petroleum products) 1.1.3 What Is the Hydrology of Contamination? Precipitation is the driving force that moves the groundwater system The groundwater system moves slowly compared to surface water Groundwater velocity is generally in the order of foot per day to foot per year throughout the United States, depending on the hydraulic conductivity and the gradient of the groundwater system Groundwater movement is generated from precipitation that mounds up the freshwater resources in an aquifer, which begins to move toward a sink, usually a creek, river, or other surface body of water These surface water bodies are lower in their energy state (elevation head), and hence the groundwater system flows from a higher energy head to that of a lower energy head and is frequently plotted and shown as water table contours or potentiometric surface maps These water table contours or potentiometric surface maps show the energy level of the aquifer and in general determine the gradient by which the groundwater is moving Flow lines are almost always drawn perpendicular to groundwater contours even though this only occurs in an isotropic homogeneous porous media (something the author has never seen) 1.1.4 What Aspects of Geochemistry Are Important in Understanding Groundwater Pollution? As mentioned earlier, precipitation is a major factor in groundwater systems Not only does it drive the groundwater system flow, but it also dissolves the contaminants that have been left on the surface of land, buried beneath land, or locked into the pore spaces Hence, the solubility of these wastes becomes a significant factor in groundwater contamination For example, road salt has almost unlimited solubility in water Once a contaminant has solubilized, it will move downward by gravity in the unsaturated zone, enter the saturated zone, and move with the groundwater However, certain contaminants absorb to and desorb from the organic material in the aquifer.This phenomenon, described as retardation, slows down the contaminant Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER GROUNDWATER 1.3 transport but does not affect the molecules themselves Indeed, retardation coefficients of 10 to 20 have been documented for some waste Some of the inorganic compounds such as nitrates and chlorides show almost no retardation at all, moving with the speed of the groundwater Additional significant factors in contaminant transport include biodegradation and biotransformation; many compounds undergo biodegradation both aerobically and anaerobically This process can account for significant amounts of destruction of toxic molecules Indeed, biodegradation as recently as 10 years ago was considered as only a natural process, but today, biodegradation has been marketed by hundreds of companies for specific and nonspecific compounds where bacteria, fungi, and other micro-organisms have been grown to break down certain contaminants Chemical reactions occur in aquifers continually Chemical transformations, including oxidation and reduction, can be major routes for destruction and transformation of contaminants as they pass through the aquifer 1.1.5 What Are the Effects of These Compounds on Human Health and the Environment? The effects these contaminants have on human health and the environment are clearly demonstrated by the amount of concern that has been shown by the United States Congress since the 1970s when the first water pollution control act was passed The threat from groundwater is one that is very real because 35 percent of the United States water supply comes from the ground Outside the major cities, 95 percent of the water supply comes from the ground (Driscoll, 1983) Documentary movies and books, such as A Civil Action, have clearly demonstrated the effect of these chemicals, some of which are both toxic and carcinogenic and directly affect the human population 1.1.6 What Are the Chemicals That Have the Greatest Impact on Groundwater Quality? One of the first overview studies of aquifer cleanup that took place was written in 1977 by Lindorff and Cartwright (1977) when they surveyed the nation for case histories of aquifer cleanup At that time, 116 cases of aquifer pollution were summarized, with most of the pollution caused by industrial waste or leaching from municipal landfills In 1977, the most common groundwater pollutional sources were gasoline, cyanide, acrylonitrile, acetone, hydrochloric acid, solvents, acids, heavy metals, chlorides, aluminum, fuel oils, insecticides, organic wastes, sulfite liquors, petrochemicals, zinc, lead, and cadmium Since 1977, when Lindorff and Cartwright did their survey, the most important new parameters to be recognized as a significant threat to our groundwater quality have been the chlorinated hydrocarbons These contaminants have very low solubilities but very high toxicities and carcinogentic potential In addition, they are denser then water and have been labeled as dense nonaqueous-phase liquids (DNAPLs) Their particular problematic attributes are that, even though they are very slow to dissolve and have low solubility, they are considered carcinogenic at extremely low concentrations and are denser than water, and hence sink through the saturated media, contaminating the deeper portion of the aquifer These compounds are typically not readily biodegradable, and if they biodegrade, it is a slow process These DNAPLs are nonwetting with respect to water and get trapped in the porous media Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.4 CHAPTER ONE for long periods of time slowly dissolving into the aquifer, causing significant groundwater contamination for very long periods of time The other low-solubility contaminants that frequently show up are the petroleum hydrocarbons commonly called light nonaqueous-phase liquids (LNAPLs) These LNAPLs also have low-solubility characteristics and can exist in the subsurface environment as pure-phase liquids However, they are lighter than water and will not sink through the aquifer but remain on the surface of the water table In addition, another difference between the DNAPLs and the LNAPLs is that the LNAPLs in general are readily biodegrable, while the DNAPLs have slower rates of biodegradability 1.1.7 Summary As the cleanup of groundwater and groundwater remediation systems is extremely complicated, I have attempted to simplify it by using solubility as a organizer of the text in this section and throughout the chapter Section 1.2, “Investigative Methods,” will report on investigative measures in three areas: (1) the aqueous groundwater contaminants that are dissolved and move in the groundwater, (2) DNAPLs, and (3) LNAPLs Section 1.3 deals with remediation methods, and again the section will be organized by: (1) the aqueous groundwater remediation methods that focus on either the in situ treatment or the removal and treatment of the groundwater, (2) DNAPLs, (3) LNAPLs Section 1.3 will also compare treatment methodologies and include cost estimates for groundwater, DNAPLs, and LNAPLs cleanup Section 1.4 will consist of case histories of aquifer restorations 1.2 INVESTIGATIVE METHODS “Every truth passes through three stages before it is recognized In the first, it is ridiculed, in the second it is opposed, in the third it is regarded as A SCHOPENHAUER, 1788–1860 self-evident.” 1.2.1 Introduction This section will be dealing with investigative methods for aqueous groundwater, DNAPLs and LNAPLs The aqueous groundwater portion will first discuss the investigative methods for the kinds of chemicals that are frequently targeted at contamination sites The three major lists of compounds that are frequently investigated come from the three major pieces of legislation for the cleanup of water: the priority pollutant list (Clean Water Act), the target compound list (Comprehensive Environmental Response, Compensation, and Liability Act—CERCLA), and the SW-846 analyte list (Resource Conservation and Recovery Act—RCRA) The list most often used for screening groundwater at contaminated sites is the Target Compound List and the Target Analyte List, TCL and TAL, respectively, will be discussed in Sec 1.2.2 Section 1.2.3, covering the DNAPLs investigative methods, will focus on the pure-phase DNAPLs Finally, Sec 1.2.4 will discuss investigative methods for LNAPLs Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER GROUNDWATER 1.5 1.2.2 Aqueous Groundwater Prior to discussing investigative methods for groundwater, we first must define what kinds of compounds we are going to investigate Table 1.1 shows the Target Compounds List (TCL/TAL), the priority pollutants, and SW-846 compounds The most widely used list of investigative compounds today is the U.S EPA TCL and TAL.The first list of compounds was the EPA Priority Pollutant List, which was established in 1974 and was the first comprehensive list of compounds identifying the most frequently used compounds in industry as well as the ones we had laboratory methods to test for Since then, great accomplishments have been made in laboratory analysis, expanding this list In addition, compounds that were toxic and persistent were included Today the Target Compound List is usually the measure by which contaminated sites are characterized The TCL is broken up into several chemical categories The first category is the volatile organic chemicals (VOCs), which have a vapor pressure greater than mmHg These chemicals are almost all organically based and present a class of compounds that can easily volatize in the environment.The number of compounds included in this category is 34 The second group of compounds in the TCL is the semivolatiles made up of the base neutral and acid-extractable compounds The base neutral compounds are so called because of the way they are extracted and analyzed in the laboratory There are 49 of the base neutral compounds given in the TCL The acid-extractable compounds are so called because of the laboratory method of extraction They are all organic There are 15 acid-extractable compounds in the TCL The next groups of compounds are the pesticides and PCBs, and they comprise a total of 29 compounds in the TCL The final group are elements and are inorganic This group has 23 metals associated with them The analyses of these compounds and elements are shown in Table 1.2 along with the recommended containers, preservation, holding time, and analytical methodology The More Important Chemicals The more important chemicals are those that show up more frequently in the groundwater and are more toxic, thereby causing more problems for cleanup The most frequently detected compounds in groundwater at the waste disposal sites in Germany and in the United States have been reported by Keeley (1999) Chlorinated hydrocarbons dominate the list of frequently detected compounds at these waste sites (Fig 1.1) All of the top-ranked contaminants in the United States are chlorinated hydrocarbons In the dissolved phase, most of these contaminants have drinking water standards in the low parts per billion range In the pure phase they all would be classified as DNAPLs Though EPA requires preliminary screening using the TCL and TAL, clearly some compounds are of more concern Presently, the most important compounds are the chlorinated hydrocarbons in the pure phase (DNAPL) and in the dissolved phase They can be carcinogenic at a very low level, they pose significant additional problems because of their ability to sink through the aquifer as a pure DNAPL, they are of low solubility so water cannot easily flush out the problem, their retardation is usually high so their movement is slow, and the compounds are usually resistant to biodegradation so their natural attenuation is low Monitoring Strategies Prior to discussing monitoring strategies, a brief discussion of well drilling methods is needed Table 1.3 is an adaptation of Cohen and Mercer’s Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.6 CHAPTER ONE TABLE 1.1 Comparison of Chemicals on Three Regulatory Lists Compounds TCL* PPL† SW-846‡ Volatiles and semivolatiles Acenaphthene x x x Acenaphthylene x x x Acetone x x Acrolein x Acrylonitrile x x x Anthracene x x x Benzo (a) anthracene x x x Benzo (a) pyrene x x x Benzene x x x x x 10 Benzidine 11 Benzo (b) flouranthene x x x 12 Benzo (ghi) perylene x x x 13 Benzo (k) flouranthene x x 14 Benzoic acid x 15 Benzyl alcohol x 16 Bis (2-chloroethoxy) methane x x x 17 Bis (2-chloroethyl) ether x x x x x x 18 Bis (2-chloroisopropyl) ether x x x 19 Bis (2-ethylhexyl) phthalate x x x 20 Bromoform x x x 21 Bromodichloromethane x x x 22 Bromomethane x x x 23 4-Bromophenyl phenyl ether x x 24 2-Butanone x 25 Butyl benzyl phthalate x 26 Carbon disulfide x 27 Carbon tetrachloride x x x x x x x 28 4-Chloro-3-methylphenol (P-chloro-M-cresol) x x 29 4-Chloroaniline x 30 Chlorobenzene x x x 31 Chloroethane x x x 32 Chloromethane x x x 33 Chlorodibromomethane x x x x x x x 34 2-Chloroethyl vinyl ether 35 Chloroform x x x 36 2-Chloronaphthalene x x x 37 2-Chlorophenol x x x 38 4-Chlorophenyl phenyl ether x x x Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.7 GROUNDWATER TABLE 1.1 Comparison of Chemicals on Three Regulatory Lists (Continued) Compounds TCL* PPL† SW-846‡ x x Volatiles and semivolatiles 39 Chrysene x 40 Di-n-butylphthalate x x x 41 Di-n-octylphthalate x x x 42 Dibenz (a,h) anthracene x x 43 Dibenzofuran x 44 1,2-Dichlorobenzene x x x 45 1,3-Dichlorobenzene x x x 46 1,4-Dichlorobenzene x x x 47 3,3-Dichlorobenzidine x x x 48 1,1-Dichloroethane x x x 49 1,2-Dichlorothane x x x 50 1,1-Dichloroethylene x x x 51 1,2-Dichloroethylene (total) x 52 Tran-1,2-dichloroethylene x x x x 53 2,4-Dichlorophenol x x x 54 1,2-Dichloropropane x x x 55 c-1,3-Dichloropropylene x x x 56 t-1,3-Dichloropropylene x x x 57 Diethyl phthalate x x x 58 Dimethyl phthalate x x x 59 2,4-Dimethylphenol x x x 60 4,6-Dinitro-2-methylphenol x x x 61 2,4-Dinitrophenol x x x 62 2,4-Dinitrotoluene x x x 63 2,6-Dinitrotoluene x x x x x 65 Ethylbenzene x x x 66 Flouranthene x x x 67 Flourene x x x 68 Hexachlorobenzene x x x 69 Hexachlorobutadiene x x x 70 Hexachlorocyclopentadiene x x x 71 Hexachloroethane x x x 72 2-Hexanone x 73 Indeno (1,2,3,-cd) pyrene x x x 74 Isophorone x x x 75 Methylene chloride x x x 76 4-Methyl-2-pentanone x 64 1,2-Diphenylhydrazine x x Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.8 CHAPTER ONE TABLE 1.1 Comparison of Chemicals on Three Regulatory Lists (Continued) Compounds TCL* PPL† SW-846‡ Volatiles and semivolatiles 77 2-Methylnaphthalene x 78 2-Methylphenol x 79 4-Methylphenol x 80 N-Nitrosodipropylamine x 81 N-Nitrosodimethylamine x x x x x 82 N-Nitrosodiphenylamine x x x 83 Naphthalene x x x 84 2-Nitroaniline x x 85 3-Nitroaniline x x 86 4-Nitroaniline x 87 Nitrobenzene x x x x 88 2-Nitrophenol x x x 89 4-Nitrophenol x x x 90 Phentachlorophenol x x x 91 Phenanthrene x x x 92 Phenol x x x 93 Pyrene x x x 94 Styrene x 95 1,1,2,2-tetrachlorobenzene x x x 96 Tetrachloroethane x x x 97 Toluene x x x 98 Total xylenes x 99 1,2,4-Trichlorobenzene x x x 100 1,1,1-Trichloroethane x x x 101 1,1,2-Trichloroethane x x x 102 Trichloroethylene x x x 103 2,4,5-Trichlorophenol x 104 2,4,6-Trichlorophenol x x x 105 Vinyl acetate x 106 Vinyl chloride x x x 107 Aldrin x x x 108 Dieldrin x x x x x x x x x x x Pesticides/PCBs 109 Chlordane 110 Alpha-chlordane x 111 Gamma-chlordane x 112 4,4′-DDT x Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.9 GROUNDWATER TABLE 1.1 Comparison of Chemicals on Three Regulatory Lists (Continued) TCL* PPL† SW-846‡ 113 4,4′-DDD x x x 114 4,4′-DDE x 115 Endosulfan I x x x 116 Endosulfan II x x x 117 Endosulfan sulfate x x x 118 Endrin x x x x x 120 Heptachlor x x x 121 Heptachlor epoxide x x x 122 Methoxychlor x 123 Endrin ketone x 124 BHC (alpha) x x x 125 BHC (beta) x x x 126 BHC (gamma) x x x 127 BHC (delta) x x x 128 Toxaphene x x x 129 PCB 1242 x x x 130 PCB 1254 x x x 131 PCB 1221 x x x 132 PCB 1232 x x x 133 PCB 1248 x x x 134 PCB 1260 x x x 135 PCB 1016 x x x 136 2,3,7,8-TCDD x x x Compounds Pesticides/PCBs 119 Endrin aldehyde x x x Metals 137 Aluminum x 138 Antimony x x x 139 Arsenic x x x 140 Barium x 141 Beryllium x x x 142 Cadmium x x x 143 Calcium x 144 Chromium x x x x x 145 Cobalt x 146 Copper x 147 Iron x 148 Lead x x x x x x x x Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website GROUNDWATER 1.10 CHAPTER ONE TABLE 1.1 Comparison of Chemicals on Three Regulatory Lists (Continued) Compounds TCL* PPL† SW-846‡ Metals 149 Magnesium x x 150 Manganese x 151 Mercury x x x 152 Nickel x x x 153 Potassium x 154 Selenium x x x 155 Silver x x x 156 Sodium x 157 Thallium x x x 158 Vanadium x 159 Zinc x x x x x x x * Targeted Compound List (TCL) and Target Analyte List (TAL) from the U.S EPA Contract Laboratory Programs † Priority Pollutant List (PPL) from the Clean Water Act ‡ SW-846 analyte list from the RCRA program work (1993) This table discusses the various methods for drilling and their applications, advantages, and limitations for each of the methods from hand augering through direct push methods As one can see from the table, there are various methods for drilling and installing observation wells, or for taking soil samples Although a myriad of methods exist, the hollow-stem auger is the most often used and preferred method for installing observation wells because of the lack of introduction of any foreign material such as bentonite clay, slurry, or artificial organic gum (Johnson Revert) Hence, many states will only accept hollow-stem augered wells Once the earth has been drilled, a monitoring well then must be set and gravel packed Most states have specifications on installation of monitoring wells in unconsolidated and bedrock formation (see Figs 1.2 and 1.3), double-cased wells, and deep aquifer wells Selection of a screen length, diameter, and elevation for each observation well is a function of the groundwater contamination or plume one desires to identify Once a plume has been identified as a problem by a regulatory agency, establishing its nature and extent is usually mandatory In order to accomplish this, the first thing that has to be identified is the conceptual geological model The geological model must encompass both regional information from sources such as the U.S Geological Survey, university geological reports, and local information from sources such as local borings for construction, water supply borings, or site borings The objective is to develop an understanding of all the geological substrata that may channel the flow patterns below the surface by acting as barriers to or conductors of groundwater flow Once this geological conceptual model is put together it must become a “living” model in that it needs to be updated and changed as frequently as necessary as more and more information becomes available at the site Indeed, some of the monitoring wells that will be installed may have as a secondary objective verifying certain substrata or boundary conditions that the geological model has identified as significant Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ... to the Terms of Use as given at the website GROUNDWATER GROUNDWATER 1.23 because of “background” or other offsite sources, are one of the more elusive quarries of the groundwater professional... never the case, and interpretation of slugs of contamination down the centerline of the plume is of great importance and usually elusive Indeed interpretation of variable source input is almost... samples Although a myriad of methods exist, the hollow-stem auger is the most often used and preferred method for installing observation wells because of the lack of introduction of any foreign material