August 19, 1996

Julie Roth, Executive Director

DSCSOC
Route 2, Box 2879
Davis, CA 95616

Dear Julie:

In connection with the last RPM meeting, Duncan Austin asked me specifically about my views on recharging to the local aquifer LEHR site landfill leachate-polluted groundwaters after treatment. This appears to be an increasingly prominent approach that may be used at the LEHR site. From the discussions at the last RPM meeting and my knowledge of the situation, it is going to be difficult for UCD to gain permission to discharge the polluted groundwaters from this site to Putah Creek. Further, UCD's wastewater treatment plant at this time is already overloaded and not complying with its permit requirements. To add additional groundwater flow to it will only acerbate the situation. Therefore, treatment and recharge is an option that should be considered.

My comments at the meeting in response to Duncan's question were that it is important that the recovered, treated groundwaters be properly characterized with respect to the wide range of potential pollutants that are present in landfill leachate-polluted groundwaters. In a simple groundwater pollution system such as a leaking TCE tank, it is relatively straightforward to determine whether recharge of pump and treat treated groundwater would result in continued pollution of the groundwater by constituents that are not removed by the treatment processes used. In a complex situation, however, such as landfill leachate where there can be thousands of chemicals that were originally disposed of as waste coupled with many thousands more of transformation products from the original waste components, it is difficult for the approaches conventionally used today to be certain that the treatment that is practiced is adequate to ensure that the groundwaters will not still represent a significant impairment of their use upon reinjection into the aquifer system.

There is no way to fully reliably evaluate the safety of landfill leachate-polluted groundwaters recharged to an aquifer to be certain that there are not constituents in the treated groundwaters that would later prove to be harmful to public health or some other beneficial use of the recharged water once it is recovered for domestic or other purposes. This requires that prudent public health protection policy be followed of requiring that the discharger provide high degrees of treatment before recharging a leachate-polluted groundwater.

This is an issue that I have been addressing over the past couple of years as part of my American Society of Civil Engineers Groundwater Recharge Committee activities. ASCE has a committee devoted to developing a guidance manual for groundwater recharge. This manual is now in its final editing. One of the issues that is of concern is the potential problems associated with recharge of inadequately treated surface waters, including wastewaters of various types. There is a considerable effort being made in California as well as in some other parts of the country to recharge domestic wastewaters as a means of supplementing an aquifer that is experiencing excessive drawdown (pumping). I have developed several papers pertinent to this topic. These include:

Lee, G.F. and Jones-Lee, A., "Appropriate Degree of Domestic Wastewater Treatment before Groundwater Recharge and for Shrubbery Irrigation," AWWA, WEF 1996 Water Reuse Conference Proceedings, American Water Works Association, Denver, CO, pp. 929-939 (1996).

Lee, G.F. and Jones-Lee, A., "Public Health and Environmental Safety of Reclaimed Wastewater Reuse," IN: Proc. Seventh Symposium on Artificial Recharge of Groundwater, University of Arizona Water Resources Research Center, Tucson, AZ, pp. 113-128, May (1995).

Lee, G.F. and Jones-Lee, A., "Water Quality Aspects of Groundwater Recharge: Chemical Characteristics of Recharge Waters and Long-Term Liabilities of Recharge Projects," IN: Proceedings of the American Society of Civil Engineers Second International Symposium on Artificial Recharge, New York, NY, July (1994).

Lee, G.F. and Jones-Lee, A., "Water Quality Aspects of Incidental and Enhanced Groundwater Recharge of Domestic and Industrial Wastewaters - An Overview," IN: Proc. of Symposium on Effluent Use Management, TPS-93-3, pp. 111-120, American Water Resources Association, Bethesda, MD (1993).

Lee, G.F. and Jones-Lee, A., "Does Meeting Cleanup Standards Mean Protection of Public Health and the Environment?," IN: Proc. of Superfund XV Conference, Hazardous Materials Control Resources Institute, Rockville, MD, pp. 531-540 (1994).

These papers contain numerous references to the literature on this topic. I can make copies of my papers available to anyone who is interested.

It is being found that while some constituents in domestic wastewaters and, for that matter, in landfill leachate do not travel for significant distances in groundwater systems, there are others, some of which are potentially hazardous, which do travel for considerable distances. Some of the best work being done on this topic is being done as part of the Orange County Water District's groundwater recharge studies. The studies conducted by Stanford University faculty at the Orange County recharge sites have found that there are components of domestic detergents that are used in the home that appear to be unimpeded in travel through aquifers. Some of these components are of concern because of potential hormonal impacts.

Several years ago the National Research Council convened a panel of experts to review this topic. The review resulted in the publication of Ground Water Recharge Using Waters of Impaired Quality, National Research Council, National Academy Press, Washington, D.C., 1994. Much of what is said in the NRC review is applicable to recharge of leachate-polluted groundwaters that have been treated to varying degrees before recharge.

It is my view and the general consensus of many that the recharge of waters to an aquifer of this type must be done under the conditions where the greatest possible treatment is achieved before recharge. For situations where there are large numbers of non-conventional organics present, i.e. unidentified TOC components, the groundwaters should receive at least activated carbon bed treatment and, in some cases, reverse osmosis (RO) treatment. This is the current state of technology that is being used as part of the recharge of domestic wastewaters by the Orange County Water District aquifer enhancement activities.

The problem is that there are such a large number of potentially hazardous chemicals in mixed wastes, like landfill leachate, that are unidentified and unregulated. While there are tests available that could be used to detect whether residues that pass through various treatment processes could be a potential carcinogen, mutagen or teratogen, these tests are not being used yet by regulatory agencies to screen treated waters for potential impact before recharge. Eventually, this type of testing will be done.

Overall, the recharge of a treated landfill leachate-polluted groundwater which could be proposed as a means for treatment and disposal of the polluted groundwaters as part of remediation of the LEHR site carries with it potentially significant risks to the groundwater and property owners-users down groundwater gradient of the recharge site. The groundwaters under their properties can never be considered safe, even though they meet the same standards as groundwaters that have not been polluted by landfill leachate. DSCSOC will need to carefully consider these issues as part of its review of any remediation approach involving groundwater recharge of landfill leachate-polluted groundwaters at the LEHR site.

One of the issues that is still not clear to me is the magnitude of the unidentified TOC that is associated with the large chloroform plume at the LEHR site. Is this only chloroform and some of its transformation products or does it consist of a variety of organics derived from the landfill that represent potential threats through the non-conventional pollutants? I have suggested on a number of occasions that a more appropriate characterization of these leachate-polluted groundwaters be conducted. Thus far, this has not been done. It will have to be done before any valid decisions can be made on whether UCD's proposed pump and treat operations which would involve groundwater recharge or surface water discharge can and should be approved. UCD in the past in connection with its west landfill has taken a very narrow view of what constitutes potential pollutants in leachate-polluted groundwaters arising from its campus landfills. Thus far, the Regional Water Quality Control Board has not required that UCD properly characterize the wide range of potential pollutants in this groundwater associated with the plume at the west landfill. DSCSOC must require that a much more appropriate characterization of the leachate-polluted groundwaters be conducted for the three landfills that UCD has constructed at the LEHR site as well as other waste management units at this site which are now polluting groundwaters than is being accomplished for the west landfill site.

If there are questions on these comments, please contact me. I suggest that you pass them on to the RPMs and others as appropriate, indicating that if anyone has questions on them to please contact me.

Sincerely yours,

G. Fred Lee, PhD, DEE
Technical Advisor, DSCSOC

Copy to: D. Austin

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