MTBE in California's Drinking Water: A Comparison of Groundwater Versus Surface Water Sources

During the last decade, the fuel oxygenate methyl tertiary butyl ether (MTBE) has received widespread attention as a potential threat to water quality, primarily due to leaking underground gasoline storage tanks and watercraft with two-stroke engines. In this article, we examine the annual detection frequency, number of new source detections, and concentration of MTBE detected in California's public drinking water groundwater and surface water sources from 1995 to 2002. This work builds on our previous evaluations of California's water quality monitoring database. However, it is unique in that it includes separate evaluations for groundwater and surface water sources that are of greatest concern to regulators, and which are likely being used for current public consumption. Our evaluations also include full-year data for 2002 (which have not been published previously) and an analysis of how the sampling and reported detections of MTBE vary by geographic location. We find that MTBE was generally detected (at any level) in approximately 0.5-0.9% and 0.2-0.4% of all groundwater sources assuming a one-detection and two-detection criterion, respectively. The overall detection frequency for MTBE in surface water sources is significantly higher than for groundwater sources, although these surface water detections appear to have substantially declined since 1996 (e.g., 7-9% for all surface water sources during 1996 to 1999 and 4% for all surface water sources during 2000 to 2002, assuming a one-detection criterion). The detection frequency of MTBE concentrations at or above the state drinking water standards in all drinking water sources (both groundwater and surface water sources) and the subset of drinking water sources that are likely to currently be delivered to consumers is markedly lower (and often zero). Despite the significant increase in water sampling over time, the number of new drinking water sources found to contain MTBE in California has not increased at the same rate and appears to have remained relatively stable or to have decreased since 1998. The data also show that nearly all of the 58 counties in California have routinely sampled at least some of their groundwater and surface water sources for MTBE over the last 8 years. Geographical evaluations show that MTBE has been detected (at least once) in groundwater sources in 34 counties and in surface water sources in 18 counties but has only been detected routinely (i.e., for 3 or more years) in 16 and 7 counties, respectively. Detected concentrations of MTBE are also generally below state drinking water standards, particularly for surface water sources. In short: (1) MTBE is rarely found in California groundwater or surface water sources that are of greatest concern to regulators or the public, and (2) drinking water detections of MTBE are expected to decline in the future due to the pending phase-out of MTBE and recent regulatory programs aimed at controlling gasoline releases from underground storage tanks and two-stroke-engine watercraft.     

Salem Revisited: Updating the MTBE Controversy

I am wronged. It is a shameful thing that you should mind these folks that are out of their wits.* *Statement of Martha Carrier (excerpt), hanged as a witch on 19 August, 1692 in Salem, Massachusetts. In all, 20 innocent persons were executed in 1692 as a result of the hysteria attending the Salem witch trials. After the executions, the court was prohibited from "reliance on spectral and intangible evidence". No prosecutions were successful thereafter. See generally, The Salem Witch Trials 1692: A Chronology of Events , at www.salemweb.com/memorial This article provides background information regarding the emerging controversies involving methyl tert -butyl ether (MTBE) and litigation involving leaking underground storage tanks (USTs) in general. It examines (1) the administrative, legislative and litigation history of MTBE in the context of the Clear Air Act and state environmental statues; (2) the importance of applicable RCRA (Resource Conservation and Recovery Act) deadlines regarding UST compliance in these cases; (3) the question of MTBE toxicity for personal injury claims; and (4) the scope of damages available in cases filed by plaintiffs who are not physically impacted by contamination. The authors conclude that the MTBE controversy does not appear to be a legitimate public health or environmental crisis, but rather is yet another speculative product of the American legal industry.     

Characterisation of prompt and delayed atmospheric radioactivity releases from underground nuclear tests at Nevada as a function of release time

A database with information on about 500 cases of atmospheric radioactivity releases from underground nuclear tests is analysed. The data are statistically evaluated and systematically aggregated in order to characterise prompt uncontrolled as well as delayed operational releases of radioactivity into the atmosphere. The focus is put on the latter. The reported data compare well with theoretically derived xenon activities for reasonable nuclear test scenarios. Conclusions are drawn on the main features of releases that can be expected from underground nuclear tests as a function of release time. These findings are relevant for developing and validating methods to be applied in global monitoring of atmospheric radioactivity with respect to indications of an underground nuclear explosion.     

童家院三中段127～193采区域地压活动分析及其控制措施

对127～193采区域产生剧烈地压活动的原因进行了综合分析,并找到了它的一般规律,提出了控制措施。     

地下水动态变化的成灾现象

对由人类活动引起的地下水动态变化所诱发的各种类型的灾害事件进行了分类研究;并对其成因及防治措施分别作了探讨。     

井下运输人—机—环境系统安全性灰色多层次综合评判

为了分析与评价井下运输系统的安全状况,笔者基于灰色关联分析理论,确定了井下运输系统安全状况综合评判的指标体系,建立了灰色多层次安全综合评判模型。通过对影响井下运输系统安全的人、机、环境的１１ 种因素进行的实际分析与计算,指出了井下不同运输子系统的安全状况及其薄弱环节。该方法使评判结果更具科学性、可比性和实用性,而且为进一步搞好安全评价工作提供了理论依据。     

地下结构震害类型及机理研究

地下结构由于受到周围岩体或土体的约束 ,一直被认为具有良好的抗震性能。但是 ,随着地下结构数量的增多和地下结构震害的频繁出现 ,地下结构的震害问题日益受到世界各国地震工作者的高度重视 ,笔者通过对大量地下结构震害的分析研究 ,对地下结构震害进行了分类 ,并研究了震害的影响因素及机理 ,以期为地下结构的抗震设计提供科学依据和有益的参考。     

地下采矿系统分析与安全生产管理

基于采矿效益和安全生产的双重目的,考虑到地下采矿生产环境与安全管理的复杂性,提出了地下采矿系统分析思想与方法。系统分析方法不仅注重采矿理论与技术在生产管理中的作用,更重要的是强调采矿技术与安全生产管理的结合,即采矿生产系统分析方法。作为应用实例,针对金川二矿区采矿、地质条件,简要介绍了用系统分析方法所开发的安全生产管理系统。     

埋地管道震害的多因素灰色关联分析

根据多次历史地震埋地管道震害调查资料的统计和定性分析，应用灰色系统理论，以管道震害率作为参考数列，以地震烈度、场地类型、管道材料、接口构造和管径尺寸作为比较数列，对埋地管道震害率进行了多因素灰色关联分析，排出了关联序．研究结果客观地揭示出震害率与各影响因素之间的相互关系，为进一步研究理地管道的震害预测方法提供了科学依据．     

泾阳、临猗地震的地下流体异常特征

总结了１９９８ 年泾阳Ｍｓ４．８ 及临猗Ｍｓ ４．６ 级地震的地下流体异常特征, 结果表明： 异常点数量有随震中距的增大而减少的趋势, 同时又受构造条件的制约; 异常时间以短临为主, 短期异常主要集中在震前３ 个月左右, 临震异常出现在震前１０ ｄ 左右; 异常幅度与地震三要素关系不明显。