Costs And Benefits Of Mitigating Radon In Drinking Water
The Environmental Protection Agency (EPA) is considering regulating radon, a naturally occurring soil gas dissolved in drinking water, because it poses a lung cancer risk. Benefits and costs of compliance are estimated for 29 water systems with radon above the proposed maximum contaminant level. The estimated cancer risk is three times higher than assumed by EPA, making it likely that a national regulatory standard of 300 picocuries per liter of water would pass a cost-benefit test. Site specific estimates of compliance costs are also substantially greater than EPA estimates. Nevertheless, the estimated cost per avoided death is only about $1 million.
Inferring the Distribution of Households' Duration of Residence From Data on Current Residence Time
Estimates of households' expected duration of residence are important to private and public decisionmakers. The common methods of estimation have been shown to be unreliable. This article presents a measurement framework for estimating total time of residence using five large sets of published government census data on the housing market. By developing a moving-behavior model, the distribution of total residence duration can be estimated from the census data on the age of current residency (i.e., time since moving into current residence). Among other results, the authors found that the average total residence duration for all U.S. households, 5.5 years, is about half the average age residence time, 10.7 years. This extended intertemporal model provides more reliable estimates for the age and expected duration of occupancy. Therefore, the model better explains and predicts housing-market behavior and also the demand for the many housing-related products and services.
Experimental study of water fluxes in a residential area: 2. Road infiltration, runoff and evaporation
Lack of accurate data has led some hydrologists and city planners to assume that urban infiltration is zero and runoff is 100% of the rainfall. These assumptions lead to an over estimation of road runoff volume and an underestimation of direct recharge to groundwater, which is already rising under some UK cities. This study investigates infiltration and runoff processes and quantifies the percentage of rainfall that contributes to storm drainage, and that which infiltrates through different types of road surface. Access tubes were installed for measuring soil water content using a neutron probe in three car parks, a road and a grass site at the Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford. Storm drainage was recorded at the exit of the Thamesmead Estate in Crowmarsh Gifford, just before the drain joins the River Thames at Wallingford. Rainfall and water table depth were also recorded. Weekly measurements of soil moisture content indicated that the top 40 cm layer is not influenced by water‐table fluctuations and, therefore, positive changes in soil moisture could be attributed to infiltration of rainfall through the surface. Depending on the nature of the surface, subsurface layers, level of traffic, etc., between 6 and 9% of rainfall was found to infiltrate through the road surfaces studied. The storm drainage generated by road runoff revealed a flow pattern similar to that of the receiving watercourse (River Thames) and increased with the increase of infiltration and soil water content below the road surface. The ratio of runoff to rainfall was 0·7, 0·9 and 0·5 for annual, winter (October–March) and summer (April–September) respectively. As the results of the infiltration indicated that 6 to 9% of annual rainfall infiltrates through the road surface, this means that evaporation represents, 21–24% of annual rainfall, with more evaporation taking place during summer than winter. Copyright © 2003 John Wiley & Sons, Ltd.