PRELIMINARY OBSERVATIONS ON WATER QUALITY OF STORM RUNOFF FROM FOUR SELECTED RESIDENTIAL ROOFS¹

Abstract

Storm runoff from four characteristic types of residential roofs and incident rainwater were monitored for 47 storm events over a six‐month period at Nacogdoches, Texas, to study water quality conditions for 20 element and four chemical variables. The total element concentration in storm runoff from each roof type was greater than that of rainwater in the open. Differences in element concentrations in storm runoff among the four roof types were statistically significant (α≤ 0.05) with the differences for the wood shingle roof being the greatest and that for terra cotta clay roof being the least. The median concentrations of four element variables exceeded the Texas surface water quality standards, while 12 variables exceeded the standards at least one time in all samples collected. Zinc concentrations violated the Standard ranging from 85.7 percent of the samples for the wood shingle roof to 66.0 percent for the composite shingle, the greatest exceedances of all 24 variables studied. Storm characteristics and gutter maintenance level had some effects on these water quality conditions. The study suggested that roof types can be important to water pollution management programs. More detailed studies on roof water quality in major municipalities are required.

A Field Evaluation of Rain Garden Flow and Pollutant Treatment

“…The NURP event mean concentrations of 1.9 and 2.4 mg L −1 for TKN and TP, respectively (US EPA, 1983b), were higher than the mean concentrations of those pollutants found in this study (Table III). Chang and Crowley (1993) reported median NH 4 -N concentrations in runoff from an asphalt composition shingle roof in Texas of 0.859 mg L −1 , which was not significantly different from the 0.799 mg L −1 NH 4 -N measured in open rainfall at the site. Concentrations of NH 3 -N in precipitation and roof runoff from the Haddam study site were lower than those measured in Texas (Chang and Crowley, 1993), and were not significantly different from each other.…”

Quality and seasonal variation of rainwater harvested from concrete, asphalt, ceramic tile and green roofs in Chongqing, China

“…The compounds contained in roofing materials can leach into the runoff (Chang et al, 2004) and older roofs contain large amounts of suspended solids; 2) rainfall characteristics (e.g., precipitation, rainfall intensity, ADWP); 3) Environment characteristics (e.g., seasonal variation, atmospheric pollution, roof surrounding environment). In general, roof temperatures are much higher than temperatures of other surfaces due to lower albedo and reduced shading effects from surrounding trees, which increases the rates of chemical reactions and organic decomposition of materials that have accumulated on rooftops (Chang and Crowley, 1993). In addition, the leaves, dead insects, and bird waste, added to roofs by interception and deposition affect the water quality of the roof runoff (Chang et al, 2004).…”

Roofing as a source of nonpoint water pollution

“…During storms, rainwater not only adds a variety of chemicals and contaminants to the roof watershed, the acidic nature of rainwater will react with compounds retained in or by the roof and cause many elements in the roof-runoff to leach out (King and Bedient, 1982). Second, roof temperatures are much higher than temperatures of other surfaces, due to lower albedo, greater surface inclination to direct solar radiation, and less shading effects from surrounding trees (Chang and Crowley, 1993). The higher roof temperatures may accelerate chemical reactions and organic decomposition of the materials and compounds that have accumulated on rooftops.…”