Uses of PAM in Semi Arid Climate Construction Sites

摘要

Los Alamos National Laboratory Water Quality Group team members are evaluating the effectiveness and potential uses of Polyacrylamide (PAM) on construction sites. The semi-arid (< 20 inches annual precipitation), high altitude (7200 ft) climate in Los Alamos, NM, can present unique challenges in establishing vegetation and managing sediment and erosion control. The majority of annual precipitation comes during a 3-month monsoon season that often yields brief but extremely intense storm events that produce high raindrop impact and concentrated runoff. This accelerates erosion and sediment transport. The high altitude yields higher levels of UV exposure and sparser vegetation cover than is found in most regions of the country. Additionally, the local soils comprised primarily of decomposed volcanic material often exhibit the characteristics of clay particles when suspended in water. To address these conditions and challenges, PAM applications associated with revegetation, and flocculating suspended sediment in accumulated runoff prior to discharge will be evaluated. Results of these evaluations will be presented.PAM will be incorporated, through current commercial products, as a component of hydromulch to retain moisture and surface soil, and to encourage seed growth during both dry periods and exposure to intenseprecipitation events. Certain sites will be selected to apply the PAM as an additive to the hydromulch and compare the erosion and vegetation growth rates to sites that did not have PAM applications.Detention ponds and open utility trenches with suspended sediment require treatment prior to discharge to meet water quality standards and regulatory requirements for sediment yield from a construction site. Methods of using PAM to flocculate suspended sediment in accumulated runoff will be explored and evaluated. This will include developing procedures for determining appropriate quantities of PAM applied as a liquid emulsion and identifying methods of agitation to enhance flocculation.For these PAM applications, the effectiveness and longevity of the material when subjected to higher UV levels and intense precipitation will also be evaluated.