ARCHIVED REPORTS_XR0002852 - Laserfiche WebLink

Home Browse Search

` III oints sampling P fest. Therefore,the spatial frequency of l signed. 1) Questions of Scale should be carefully selected and de f Sampling Point Design A sampling plan designed to collect representative 2) Flexibility o , samples must take into account the pace tenand time as well as In most cases well-point al scale Of diametersof submer5 b g f t 7` changes in site conditions through sp inches will permit the use of most types the chemical associations and behavior of the parameters pumping devices far tow-flaw (minimal drawdown}sampling that are targeted for investigation.ln subsurface ernes aver time or P is suggested that short(e.g.,less than i.fi m}screens be physical(i.e.,aquifer)and chemlcat properties rit. In fact, incorporated into the monitoring design where Possible so space are not statistically iendeNp nd distances of samples ewmeters) that mparable results from one device to an,other gvertVcal taken in close Proxim ty{ is relative to the deg expected. Short,of course,expected at site. or within short time periods(tela,more frequently man water quality variability expo monthly)are highly auto-corrslated. This monthly)or deneans that se in frequency( .g., lin Point empial mg high-samPf' g 3) Equilibration of Sam¢ g spatial monitoring designs run the risk of 1`8 $��a'ia collection and misleading'inferences regardingactice, contaminant Time should be allowed for equilibration of the wet! values that aren't ststisticalVy valid. In rarely suffer or sampling point with the formation after installationPlace- detection `lies- detection and assessment monitoring eprogramsmerit of well or sampling points in the subsurface Produces c1•iniq s these over-sampling concerns. in corrective-action evaluation some disturbance of ambient enc ia6�y Drilling ie ed to cause Programs,ft is also Possible that too little data may be e. auger, rotary,etc.)are g Coll over space or time. In these cases,false interprets- more disturbance than direct-push technologies-s)deither;er kion of the spatial extent of contamination esus underestimation ( g there may be a period(i.e.,days different of temporal concentration variability may case, be distin Of Sam- which water quality near the point may 2) 'Target Parameters from that in the formation.Proper development of the lin Dint and adjacent formation to remove fins5 created e ov� Parameter selection in monitoring Program design is piing p during emplacement wilt shorten this water Reality most often dictated by the regulatory status of the site. period. However,background water quallty constituents8SQr9i nt targets Procedures used in and Sampling indicator parameters,and c S. Theitoo s and P11 p ticable Ill, Definition of Low-Flow Purging for data cottectlon programs. In these programs should be equally r�beneeded o deter- tt!s generally accepted that water in the well casing to atl categor.05 of data,since all may mine or support regulatory action, is non-repreSto colt a of the formation water and needs However,e pnstructi°n purged prior to collection of ground-wa 9ndeed ble represerita- C. Sarnpf1ng point Design and C the water in the screened interval may central to all five of the formation.depending purged well mnextent for the site hydrogeotogY• Welts are purg Detailed site characterization is following reasons:the presence of the air interface ra the top and the basis for this characterize- en concentration decision-making purposes 4e of the water column resulting in an OX) tion resides}i$'identificationral hniis. Fundamentalu �� dot po re p gradient with depth,loss of volatiles up the it er pack`chemical major hyd head-differences 9 point location include: subsurface lithology, tin int teaching from of sorpeeaVs orhbafilnd surface infiltration. and background geochemical conditions. Each sampling P° changes due to clay tow-flow purging,whether using portable or dedi- has a proper use or uses which should program documented a a using pump-intake located in level which!s appropriate for the program's not always be be objectives. Individual sampling points may rated systems,shouldabovsahe middle ai the screened detection. the middle or slightly able to fulfill rriultl,fe rmonitorsng objectives(e•g. interval. Placement of the pump too close to the bottom of the assessment, corrective action). well will cause increased entrainment of solids which have with Monitoring,ingrain and Data collected in the well over time.a result onor purging and sampling re present as 1) Compatibility f well development,p Quality Fjb4eotives events,and natural colloidal transport and deposition. int location and design will in the middle or toward the specifics of sampling Po 'therefore, placement of the pump suggested Placement of the be dictated by the complexity of subsurface lithology and top of the screened interval is variability in contaminant andlor geochemical conditions. It pump atQ�ede�p�of e water aquifers,ers, screenedcolumn for gacross the raund•water sam- recommended Point should Low- should be noted that, Low- regardless (e.g.,wells, drive-points, a roach, few sampling p water tabte,where this is the desired sampling P ,ling pp have zones of influence in excess of a few screened augers) 4