Well-point

There are three common methods for groundwater collection using pumping systems a well point system, a gravity drain system, and in combination with injection wells. 

A well point system consists of several individual well points spaced at 0.6 m to 1.8 m intervals along a specified alignment. A well point is a well screen (length 0.5 to 1.0 m) with a conical steel drive point at bottom. Individual well points are attached to a riser pipe (diameter 2.5 to 7.5 cm) and connected to a header pipe (diameter 15 to 20 cm). At the midpoint, the header pipe is connected to a centrifugal pump. As yield at different well points may vary, a valve at the top of each riser pipe is used to control the drawdown so that the screen bottom is exposed. The pump provides 6 to 7.5 m of suction, but friction losses reduce the effective suction to 4.5 to 5.4 m. 

The well point system is the most economical method of groundwater collection where the water table is less than 3 m and the contaminant is less 9 m below the surface. 

Where LNAPL is situated at shallow depth (<20 ft or 6 m), in moderate to high permeability soil (> 10 s cm/s), a well-point system may be the appropriate recovery technology. The use of well points for LNAPL recovery is similar to construction dewatering. A major advantage to this type of system is that it is possible to lower... 

The well-point system is used to create a flow barrier, as opposed to an open trench collection system, for three primary reasons ... 

Well points are commonly small diameter pipes (2 to 4 in., 5 to 10 cm) attached to a short length of well screen (2 to 3 ft, 60 to 90 cm), which are installed in sets and are connected to a common suction pump. This type of system is best suited... 

The design of a well-point system for remediation is similar to that of a dewatering system, with a few notable exceptions relating to the nature of the product to be recovered. Prior to the design effort, a hydrogeologic investigation is necessary to assess ... 

Calculation of well-point spacing and expected pumping rate is usually based on procedures using the Dupuit (steady-state) equation, as described in standard tests. The following factors must be considered in addition to standard water pumping considerations ... 

Well points are typically installed at calculated spacings to cause a limited drawdown over the area necessary to recover the product and contaminated water, but still maintain containment, notably on the downgradient side. A typical well point is shown in Figure 7.7 a typical well-point installation layout is shown in Figure 7.8. 

Vacuum-Enhanced Suction-Lift Well-Point System... 

The double-diaphragm suction-lift pump LNAPL recovery system is patterned after the concept of a shallow well-point dewatering system commonly used in the con-... 

FIGU RE 7.8 Typical well-point installation layout shown in plan view (top) and cross-section (bottom). 

FIGURE 7.10 Two layouts for well-point system using eductors. 

Vacuum-enhanced suction-lift well-point system ... 

VACUUM-ENHANCED SUCTION-LIFT WELL-POINT SYSTEM... 

A 10-yd3 soil sample was excavated from the site, blended, and characterized for initial hydrocarbon content and nutrient content. The reactor was filled with soil compacted to field density (Figure 12.10). The tank at the bottom was filled with water nutrients and surfactants. Water from this tank was sprayed over the top of the soil at a rate that maintained aerobic conditions. A significant amount of LNAPL was initially released from the soil, which required additional air to be pumped into the well points to maintain favorable growth conditions. After 105 days of operation, more than 87% of the total aliphatics and 89% of the total aromatics were removed. 

In concluding our discussion on inter-individual variability in hormone functions, we may well point out that with respect to hormone after hormone we have cited evidence of wide variability. Furthermore, the hormones for which the evidence is most convincing are those which have been studied in greatest detail and for the longest time. It may therefore be presumed that, as study of other individual hormone activities progresses, the role and importance of variation will become more widely evident. 

FIGURE 1. Experimental study area at the Maxey Flats shallow-land burial site. A series of experimental trench sections (T1-T5) and inert atmosphere wells (e.g. WIN) were installed adjacent to waste trench 27 to permit concurrent sampling of water from the waste trench (sump or well point), experimental trenches, and wells. 

Sansone F.J., Andrews C.G., Buddemeier R.W. and Tribble G.W. (1988a) Well point sampling of reef interstitial water. Coral Reefs 7, 19-22. 

A critical pesticide residue problem today is that of chlorinated hydro-carbon pesticides in milk. The easiest solution to this problem is an across-the-board restriction on the use of chlorinated hydrocarbon pesticides in any environment which might contaminate dairy animals or feeds. This type of restriction would doubtless create hardships on other agricultural enterprises in those areas and may in fact be unnecessary. Detailed examination of the possible sources may well point to solutions which will not sweepingly encompass all chlorinated hydrocarbon insecticides or all uses of them. 

Refer to the portion of Figure 4.6 where the source tank fluid level is below the center line of the impeller in either the system connected in parallel or in the system connected in series. At the surface of the wet well (point 1), the pressure acting on the liquid is equal to the atmospheric pressure Patm minus the vapor pressure of the liquid Py. This pressure is, thus, the atmospheric pressure corrected for the vapor pressure and is the pressure pushing on the liquid surface. Imagine the suction pipe devoid of liquid if this is the case, then this pressure will push the fluid up the suction pipe. This is actually what happens as soon as the impeller starts moving and pulling the liquid up. As soon as a space is evacuated by the impeller in the suction pipe, liquid rushes up to flU the void this is not possible, however, without a positive NPSH to push the liquid. Note that before the impeller can do its job, the fluid must, first, reach it. Thus, the need for a driving force at the inlet side. 

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