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The Wellpoint System is o ne of the m ost versatile o f pre-drainage m ethods w hich can pump afew gallons p er minute in ne s andy si lts o r many thousands o f gallons p er minute in coarsesands and gravels.

A wellpoint system consists o f a n umber of wellpoints sp aced along a trench or around an e xcavation

site, all connected to a common header, which is a ttached to one or m ore wellpoint pumps.Wellpoint systems a re most suitable in shallow aquifers w here the water level needs t o be loweredno m ore t han 15 o r 20 feet. Due t o the va cuum limitation o f the p ump, excavations t hat are d eeperwill require multiple stages of wellpoint systems.

When designing a wellpoint system, it is n ecessary t o give rst consideration to the physicalconditions o f the site to be dewatered.

Things t o consider include:

The physical layout

Adjacent areas

Soil conditions

Permeability

The a mount of water to be p umped

Depth to imperviousness

Stratication

To select the proper components o f the wellpoint system - the friction losses d eveloped in the suctionside system must be considered.

On construction projects, requirements va ry d rastically f rom one job to another. Whatever your jobrequirements, Griffin h as the e quipment available to meet your needs.

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Groundwater Modeling SystemGriffin u tilizes a G MS (Groundwater Modeling System) to a nalyze the p roject and d esign thegroundwater control system. This i s e specially t rue in cases w here the analytical method applicationsare limited due to different reason such as u nderground condition and site topography.

Examples of Numerical Analysis using GMS:

Total head c ontour from SEEP2D for a dam structure with r elief well. Case study in Fort Worth, TX.

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Case study in Fort Worth, TX: 3D view of a D am structure a nd downstream terrain, using GMS.

SEEP 2DGriffin u ses t wo dimensional seepage a nalysis i n order to calculate t he ow lines, constant headlines a nd water table for specic projects l ike dam seepage and cutoff wall dewatering.

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Cross se ction of Dewatering system design inside shoring walls, using SEEP2D. Case study in PalmDesert, CA.

MODFLOWUsing MODFLOW helps an alyze t he 3D models for the dewatering system. The cone of depressionresulting from dewatering can be simulated and shown in 3D view. The owrate required fordrawdown at each jobsite can b e e stimated for each well location.

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Equipotential lines i llustration for a Dewatering system inside shoring walls, using MODFLOW.

Dewatering depression cone (3D iew! and radiuso" in#uence around t$e %o&site "rom MODFLOW'

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Deep well system design in c ombination w ith C utoff walls t o c ontrol the g roundwater . Case study:Polk co unty, Iowa.

MODFLOW ransient ModelThe drawdown at any time of dewatering can be estimated using MODFLOW transient model. Thisalso provides t he initial to steady s tate ow rate of dewatering which is h elpful to predict the Pump’shorse power, discharge pipe size and treatment system capacity requirement at the discharge point.

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Water table co ntour on Day 7 th o f dewatering, using a MODFLOW transient model. Case study inIndependence, MO.

Radius o f inuence from a d ewatering system, using MODFLOW Steady st ate. Case study in NY.

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Site )n estigationSite Investigation for Construction Below the Water Table is i mportant in dewatering design. Griffinengineers r eview the geotechnical reports a nd available boreholes i n order to nd out more aboutthe site aquifer and soil stratigraphy. This helps us gain a better understanding of the soil prole at

the jobsite. Then, using t hat information in the model analysis, we use soil and b orehole m odulesfrom GMS.

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Soil stratigraphy, using G MS Borehole Module, based o n the a vailable b orehole d ata. Case study:Ammonia Plant in Louisiana.

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Soil stratigraphy, using G MS Borehole Module, based o n the a vailable b orehole d ata. Case study:Treatment Facility in Norfolk, VA.

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