NGWA CWD case studies
NGWA CWD · Put your knowledge to work in context.
The NGWA Voluntary Certification Program, started in 1970, is described by the National Ground Water Association as the only national certification program for contractors and pump installers in the groundwater industry. It is designed and governed by groundwater contractors and is recognized by numerous state agencies, some of which have adopted the NGWA exams for their own licensing programs. The NGWA CWD case studies are 5 cases and about 2,808 words.
1Granite Well: Casing Seat, Yield Test, and Arsenic Concern
An 8-inch down-the-hole hammer hole is drilled to 400 ft for a four-bedroom home with lawn irrigation. The 6-inch steel casing is set to 40 ft and grouted to surface.
593 words, about 3 min2Sand Aquifer: Screen Slot, Gravel Pack, and 200-gpm Demand
An irrigation well is drilled with bentonite mud to 140 ft in a confined sand aquifer. The borehole is 12 inches; 8-inch PVC casing is set to 90 ft, and a 40-ft screen is planned from 90 to 130 ft.
599 words, about 3 min3Karst Annular Seal: Lost Returns and a Down-Gradient Spring
A 10-inch borehole is drilled to 220 ft through 20 ft of clay and then karst limestone. A 6-inch PVC casing is set to 180 ft, leaving a 2-inch annulus.
531 words, about 3 min4Low-Flow Purging and VOC Sampling in a Monitoring Well
A 2-inch Schedule 40 PVC monitoring well is installed to 40 ft with a 10-ft screen from 30 to 40 ft. The water column is 25 ft, and the casing ID is 1.5 inches.
537 words, about 3 min5Dewatering System: Poor Drawdown Near a Sensitive Building
A contractor is dewatering a 20-ft-deep excavation, 100 ft by 60 ft, in silty sand with groundwater at 8 ft. The design requires drawdown to 22 ft, or 14 ft below static, to keep the base dry.
548 words, about 3 min