PERFORMANCE COMPARISON:
DIRECT-PUSH WELLS VERSUS DRILLED WELLS

"No significant performance differences were observed between the direct-push wells and drilled wells."

EXECUTIVE SUMMARY

A comparison between ground water monitoring alternatives (direct-push installed monitoring wells and hollow stem auger drilled monitoring wells) was conducted on the leading edge of a methyl-tertiary butyl ether (MTBE) plume located at Naval Base Ventura County (NBVC) Port Hueneme, California. The purpose of this effort was to determine whether representative chemical and water table data could be generated using properly designed direct-push monitoring wells. An advisory committee comprised of experts from industry, government regulatory entities, and academia assisted with the project design and review of the work plan and all reporting efforts.

Field efforts included piezocone measurements, collection of core samples, pre-installation collection of water samples from selected depths, installation of customized monitoring well test cells, and sampling of the wells in triplicate. Laboratory efforts included chemical analysis of water samples (for MTBE and various inorganic materials and parameters), determination of permeability for selected core samples, and determination of grain size distribution for selected samples.

From February 8 to February 14, 2000, a total of 32 wells were installed in two cells. Twelve wells were installed in Cell A, while a total of twenty wells were installed in Cell B. Specific well screen design (sand filter pack and slot size) was determined using several criteria. To evaluate performance of wells adhering to the ASTM specifications (ASTM D5092), grain size distribution curves (Appendix C) were used to determine filter pack grain size and corresponding slot size recommendations (Appendix D). For Cell A, each of the wells was designed using ASTM specifications. For Cell B, two additional well designs were also employed to account for the most common well installation designs used by drillers and direct-push device operators.

An extensive statistical effort was conducted to compare the performance of the different well designs for the Port Hueneme hydrogeologic regime. Analysis of variance (ANOVA) was selected as the best technique for analyzing data consisting of categorical factor predictors and a continuously varying response variable.

In summary, no significant performance differences were observed between the direct-push wells and hollow stem auger drilled wells. Within experimental error, the performance was comparable for the hydrogeologic setting of Port Hueneme, California. More specifically, the chemical variability among the different well types was less than that displayed by spatial heterogeneities associated with well screen depth differences and temporal variability. Although a comprehensive hydraulic evaluation was not conducted, water level values also appeared to yield comparable results for the different well designs. Since the study duration was limited to approximately 6 months, a longer observation period may be required to evaluate the long-term and seasonal (greater than 1 year) performance of direct-push wells.



The complete report has been divided into
10 pdf's. The contents of each pdf are list below:

Part 1 (292 KB)
INTRODUCTION

Part 2 (1.0 MB)
DESCRIPTION OF FIELD AND LABORATORY EFFORTS
Piezocone Pushes
Core Samples

Part 3 (907 KB)
Direct-Push Water Samples
Permeability Tests for Selected Samples
Grain Size Distribution of Selected Samples
Well Construction and Installation
Well Development

Part 4 (154 KB)
Sampling and Analytical Logistics
ANALYTICAL RESULTS
WATER LEVELS

Part 5 (207 KB)
INSTALLATION COSTS
STATISTICAL ANALYSES
MTBE Concentration Data

Part 6 (181 KB)
Geochemical Data
Water Level Data
SUMMARY AND CONCLUSIONS

Part 7 (431 KB)
ACKNOWLEDGEMENTS
REFERENCES
APPENDICES
A – Piezocone Data Logs
B – Permeability Test Laboratory Data
C – Grain Size Distribution Curves
D – Filter Pack Design Worksheet

Part 8 (704 KB)
E – Well Construction Logs

Part 9 (186 KB)
F – Well Development Logs

Part 10 (493 KB)
G – Analytical Results
H – Ground Water Levels
 I – Images

Complete Report (3.72 MB – This is a very large file and could cause your browser to crash if opened on line. We suggest "right-click, save target as" to your desktop)

By Mark Kram (NFESC), Dale Lorenzana (Intergraph), Dr. Joel Michaelsen (UCSB) and Ernest Lory (NFESC). Naval Facilities Engineering Command, Washington DC 20374-5065, January 2001, NFESC Technical Report TR-2120-ENV