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Arsenic management through well modification and simulation

Ground Water

By:
, , ,
DOI: 10.1111/j.1745-6584.2009.00670.x

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Abstract

Arsenic concentrations can be managed with a relatively simple strategy of grouting instead of completely destroying a selected interval of well. The strategy of selective grouting was investigated in Antelope Valley, California, where groundwater supplies most of the water demand. Naturally occurring arsenic typically exceeds concentrations of 10 (mu or u)g/L in the water produced from these long-screened wells. The vertical distributions of arsenic concentrations in intervals of the aquifer contributing water to selected supply wells were characterized with depth-dependent water-quality sampling and flow logs. Arsenic primarily entered the lower half of the wells where lacustrine clay deposits and a deeper aquifer occurred. Five wells were modified by grouting from below the top of the lacustrine clay deposits to the bottom of the well, which reduced produced arsenic concentrations to less than 2 (mu or u)g/L in four of the five wells. Long-term viability of well modification and reduction of specific capacity was assessed for well 4-54 with AnalyzeHOLE, which creates and uses axisymmetric, radial MODFLOW models. Two radial models were calibrated to observed borehole flows, drawdowns, and transmissivity by estimating hydraulicconductivity values in the aquifer system and gravel packs of the original and modified wells. Lithology also constrained hydraulic-conductivity estimates as regularization observations. Well encrustations caused as much as 2 (mu or u)g/L increase in simulated arsenic concentration by reducing the contribution of flow from the aquifer system above the lacustrine clay deposits. Simulated arsenic concentrations in the modified well remained less than 3 (mu or u)g/L over a 20-year period.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Arsenic management through well modification and simulation
Series title:
Ground Water
DOI:
10.1111/j.1745-6584.2009.00670.x
Volume
48
Issue:
4
Year Published:
2010
Language:
English
Publisher:
Wiley
Publisher location:
Hoboken, NJ
Contributing office(s):
California Water Science Center
Description:
12 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Ground Water
First page:
526
Last page:
537
Number of Pages:
12