# Configuration of Non-Pumping Reactive Wells Considering Minimum Well Spacing
## 1 Introduction
Various configurations of non-pumping wells have been studied for remediating contaminated groundwater. [PERSON] et al. [28] studied configurations of an array of non-pumping wells with single- and multi-transects for remediating contaminated groundwater. [PERSON] [31] compared contaminant blocking in groundwater according to the number of transects (single, double, and triple transect) of non-pumping wells. He also studied triple transect consisting of linear segments arranged at 45-degrees with respect to the direction of groundwater flow and evaluated a nonlinear array of non-pumping wells [26; 31]. [PERSON] et al. [30] proposed a configuration of possible DART well arrays for contaminant removal in a circular arrangement by combining them with pumping wells. [PERSON] et al. [32] examined the effect of non-pumping reactive wells orientations such as vertical, horizontal, and slanted with inclination angle of 45\({}^{\circ}\) on hydraulic contact time and well capture zone. Several factors should be considered when designing PRB configurations. Among the field conditions, the hydrogeological properties of the aquifer, such as hydraulic conductivity, hydraulic gradient, and aquifer heterogeneity are important factors that determine PRB performance [33; 34; 35]. The design of PRBs should also consider the levels of contamination, sizes, and depths of contaminant plumes that need to be remediated [36; 37]. In addition to these determinants of PRB performance, the size of wells and their arrangement should be carefully determined when designing the configuration of non-pumping wells. A larger well diameter could capture more of contaminant plume, but the well diameter should be determined by considering the cost, technical limitations, as well as the field conditions. The wells should be sufficiently spaced to prevent wall collapse between adjacent wells. Several researchers conducted experiments to remove contaminants using an array of non-pumping wells [25; 32]. Their array of non-pumping wells were practical configurationsthat could remove contaminants and did not cause the wall collapse between adjacent wells, and they also presented the value of the spacing of the wells used in the experiment considering the well capture zone according to hydraulic conductivity. However, studies that considered both the well capture zone and the construction stability of wells as construction constraints were not conducted. Most of the PRB configurations in previous research have focused only on capturing the contaminant plume without considering construction constraints, such as well spacing. Rarely have there been attempts to develop a practical configuration of non-pumping wells considering construction constraints like minimum well spacing and well diameter. In this study, we propose a practical configuration of a non-pumping reactive well (NPRW), considering the construction constraints such as the minimum well spacing and well diameter. To investigate the applicability of the proposed configuration, the removal efficiency of the PRB was evaluated and compared with the alternative configurations.