Advances in Design Procedures for Relief Well Lines in Variable Urban Settings

Lines of equally-spaced relief wells can often be evaluated and designed using simplified design procedures. However, design of relief wells in an urban environment can pose significant technical challenges with respect to variable relief well spacing and offset from the landside levee toe, which are not readily accounted for in simplified relief well design procedures. Additionally, considerations such as variable aquifer conditions, topography, well screen lengths, and interfacing with cutoff walls are beyond the capabilities of simplified design procedures and thus require more advanced analyses. This paper describes a staged analysis and design approach developed and implemented to design lines of relief wells along the Sacramento River East Levee (SREL) in northern California. The approach incorporates three analysis stages: (1) simplified analyses with the USACE EM 1110-2-1914 procedure, (2) SEEP/W plan view analyses assuming fully- penetrating wells, and (3) SEEP/W plan view analyses accounting for partially- penetrating wells, if applicable. For Stage 1, the USACE simplified procedure was implemented with corrections and modifications as presented in Guy et al. (2010) and Guy et al. (2014). Stage 2 analyses included SEEP/W plan view analyses assuming fully- penetrating relief wells with efficiency-related head losses calculated with the approach presented by Guy et al. (2010). Stage 3 analyses for partially-penetrating wells were analyzed by applying flow rate boundary conditions, where flow rates were estimated from Stage 2 analyses and partial-penetration flow factors per USACE EM 1110-2-1914. An application of the proposed approach to the SREL is presented. Comparisons of aquifer heads and relief well flow rates from Stage 1 and Stage 3 analyses indicated similar results for wells near the middle of the relief well lines, but significant differences were calculated at the ends of the relief well lines due to end around effects and interactions with existing relief wells.