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RCWD Alternative Compliance Sequencing Report City of St. Anthony Village PAGE 8 WSB Project No. 1626-53 surface coverage will allow the existing runoff from streets to be maintained or reduced, thereby protecting downstream resources. The City’s ability to implement priority BMPs outlined by the RCWD are addressed on a City-wide basis as follows: A. Infiltration Opportunities for infiltration BMPs do not exist within the City due to the poor- draining soils present. Native soils within the City of St. Anthony Village are clay or clayey soils (Hydrologic Soil Groups C and D) that have poor infiltration characteristics and are unsuitable for infiltration BMPs. These clay / clayey soil characteristics are uniform throughout the entire City. Extensive observation and substantial documentation of the clay / clayey soils is summarized below and demonstrates that opportunities for reasonable infiltration BMPs do not exist. 1. Infrastructure Improvement Projects Numerous infrastructure improvement projects have occurred throughout the City over the past two decades. These projects include street and utility reconstruction, park renovations, flood improvements, and private redevelopment sites. Throughout all of these efforts, clay / clayey soils were observed, and soils suitable for infiltration BMPs were not encountered in any location. Figure 2 shows the location of these projects, and illustrates that the majority of native soils within the City’s right of way have been exposed and observed during these projects. 2. Soil Sampling Soil borings were completed for nearly all of the improvement projects indicated on Figure 2. Soil boring logs indicate that clay / clayey soils native are present and no soils suitable for infiltration BMPs were observed. Available soil boring logs and a summary of available geotechnical reports are provided in Appendix A. Additional soil samples were taken at select locations where RCWD staff felt there were gaps in soil data. Figure 3 shows the sampling locations. All of the additional samples were classified as clay or clayey soil. See Appendix B for classification of soils for each sample. 3. Repair of Watermain Breaks The City has repaired hundreds of watermain breaks and or curb stop leaks over the past decades. Throughout all of this work, the same uniform clay soils have been observed by Public Works Department Staff. The location of these breaks are scattered throughout the entire City including many additional areas that are not in soil sampling data. See Appendix C for a list of watermain break repairs.