Agenda - Council - 04/14/2020 - Laserfiche WebLink

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20-01 Variolite Street Reconstruction Ramsey, Minnesota NTI Project No. 19. MSP09109.000 Native glacial deposit soils consisting of poorly graded sand (SP), poorly graded sand with silt (SP-SM), and silty sand (SM) were commonly observed extending to the boring termination depths. Groundwater was not observed in the boreholes at the time of drilling. Table 2 summarizes the encountered subsurface conditions for 161' Avenue Northwest. Table 2: Pavement and Subgrade Summary' 161st Avenue Northwest Bituminous Apparent Pavement Aggregate Base Fill Subgrade Native Subgrade Boring No. Thickness2 (inches) Thickness' (inches) Material4 Material SB-58 3.0 12.0 SM SP SB-59 3.0 8.0 SM SP, SM SB-60 3.5 8.0 SM SP-SM, SP SB-61 3.5 18.0 SP-SM SP 1. Table summary is a generalization of subsurface conditions at the individual soil boring locations only. They may not reflect variations in subsurface strata occurring on site between boring locations. The general geologic origin of retained soil samples is listed on the boring logs. 2. Measured thickness of the pavement core. 3. Apparent aggregate base thickness, at time of our fieldwork, by visual inspection only. The classification is not mean to confer conformance with DOT specifications. 4. Undocumented fill soils. GROUNDWATER AND GROUNDWATER CONTROL Groundwater was observed in all of the project areas at the time of drilling. Variolite Street Northwest: Groundwater was observed in thirty-five of the fifty-seven (57) boreholes at the time of drilling. The groundwater depths ranged from approximately 2.5 to 11.5 feet below the top of pavement. 161' Avenue Northwest: Groundwater was not observed in the boreholes at the time of drilling. In addition, the on -site silt based soils have the potential to be somewhat impervious and conducive to the development of zones of perched water at varying elevations and locations across the project area. Depending upon elevations of underground utilities, groundwater may be an issue during construction. If excavations are proposed below the groundwater level, the granular nature of the on -site soils will likely result in significant volumes of water entering the excavations unless proper dewatering measures are implemented. If dewatering is needed during construction, we recommend that the groundwater be maintained a minimum of 2 feet below the bottom of the excavation. LABORATORY TEST PROGRAM Our analysis and recommendations of this report are based upon our interpretation of the standard penetration test resistance determined while sampling soils, laboratory test results, and experience with similar soils from other sites near the project. The results of such tests are summarized on the boring logs or attached laboratory test reports. Page 6 of 10