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9.a) Uptown Sewer System Master Plan, Part 2 � � � � � � � ` � � � � � � � � � � � � � � SOIL BORING REPORT AND LOGS r • • • • • � i � • � ! • • • • • • • � Cit��of Scandra—Nl 1.103386 Appendix U��town Wastew�ater Sti'stern Master Plan Prepared b}'Bol/a2 &Me�ik, Inc. . � � � � � � � � � i • • • • • • • � • • • • • r • • • • • • i � • � ! • • • • • • • • • • • � � � � � � • SOILS INVESTIGATION REPORT • � For: � Brian Malm, P.E. � Bolton and Menk, Inc. � Mankato, MN � � � Project: � Village of Scandia � Onsite Sewage Treatment System • Section 23, T.32 N., R.20 W., • Washington County, Minnesota � � By: � Terry L. Bovee � Professional Soil Scientist � Minnesota State License #30269 � MPCA SSTS License #L3043 � 620 Ridge Road • Henderson, MN 56044 � June 23, 2011 � � � � TERRY L.BOVEE,PROFESSIONAL SOIL SCIENTIST: 1 hereby certify that this plan,document,or report was • prepared by me or under my direct supervision and that 1 am a duly licensed Professional Soil Scientist under the laws of the State of Minnesota. Print name: Terrv L. Bovee � "`C�,c._.=.�t,_C�.,�- Signature: Date: 6/23/201 1 License#30269 � � � � � � � � � � � � � � � � • June 23,2011 � Mr. Brian Malm, P.E. � Bolton and Menk, Inc ` 1960 Premier Drive Mankato, MN 56001-5900 � • Re: Scandia Community Sewage Treatment System � Dear Mr. Malm: • Introduction �i � I • Upon your request on June 1,2011 I conducted a soils investigation in Scandia,Minnesota for three purposes: 1)determine soil characteristics at a publically owned and operated subsurface ' � soil treatment site,2) gather preliminary soils data at a site that may be used for a future soil- � based sewage treatment system,and 3)determine soil properties at an abandoned soil absorption system adjacent to the Community Building. This report includes how the field work was � completed,results and recommendations. • Methodologv � � In preparation priar to conducting this site investigation I reviewed two soil reports dating from � July, 1995 and August, 2005. The earlier report apparently was conducted at about the time the existing onsite soil absorption system was originally designed and installed. The later soils • report was associated with an area that was being considered for drain field expansion. I also • reviewed the Washington County Soil Survey to understand what soils had been mapped in the area and what their general morphological characteristics are. � The existing drain field is a trench-type and is within a fenced area with each drain line clearly � defined with an inspection pipe on each end and at the drop boxes. Using a plan drawing of the • drain field and comparing the drawing to the actual inspection pipes and boxes observed in the • field, I chose seven soil observation sites roughly evenly spaced around the outside perimeter of the drain field area. All soil sampling sites were between 5 feet and 10 feet away from the � outermost drain field pipe. Within the expansion area(south of the drain field area), four soil � borings were done at random spacing. I attempted to complete a soil boring adjacent to the abandoned drain field near the Community Building but could not exceed a depth of about 29 � inches due to obstructions(likely cobbles). � A hand tool (3"diameter bucket auger)was used for all soil barings. Soil morphological � characteristics such as texture, color, soil structure properties,depth to redoximorphic features • and other soil features or properties were recorded for each baring. Each site was marked with a red-tipped lathe and numbered SB-1, SB-2, etc. It was understood that Bolton and Menk, Inc. � was to accurately locate each of the soil boring lathes. � � � � � � � � � � � � � � . Mr. Brian Malm, P.E. • June 23,2011 Page 2 � � Results � In general, a review of the soils mapped by the USDA-Natural Resource Conservation Service in • the area of the drain field and potential expansion area indicates a parent material that is outwash overlying glacial till. The coarse-textured outwash is typically brown in color with the � underlying till typically reddish in color. The till is characterized as generally having a moderate • amount of clay and high sand content in the upper parts grading to sands and gravels with depth. Strata of pebble to cobble-sized gravels interspersed throughout the profile are common. The � mapped soil in the drain field area is called Demontreville loamy fine sand and is considered • well to moderately well drained. � The soils actually observed vary considerably from the soil characteristics described for • Demontreville in the soil survey report. Most of the soil boring sites indicate soil profiles that have been modified by water-sorting processes resulting in varying thicknesses of finer-textured � lacustrine sediments (clays and silts)and bands of various-particle sizes of loams, sands and � gravels. Strata of sediment with contrasting textures(i.e. clay or sand)produce soil conditions • that can restrict the downward movement of soil water through a soil profile and create periodic, or temporary saturated conditions. This phenomenon can produce mottled colors in the soil � which are called redoximorphic features and are an indicator of periodic saturation. The soils • observed are typically not within the range of characteristics for the Demontreville soils mapped in the soil survey;primarily because of redoximorphic features present in the upper portions of . the soil profile and the presence of clayey and silty lacustrine sediments. � The following is a brief narrative of the soils investigated on the site of the Scandia onsite • sewage treatment area, a potential expansion area and an abandoned soil treatment site. See • Attachment A for detailed descriptions of each soil boring. � Existing Soil Treatment Area � Seven soil borings where described around the perimeter of the drain field with two located on � the east side (SB-1 and SB-2), one on the south side(SB-3),three on the west side(SB-4, SB-5 • and SB-6) and one on the north side(SB-7). The area investigated is a westerly facing,plane to slightly convex-shaped, gently sloping side slope. � • The soils at SB-1, SB-2 and SB-3 generally have coarser-textured sediments to a depth of about 30 to 36 inches below the surface. Typically, each site has a dark-colored surface horizon less � than 10 inches thick with loam, sandy loam or loamy sand textures and weak subangular blocky • structure. The subsoil horizons are stratified with loam, sandy loam and loamy sand textures dominating with occasional gravelly bands. Soil structure in the subsoil is typically subangular � blocky. The underlying soil material is mostly stratified, sandy clay loam or coarser-textured • sediments,but SB-3 does have an 8 inch band of clay loam present. Structure in the lower � � � � � � � � � � � � � � � � � � � � � ' � � � � ` • � � � � � e � � � � � � � � � � � � � � � � � � � � � � � S Mr.Brian Malm,P.E. � June 23,2011 Page 3 � • portion of the soil profile is typically massive(no structure). Consistence is typically very friable in the upper soil profiles but ranges to firm in some portions of the lower profile. All three sites � exhibited saturated conditions within 36 inches of the surface. Depth to redoximorphic features • range from 18 inches to 34 inches below the surface. � Soil borings SB-4, SB-5 and SB-6 have upper sediments very similar in texture, structure and • color to the previous three sites but fine-textured lacustrine deposits are present beginning at a depth of 55 inches at SB-4 and at 31 inches at SB-5. Textures in the lacustrine materials are silt � loam,silty clay loam and clay, with little or no structure (massive). Boring SB-6 has a 10 inch • band of clay loam with firm consistence and massive structure beginning at 26 inches below grade. Depth to redoximorphic features in SB-4, SB-5 and SB-6 range from about 15 inches to ! 26 inches below the surface. • Soil boring SB-7 is remarkable in that the upper 23 inches appears to be fill indicated by mixed � textures and colors. This may be a result from final landscaping during the construction of the i drain field. This boring stopped at 34 inches due to cobbles or rock obstruction. No • redoximorphic features were observed in that portion of the soil profile assumed to be original. • Slopes in the existing drain field area were typically less than 8 percent and have linear(plane) • shape horizontally(across the slope)and are convex to plane-shaped vertically(up and down the slope). � • Expansion Area � Of the four soil borings observed in the potential expansion area, SB-8, SB-9 and SB-10 were � similar in having loamy surficial sediments followed by(high clay content)clay loam upper subsoils and lacustrine-derived bands of clay 2 to 10 inches thick in the lower portions of the • profiles. Soil structure in these profiles is typically subangular blocky with friable consistence • with the exception of the clay layers which have no structure(massive)and are firm or very firm in consistence. Redoximorphic features observed at SB-8, SB-9 and SB-10 ranged in depth from � 16 inches to 30 inches below the surface. Saturation was evident in each boring,typically above • a clay layer. Soil characteristics at SB-11 exhibit loam surface textures with underlying stratified sands,loamy sands and till-like sandy clay loam textures to a depth of at least 29 inches where � the boring ended due to an obstruction. Soil structure is mostly subangular blocky, but is single • grained in those horizons of sand. Consistence is typically friable or very friable. Redoximorphic features are evident as shallow as 13 inches below the surface with thin strata of � sandier materials from 13 to 29 inches nearly saturated. • Slope characteristics within the expansion area were typically less than 3 or 4 percent with plane � to sli�htly convex-shaped slopes. � � � � � � � �