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�� , � WENCK �� Responsive partner. Exceptional outcomes. July 15, 2016 Shawn Wischmeier 2851 Washta Bay Rd Excelsior, MN 55331 Subject: Individual Sewage Treatment System (ISTS) Design This is a revised version of a design submitted in May 2016. The revised design is for a four bedroom home instead of a three bedroom home as originally submitted. 1. Leaal Description - 540 Big Island; City of Orono; Hennepin County, Minnesota 2. Site Conditions - A three bedroom, Type II, approximately 2,000 square foot residential home is proposed. The exact footprint of the proposed home has not yet been determined; final tank location and length of pipe may change with the final installation. An approximately 15% slope exists at the proposed drain field location. The proposed home will be served by a new well that will be located outside the required 50 foot drainfield and tank isolation distances. 3. Soil Conditions - The Hennepin County Soil Survey was reviewed prior to our site visit; the soil survey indicates the site is underlain by glaciai till deposits. The soil profile description completed from the soil borings is found in Appendix A. The location of the soil tests are found on Figure 2. The site is suitable for a subsurface drain field. Seven years (2007-2014) of site-specific well and piezometer monitoring data indicate the site does not experience seasonal saturation within 66 icnhes of the surface (depth of monitoring well), even during record high water levels and record precipitation (May 2014). Observed soil mottling is due to calcium carbonates, iron concretions, or relict redoximorphic features and not due to seasonal soil saturation. See Appendix A for a Technical Memorandum submitted by Wenck to the City of Orono regarding Big Island soils and groundwater monitoring. Four percolation tests were conducted in the area of the proposed drain field. The most restrictive result was approximately 9 minutes per inch. Based on the soil profile descriptions and perc tests a loading rate of 0.45 gallons per day per square foot was selected. See Appendix B for soil information. 4. Sizinq of Treatment Svstem - The ISTS is designed for a four-bedroom Type II residence; the estimated daily flow for this residence is 375 gallons. Sink and toilet fixtures need to be monitored closely to ensure proper operation. A leaking faucet or toilet can more than dout�le the daily flow to the ISTS and cause hydraulic failure. 5. Description of the Treatment Process - • Primary Treatment - Sewage is gravity discharged from the house to a septic tank. Natural biological activities taking place inside of the septic tank will separate solids and suspended particles. Solids are reduced to some extent through this process. Wenck Associates, Inc. � 1802 Wooddale Drive � Woodbury, MN 55125-2937 Toll Free 800-472-2232 M�in 651-294-4580 f m�il wenckmp@wenck.com �'veb wenck.com