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<br />Wenck Associates, Inc. | 1802 Wooddale Drive | Woodbury, MN 55125-2937 <br />Toll Free 800-472-2232 Main 651-294-4580 Email wenckmp@wenck.com Web wenck.com <br />- <br />May 3, 2018 <br /> <br />Roger Peitso <br />Building Official, City of Orono <br />2750 Kelly Parkway <br />Orono, MN 55356 <br /> <br />Subject: Individual Sewage Treatment System (ISTS) Design. <br /> <br />THIS DESIGN APPLICATION WILL REQUIRE A VARIANCE FROM THE CITY OF ORONO <br />PROPERTY LINE SETBACK REQUIREMENTS. THE CITY WILL ADVISE THE OWNER IF A <br />PROPERTY LINE SURVEY IS REQUIRED. <br /> <br /> <br />1. Legal Description – 300 Big Island; City of Orono; Hennepin County, Minnesota. PID <br />053-2311723320027. <br /> <br />2. Site Conditions – The approximately 0.25 acre parcel contains a two-bedroom, Class II <br />dwelling as well as two storage sheds. Water service is via a private well. The site slopes <br />toward Lake Minnetonka at a 5-10% grade. A new well has been drilled near the <br />dwelling to allow for the required 50-foot well setback from the proposed septic <br />drainfield in the rear of the yard. <br /> <br />3. Soil Conditions – The Hennepin County Soil Survey was reviewed prior to our site visit; <br />the soil survey indicates the site is underlain by glacial till deposits. The property is <br />mapped as the L22C2 Lester loam map unit. Soil investigations indicate the presence of <br />clay loam subsoil at the proposed system depth of 24 inches. Clay loam soil has a <br />recommended loading rate of 0.45 gpd/sqft. Hydraulic conductivity testing confirm the <br />soil can accept a loading rate of 0.45 gpd/sqft, and the drainfield has been sized <br />accordingly. Soil profile descriptions can be found in Appendix A. Hydraulic conductivity <br />testing results are in Appendix B. The locations of the soil tests are found on Figure 1. <br />The depth to seasonal saturation and/or bedrock was determined to be at or <br />below 60” during a site visit with Roger Peitso on April 28, 2017. <br /> <br />4. Sizing of Treatment System – The ISTS is designed for a two-bedroom Class II dwelling; <br />the estimated daily flow for this residence is 225 gallons. Soil loading rate is 0.45 <br />gpd/sqft. Infiltrator Quick4 High Capacity chambers provide 12 inches of sidewall <br />absorption area, which allows for a 20% reduction in the final bottom surface area of the <br />trenches per MN 7080.2210 Subp 3(B). Final total bottom area is 420 sqft (minimum <br />required bottom area is 400 sqft) divided into five 28-foot trenches. Each chamber is <br />four feet long, and each trench length must be divisible by fou r feet. A total of 35 <br />chamber units will be installed. Sink and toilet fixtures need to be monitored closely to <br />ensure proper operation. A leaking faucet or toilet can more than double the daily flow <br />to the ISTS and cause hydraulic failure. <br /> <br />5. Description of the Treatment Process – <br /> <br /> Primary Treatment - Sewage is gravity discharged from the house to a septic <br />tank. Natural biological activities taking place inside of the septic tank will <br />separate solids and suspended particles. Solids are reduced to some extent <br />through this process.