WorldWide Drilling Resource®

Environmental Monitoring by Thomas Kwader, Ph.D., P.G. WorldWide Drilling Resource ® Hydrogeologist Considerations for Locating Wells and Septic Tanks on Small Residential Lots Part 1 This is the first of a two-part series regarding locating shallow wells and septic tanks on small residential lots. This first article discusses the relative placements of the well on the property. Next month, part two will discuss factors regarding the location and construc- tion of the septic tank and optimum hydroge- ologic conditions for the septic tank and drain field. So, let’s assume your customer just purchased a small residential lot in a newly platted subdivision in an underdeveloped rural area. The lot is about ¼ of an acre, or 100 feet x 100 feet. The lot is high and dry and has a slight slope from north to south. Assuming the house will be located near the center of the 100-foot square lot, where should the shallow well and septic tank be located? Generally, the well should be upgradient of the septic tank (north, uphill) and the septic tank downgradient of the well to minimize cross-contamination to the well. Also, you must consider the fact adjacent new lots may also be developed in the future and there may be a “setback dis- tance” for septic tanks. (The septic tank will be addressed in a separate discussion at another time.) Factors to consider regarding construction of the well include: 1) Depth of Well - Ideally, the screen or producing zone of the well should be at a sufficient depth below a clay or low per- meability confining bed that retards downward movement of shallow water. This confining layer will help ensure adjacent septic tank drain fields will not directly percolate downward into the local aquifer. 2) The annular space of the well (outside of the well casing) must be sealed with cement grout from the top of the producing zone to land surface to prevent vertical migration of surface water into the producing aquifer. 3) The pumping rate of the well should be restricted to a low rate (1-5 gallons per minute) to ensure a large “cone of de- pression” is not created that could “pull” groundwater from nearby septic tank drain fields. An initial test boring should be installed at the well site to ensure the water table is at least five feet below land surface most of the year, and a low permeability clay layer or other soil material for a sufficient unsaturated zone is present for the septic drain field to properly function. It is recommended a bacteria test be peri- odically performed to assure the well is not contaminated. Tom Tom Kwader may be contacted via e-mail to michele@ 48 AUGUST 2020 WorldWide Drilling Resource ® ENV Congratulat ions to: Crowell Drilling Co., Inc. Louise , TX Louise , TX Winner for July! Time for a Little Fun! On theme with the Editorial Focus of Protection and Safety, fill in the missing vowels. D _ N G _ R G _ _ R D S H _ Z _ R D S _ F _ T Y S _ C _ R _ S H _ _ L D G L _ V _ S C _ V _ R S P _ L _ C Y M _ N _ _ L Win a prize! Send completed puzzle to: WWDR PO Box 660 Bonifay, FL 32425 fax: 850-547-0329 or e-mail: michele@ July Puzzle Solution: October Issue Deadlines! Space Reservation: August 25 th Display & Classified Ad Copy: September 1 st