Lake Lanier is a reservoir in Georgia with TMDL calling for a reduction in nitrogen and phosphorus inputs (GA EPD, 2017). Our objective was to estimate the contribution of nutrients from domestic OWTS along the shoreline. Groundwater samples were taken at 4 home sites while soil samples and Ks measurements were taken at Site 2. We used HYDRUS (2D/3D) to simulate the OWTS N load at Site 2 and to develop a box model able to assess the importance of factors in affecting the load to the lake. Preliminary results showed groundwater concentrations of nitrate-nitrite up to 9 mg N L-1 at Site 1, revealing that OWTS can contribute N to Lake Lanier. The box model appeared to be a promising tool. Investigation of P did not reveal evidence of OWTS contributing to the P load at Lake Lanier, however P may have moved 27 m downslope from the OWTS.