Decatur is a Tennessee Valley city in Morgan County, Alabama, situated on the south bank of Wheeler Lake — the TVA reservoir created by Wheeler Dam, one of the original New Deal-era Tennessee Valley Authority projects. The city is an industrial and manufacturing center, home to chemical, automotive parts, and food processing industries, and serves as the economic hub of the Lawrence-Morgan-Limestone county area in North Alabama. Wheeler Lake and the adjacent Wheeler National Wildlife Refuge create an environmental overlay that affects property development throughout the county — TVA maintains flowage easement rights below the 760-foot shoreline elevation, limiting development and septic system placement near the reservoir. North Alabama's high annual rainfall (averaging 56 inches in Decatur) makes proper drain field function more challenging than in drier Alabama regions: soils are seasonally wetter, the drain field's natural evapotranspiration is limited, and the margin between design capacity and failure is narrower. Morgan County homeowners in the Tennessee Valley floodplain face the additional risk of TVA-managed flood releases that can temporarily inundate low-lying properties and their septic systems.
Soil Conditions
Morgan County soils span the Tennessee Valley physiography with Hartsells fine sandy loam, Leesburg gravelly fine sandy loam, and Tupelo silt loam as key series. Hartsells fine sandy loam — a Mollisol-influenced Inceptisol of the Highland Rim — has a fragmental cherty lower profile overlying Pennsylvanian sandstone at 20-40 inches, moderately permeable. Leesburg gravelly fine sandy loam forms on colluvial footslopes with good drainage. Tupelo silt loam is found in the Tennessee River floodplain and low terraces — a poorly drained Entisol with seasonal water tables at 0-18 inches. The Wheeler Lake reservoir shoreline creates lacustrine sediments with high clay content and variable saturation.
Morgan County's upland residential soils — primarily Hartsells fine sandy loam — are Inceptisols formed in residuum and colluvium from Pennsylvanian sandstone on the Highland Rim. Hartsells has a B horizon with moderate clay content (12-20%) and good to moderate permeability, making it one of the more favorable soil series for conventional septic design in this part of Alabama. The cherty lower profile may limit excavation depth on some lots. Leesburg gravelly fine sandy loam on footslope positions is similarly favorable. The critical limitation for many Decatur-area properties is not soil quality but landscape position: Tennessee River floodplain soils (Tupelo silt loam, Dowellton clay) are seasonally saturated to near the surface and unsuitable for any conventional on-site wastewater system.
Water Table: Upland Hartsells and Leesburg soils have water tables at 36-60+ inches. Tennessee River terrace and floodplain soils have seasonal water tables at 0-24 inches. Wheeler Lake level fluctuations affect shoreline property water tables seasonally.
Local Regulations
Morgan County Health Department enforces Alabama DPH Chapter 420-3-1. The 1-acre minimum lot requirement applies countywide. TVA's flowage easement below elevation 760 feet mean sea level (Wheeler Lake's full pool) restricts development and septic system installation in floodplain areas. TVA easements must be verified before any septic permit application on riverside or lakeside property. Upland Hartsells and Leesburg soils are generally suitable for conventional systems. Setbacks: 50 feet from water supply wells, 75 feet from streams and surface water (including Wheeler Lake), 10 feet from property lines.
Morgan County Health Department (Alabama DPH Chapter 420-3-1) issues onsite sewage system permits. Site evaluation by county sanitarians required. Decatur is a TVA (Tennessee Valley Authority) region city where Wheeler Lake and Wheeler Wildlife Refuge create significant environmental overlay constraints. The Tennessee River floodplain soils are unsuitable for conventional septic, and TVA's 760-foot above-sea-level shoreline boundary excludes development below this elevation. ADPH 1-acre minimum lot rule applies.