Ala. Admin. Code r. 335-7-15-.04

Current through Register Vol. 43, No. 1, October 31, 2024

Section 335-7-15-.04 - SWAA Delineation For A Groundwater Community Water Source

All community groundwater systems shall delineate appropriate SWAA I and II in accordance with the requirements of this section.

(a) The delineated SWAA shall be drawn on a 24" X 36" US Geological Survey (USGS) 7.5 minutes topographic quadrangle (more than one sheet may be used if necessary). Color photos or color print copies shall be used. The delineation may utilize natural or man made structures to define the SWAA as long as these structures are located in close proximity to the calculated or mapped SWAA boundary.

(b) A geologist licensed in Alabama shall perform all SWAA area delineations, other than the fixed radius method.

(c) To identify aquifer flow characteristics, a potentiometric map shall be constructed using local water level measurements and show gradient and flow direction.

(d) The degree of confinement shall be determined by geologic or hydrologic approaches and using the documents listed in 335-7-15-.04. Geologic, graphical and drilling logs, geologic descriptions of local stratigraphy, and cross-sections derived from local stratigraphy shall be included and used to determine confinement.

(e) Geologic, geophysical, graphical and drilling logs, geologic descriptions of local stratigraphy, physiographic description, description of the hydrogeology and cross-sections derived from local stratigraphy shall be included in the report.

(f) Construction of the SWAA shall be according to Table 1. All data and calculations used to determine the SWAA shall be included in the report. One of the following methods should be used.

1. Fixed radius (400 feet or 1000 feet radius).

2. Analytical methods or numerical modeling for Time of Travel (TOT) with hydrogeological mapping of flow boundaries.

3. Conduit flow. SWAA for wells in karst or conduit flow aquifers should be established using hydrogeological mapping of flow boundaries and karst features such as sinkholes and sinking stream, lineament analyses and dye tracer tests.

4. Special Conditions.

(i) Confined aquifers.

(ii) The SWAA I for public water supply wells in coastal plain confined aquifers, with the top of the first screened interval at 600 feet below ground surface or greater, may be established by a 400 foot fixed radius. A SWAA II is not required.

(iii) A waiver from the full TOT SWAA delineation requirement may be requested of the Department by systems that have wells with the first screened interval less than 600 feet below ground surface. If the aquifer is under confined conditions waivers may be considered based on site-specific considerations such as degree of confinement.

(g) Gulf Coast aquifers. Wells that have been identified as being in the coastal zone of Alabama shall comply with the Alabama Coastal Area Management Program Regulations (Division 335-8) as well as this chapter.

(h) Wellfields. Systems with large wellfields, where wellhead areas may overlap, may define a SWAA I and II that encompasses all of the wells to create a composite SWAA I and II. This area shall be based on cumulative drawdown and interference of all the wells in the wellfield.

Table 1Alabama Source Water Assessment Area (SWAA) Delineation Criteria & Threshold
Porous: porous flow	Karst: porous flow	Karst: conduit flow	Fractured: porous flow	Fractured: conduit flow
SWAA I	180-day TOT or 400 ft radius*	180-day TOT or 400 ft radius*	1000 ft radius	180-day TOT or 400 ft radius*	1000 ft radius
SWAA II	10-year TOT with hydro-geologic flow boundaries	Hydrogeologic flow boundaries and TOT (where appropriate)	Hydrogeologic flow boundaries and dye tracing	10-year TOT with hydrogeologic flow boundaries	Hydrogeologic flow boundaries and dye tracing (where appropriate)

* Whichever is greater

Ala. Admin. Code r. 335-7-15-.04

New Rule: Filed November 7, 2005; effective December 12, 2005. Amended: Filed December 18, 2007; effective January 22, 2008.

Authors: Edgar K. Hughes, Dennis D. Harrison

Statutory Authority:Code of Ala. 1975, §§ 22-23-33, 22-23-49, 22-22A-5, 22-22A-6.