MDEQ FORM #4 – SUSCEPTIBILITY ASSESSMENT

 Please use one form for each ground water source (well or spring)

Public Water System:________________________________ PWSID #:__________________
Address:_____________________________________________________________________
City:  __________________________________________ County:______________________
Contact Person:_________________________________Telephone:_____________________
Number of Service Connections: _________________Population Served:_________________
Township: _____________________________Range:________________________________
Section: ______________________________¼  ¼  Section: ___________________________
Latitude/Longitude: ____________________________________________________________

Well Construction Information

Date well constructed: __________________________________________________________
                                        (mm/dd/yy)
             reconstructed:__________________________________________________________
                                        (mm/dd/yy)
Well driller (if known): _________________________________________________________   

Type of  Well (circle appropriate description)

Drilled:  rotary                                                  Dug:   hand
            auger                                                              lateral collector
            cable                                                              excavated
                                                                                  springs
                                                                                  tile
                                                                                  driven
                                                                                  infiltration
Please provide additional information as necessary. __________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________

Well log available (circle one)       yes  /  no              (if yes, please attach copy to this form)

If no well log is available, other records may be substituted as documentation construction.  Other construction
 records may include boring logs, as-built drawings, engineering reports and reconstruction logs completed by
certified drillers.

Wellhead Information

 Depth to top of well screen (circle one)

 <20 ft               20 – 50 ft                 50 – 100 ft                    100 – 200 ft               >100 ft
                                                                                                (coarse setting)

Coarse setting includes: predominant sand and gravel materials in unsaturated zone above aquifer.

Depth to groundwater (circle one)

<20 ft               20 – 50 ft                 50 – 100 ft                    100 – 200 ft               >100 ft

Well head elevation _____________________________(height above mean sea level)

(check one)

________   no evidence of confining layer

________   evidence of confining layer and < 20 ft piezometric head

________   evidence of confining layer and > 20 ft piezometric head

________   no well log available

Thickness of each confining layer: ______________________________________________
                                                   ______________________________________________
                                                   ______________________________________________
 Well Head Construction (circle one):

Well head enclosed                   Controlled access to                 Other: _____________________

in well house                             well head                                   __________________________

Grouting Depth  (check one)

Regional Water Quality Information (check appropriate lines):
________   Other water systems with reported water quality problems within ½ mile.
________   Record of groundwater contamination within ½ mile.
________   Record of groundwater contamination within 1 mile.
________   Identified clean up site within ½ mile.

Source Specific Water Quality Records (check appropriate lines):
________  MCL violations for nitrate/nitrite
________  >5 mg/l nitrate
________  2 to 5 mg/l nitrate
________  nitrate <2 mg/l
________  no nitrate sampling records
________  MCL violations for VOCs
________  VOCs detected
________  VOCs not detected
________  VOC tests not completed
________  SOC analysis completed with no detection
________  SOC analysis completed with detection
________  History of bacterial contamination within last three years
________  Classified as groundwater under direct influence of surface water by MDEQ 

Weighted Hydraulic Conductivity Calculation
The weighted hydraulic conductivity is calculated according to the following equation¹:
Kw =                                            Z(total) +
             (Z1/K1) + (Z2/K2) + …… + (Zn/Kn)

where Kw is the weighted hydraulic conductivity, Z (total) is the total thickness of  n layers, Z1, Z2,…., Zn represent the thickness of individual layers 1 through n.  K1, K2, ….., Kn represent the hydraulic conductivities (permeabilities) of layers 1 through n.
 Layer                                Thickness  (ft)                                       Permeability (ft/sec)                       Zi/Ki
                                                    (Zi)                                                         (Ki)

FIGURE 1 – TRANSVERSE POTENTIAL¹

(Hydrogeologic Characteristics Related to Water Movement to the Aquifer)

Depth (feet) to the Aquifer

1.       A Transverse Potential of 1 = low potential for water movement, 10 = high

2.       Kw =                                    Z _(total)  ¸
                       (Z1/K1) + (Z2/K2)  + ….  (Zn/Kn)

where Z^(total)  = total thickness of n layers, Z1, Z2….Zn represent individual thickness of layers 1 through n.  K1, K2….Kn represent permeabilities of layers 1 through n.  Permeabilities should be in units compatible with thickness, i. e., ft/sec if thickness in feet.  Final value should be converted to gallons/day/ft² for use in matrix.  For example, if thickness is in feet, permeabilities in feet/second, multiply the result from the formula above by 646,340 to convert to gal/day/ft².

FIGURE 2 – INFILTRATION POTENTIAL¹

 (Relating Water Availability to Transverse Potential)

 Hydraulic Surplus² (inches)

1.       An infiltration potential of 10 indicates a high probability that the combined availability of water (hydraulic surplus) and geologic conditions (transverse potential) will lead to water from the surface reaching the aquifer.  A score of 1 indicates a low probability.
 

2. Hydraulic Surplus = Rainfall + Irrigation – Evapotranspiration – Runoff, from Vogue et al., 1991.  Guidelines for Minimizing Movement of Pesticides to Groundwater: Oregon State University, draft manuscript.  See text for substitution for this parameter if data not available to calculate the value according to the equation given.
3. 
   Transverse Potential Score.