Groundwater Monitoring Well/Piezometer Installation Details

Related pages: Monitoring well screened over a single vertical interval (pdf file); ground water monitoring well in bedrock (pdf file)

Monitoring well or piezometer locations, depths, and construction details must be determined by a Maine Certified Geologist (C.G.), based on interpretation of the geology and hydrogeologic regime at a project site, in order to provide valid groundwater monitoring data.

To adequately interpret information obtained from monitoring wells or piezometers, the investigating C.G. must provide a properly-endorsed monitoring well or piezometer installation report to the Department. This report should contain a brief narrative which indicates the date each monitoring point was installed, the method of installation, the purpose/objectives of the monitoring network, and a discussion on the basis for selection of monitoring well/piezometer locations and depths. The following data must also be included in the report:

1. A map showing final groundwater monitoring well or piezometer locations, with identification symbols (alpha or numeric) for each monitoring point, including the location of the benchmark (BM) used to de-termine well/piezometer and ground surface elevations. Include notes describing the BM, its reference elevation, and name/title/address of party responsible for establishing BM.

2. Elevations (to the nearest tenth of a foot) of the following for each monitoring point: ground surface, top-of-casing (at specific point on casing from which ground-water depth will be measured), and the top and bottom of the well/piezometer screen interval, referenced to an identified BM. Elevations based on the NGVD (1929) are preferable, however, an assumed datum may be used.

3. Measurements (to the nearest tenth of a foot) of the following for each monitoring point: depth to bottom of borehole and well casing from ground surface, and height above ground surface of top-of-casing (i.e. pipe "stickup" height).

4. Description of type and thickness of seals, texture of packing used around screened interval, and diam-eter/specifications of well screen and casing.

5. Borehole logs (annotated by a Certified Geologist if original logs recorded by a well driller).

6. Summary of depths and elevations measurements to phreatic or potentiometric groundwater surface.

7. Hydraulic conductivities of subsurface strata, and associated field data/calculations. Include estimated groundwater time-of-travel from potential contamination sources to each monitoring point.

8. Copy of well/piezometer drilling/installation contract and specifications, if any.

Notes:

• The information outlined in items 2 through 6 above should be provided by schematic cross-section dia-grams for each monitoring point installed.

• A summary table must be included for all monitoring points, that contains the monitoring point identifi-cation (I.D.) symbol, top-of-casing elevation, pipe stickup height, ground surface elevation, and well/ piezometer depth.

• Protective steel casing, with a lockable cap, must be installed around monitoring points to prevent dam-age or destruction. Near areas of traffic, bollards may be necessary for further protection.

• Permanent I.D. markings, such as a tag inside the well cap and I.D. markings on the outside of the pro-tective casing, must be provided. A witness stake or flagging at each monitoring point, or brightly paint-ed casing are optional, but are recommended so monitoring points may be easily-found.

rev. 6/99 DEPLW-129-A1999