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STATE OF NEW HAMPSHIRE —

INTER-DEPARTMENT COMMUNICATION ...

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ernard D. Lucey, P.E. Chief, Water Supply Division

DATE February

AT (OFFICE) Water Supply and Pollution Control

Commission SUBJECT POSSIBLE WATER SUPPLY SOURCE

ROUTE 102, LONDONDERRY Page 1

TO Michael P. Donahue, P.E. Director, SDMSDocID 571639 Division of Municipal Services

This letter summarizes our evaluation of establishing an alternate public water supply North of route 102 in Londonderry New Hampshire, to provide a perma­nent water supply to Londonderry Green Apartments and the area of Mercury and McAllister Drives.

As you know, we do not believe that this alternative is desirable for the following reasons:

SOURCE

(1) By Commission policy, a surface water supply would not be considered appropriate for such a system.

(2) Two types of groundwater supplies could be considered:

(a) dug wells into unconsolidated soil strata or; (b) "artesian" wells into the bedrock strata.

It is our belief that unconsolidated soils in this area have low perme­ability, are of shallow depth, and have a water table that fluctuates to dangerously low levels. For these reasons we do not believe that a well into the soil strata would be feasible. An artesian well into bedrock could conceivably provide adequate quantity. However, the drilling of these wells is very much of a hit or miss operation, and many wells might be necessary to satisfy even the average day demand of Londonderry Green. We are concerned that the greater depth of these wells and the greater cone of depression could draw the pollutants in a northerly direction from the Tinkham property. There is essentially no topographic difference between this general area North of Route 102 and the Tinkham site. Bedrock well depths of 300-500 feet deep could be expected.

(3) Assuming the basic groundwater water resource could be developed, the State of New Hampshire Public Water Supply Program requires a minimun 200 feet protective radius around such sources for very small systems and up to 400 feet for municipal water supply sources. In view of the size of the contemplated service area, we believe a radius of 250-300 feet should be provided. This protective radius requirement would result in an approximate 5.0 acre parcel that would cost approximately $125,000.

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STATE OF NEW HAMPSHIRE INTER-DEPARTMENT COMMUNICATION

FROM Bernard D. Lucey, P.E. Chief, Water Supply Division

DATE February 15, 1983 Water Supply and Pollution ControlATAT (OFFICE)(OFFICE)

Commission POSSIBLE WATER SUPPLY SOURCE page 2 ROUTE 102, LONDONDERRY

TO Michael P. Donahue, P.E. Director, Division of Municipal Services

(4) The quality of water from either type well may or may not be potable. The area to the North of Route 102 has a number of apple orchards on which pesticides are regularly used. This could present a problem out­side the 250-300 foot protective radius. If bedrock well is attempted, it must be recognized that there is a chance of encounting naturally occurring arsenic, radioactivity, or fluoride above the EPA maximum contaminant limit. Additionally, there is a greater probability of elevated levels of iron or manganese which would require a treatment process. The cost for one bedrock well and submersible pump would run somewhat less than $10,000.

Pump Station and Control Building

This new source location would require a pump station and control building to include an approximate 10,000 gallon atmospheric storage tank, and a 4,000 gallon pressure tank with duplicate booster pumps.

Distribution System Tie-In

The tie-in to the existing piping system would necessitate an unknown length of additional piping, including a highway tunnel crossing on Route 102. State Department of Public Works policy does not allow open cuts across state highways.

SUMMARY

Due to the expected delays in obtaining land and easements, no safeguards of adequate quality or quantity, with no provision for fire protection, we cannot recommend further investigation of this alternative.

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