In accordance with your instructions I have made a careful examination of your present source of water supply and of the adjoining neighbourhood and hare the pleasure to report as follows:-
The present supply to the town is obtained from two wells, and a supplementary sinking in the lower beds of the "Oolite" lying immediately on the "Upper Lias"; these Strata in this particular spot cannot be expected to yield any large quantity of water from the fact that they 'crop out' at a very short distance to the north west and that the 'Dip' or inclination of the Strata lies in the direction away from the outcrop.
The fact of the general dip of the Strata being to the south east, of the Nene Valley carries the water falling on the surface away from the present source of supply so that only a small portion can be intercepted for the use of the Town.
Accompanying this report is a sketch of the general disposition of the Strata in the neighbourhood, which will more clearly explain the above remarks.
The Strata to the south east consists of the outcrop of the 'Oolite beds' underlying the "Oxford Clay," the tendency in this case being to lead the water falling as rain away from the south east banks of the Nene, consequently there is not much hope of obtaining any large supply of water from the Strata overlying the clay in this direction.
Water may be obtained in most districts by selecting a suitable area and collecting the rainfall in a surface Reservoir, but the land within reasonable distance of Rushden does not present any very suitable spot for obtaining such a supply, and also this system of water supply except under exceptional circumstances is costly in respect to first outlay.
The Valley of the Nene contains an extensive bed of gravel carrying a large quantity of water quite independent of the river itself.
An abundant supply of water 'of good quality' might be obtained from this source were it not for the risk of contamination from the towns and villages in the valley above.
At a considerable depth in the clay which comes to the surface in the Nene Valley there is a stratum of rock known as the 'Middle Lias' which in many places contains a large supply of pure and excellent water. I have made a number of borings and sinkings into this stratum with varied success, in some cases the yield of water has been very great and in others so small as to be of little value.
Under the peculiar circumstances of vour surroundings and the prospective rapidly increasing demand for water, I do not hesitate to advise looking to the Middle Lias rock for water.
If you are fortunate in the selection of the spot a supply from this source would provide for many years to come, even with the great prospective extension of your Town.
I calculate that the water bearing rock may be met with between the depths of 200 and 300 feet, and if water in quantity is present it would probably rise to within 150 feet of the surface so that in case of success, lifting the water to the necessary height to supplv the Town would not be excessive.
The first step would be to put down a borehole of sufficient size to enable a test for quantity to be made, this would cost probably not less than £500 and might terminate in no satisfactory results, but if water were found in quantity the ultimate cost of providing would be less than any other of the possible sources.
Herewith is a sketch section of the Strata in the neighbourhood showing how it is that the rainfall on the adjoining land is not found in sinking in the neighbourhood in consequence of the dip or inclination of the Strata being away instead of falling towards the Town, I have also marked the probable position of the "Middle Lias" stratum from which such a satisfactory supply may probably be obtained.
I have also attached an Ordnance Map with the high, or gathering grounds marked from which you will see that there is very little high land on the south side of the Nene and the greater part discharges its rainfall into the river Ouse.
Should the Council desire to make a test boring, great care should be exercised in the selection of the spot, as I have ascertained in some of my sinkings that there are several "faults" in the "Lias Clay" which are in some cases the means of cutting off the supply of water in the Middle Lias Strata.
Should the Council desire any further particulars I shall be happy to give them.
I am, gentlemen,
JOHN EUNSON, C.E., F.G.S., etc.
Northampton, September 27th, 1897.