Wanstead Park

The Lake System of Wanstead Park - Part 2

Heronry Pond

Reprinted (with minor modifications) with acknowledgements to James Berry & Alan Cornish, from their work "The Lake System of Wanstead Park & The Mystery of The Heronry Pond" © James Berry & Alan Cornish, March 1978.

Site Exploration

Geological data indicated that the north east quarter of Heronry Pond was bounded by Taplow Gravel, whereas the remainder of the lake appeared to be seated directly onto London Clay. Since the latter is impervious to water, it seemed probable that any leakage would occur into the Taplow Gravel, (see geological map - page 9).

This posed the question: how deep was the layer of Taplow Gravel adjacent to Heronry Pond? Did the bed of the pond rest on the underlying London Clay, or was there a layer of gravel between the bed of the lake, and the underlying clay?

In order to gain information on this point, geological survey specialists were contacted early in 1975. Albury Laboratories Site Investigation Ltd., kindly undertook to make available a test crew for one day, at cost. No transport charges were incurred since the crew were not far from the area at the conclusion of a previous contract.

The Conservators of Epping Forest generously agreed to finance this one day exploration, which took place on 9 April 1975.

At this time Heronry Pond was filled completely, and for the first time in some years, the entire system was functioning as its designers had intended.

Additional geological data has been made available by the Borough Engineer of Redbridge, so that in all, we have information from three boreholes sunk into the Taplow Gravel:

Albury Borehole No. 1 --------- (
Albury Borehole No. 2 --------- (See map at page 26)
Redbridge Borehole No. 1------ (

Page 26 shows the surface and sub-surface geology (in elevation) at the eastern end of Heronry Pond. From this it will be seen that there appears to be a substantial bed of gravel between the bottom of Heronry Pond, and the under-lying London Clay. The underlying clay appears to slope gently downwards in an easterly direction, from the point north of the East Island where it is exposed on the surface, to somewhere near the eastern edge of Heronry Pond, where at Albury Borehole No. 1 the clay is six metres below ground level.

Since the bed of the pond is about 1.8 metres below ground level by Albury Borehole No. 1, this suggests that a layer of gravel stretches across Heronry Pond beneath its eastern end, about 4.2 metres thick. The underlying clay then appears to rise very gently further eastwards, beneath Perch Pond on its south side, across the valley.

These findings are consistent with the geological survey map of 1921, and the geological "setting" of the lakes system.

It seems quite likely that whilst the gravel beneath Perch Pond may be two or three metres thick at its western end, where the lake is shallow, this may diminish towards the eastern end where the lake is much deeper. In other words, the eastern end of Perch Pond appears likely to be bedded upon clay, but not the eastern end of Heronry Pond (or at least not the south-eastern corner of Heronry Pond).

Permeability Tests

Details of the Albury Laboratories report are at Annex ll & III. (not available). From these it will be seen that a falling head permeability test was undertaken at Borehole No. 2. The method is described in Albury Laboratories letter CVS/MAJ/752 of 1 May 1975 (Annex II). (not available).

The permeability of the granular soil, i.e. the Taplow Gravel, was found to be a value of:

1 x 10-4 cm/sec.

It can be seen from the chart included with the Albury report that this order of permeability lies on the boundaries of good to poor drainage.

We understand that when soil of any nature is disturbed, permeability is likely to be substantially increased, if no counter-measures are adopted. The result would be as if an "improved" route for seepage had been created, through the area of disturbed soi1.

Conclusions of Exploration

The above findings indicate that the initial cause of seepage from Heronry Pond probably lies in the form of construction at its eastern end, and specifically that the eastern embankment, between Heronry Pond and Perch Pond

a. Was not made of sufficiently water-tight material, e.g. solid clay.
b. Was not carried down and seated into the underlying London Clay.

It is not known whether these weaknesses in construction date from the original eighteenth century designs, or from the later remodelling (see below).

However, so long as the inflow was sufficient to counter such weaknesses, there would be no problem. In drought years though, e.g. 1929, when inflow diminished, Heronry Pond water level would tend to fall during the summer months.

One would also expect the pond water level to be sensitive to any significant disturbances to the adjacent terrace of Taplow Gravel, i.e. excavations.

Finally, in so far as the distribution of gravel may be uneven from place to place, the determination of any more precise conclusions would be dependent upon establishment of interface of the gravel and clay at many more locations in the area.

Decline of the System and Heronry Pond

Virtually any pond or lake leaks to some extent, or loses water through evaporation, or both. In this sense then, it is relevant to define precisely how such features are created.

Our definition is that a lake or pond is created when there is a net surplus of inflow over outflow at some point, or when the two are in equilibrium.

In other words, if water flows away from a point at a faster rate than it arrives at that point, then conditions are not conducive to the formation of a lake or pond.

Thus to understand fluctuations in the water level of Heronry Pond, it is necessary to examine closely any factors likely to vary:

a. The inflow.
b. The outflow.

Furthermore, to the extent that Heronry Pond is simply one link in a chain of lakes, it is necessary to examine such changes not just to Heronry Pond, but to the overall system.

Such an examination must start by asking the question: was the total inflow surplus to the total outflow from the time when the system came into existence?

Two pointers suggest this was not the case. We have noted the ambitious designs drawn up by Jean Rocque in 1735, and how these differed from the map of 1745 which probably showed the reality of what was achieved (see page 14).

It never proved possible to realise either of the grand designs for The Great Lake, which remained a rather irregular shape, reputedly very shallow, and by the time of its disappearance in about 1908, no more than a collection of marshy puddles.

Secondly, it never proved possible to raise the level of Heronry Pond, or otherwise extend it westward, to join up with Shoulder of Mutton Pond.

These two factors, plus the construction of a special artificial river - the "River Holt" - to tap a wider catchment area, suggest that it was realised by the mid-eighteenth century that the Rocque designs were over-ambitious.

Furthermore, there is some evidence that difficulty was being encountered with Heronry Pond itself. In 1762, Jean Rocque was commissioned by Prince John, Duke of Montague, to produce a plan of London, which "just happened' to include in its north east corner, the park at Wanstead. This plan shows an embankment running north-south across Heronry Pond, about three-quarters of its length from the western end, and parallel with the embankment separating Heronry Pond with Perch Pond (see page 29) On such a small scale as this however (on a plan of the whole of London), such precise accuracy may be in question for eighteenth-century cartographers. However, Jean Rocque would have had a personal interest in ensuring that the features illustrated at Wanstead were reasonably accurate, bearing in mind his previous contact with the area. The purpose of such an embankment could very possibly have been to hold back the descent of water down into the Roding, as in the case of the other north-south embankments down the valley. If this was the case, it could be construed as showing that Heronry Pond was not, even at that time, maintaining its full level.

On another map, this time by Chapman and Andre (Plate XXI) and dated 1777, no "supplementary" north-south embankments are shown along the length of Heronry Pond. Likewise on an estate plan of the area following a survey in 1779, Heronry Pond is shown with several large islands close to its south side, but with no additional north-south embankments (see page 31). Both these maps are available in the Essex Record Office, and our attention was drawn to them by Mr J. Elsden Tuffs.

Yet on a map of the area about forty years later - dated around 1820 by Mr Elsden Tuffs - Heronry Pond is shown with a north-south embankment about one-quarter of the way along from its western end (see page 32). The map is dated about 1820 because it shows The Reservoir no longer in existence, but replaced by Reservoir Wood - work undertaken in 1815/16. It also shows Wanstead House itself, which was demolished completely between 1822 and 1824.

Construction of this second embankment across Heronry Pond again suggests that attempts were being made to stop its water from draining away, eastwards, down into the valley of the Roding.

Disappearance of The Reservoir in 1815 is a further pointer to the fact that even the extended catchment area of the system, as fed by the "River Holt", could not provide a satisfactory inflow. Naturally there would be fluctuations over time, due to the local weather conditions and particularly the rainfall, but we feel there are sufficient indicators to believe that there was a deficit balance between inflow and outflow, throughout the eighteenth century and into the early nineteenth century.

Break-up of the Estate

In the period 1822-24 the great house of Wanstead was demolished, and the main part of the grounds were closed and placed under the care of various game-keepers for the following sixty years.

The Great Lake, containing its island with Lake House built upon it, was outside the closed area. The house was occupied by various families of renown, e.g. the author Thomas Hood, but it was deteriorating rapidly. It was also made the less attractive by the fact that its surrounding lake had, by the 1830's, dwindled to no more than ditches around the edge. * Here then, is further evidence that there was a deficiency in the inflow, with two of the top-most lakes of the system lost to all intents by the early nineteenth century. (The Great Lake was not properly filled-in until about 1908, when the site was acquired for property development, and the Lakehouse estate was built).

* (See 'The Story of Wanstead & Woodford" pp 77, by J Elsden Tuffs).

Between 1824 and 1880, there was very little change made to Heronry Pond - at least intended change. Much of its surrounding area was given over to rough grazing.

The most significant event for the system occurred in the middle of the nineteenth century, in an apparently unrelated spot. The Eastern Counties Railway was opened in l843, and a branch line from Stratford - called the Woodford and Loughton Railway - started operating in 1856. As a consequence, the "River Holt" that had been channelled from Leytonstone Flats, down Spratt Hall Road, to The Basin, was severed in two by the railway cutting. Suddenly, a substantial part of the catchment area of the system, so painstakingly tapped by Adam Holt more than a century before, was completely isolated from the lakes of the park.

As a result of the further deterioration of inflow of water into the lake system, and with the lack of proper care and maintenance to it because of its closure and the demolition of the great house, the facilities of the park were under pressure in the latter part of the nineteenth century. A six-inch Ordnance Survey map of the area, dated 1873-81, showed Heronry Pond only half its normal size, and with the entire western end no more than a marsh.

Such was how the Conservators of Epping Forest found the pond in 1882, when the park came into the ownership of the Corporation of the City of London (see page 34). Not only that, but it was found that the previous tenant of the park had dug a ditch through the embankment between Heronry Pond and Perch Pond, in order to keep the former at a minimal level, and so increase his grazing areas

The previous history of Heronry Pond makes it likely that the ditch in question was dug not to drain the pond - because we believe it tended to do that periodically with the weather in any case. The ditch was probably dug to prevent the lake from flooding - or reverting to its larger size - at times when there was a surplus of inflow over outflow. It was intended to keep the level down, rather than to get it down initially. Had the pond been full and stable at all times, it seems much less likely that such a ditch would have been dug, although this is speculation.

One of the first acts of the Epping Forest Committee of the Corporation of London was to have the offending ditch filled in, thus restoring Heronry Pond to its original size.

In the following year, 1883, the Committee came to an agreement with a Mr Chapman, for the boating rights covering both Heronry Pond and Perch Pond. This agreement lasted for many years.

From 1883 until the end of the century, the records show a number of complaints about the state of Heronry Pond - primarily in 1893, 1896 and 1898.

In 1893 Heronry Pond had "dried up considerably" by the end of the summer. In October of that year the Superintendent (of Epping Forest) reported that the low water level was due to the "exceptionally dry summer" and the fact that the water had washed away the retaining bank at the lower (eastern) end of the pond, and was easily able to drain through the gravelly soil remaining. The remedy adopted was to deepen the sides and strengthen the banks of the pond.

In 1896, and again in 1898, Mr Chapman complained of loss of income from his boating rights, and asked that the pond should be "cleaned out." It is impossible to determine how much Mr Chapman's complaints concerned the condition of the water, as distinct from the lack of it, but certainly all was not well.

1900 - 1905

The drainage problem grew much worse from 1900. The Committee received public complaints about the low water level every year from 1900 to 1904, and it appears that the pond was dry every summer from 1900 to 1907. As a result, Mr Chapman's annual rent was reduced from £100 to £65 in 1900 and to £20 in 1901.

The problem can be illustrated by two maps which appear in different editions of a booklet entitled "Epping Forest" by Edward North Buxton, and published by Edward Stanford. In early editions of the guide, Heronry Pond is shown in its largest area, as restored by the Epping Forest Committee in 1882 (see page 36). But in the seventh edition of the same guide, published in 1905, Heronry Pond (un-named) is shown in almost its pre-1882 condition - half size, eastern end only. Indeed, one might easily confuse the seventh edition (1905) map with others of thirty years before (e.g. the six inch 0rdnance Survey of 1873-81 - page 34), were it not for the Midland Railway line running through Leytonstone Station and Wanstead Park Station, (page 37). The railway runs across the bottom third of map, from left side). (see also Edwardian postcard view of the pond)

At first, the huge deterioration of Heronry Pond was attributed to the dry summers of 1900, 1901, and 1902. However, after the wet summer of 1903, it was clear that some long-term factor(s) underlay the problem.

In October 1903, the Superintendent reported that:

"Owing to the very wet summer, all the lakes are full for the first time for some years. We shall not be able to keep them so for long as directly we get two or three dry days the Heronry and Perch Ponds commence to go down at the rate of rather over half an inch daily. This is due to the sewer that was made immediately outside our boundary. The sewer was most carelessly made as in some places for yards and yards the pipes are not cemented at all."

The sewer in question was laid in 1900 to serve the Aldersbrook Estate, and runs within a few yards of Heronry and Perch Ponds for most of their length, beneath Northumberland Avenue. It should also be noted that most sewers of that period throughout Wanstead were of the semi-segregated variety, such that rain falling on roads, footpaths, and roofs of houses, ultimately found its way largely into the foul sewer pipes, just as much as into the storm sewer system. When this occurred, the rainfall was lost to the catchment area of the lake system - a further significant reduction in inflow as the suburban development of Wanstead gradually progressed at the turn of the century.

However, it was not to inflow, but to outflow, that the Epping Forest Committee initially turned their attention. They asked the Superintendent to consult "an expert as to the cause of the depletion and the remedy therefore." The expert, Mr Lawford of Messrs Bailey Denton & Co., reported in December 1903 that:

"The new sewer is evidently the source of your trouble. On the day of our inspection it was two-thirds full of practically clean water, thus showing that the joints had been improperly made and that it was in effect acting as a subsoil drain rather than a sewer. The volume of subsoil water finding its way into the sewer is approximately 1,250,000 gallons daily and would, in dry summers such as those of 1900-2, readily account for the depletion of the lakes."

We have no reliable means of substantiating this report, and must take it at face value, bearing in mind that civil skills were well-developed by the turn of the century. However, the report makes no reference to the semi-segregated nature of the new sewer system, nor to weather conditions prior to the inspection, to indicate anything about the source of the clean water, apart from the adjacent lakes. When this sewer was excavated in 1977, there were differing reports about its soundness. It is therefore impossible to say whether or not groundwater was in the pipes inspected by Mr Lawford in 1903, or whether it was rainwater - with the groundwater finding its way along the line of the disturbed gravel of the sewer trench on the outside of the actual sewer pipe (see page 27 above).

Mr Lawford suggested three solutions, in order of preference. First, having the sewer re-laid in cast iron to make it watertight, at a cost of £2,500. Second, constructing a puddle trench - three feet wide and carried down two feet into the London Clay bed - around both Heronry and Perch Ponds, at a cost of £2,200. Third, draining off the water and puddling the bottoms of Heronry and Perch Ponds, at a cost of £7,000.

The immediate reaction of the Committee was to write to the local authorities surrounding Wanstead Park to ask "what sum they would be prepared to contribute on the basis of the work being carried out at a cost of £2,000."

The local authorities denied responsibility, and by 1905 it was clear that they were also unwilling to make any kind of contribution to the estimated costs.

The Superintendent therefore arranged a meeting between Mr Bailey Denton himself, and the engineers from the local authorities. According to the Superintendent, "the general consensus of the meeting was with Mr Bailey Denton "but there was apparently "little chance of getting contributions from the Councils," shortly after this meeting, Mr Bailey Denton prepared a second report in broad agreement with Mr Lawford's report. He pointed out that:

"The fact that the water is at times lowered in 24 hours to the extent of one inch, clearly proves that the sewer is at fault. The only permanent solution is a puddle trench completely encircling the Perch and Heronry Ponds, and extending down into the London Clay. I am not in favour of curtailing the water area of the lakes and puddling their bottom"

1906-1908

By 1906, the Committee had found the "ideal" solution - to have the necessary work carried out at minimal cost by unemployed men under the control of the West Ham Distress Committee. Most of the work was financed by the Local Government Board, although the Committee made a contribution of £500.

The work involved two main projects, neither of which appear to have been related to any of the recommendations of the engineers previously consulted! The first project, in 1906, was designed to increase inflow. The second, in 1907, was aimed at decreasing outflow.

The 1906 works involved the laying out of a system of drains on Wanstead Flats, with the object of draining the surface waters into the Heronry Pond. The area of the drainage system was south of Aldersbrook Road, opposite, and extending from, the south end of Park Road. It was in an area previously used as a clay pit, with associated clay mills and brick field (see map - page 34). By 1885 the clay workings had been removed, but the area then contained a shallow pond, called Brick Field Pond (see map - page 36). This pond had been filled in by about 1904, and a number of cricket pitches had been laid out over the area (see map - page 37), and it is likely the surface waters to be drained, were an indicator that the area was vulnerable to flooding.

The second project was carried out in 1907. The Heronry Pond was excavated and reduced to its present size, and the bed and banks of the pond were concreted (see diagram - page 44). This measure effectively isolated the pond from its underlying geological strata. However, we can find no records of the precise manner in which the works were carried out, nor of the skill of the supervision (though see photo). This would be a critical factor in such works, since it is never the actual concrete which provides a water-tight seal. When lakes or reservoirs are constructed, the excavation is normally lined with a thick layer of clay. It is the clay which provides the seal. Concrete is then laid on top of the clay, to protect it from damage or penetration. If this method is not followed, the lake or reservoir in question will be vulnerable to leakage in later years.

Two other works were undertaken in this period, and they are of indirect significance to the lake system. At the southern end of Wanstead Park Avenue, Aldersbrook Road had had a tendency to flood. This was because the Aldersbrook Road effectively cut off the Wanstead Flats at this point, from their natural drainage channel down a shallow valley running north-east, into the valley of the Roding. This is the area of the City of London Cemetery. In order to cure the flooding problem, Alexandra Lake was dug, on the side of the Flats, and an overflow pipeline in its north-east corner is believed to connect with the storm sewer system, and thus lead into Perch Pond via Wanstead Park Avenue. We have not been able to verify this connection however, since any overflow from Alexandra Lake is now virtually non-existent. (but see also here)

The last works of this period with a bearing on the lake system, concerned the Great Lake and lakehouse area, to the west of Blake Hall Road. By 1908 the Great Lake of a century and a half before, had dwindled to no more than a marshy bog surrounded by ditches. Its deepest part, immediately adjacent to Blake Hall Road, was made into tennis courts. The remainder was redeveloped as the Lakehouse estate. A deep drainage system was installed, about eleven feet beneath the level of Blake Hall Road on its embankment, to ensure that the tennis courts did not flood. A pipeline was laid from the tennis courts, beneath Blake Hall Road, and into Reservoir Wood, where it now emerges into open ditch, running eastwards down the valley, and into Shoulder of Mutton Pond. It is unclear whether this drainage system from the tennis courts is also connected with the ditches and drainage works in Bush Wood, immediately to the north of the Lakehouse estate, which once formed part of the catchment area of the system (see map - page 14). No direct connection can be located - and the ditches in Bush Wood are now in an appalling state of neglect (see photograph - page 16) (not available).

By the end of 1908, all relevant works had been completed. The Heronry Pond was made suitable for bathing (previously bathing had been in Perch Pond), and a new boating agreement was signed at a greatly increased rental.

It is worth noting that whilst for Heronry Pond, two measures were adopted - sealing and increasing inflow - for Perch Pond only one measure was adopted, i.e. that of increasing inflow. Yet both ponds had been the subject of serious depletion from l900, and both were considered satisfactory after 1908.

1909 - 1940

For the next thirty years, there was not a single complaint about the condition of Heronry Pond, although in 1929, Mr Chapman had his rent reduced, following the "excessive drought" in the summer of that year.

In fact, over this period the Heronry Pond was rarely mentioned at meetings of the Epping Forest Committee, apart from frequent references to swimming championships held in the pond. This demonstrates that for at least thirty years, all was well.

To the north west though, the "Green Man" pond, long since isolated from its catchment area by the same railway cutting which split the "River Holt", was itself dwindling to nothing as a source for the system, although it was not finally drained, and the site "developed" into a tower block of flats, until after the Second World War.

1941 - 1949

During the Second World War, the lake system of Wanstead Park suffered calamitous damage, which substantially affected both outflow and inflow - although the latter's significance has never been fully appreciated until now.

Full details of the extent of enemy action in this period, over the park and its surrounding area, can be gained from the booklet "It Happened Here" by Stanley Tiquet, available in the local collection of Ilford Central Reference Library. In fact this publication describes South Wanstead's F District in particular, as one of the worst affected areas of the borough. This small district - the area of Wanstead south of Eastern Avenue and The George down to the borough boundary with East Ham - is virtually the entire remaining natural catchment area of the lake system. The Lakehouse warden's post, by the tennis courts, was nicknamed "hell fire corner."

During the war, F District alone received:

110 High Explosive bombs
4 Land Mines
8 VI Flying Bombs
7 V2 Rockets
8 Oil Bombs
plus 19 other unexploded bombs
1 unexploded Land Mine
Innumerable incendiaries

Records indicate that high explosive bombs ranged from 250 lbs to 2,000 lbs. Land mines consisted of approximately one ton of high explosive, capable of causing blast effects up to 650 yards from the point of explosion. The VI flying bomb consisted of approximately 1,000 lbs of high explosive.

The map at page 42 shows the point of impact of all projectiles which landed in the areas together with drainage contour of the lake system, (watershed).

One of the main targets of the bombing was an anti-aircraft battery situated approximately in the middle of Wanstead Flats. This was in action throughout the Blitz of autumn 1940, and the subsoil vibration caused by continuous heavy firing had an extremely adverse effect upon houses throughout the area, quite apart from the bombing itself. Such subsoil vibration appears likely to have had an even more damaging impact upon the drainage system laid out beneath Wanstead Flats in 1906. In addition, the entire area of that drainage system was given over to allotments for the duration of the war, which could well have resulted in its disturbance.

In order to check on the effectiveness of the Flats drainage system, we inspected the manhole located opposite the southern end of Park Road, during February 1978.

Weather conditions at the time were dry, but heavy rain had fallen during the previous evening. The manhole had the appearance of not having been opened for a long time. The pit was about seven feet deep, opening onto a "T" junction of pipelines, with the base of the "T" pointing due west, parallel with Aldersbrook Road at this point. One arm of the "T" pointed north, beneath Park Road, and the other arm pointed south, out onto the Flats. The pipes were 1 foot inside diameter, We found a bank of silt across most of the mouth of the pipe leading from the Flats, indicating that very little flow now comes from that direction. Very light flow came from the pipe running west, parallel with Aldersbrook Road. In order to check on the intensity of this flow, we moved the bed of silt to form a bar across the mouth of the pipe leading north, beneath Park Road. The combined flows did not spill over the shallow silt bar during the time we had the drain open. Taking into account the weather conditions on the day prior to our inspection, we would have expected to find a reasonable flow of water in this drainage system. It therefore appears that the current effectiveness of the 1906 drainage works, as a source of inflow to the lake system, is now negligible. We understand from the Superintendent of Epping Forest that there are no records of any repair or inspection of the drainage system after the war, and we therefore conclude that its lack of effectiveness nowadays, is probably attributable to a combination of its age (over seventy years), and to war damage.

In 1941, two high explosive bombs fell directly into Heronry Pond, completely blocking the passage round the east island, near the north bank. The concrete base and sides were badly damaged on both the north bank, and the island opposite, and large pieces of the original concrete structure still remain on the north bank, (see diagram - page 44)

Whether from this bomb damage, or from the deteriorating inflow, or from a combination of both, the level of water in Heronry Pond was reportedly about two feet lower than normal from 1941 onwards, and boating was greatly restricted.

On 2 July 1944, a VI flying bomb fell directly into the middle of Heronry Pond, killing a soldier and his girl companion, who were boating on the lake at that time. The soldier was on leave, having just returned from the Normandy landings. The lake had only about two feet of water in it, and the flying bomb penetrated the concrete base, breaking it and leaving a large crater, (see diagram - page 44).

War damage to the Heronry Pond itself was not repaired until 1949, when the pond was completely drained, and W & C French carried out work under two separate contracts. The first contract involved repairs to the three craters caused in 1941 and 1944, at a cost of £1,160 (paid for by the War Damage Commission). The second contract involved the removal of silt from around the two islands, and the landing stage - the silt being placed in two "unused" bays of the lake at a cost of £5140 (financed by the Epping Forest Committee).

Unfortunately, so long after these contracts, W & C French cannot locate any papers relating to the works which might indicate either old or new construction details, nor do they have anybody in their employ who was concerned with the work.

1950 - 1958

In February 1952, the Superintendent reported that the repairs to Heronry Pond had not solved the seepage problem:

"The water level, even during the winter months, remains much below the overflow mark. Due to the long period of years during which the pond was dry, undetected points of seepage may have occurred which, in point of time, would probably have become overlaid with silt and thereby reasonably effectively sealed."

The Committee asked him to organise weekly readings of the water level, and report back in twelve months.

The Superintendent reported back in April 1953 that:

"It is impossible to suggest from the weekly readings that the defect in the pond is remedying itself in any way." (see top diagram - page 46).

In the winter of 1953/54, the pond was drained and the Wanstead Park staff carried out repairs to all noticeable defects in the concrete base, in an attempt to seal leaks, Then, between July 1954 and October 1955, monthly readings were taken of the depth of the pond (see middle diagram - page 46). Comparison with the 1952/53 readings demonstrated that the repairs had not reduced seepage.

In the winter of 1955/56, the pond was again drained and repairs were made this time to the concrete sides. Further monitoring in 1956 and 1957 found no improvements (see bottom diagram - page 46).

Apparently disheartened by so little progress achieved in return for such diligent effort, the Conservators thereafter paid no further attention to the problem of Heronry Pond, which continued to fill to a varying extent each winter, and empty each summer. Specifically, no attention was turned to the other side of the equation of inflow and outflow. All efforts had been directed at curbing outflow, and none at all at increasing inflow.

1974 - 1978

In 1974, the Conservators of Epping Forest were approached by contractors seeking locations for the disposal of spoil, with a view to filling Heronry Pond.

Although all concerned were agreed that the condition of the pond - entirely unstable and with no amenity value - was unacceptable, there was division over whether all or part of the pond should simply be written off.

The 1974 filling proposal comprised the filling of approximately one third of the pond, with an undertaking from the contractors to make good the surface, and lay drainage pipes to the remaining two thirds of the pond. The attraction from the viewpoint of the Conservators was that the entire works would be done at no cost to them - simply in return for permission to dump spoil on the site.

However, it was pointed out by those interested in a more positive solution, that there was no guarantee that filling one third of the pond would necessarily result in the remaining two thirds suddenly achieving a stable water level. Furthermore, since the pond had a very long and significant history, and formed a central link in the chain of remaining lakes which would otherwise be broken, the opportunity should be given to carry out a further investigation to determine the basic problem, and to propose a solution if possible.

This viewpoint received some sympathy from the Conservators, and this investigation was begun.

In 1976, a further suggestion was put forward to the Conservators for filling Heronry Pond, and restoration of a satisfactory ground surface, as a project in connection with the Coronation Silver Jubilee in 1977. However, by this time the Albury Site Investigation data was available (see Site Exploration and Permeability Tests, above), and the preliminary findings of this study were passed to the Superintendent. Consequently, the decision of the Conservators went against filling Heronry Pond. However, the Conservators also decided that:

"...the matter be left in abeyance in the present financial situation."

- so that no progress was made in the direction of saving Heronry Pond either!

In spite of their reluctance to move in this direction, the Conservators had, in the meantime, seen fit to replace the pump which raised water from the Roding into the Ornamental Water (see details above).

In an effort to determine more precisely the extent to which Heronry Pond suffered seepage, 1t was then decided to commence a monitoring exercise on Heronry Pond. This was conducted in the winter and spring of 1977, and is explained in detail from page 49 below. (not available)

Relaying of Northumberland Avenue Sewers (1977)

During 1977, Northumberland Avenue was excavated along its entire length, and the sewer system laid in 1900 was completely replaced. The works were continued along the complete length of Woodlands Avenue during the winter of 1977/8.

The new system is a completely segregated one, i.e. the foul sewer and storm sewer are completely segregated, and the storm sewer has outlets into both Heronry Pond and Perch Pond.

During the period of the excavation, significant amounts of water were finding their way into the sewer trench. This caused delay to the progress of the work at the eastern end of Northumberland Avenue, where the work commenced. Whilst it was not found possible by the site engineer to calculate the precise quantity of water flowing through the ground into the trench, two 3 inch pumps were required to operate during working hours, to prevent the trench flooding, even though they were not in use the whole time, and not to full capacity.

As previously stated, when the original 1900 sewer was excavated, there were differing reports about its soundness (see above).

It was hoped that as a result of the relaying of the system, and the introduction of a completely segregated storm sewer, a significant difference would be made to the inflow into Heronry Pond. There is little evidence of this being achieved at the time of writing (March 1978), although the works in Woodlands Avenue will not be completed until May or June sufficiently to make their contribution felt.

It also remains to be seen whether the excavation of Northumberland Avenue to a greater depth in 1977 (-4.2 m) than in 1900 (-3.3m), will exacerbate the seepage problem, due to deeper disturbance of the gravel, (see page 26).

In addition, it will be noticed that the level of the new foul sewer is below the level of the bed of Perch Pond at its western end, whereas the old foul sewer was very nearly on the same level as the bed of the lake at this point. Such additional disturbance of the Taplow Gravel almost one metre deeper than before, could lead to problems of maintaining water level stability in Perch Pond, of a similar kind to those which have plagued Heronry Pond for the past years. However, there is no evidence of this to date.

With hindsight, it appears that an opportunity was lost during 1977 to try to block the line of the trench as a seepage route. Had the trench been excavated to the six metre London Clay level, and then re-packed with solid clay, rather than loose spoil and gravel, for a length of say, 200 feet between Wanstead Park Avenue and Clavering Road, this might have blocked off or at least diminished the probable escape route for seepage. It is unlikely, however, that such a measure would have provided a complete solution.

(See also Part 1 - The Lake System of Wanstead Park by James Berry & Alan Cornish)

(See also Wanstead Watercourses: the "River Holt" by Barry Hughes)

(See also The City of London Cemetery/Ponds)