THE LAKE SYSTEM OF WANSTEAD PARK

&

THE MYSTERY OF THE HERONRY POND

James Berry B Sc (Geog)

Alan Cornish M Sc (Tpt)

March 1978

NB. Click maps for larger versions that open in a new window. Make sure your browser is not set to "fit images to window"

1.01 SUMMARY

Heronry Pond is one of a system of lakes in Wanstead Park. When full, it has a water surface area of over eight acres. But each summer, it usually dries out to nothing.

The mystery is - what causes this to happen? Also, if the cause can be established, can anything be done to stabilise the pond and so realise its great potential amenity value?

To answers these questions, the authors first show how the lake system of Wanstead Park was put together, between about 1670 and 1740. They trace the many factors in the past two centuries and more, which have changed the system to its modern form.

The implications of enemy action during the Second World War and of storm sewer reconstruction nearby are identified.

In particular, they show how Heronry Pond has twice previously gone through periods of serious decline, and how each time, it was saved.

Geological data from a series of test borings is analysed to illustrate how Heronry Pond is both the central - and the weakest - link in the remaining chain of lakes.

Results are assessed from a monitoring exercise undertaken on the pond during 1977.

Finally, data from the monitoring exercise is used to test a range of alternative proposals aimed at countering the instability of the water level of the pond, and recommendations are made which will secure the future of both Heronry Pond and the rest of the historic lakes in Wanstead Park.

In the year of the centenary of the establishment of Epping Forest - of which Wanstead Park is a part - it is to be hoped that the recommendations of this report are implemented in the spirit of the Epping Forest Act of 1878, i.e. for the recreation and enjoyment of the public.

1.02 ACKNOWLEDGEMENTS

The authors wish to express their grateful thanks to the following individuals and organisations, for their generous advice, assistance and suggestions in the preparation of this report.

The views and conclusions expressed are either those of the authors, or have been accepted from sources considered to be reliable.

Copyright Items may be freely reproduced from this report, either in part or in whole, but full acknowledgement to the authors is required.

© James Berry & Alan Cornish, March 1978.

1.03 RECOMMENDATIONS FOR ACTION

We recommend that all possible measures should be taken to increase the inflow of water into the lake system of Wanstead Park, and in particular:

1. The installation of a new pump, to pump water from the River Roding to the Heronry Pond (via the Basin and Shoulder of Mutton Pond), at an estimated capital cost of less than £5,5OO.
2. To counter-balance seepage from Heronry Pond of an estimated 50,000 cubic feet of water per week, a corresponding volume should be pumped into the system weekly between March and September annually. We estimate that this would cost about £110 annually. Such a cost could easily be recovered by letting the boating rights on Heronry Pond.
3. The attention of the London Borough of Redbridge should be encouraged in the conversion of local storm sewers to fully segregated systems, and such systems should be directed towards maximising the flow of clean surface water into the lakes, especially from Blake Hall Road.
4. Existing ditches in Bush Wood should be cleaned out, their connection with the existing drains into the lake system verified, and consideration be given to their encasement in buried agricultural drainage pipes to improve efficiency and minimise future maintenance.
5. Existing open ditches running through Reservoir Wood should be cleaned out, and encased in buried agricultural drainage pipes to eliminate blockage by falling leaves and vandalism.
6. The existing buried drainage pipe from the overflow sluice in The Basin, leading across the golf course and into Reservoir Wood, should be re-laid to run in a straight lines from The Basin directly into Shoulder of Mutton Pond, to eliminate the possibility of blockage at its existing three bends.

In addition, heavy deposits of silt in Heronry Pond, Perch Pond, and also in the south west corner of Shoulder of Mutton Pond, should be removed, to improve flow through the system.

 1.04 CONTENTS

1.05 The Reason for Our Interest

The objectives and activities of the Wren Conservation Group are outlined at Annex I.

Saving Heronry Pond in Wanstead Park, and restoring it to its original role, meets a number of positive objectives:

1. The amenity value and attractiveness of the entire park is greatly diminished at present each summer by the draining of Heronry Pond into an eight acre, rather smelly black hole, which is both an eye-sore, and a great disappointment to the park visitor.
2. Although all are agreed that the present position is most unsatisfactory, to fill in part or all of Heronry Pond would seem a most retrograde step, breaking the chain developed over three centuries, and it would also impose considerable disruption upon the local community in the process.
3. Pre-war accounts show the lake to have held great amenity attraction, as a centre for boating and sailing, and even swimming galas were held there at times!
4. The present clash of fishing and boating activities on Perch Pond, which is much smaller, could be avoided, with fishing confined exclusively to Perch Pond.
5. The background research and field monitoring exercise in this study have involved and stimulated the interest of a number of individuals, young and old, in their local environment.
6. The park and especially the islands in the park, provide a unique sanctuary and staging area for the profusion of bird life, which is remarkably close to London - only seven miles from The Mansion House.
7. Restoration of Heronry Pond would re-create its two islands as safe and proper sanctuaries for wildlife, where now they suffer an annual "invasion" as their surrounding waters decline each summer.

PART ONE:

THE LAKE SYSTEM

2.01 Before Man – the Physical Setting

The southern end of Epping Forest has a surface largely composed of gravels of lower level, belonging to the present systems of the valleys of the Thames and Lea. London Clay underlies all formations. The gravels were deposited in terraces when the rivers flowed at a somewhat higher level than they now do, and having more fall, brought down coarser material.

After the Glacial Period, the present river system came into being, and the Lea, Roding and Thames cut their way through preceding deposits of gravels, deepening and widening their valleys as they did so, and leaving behind them various beds of gravel, peaty matter and loam.

A deep boring made by the Metropolitan Water Board prior to 1921, in the grounds of the Redbridge Pumping Station, gives some idea of the nature and thickness of the underlying strata:

The immediate area of Wanstead Park is subject to two major river valleys. The Thames gives the park a gentle southward slope. The Roding is on the eastern boundary, and an eastward slope becomes very pronounced in the vicinity of the river.

To the north of the park lies a terrace of Boyn Hill Gravel, which extends beneath most of modern Wanstead centre, as well as Leytonstone Flats, and the Hollow Ponds. The terrace rises to over 100 feet above Ordnance Survey Datum (OSD), and runs northwest at that level, merging into the main forest area to the north.

From the southern face of this northern terrace a number of natural springs emerge, from perched tables within the gravel, due to the impermeable nature of the underlying London Clay.

One such spring is shown on a map in John Norden's "Description of Essex" (1594), feeding a stream running due east into the valley of the Roding, across the enclosed estate: "At Wanstead A Statelye Howse" (Fig.1)

This small stream in its shallow valley of exposed London Clay, between deposited gravel terraces to north and south, no doubt originally formed the drainage channel for the surrounding area, which we now know as Wanstead Park.

Finally, to the south of the park, another gravel terrace, this time of Taplow Gravel, rises to just over 50 feet above OSD, and underlies Wanstead Flats. However, this terrace also juts northwards slightly at its eastern end, near the Roding (see bottom map, Fig.3).

The bed of the Roding itself now consists of quite extensive deposits of alluvium drift, see maps – Figs.2 & 3.

Figure 1. "At Wanstead - A Statelye Howse". Western half of a map of the County of Essex in John Norden's "Description of Essex" (1594).

Figure 2. The Lake system. The physical setting

Figure 3. The Wanstead Park System, Relief and Geology

2.02 Historical Development of the Lakes System

The Park was first enclosed in 1545 and its history in the 16th and 17th centuries would require a complete separate book. However, apart from the stream indicated by Norden's map (l594), running west/east across the estate and down into the river Roding on the eastern boundary, no reference to other waterways can be found.

2.03 In 1667, the estate came into the ownership of Sir Josiah Child, who immediately began to spend large sums in improving the gardens, planting trees, laying out avenues, and forming a lake and canals. In the spring of 1683, the diarist Evelyn went to look at his improvements:

The works appear to have consisted at that time of two separate endeavours. The major work consisted of extending the Roding into a series of ornamental waterways, known at that time as "The Serpentine River" later to become "The Great Lake" and now known as "The Ornamental Waters." Initially the river actually flowed through the system, but in time a scheme was worked out so that dams across the Roding turned the waters of the river into the system when necessary, and by-passed it when not.

2.04 The other work was the creation of two semicircular or kidney-shaped lakes, between the great house and its entrance drive to the west. In fact, the entrance drive led through an avenue of trees from "The Green Man" Leytonstone, along what is now Bush Road, through the gates where massive gateposts now stand at the beginning of Overton Drive, and then between these twin lakes, which each had its base, or flat side, actually alongside the approachway.

Thus from the great Wanstead House, one could look to the east, down into the valley of the river Roding, and see the Serpentine River, complete with artificial canal in the distance. Alternatively, if one looked westward from the front of the house, a driveway sped straight towards Leytonstone, with twin semi-circular lakes on either side in the foreground,

In fact precisely these views were shown in a series of three plates etched by Kip and dated about 1710, one of which (looking eastwards) is reproduced in the booklet on Wanstead Park published by the Conservators of Epping Forest.

2.05 Sir Josiah Child died in 1699, and the estate came into the ownership of the Hon. Josiah Child, his eldest son by his second wife. By about 1709 however, the estate was in the control of Sir Richard Child, who was born of Sir Josiah Child's third marriage, and was the Hon. Josiah's step-brother. Then began a most significant period of development, both for the great house, and for the lake system.

2.06 Sir Richard Child, created Lord Newton, Viscount Castlemaine and Earl Tylney, rebuilt the house in 1715, and about this time he also spent over £100,000 on the already magnificent gardens, lakes and grounds. Plans prepared by Colen Campbell in the Italian style, were considered by contemporaries as his best ever, and are detailed in his "Vitruvius Britannicus" Vol. I.

2.07 Again the works appear to have been approached in two distinct areas, the first of which concerned the approach to the front of the house. Here, the Earl's gardener, a man named Adam Holt, was required to turn his attention to the two semi-circular lakes which lay on either side of the approachway.

2.08 Adam Holt appears to have been something of both a landscape artist, and no mean engineer. The two small semi-circular lakes were joined together, by the simple method of cutting down the level of the road which ran between them. Thus joined into virtually a single almost circular pond, with the approachway to the house diverted round the northern side, formality was introduced. The circle was given eight corners, and a sluice gate was located on its southwest side to prevent overflow other than via an underground pipeline and open ditchway, running southwest and then south, into the valley.

2.09 The origin of what thus became The Basin, can be seen from both its shape, and contents. It is not a perfect octagon, for instance, being longer on the two parallel sides running north-south. This is because the original two semi-circular ponds had between them the approach road to the house, and thus did not form a perfect circle when joined, but more an oval. In addition, the original approachway to the house still runs across the lake, at a depth of about five feet in places. Investigations by the London Underwater Research Group in 196l found several courses of brickwork still in situ, showing that the original lakes had been brick edged where they flanked the roadway.

2.10 It is probable that as well as re-modelling the Basin, Adam Holt also increased its depth somewhat, by an extremely ingenious method of increasing the inflow. Just how ingenious were his engineering works can only be judged by reference to an accurate Ordnance Survey map, and a careful tracing of the contours to the north of the Basin. Essentially he managed to tap a catchment area which faced entirely the wrong way for his purpose.

2.11 The catchment area was Leytonstone Flats, which are situated on higher ground to the northwest of the Basin. As previously noted, Leytonstone Flats are located on the top of a terrace of Boyn Hill Gravel, and this terrace slopes gently down to the northeast, ending in Eagle Pond. However, a shoulder of higher ground juts out at the south east edge, between the natural drainage slope, and the Basin.

2.12 The solution adopted by Adam Holt was to construct a ditch - known locally at the time as the "River Holt" after its designer - around the eastern edge of the offending spur of high ground, virtually following the contour round and into the Basin. On 1735 estate plans a small collecting reservoir is shown on the higher ground to the south of Eagle Pond, behind the former Royal Wanstead School, and abutting what is now Hollybush Hill. We cannot be certain that this collecting reservoir was ever so formerly shaped as in the 1735 estate plans - see below - but its purpose was clear. From it the "River Holt" ran south east, close by where the "British Queen" public house now stands, and along what is how Spratt Hall Road. It then ran just east of due south, feeding into the Basin probably near its north east corner.

2.13 The south side of the same terrace of Boyn Hill Gravel probably drained naturally into the "Green Man" pond, and this too was probably tapped by Adam Holt, via ditches in the formal layout of the west gardens south-eastwards, although any such ditches are not distinguishable (map – Fig.4).

2.14 In the second area of works conducted for Earl Tylney, attention was turned to the shallow valley to the south of Wanstead House and its now formalised west approachway. This was the valley which contained the stream running west-east into the river Roding, as indicated on John Norden's map of 1594 (Fig.4).

2.15 A series of embankments were thrown north-south across the valley, damming the stream to form a chain of ponds, up the floor of the valley. From east to west, these were:

Perch Pond
Heronry Pond
The House Pond
The Reservoir
The Great Lake

2.16 Perch Pond and Heronry Pond were apparently known collectively at the time as "The Serpentine Ponde" - as distinct from "The Serpentine River" so called of Sir Josiah Child's first waterway diversions of the Roding. Earth embankments still exist at the eastern end of both ponds, holding them back within the valley.

2.17 The House Pond, or House Field Pond, later to become known as Shoulder of Mutton Pond from its odd shape, may not have required much development, since it appears to lay in a natural depression, and is reputed to be fed by its own independent underground spring, in addition to the stream flowing through it and down eastwards into the Roding. One may even speculate that it could have been a pond dug sometime much earlier, to serve as a source of domestic water for an adjacent large house, hence the name House Pond. When Richard Rich, 1st Lord Rich, built Wanstead House in 1549/50, he is known to have chosen higher ground as his site, rather than that of an older house, nearly derelict at that time, which he demolished. This was Naked Hall House, reputedly timber-built. However, against such a theory it must be noted that no such pond was indicated at this site on Norden's map of 1594 - although that is not necessarily conclusive, taking into account the small scale, etc.

2.18 The Reservoir was intended to be roughly square in shape, and probably had retaining banks on all four sides. The north and south embankments have long since disappeared, but the eastern embankment still remains as a large and rather incongruous reminder, stranded on dry land now, and pierced by several footpaths and a ditch. The Reservoir was probably so-called with the aim of providing a steady source for the ponds down the valley, to the east of it.

2.19 Separating the west end of The Reservoir from the Great Lake was another massive earth embankment thrown north-south across the top end of the valley. This embankment also still remains - but is not recognised by the casual observer as anything but Blake Hall Road, between Wanstead Park and the Aldersbrook tennis courts.

The Great Lake was the subject of greatest design-change between the time of its conception and ultimate creation, and the different designs, some of quite startling imagination, are of considerable interest.

Various designs and estate plans were drawn up by the French cartographer, Jean Rocque, for Earl Tylney in 1735. It was this same Jean Rocque who ten years later published the large-scale series "Environs of London" - and it is no pure coincidence that on this and other of his subsequent plans, he managed to just so "stretch" the boundaries of the capital city to include the lake system of Wanstead Park - in the design of which he had a hand in 1735!

2.20 Rocque plans of the Great Lake show at least two designs. One is an incredible cartwheel, with an island at the centre as a hub, and four great waterways radiating from it like spokes, ending in a circular waterway right around the rim. Had it been constructed, it would have been almost 1,000 feet in diameter at its widest point! A second design took the form of a trapezium, on a similar massive scale. Complete plans of the entire estate show each of these designs as if they existed, and for the unwary can cause confusion between intent and reality. Rocque designs of 1735 also show Heronry Pond joined to a symetrically-shaped House Pond - and the whole called "Leg of Mutton Pond." Imagination really ran amok with some of the islands on the lakes - for instance one plan shows the island in the Great Lake as a perfect miniature of Britain!

2.21 Even though some fairly amazing designs were dreamt up, there is no doubt that, all of the lakes were constructed in some form, and reality can be established from the separately commissioned Rocque work of 1745 - "Environs of London" (Fig.4). Only ditches in the formal gardens, e.g. the "River Holt" and the connection with the "Green Man" pond, are indistinguishable from the formal walkways, and this "omission" signals the difference between their engineer-creator (Adam Holt), and the less practical, more artist-designer (Jean Rocque).

Nevertheless, it is considered that the map produced by Jean Rocque in 1745 shows the lakes system of Wanstead Park at probably the greatest point of its actual development.

2.22 Around seventy years (1670-1740), and several generations of immensely rich patrons and brilliant landscape artists and engineers had combined to produce a chain of artificial waterways meticulously set into the parkland, taking advantage of every contour and every possible source of precious water.

2.23 It will be shown that as the various sources of water were diminished or diverted - through ignorance, neglect, accident or malice - so the weak links in this chain revealed themselves, right through to the present day.

Figure 4

2.24 The Lake System Today

The lake system of Wanstead Park as we now know it comprises five separate lakes, forming a chain running in a semi-circle from west, through south, to east.

Each lake is joined to its neighbour by underground drains, open ditches, or open spillways, and the system finally finishes with a weir at the southeast corner, feeding a spillway/overflow into the river Roding.

From the top lake to the bottom lake, there is a drop of over fifty feet, into the valley of the Roding. Lying entirely within the Wanstead Park designated Conservation Area, the system comprises, in descending order:

The Basin
Shoulder of Mutton Pond
Heronry Pond
Perch Pond
The Ornamental Water

Two lakes of the originally developed system, i.e. The Reservoir and The Great Lake, have already been lost (see paras 3.10 – 3.12 below). Of the remaining five, one - Heronry Pond - is under serious threat. Its loss would completely break the chain of which it forms the central link.

Brief details of each of the present lakes are given below, and Figs.7 & 8 show working plan and elevation.

2.25 The Basin

Area about 10.12 acres. Octagonal in shape, exactly aligned on a north-south axis, and originally part of the formal frontpiece to Wanstead House (demolished about 1822). No islands. Now situated within Wanstead Golf Course, and not accessible to the general public. Overflows via a sluice located in its southwest side, now heavily rusted through dis-use. From the Basin an underground pipeline runs southwest about 150 feet, almost to the boundary of Silcocks & Collins Sports Ground, which it then follows, south and then west, for about 600 feet. It then turns south, emerging about 120 feet south of the sports ground boundary into open ditch alternating with covered pipeline in sections as it crosses the golf course.

The pipeline thus has three right-angle corners, none with inspection/clearage manholes, and has occasionally been the cause of blockage. Where submerged, the flow is carried in one foot inside diameter heavy glazed earthen-ware pipe, and it finally emerges into open ditch when it passes beneath the boundary fence between golf course and Reservoir Wood - a part of Epping Forest and open to the public.

The open ditch continues south a further 230 feet before joining the original main stream, running in an easterly direction a further 800 feet before flowing into the southwest corner of Shoulder of Mutton Pond. This section of open drain through Reservoir Wood is subject to frequent blockage by falling leaves, other debris, and by general vandalism. See top left photograph on Fig.5.

Figure 5

Top Left Main feeder stream looking south in Bush Wood. Neglect of ditch cuts flow to virtually nil. We recommend that this ditch be cleared out.

Top right Stream from Basin (via Golf Course) looking south into Reservoir wood. Junction with main feeder stream near houses in background. Pipeline beneath forest track blocked by vandals. We recommend that both these streams be enclosed in piping and covered.

Bottom left Main feeder stream as it enters Shoulder of Mutton Pond (looking east). Note heavy silting blocks inflow. We recommend that this silt be removed.

Bottom right Pipeline into Heronry Pond bringing overflow from Shoulder of Mutton Pond. All water caught in timed period was measured and flow was calculated in gallons per minute.

2.26 Shoulder of Mutton Pond

Area about 3.5 acres. Takes its modern name from its distinctive shape. Formerly called House Pond or House Field Pond. No islands. Swimming is permitted daily before 8.30 a.m.

The southwest corner is now a marshy delta, caused by the carriage of silt into the pond from the feeder stream at this point. See bottom left picture – Fig.5.

North of the pond, inside the golf course, a line of bunkers running north-south tends to feed a surface stream which delivers small amounts of water into the pond during periods of heavy rain. This inflow is not significant.

Shoulder of Mutton Pond overflows into an underground drain on its east side, which runs east about 340 feet in twin pipes, to spill into Heronry Pond. See bottom right photograph Fig.5. Halfway along this twin pipeline it crosses a gas main, laid at a lower level, in about 1974. Precautions were taken at the time of these works to ensure that the drain was kept water-tight.

Technically, Shoulder of Mutton Pond is not in Wanstead Park, but is within Epping Forest.

2.27 Heronry Pond

Area about 8.38 acres*. Contains two islands, each about half an acre in size. The only lake in the system with concrete base and sides, which slope inwards at about forty degrees. The concrete base is not generally apparent, due to an accummulation of silt several inches thick in most places.

* Areas recorded in this descriptive section are as given in the 1954 Ordnance Survey. However, our measurements of Heronry Pond and of the survey maps indicate a water surface area for Heronry Pond of 382,788 sq.ft., or 8.7876 acres, and this slightly larger figure is used in our calculations. The difference is very small (less than 5%), and may be accounted for by the slope of the sides of the pond. Our larger figure is taken from the top edge of the concrete rim of the lake.

Heronry Pond is also fed by several other sources. The principal one is a storm sewer running into the south west corner of the lake, from the junction of Park Road and Northumberland Avenue, about 310 feet away. The catchment area for this storm sewer is approximately the area bounded by Park Road, Aldersbrook Road, Blake Hall Road, and Woodlands Avenue, i.e. about 31 acres, plus a connecting pipe at the end of Park Road across to a drainage system beneath Wanstead Flats (see para 3.33 below). The storm sewer pipe leading into Heronry Pond has been designed to flow full once every two years, at a discharge rate of 280 litres per second for the duration of a storm, i.e. about 3,695 gallons per minute. It was re-built during the winter of 1977-8, as part of the re-laying of the foul and storm sewer systems beneath Woodlands Avenue and Northumberland Avenue. Originally however, this feedpipe was laid out in 1906 as part of a scheme to increase inflow into Heronry Pond, by feeding water drained from Wanstead Flats. The arm of Heronry Pond into which the storm sewer flows is now heavily silted to a depth of 21 inches, i.e. almost half the original depth.

Heronry Pond is also fed by a small underground drain from the golf course, entering the pond a few yards east of the main inflow pipes from Shoulder of Mutton Pond.

During periods of heavy rainfall, a surface stream is often formed which also flows into Heronry Pond at about its northern midpoint. It brings the surface run-off from the golf course, and the southern part of Warren Road (unadopted). At this point, immediately north of the East Island in Heronry Pond, there is also a small underground drain in the bankside. However, this appears to be blocked, and no flow occurs.

Technically, the west half of Heronry Pond is within Epping Forest, and only the eastern half or slightly less, is actually in Wanstead Park. Since both are under the control of the Conservators of Epping Forest however, this distinction is not of great consequence. Boundary fences between forest and park run into the pond on its north and southeast banks.

The most significant feature of Heronry Pond is its inability to maintain a stable water level. In most winters it fills to a varying extent, peaking at about the end of March. It then dries to practically nothing by about end August each summer.

Only very exceptionally, and last in the winter of 1974/5, does it overflow via an underground spillway in its eastern bank, into neighbouring Perch Pond. See bottom right photograph at Fig.6.

2.28 Perch Pond

Area about 5.5 acres. Seven small islands at its western end. Used intensively for fishing (see bottom right photograph – Fig.6), together with some boating in summer. A dilapidated boathouse is situated on the north bank, and a few yards to the west of the boathouse, Roman ruins and a mosaic flooring were found both when the park was laid out in the 1730's, and again in the early 1960’s*.

*See "The Re-discovery of the Roman Site in Wanstead Park" (1963) by J. Elsden Tuffs, available in Ilford Reference Library.

Boat maintenance is carried out in a second building, Just north of the embankment running between Heronry and Perch Ponds, and this building also serves as a snack and coffee kiosk at weekends and Bank Holidays throughout the year.

Perch Pond is also fed by a storm sewer of similar dimension to the one feeding into Heronry Pond (see preceding description). It leads into the southern side, just south of the peninsular at the south western corner of the lake. This corner of the lake is heavily silted, and a ditch has been cut from the mouth of the storm sewer pipe, through the silted area, to the open lake beyond the islands. A substantial amount of silt remains to be removed.

Top Albury borehole number 2. 9 April 1975. Note Heronry Pond is full. Centre Summer 1975. Heronry Pond is almost empty. Children ‘invade’ east island from north bank. Bottom left Overflow from Heronry Pond which leads to Perch Pond. Bottom right Perch Pond in January 1978, about to overflow down spillway (in left foreground) through Dell Wood to Ornamental Water. Note intensive fishing activity.

Figure 6

Reconstructed in 1977, the catchment area of the storm sewer is Northumberland Avenue, and the roads running south between Ingatestone Road and Clavering Road, plus some drainage from Alexandra Pond on Wanstead Flats (but see para.3.35 below).

From the north east side of Perch Pond, an open spillway, crossed by a small wooden footbridge, leads down into the Dell, a small wood. See bottom right photograph at Fig.6. Open ditch then leads beneath a brick bridge which carries the forest track, ending in the Ornamental Water.

2.29 The Ornamental Water.

Area about 15.0 acres. Various islands totalling a further ten acres approximately. Considerable wildfowl with many nests on the islands. No fishing permitted.

The level of water is maintained at a higher level than the adjacent river Roding by pumping water from the river, and a pumphouse is situated at the northern-most point of the lake.

Between the 1930's and 1976, this contained a 6 inch Gwynne's Invincible pump, type KL, No. 52669, originally rated for a duty of approximately 800 gallons per minute at 10 feet total head when operating at 730 r.p.m., fitted with a 10.75 inch diameter impeller. It had a 9 inch diameter intake, and was driven via a belt, by a 7.5 HP 400V Brook electric motor, No. H3-9476O.

The Conservators of Epping Forest hold a licence from the Thames Water Authority, permitting extraction of water at this point, from the Roding, as follows:

27,000,000 gallons per year

Maximum 50,000 gallons per hour

Maximum 350,000 gallons per 24 hours

In 1972, the Conservators embarked upon a programme of dredging, to remove silt deposits from the lake, and a crude silt trap was constructed near the point where water is pumped in. During the period 1972-76 the pump was hardly used, for reasons associated with adjacent engineering works conducted first by the Gas Council, then the Greater London Council (main sewer) and subsequently by the drought conditions which led to the virtual drying up of the Roding in the summer of 1976.

In November 1976, the Conservators instructed the London Electricity Board to install a new meter and a new power outlet in the pumphouse, prior to the installation of a new pump. The Conservators then went ahead in February 1977 with the installation of a Flygt medium pressure pump, which is located in a pit outside and behind the pumphouse. This is a submersible dewatering pump, intended for the prevention of flooding of construction sites. The model installed is type B 2102, fitted with a three-phase a.c. motor, 5.2Kw (7 HP), working at 2,850 r.p.m. It has a 4 inch discharge connection, and the complete unit is described by the manufacturer as being "...easy to handle by one man between sites." Its speed and capability, compared with its predecessor, are as follows:

We do not consider the unit is suited to its current use. Low capacity has meant high speed operation over long hours to deliver any given volume of water. This, coupled with the very long period (1972-76) when the Ornamental Water had been allowed to drop considerably in level, has led to heavy utilisation of the pump. In addition, there is the possibility that disturbance of the adjacent sub-soil may have accelerated the rate of natural seepage from the lake, leading to a requirement for more pumping than in the past, simply to maintain a stable and satisfactory level. In any event, between 30 November 1976, when the new meter was installed, and 22 February 1978, a total of 21,080 units of electricity were consumed - mostly from February 1977 when the new Flygt pump came into operation.

By false economy with installation of an inadequate pump, the Conservators are now consuming electricity at the Installed Load Rate of 2.545p per unit on a continuing basis. Had a more powerful pump been installed at a higher one-time initial cost, the same total volume of water could have been pumped in much shorter periods, e.g. nightly between 2300 hrs and 0700 hrs, enabling advantage to be taken of the Day/Night Rate of only 1.14p per unit – less than half the current cost.

2.30 Dutch Elm disease has recently destroyed many of the larger trees surrounding the Ornamental Water and on its islands, so that heavy leaf falls are unlikely to cause pollution as they have done in the past. Dead trees on the islands still provide valuable refuge for the prolific wild life however, and it is hoped they will not be disturbed.*

At the south east corner of the lake is a weir, feeding a spillway/overflow into the river Roding, to complete the system.

2.31 Ornamental Water has many attractive and unusual features which date back to previous centuries. They include a purpose-built Grotto (now in ruins following a fire in 1884, and years of vandalism), "Fortifications" which are now partially flooded due to raising of the lake level - but which once were the centre-piece of a wildfowling lair for the residents and guests at the great Wanstead House, and a Canal" to provide a fine view through an avenue of trees, from the great house on the brow of the hill above.

* See also "The Lake Sanctuary at 'Wanstead Park" by CJ Cornish, Country Life, vol VII, pp 643-8, 26 May 1900, for a description of the profusion of bird life in the park. This is still the case, and the Wren Conservation Group bird survey of 1977 identified 100 different species in the park during the year.

Figure 7

Figure 8

2.32 Amenity Value of the Lake System

In the system of lakes today, each one - with a single exception - has a high amenity value.

The Basin is not directly accessible to the public, but it is skirted by Overton Drive to the north, and so contributes an open and pleasing perspective to the casual passer-by. For the golfer it provides a most interesting obstacle, and a focus of the course. It is also available to members and friends for fishing.

Shoulder of Mutton Pond is available to the public for swimming in certain hours, and is a peaceful haven for waterfowl.

Perch Pond is used intensively for public fishing, and this is in conflict with boating which is also available to the public on the lake.

The Ornamental Water provides a beautiful lake-side walk over l.5 miles in circuit, and is an area of great tranquility for man and the profusion of birdlife which uses it as a staging post along the Roding valley.

The complete system offers a unique centre so close to central London, for ornithologists and any others seeking outdoor recreation.

Only Heronry Pond makes a nil contribution, and its sad state is both an eyesore and a continuing threat to the integrity of the chain, of which it is the central -and weakest - link.

This research project was started in 1974, under the auspices of the Wren Conservation Group*, in an effort to discover what lies behind the problem of Heronry Pond, and if possible, to offer a solution.

* See Annex I

PART TWO:

THE HERONRY POND

3.01 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 – Fig.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 (see top photograph – Fig.6).

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 – Fig. 9

Redbridge Borehole No. 1)

Fig.9 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).

Figure 9

3.02 Permeability Tests

Details of the Albury Laboratories report are at Annex II & III. 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).

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 soil.

3.03 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:

1. Was not made of sufficiently water-tight material, e.g. solid clay.
2. 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 re-modellings (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.

3.04 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:

1. The inflow.
2. 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?

3.05 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 Fig. 4).

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.

3.06 These two pointers, 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.

3.07 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 from Perch Pond (see Fig. 10). 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.

Figure 10. Reproduced from Map of London (1762) by Jean Rocque.

Figure 11. Reproduced from an estate map of the grounds of Wantead House, held by the Essex Record Office.
Dated by Mr J. Elsden Tuffs at about 1820: Reservoir Wood was planted by 1924.

3.08 Another map, this time by Chapman and Andre dated 1777, shows no "supplementary" north-south embankments 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 Fig. 11). Both these maps are available in the Essex Record Office, and our attention was drawn to them by Mr J. Elsden Tuffs.

3.09 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 (Fig. 12). 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.

Figure 12

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.

3.10 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.

3.11 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.

3.12 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 atractive 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 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).

3.13 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.

3.14 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 1843, and a branch line from Stratford - called the Woodford and Loughton Railway - started operating in I856. 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.

3.15 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.

Figure 13

3.16 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 Fig. 13). 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 area!

3.17 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.

3.18 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.

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

3.19 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.

3.20 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.

3.21 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.

3.22 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 Fig. 14). 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 Ordnance Survey of 1873-81 – Fig. 13), were it not for the Midland Railway line running through Leytonstone Station and Wanstead Park Station, (Fig.15 - railway runs across bottom third of map, from left side).

Figure 14. The Lake System about 1885
Pre-produced from "Epping Forest" by Edward North Buxton, published by Edward Stanford.
From an early edition, showing Heronry Pond at its largest, as restored by the Epping Forest Committee in 1822.

Figure 15. The Lake System about 1904
Pre-produced from "Epping Forest" by Edward North Buxton, published by Edward Stanford.
From the seventh edition, published 1905, showing Heronry Pond (un-named), in almost its pre-1882 condition, after the sewer was laid in Northumberland Avenue.
The Midland Railway line through Leytonstone Station and Wanstead Park Station confirms the dating.

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.

3.23 In October 1903, the Superintendent reported that:

3.24 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.

3.25 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 therefor." The expert, Mr Lawford of Messrs Bailey Denton &. Co., reported in December 1903 that:

3.26 We have no reliable means of substantiating this report, and must take it at face value, bearing in mind that civil engineering 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 para. 3.02).

3.27 Mr Lawford suggested three solutions, in order of preference. First, having the sewer relaid 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.

3.28 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."

3.29 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.

3.30 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."

3.31 Shortly after this meeting, Mr Bailey Denton prepared a second report in broad agreement with Mr Lawford's report. He pointed out that:

3.32 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.

3.33 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 – Fig.13). By 1885 the clay workings had been removed, but the area then contained a shallow pond, called Brick Field Pond (see map – Fig.14). This pond had been filled in by about 1904, and a number of cricket pitches had been laid out over the area (see map – Fig.15), and it is likely the surface waters to be drained, were an indicator that the area was vulnerable to flooding.

3.34 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 map – Fig.17). 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. 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.

3.35 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.

3.36 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 – Fig.4). No direct connection can be located, and the ditches in Bush Wood are now in an appalling state of neglect (see top left photograph – Fig.5).

3.37 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.

3.38 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 1900, and both were considered satisfactory after 1908.

3.39 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.

3.40 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.

3.41 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."

3.42 During the war, F District alone received:

110 High explosive bombs
4 Land Mines
8 V I Flying Bombs
7 V 2 Rockets
8 Oil Bombs
plus 19 other unexploded bombs
and 1 unexploded land mine
and 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.

3.43 The map at Fig.16 shows the point of impact of all projectiles which landed in the area, together with the drainage contour of the lake system, (watershed).

3.44 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.

See also Second World War and Wanstead Park - Figures 9 & 10.

3.45 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.

Figure 16

3.46 In 194l, 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 map – Fig.17).

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 194l onwards, and boating was greatly restricted.

3.47 On 2 July 1944, a V I 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 map – Fig.17).

3.48 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 194l 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 £540 (financed by the Epping Forest Committee).

3.49 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.

Figure 17

3.50 1950 – 1958

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

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

3.51 The Superintendent reported back in April 1953 that:

3.52 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 – Fig.18). Comparison with the 1952/53 readings demonstrated that the repairs had not reduced seepage.

3.53 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 – Fig.18).

3.54 Apparently dis—heartened 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.

3.55 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.

3.56 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.

Figure 18

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.

3.57 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 paras 3.01 – 3.02 & Fig.9). 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:

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

3.58 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 para 2.29).

3.59 In an effort to determine more precisely the extent to which Heronry Pond suffered seepage, it 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 para 3.66 below.

3.60 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 (see paras 2.27 & 2.28).

3.61 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 (para 3.25).

3.62 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.

3.63 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 lower diagram Fig.9).

3.64 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.

3.65 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.

3.66 THE 1977 MONITORING EXERCISE

The purpose of the exercise

It was clear from our examination of the historical evidence that the condition of the Heronry Pond depended on the delicate balance between two factors - inflow and seepage. For example, before 1900, and between 1908 and 1941, inflow generally exceeded seepage, and the pond maintained a reasonable level throughout the year. Between 1900 and 1908, and since 1941, seepage generally exceeded inflow in the spring and summer months, and the pond usually dried up each summer. (See diagrams at Fig.18)

In 1977 we carried out a monitoring exercise with the aim of quantifying the present imbalance between inflow and seepage.

3.67 The method and the measurements

We started by identifying the relevent factors. We knew that rainfall and inflow would tend to increase the water level in the pond, whilst evaporation, seepage and overflow (into the Perch Pond) would tend to reduce it. In fact, there was no overflow at any time during the monitoring exercise. Therefore, the relationship between the remaining factors involved could be expressed in the following equation:

change in the depth = rainfall + inflow – (evaporation - seepage of the pond)

We took the following measurements each Sunday between 6 February and 18 September 1977.*

1. The depth of the pond (at the locations marked on the map at Fig.19).
2. The depth of a control tank, reflecting the combined effect of rainfall and evaporation (situated about 750 yards from the pond).
3. Inflow from the Shoulder of Mutton Pond and from various other sources (shown on the map Fig.19).

As we were able to measure four out of the five variables in the equation above, we could calculate the "unknown" factor, seepage, as follows:

seepage = change in the depth – (inflow + rainfall) - evaporation

* Unfortunately the inflow results for February had to be discarded because of difficulty in finding a method for accurate measurement. This was eventually overcome by catching all inflow at each point for a given time interval in a system of guttering leading to a large plastic sack. Inflow accumulated in the sack was then carefully measured and flow was determined in gallons per minute. (See bottom right photograph at Fig.5).

Figure 19

3.68 The results - the depth of the pond

The 1977 depth measurements are shown in the diagram at Fig.20. Measurements for 1952 and 1953 have been included for comparison. Two conclusions can be drawn.

1. In all three years, the pond accumulated water in the wet winter months (October to March) but lost water in the drier summer months (April to September).*
2. In all three years, during the deficit period the water level of the pond fell at approximately the same rate (ie about one inch each week).

Clearly the position of the pond has not deteriorated over the last 25 years. On the other hand, the position today is much healthier than it was 75 years ago. For example, between 10 March and 9 May 1904, the level of the pond fell by 21 ins (a rate of about 2.5 ins/week).

3.69 The results - inflow and seepage

The results of the monitoring exercise are summarised in the table at Fig.21 and the diagram at Fig.22.

Taking an average week for the monitoring period, the results are as follows.

1. The level of the pond fell by 0.9 ins.
2. Rainfall and evaporation were in balance.
3. Inflow increased the level of the pond by 0.6 ins.
4. Therefore seepage reduced the level of the pond by 1.5 ins.

Given that the area of the pond is 383,000 sq ft, the average volume of seepage was about 50,000 cu ft/week.**

3.70 It can be seen from the diagram at Fig.22 that the rate of seepage did not vary significantly over the monitoring period. For example, it did not increase when the depth of the pond was greatest, nor did it decrease when the depth of the pond was negligible.

3.71 It is important to put our estimate of seepage (ie 50,000 cu ft/week) into perspective. In December 1903, the total volume of subsoil water finding its way into the sewer laid alongside the pond was estimated at 1,250,000 gallons daily. If one assumes that half of this subsoil water was seepage from the pond, this would have represented 700,000 cu ft of seepage weekly (ie 14 times the current rate).

Obviously, seepage today is much lower than it was at the beginning of the century. This suggests that the current problem is one of inflow rather than seepage.

* This pattern is not peculiar to the Heronry Pond. For example, in 1977, 62% of rainfall fell in the winter months (January to March, October to December) but only 38% fell in the summer months (April to September).

** (1.5 ins x 383,000)/12 = 47,875 cu ft

3.72 The results - are they representative?

Two pieces of evidence suggest that the results of the monitoring exercise are probably representative.

1. 1977 was a typical year for rainfall, according to an article by John Grindley of the Meteorological Office in The Times on 28 January 1978.
2. The pond clearly fills to different levels in different years, depending on the rainfall. Nevertheless, in 1977 both the depth measurements and the rate of fall in the water level were very similar to figures 25 years earlier. (See diagram at Fig.20).

3.73 Conclusion

The water level in the Heronry Pond depends on the balance between inflow and seepage. Each year, the pond accumulates water during the wet winter months (October to March) when inflow exceeds seepage, but loses water during the drier summer months (April to September) when seepage exceeds inflow. Our calculations for 1977, which we consider was a typical year, indicate that seepage averages about 50,000 cu ft/week.

Figure 20

Figure 21

Figure 22

PART THREE:

COUNTERING THE PROBLEM

4.01 COUNTERING THE PROBLEM

All of the preceding information has been used in comparing the likely success of different measures which might be adopted to solve the problem of Heronry Pond.

Such measures fall into three categories:

1. Stopping seepage.
2. Reducing the size of the pond to the point where inflow and outflow are in equilibrium, and stability is achieved.

1. Increasing inflow to the extent that it equals or exceeds outflow, so that stability is achieved.

We have examined each alternative in turn, and calculated the likely outcome had each been separately in evidence during the monitored period in 1977. A summary of the effect such measures would have had, in diagrammatic form, is shown at Fig.23.

4.02 Stopping seepage entirely seems extremely unlikely. The record indicates that determined efforts were made in the 1950's to trace and seal all possible leakage points, and it seems very doubtful whether any further significant reduction in seepage could be achieved at realistic cost. We can find no record of the manner of construction of the 1907 re-modelling and concreting, to be able to judge whether there is a proper clay base behind the concrete, and we do not know whether it was the act of concreting the pond in 1907, or the measures to increase inflow also during that period, which achieved the stability recorded between 1910 and 1940. In other words, it is conceivable that the concrete sides and base are entirely irrelevant to the problem.

4.03 However, even if seepage was halved, this would now go a long way towards solving the problem. The diagram at Fig.24 indicates the probable outcome over the monitored period, had seepage been either eliminated, or halved. The question to be answered in such a course however, is where to start? Given a level of water in the pond, it might be possible to introduce specialised materials such as Bentonite. This is a semi-soluble clay-like material, which tends to find its way into lines of seepage suspended in the seeping water, and then adhere to the material through which seepage is occurring, thereby building up a deposit, and ultimately sealing the route. We understand that it is an expensive material, and that its success cannot be assured. In a lake the size of Heronry Pond, its chance of success would not be great.

4.04 Reducing the size by filling might well provide a more satisfactory answer, depending upon the area filled. The likely outcome of filling eastern or western half of the pond is shown at Fig.25. It will be appreciated that very similar measures were attempted during the eighteenth century, when various steps were taken to divide Heronry Pond, and hold water back from its descent down the valley into the Roding, (see Figs.10 & 12).

Figure 23

Figure 24

4.05 There are also several aspects of the filling policy which make it undesirable as a course of action, except in the last possible resort.

4.06 The Acts of Parliament and bye-laws from which the Conservators of Epping Forest derive their powers, clearly place upon the Conservators a duty to ensure the maintenance of the Forest, with all its amenities, for the enjoyment of the public. The Conservators acted in accordance with this duty at the time of their establishment, when they found that the previous owner had constructed a ditch and had partially drained Heronry Pond in order to maintain more grassland for grazing. The ditch was filled, and Heronry Pond was restored to its original size (see para 3.18).

4.07 Again in 1900-08, when the pond was adversely affected, the Conservators ultimately took steps to correct the situation. Although the shape and size of Heronry Pond were altered to some extent, in essence it was restored to its original amenity value (see map – Fig.17).

4.08 Although in the period 1945-56 the Conservators clearly made a number of attempts to restore the amenity value of Heronry Pond following its deterioration during the second World War, these attempts have not been successful.

4.09 We feel that so long as the possibility remains of Heronry Pond being restored to its full amenity value - and later sections of this report make specific proposals to this effect - then to fill in some part of Heronry Pond would be an act against the statutory duties and obligations of the Conservators. We hope and trust that the Conservators will, with us, regard any filling-in of Heronry Pond as an absolute last resort, to be resisted until every other reasonable course of a more positive nature has been exhausted.

4.10 The second aspect on which we question the policy of filling some part of Heronry Pond relates to water regulations. Any materials dumped into Heronry Pond would, by the nature of the valley-site, tend to leach into the lakes downhill, i.e. Perch Pond and Ornamental Water, and ultimately into the River Roding. We understand that any such dumping, or tipping, into Heronry Pond, would have to be subject to the statutory authorisation of the Thames Water Authority, who would, in turn, need to be convinced that no risk of pollution existed to the other lakes and waterways, before granting such authorisation.

4.11 These considerations apart, we have tried to assess the likely outcome, and parallel consequences, of filling some part of Heronry Pond.

The lake has an average depth of about four feet, and we have calculated its total capacity at just over 1.5 million cubic feet. Clay weighs about 99 lbs per cubic foot, and average topsoil about 83 lbs per cubic foot. We have therefore assumed in these calculations, a fill material weighing somewhere in between, i.e. 91 lbs per cubic foot. On this basis, to turn Heronry Pond into a flat plain, level with the existing rim, would require about 62,200 tons of fill.

4.12 To fill half the pond would require 31,100 tons of fill material. Put another way, this involves about 3,100 lorry loads being tipped into the site. In addition there would also be substantial amounts of concrete and aggregate required, to construct by-pass drains, concrete facings to any new embankment, &etc., (see below).

4.13 There are two vehicular routes to Heronry Pond:

1. Through the Aldersbrook estate to Northumberland Avenue, and then across the parkland, on the south side.
2. Through the Warren estate, along Warren Road, to opposite the east island in Heronry Pond on the north side.

Either route would involve passage through dense residential areas, and the degree of local disruption engendered by heavy lorry movements and tipping on such a scale would be considerable.

4.14 This factor apart however, there are both advantages and disadvantages associated with the filling of either the eastern or western half of Heronry Pond.

4.15 Filling Eastern Half

This course could also be described as confining the lake to the area where the subsoil is known to be London Clay and therefore impervious, rather than Taplow Gravel. It would be essential to undertake site investigation to determine the exact boundary of the clay, before embarking on this course (see map – Fig.3).

In addition, it would be essential to "key" any new eastern embankment firmly and thoroughly into the underlying clay, to a depth of at least two feet. If this were not done properly, the strong probability would remain that water would continue to seep through the eastern end of Heronry Pond.

Part of the works would also have to include the construction of a new drain, to cater for overflow. This would have to run from the new eastern embankment, through the filled area, and into Perch Pond.

Any new (smaller western) Heronry Pond would probably be more suited to fishing, rather than boating, since it would be remote from the existing boat house and kiosk, from which boating is now run. It would therefore require stocking with fish - yet its concrete sides and base would not be favourable for fish or plant life, at least initially.

Such concentration of fishing on Heronry Pond would leave the boating facilities still on Perch Pond, where there is a dangerously deep level of water at the eastern end, furthest from the boat house.

Figure 25

Figure 26

The advantages of filling the eastern half of Heronry Pond are two-fold:

1. Virtually all the present inflow channels would remain undisturbed, as they all flow into the western half of the lake. Only the surface run-off north of the east island would require some special drainage.
2. Provided proper steps were taken to seal the new eastern embankment, it is likely that seepage would also be reduced, since all evidence points to the eastern end, near Perch Pond, being the area of most seepage.

If this filling policy were to be adopted, then the first source of spoil for filling should be the western half of the lake itself, which is silted to a depth of 21 inches in places, e.g. by the storm sewer inflow from Northumberland Avenue.

4.16 Filling Western Half

The only advantage of this course would appear to be that the present overflow and piped spillway to Perch Pond would remain undisturbed. However, since the main area of a new (smaller eastern) Heronry Pond would be located precisely on the probable zone of maximum seepage, which would continue, it is highly unlikely that this overflow spillway would ever be required.

In addition, there are substantial disadvantages to this course, primarily related to the fact that new pipes or spillways would be required to join with all the inflow points which are now located in the western half - the filled area.

4.17 We have summarised the likely effect during the monitored period, had either eastern or western half of the lake been filled in beforehand (see diagram – Fig.25). It will be seen that filling the western half of the pond would have provided no solution at all. Heronry Pond would have continued to empty, making it of nil amenity value. The present conflict of fishing and boating would have continued on Perch Pond.

4.18 Increasing Inflow

This was the first measure attempted by the Conservators of Epping Forest in 1906, following upon the deterioration of Heronry Pond at the turn of the century.

As previously noted, drainage works were laid out on Wanstead Flats, with the object of draining the surface waters into Heronry Pond. Coupled with the virtual re-construction of Heronry Pond in the following year (l9O7), a satisfactory result was achieved - although it is not possible to say which measure contributed most to this success.

4.19 We inspected the manhole over the main junction between the Flats drainage system, and the storm sewer beneath Park Road which leads to Heronry Pond, and found the flow of water from the Flats towards the park to be negligible (see para 3.45).

4.20 We also inspected the manhole over the main junction of the system installed in 1908 to drain the Lakehouse estate area (see para 3.36). Conditions were identical to those described for the Flats drain inspection. Again there was evidence that the manhole had not been opened for a very long time. The manhole is situated just inside the boundary fence of the Aldersbrook tennis club, opposite Reservoir Wood.

We found a pit a