Water, the bromate plume and effects of quarrying

The Aquifer - a body of permeable rock which can contain or transmit groundwater

When water-bearing rock readily transmits water to wells and springs, it’s called an aquifer. Aquifers are underground reservoirs – this is where 97% of the planet’s liquid fresh water is stored - almost no bacteria live in aquifers.

We use several different treatment processes to turn raw water into safe and wholesome drinking water.We get our water from two types of sources. About three quarters of our supplies are from rivers and the rest is taken from groundwater sources.The water then goes through a rigorous set of processes at our water treatment works before being pumped into the network to your home or business.The treatment process varies according to the type and quality of the source of water.Storage reservoir Water abstracted from surface sources such as rivers can be temporarily held in large, open storage reservoirs.Storage reservoirs allow the blending of abstracted water with water already held in the reservoir, which permits dilution of incoming contaminants.Water can be held in storage reservoirs for hundreds of days before it is pumped to the works for treatment.The long storage time allows for some water quality improvements:Debris and solid contaminants settle-outSunlight breaks down organic materialSome bacteria die offClarification A chemical coagulant is dosed into the water, and acts to bind together fine suspended material such as silt and mud particles.The coagulant forms a 'floc', which traps the clumps of material, and is then removed from the water by settlement or flotation.Filtration There are several different types of filter available for use in the water industry.However, all function in a similar way by sieving suspended material from the water.Slow sand filters also have a biological action, as the top sand layers trap organic material, and support the biological growth of bacteria and other micro-organisms.These micro-organisms breakdown organic compounds held within the water as it trickles through the filter, thereby providing an additional cleaning action.Aeration This process can be used to remove, or reduce the level of or oxidise:Unwanted compounds such as hydrogen sulphide and carbon dioxide from water.Dissolved metals such as iron in order to ease subsequent removal.Granular Activated Carbon (GAC) This process is an advanced system used to remove pesticides, organic compounds and unpleasant tastes and odours.Water is directed into GAC vessels, which contain highly porous carbon particles.These particles are able to adsorb organic compounds from the water, thus improving its quality.Disinfection Chlorine is used as a disinfectant and can be added to water as either a liquid or a gas.It can be dosed immediately into the incoming raw water for various reasons, to:Benefit downstream treatment processesHave an immediate anti-bacterial effectOxidise unwanted chemicals in the water.Chlorine is dosed at the end of treatment, before the water is sent into supply to destroy harmful micro-organisms.The disinfection process is performed in specially designed contact tanks, which contain a series of baffles.The tanks ensure that the chlorine remains in good contact with the water for a set amount of time, to ensure effective disinfection, before it is sent into the distribution network

Steetley chemical works Sandridge 1955 – 2000

The Steetly Chemical Works was a chemical manufacturing plant which specialised in the manufactureof industrial and pharmaceutical intermediates including potassium bromate and organobromine compounds.Raw materials including bromine, red and yellow phosphorus, and caustic soda were processedinto products including ceta-stearyl bromide, sodium and potassium bromate, and zinc bromide.

Bromate & Bromide salts were used in the factory. These toxic chemicals were dumped into large sumps that eventually drained into the aquifer; so, causing Europe’s largest underground pollution.

A plume of groundwater has now been contaminated. Bromate & bromide cannot be removed, it may pass through to our drinking water unless inhibited at pumping & treatment works.

1955 Steetley:Existing buildings started to be used for manufacture of chemicals described as ‘industrial and pharmaceutical intermediates’ including potassium bromate and organic bromine compounds

Around 1980 The chemical works closed. 1981- 1986 Buildings on site were demolished and pollution in the soil and groundwater was investigated. Any surface soil which was unacceptably contaminated was removed to a depth of approximately 1 metre and replaced with clean material. 1987 The site was redeveloped as St Leonard’s Court.

Steetley chemical works, the company was acquired by Redland Minerals Ltd in 1992

Cessation ofabstraction from Bishops Rise in 2000

IPCS set a guideline value of 10µg/lIs therefore recommend WHO 2000

WS Atkins Ltd in 2002, which identified bromate in the chalk aquifer

In 2007, Affinity Water was granted an Abstraction Licence for the Hatfield Pumping Station site for the purpose ofGroundwater Remediation.

In 2008, the groundwater remediation works commenced under an EnvironmentalPermit (Mobile Plant) and have continued since this date.

1955 1980 1992 2000 2007 2008 2015 2019

Essendon: The highest concentration of bromate was seen in May 2015 at 37.6μg/l andthe lowest in March at 7.6μg/l. The annual average value was 26.67μg/l.

permanently removed from the Chalk aquifer at Hatfield, bringing the totalsremoved to 4553kg of bromate and 10997kg of bromide.

Abstraction: this licence will expire on31st August 2019.

2000 Three Valleys Water detect bromate concentrations of 100µ/l, well in excess of the future drinking waterstandard of 10µg/l, at Hatfield PWS. The EA are informed and abstractions for public water supply

are ceased. A sampling programme is undertaken that identifies St Leonard’s Court as the sourceof the contamination.

Ciara Marie Fitzpatrick

Fig4.11, shows the plume reaching Bishops Rise PWS in year 2000. It is not clear the exact amount of bromate but the shaded blue area may indicate 201µg/l to 300µg/l. The exact amount before 2000 is not known – testing frequency of this pollution is indeterminate. The only conclusion due to such high values is that this pollution may have occurred 20 years prior to Bishop Rise closing.

Dr Paul Aylin investigated cancer incidence in exposed areas of East & West Herefordshire and found that the region did not appear to have a higher risk of developing cancers.

The website is:

http://www.euroheis.org/archive/downloads/finalreport3.pdf

Title:

Case study - An investigation into cancer incidence in areas exposed to high levels of bromate in East and West Herts. P87.

Dr Paul Aylin, Pauline Savigny, Susan Hodgson (SAHSU)

EUROHEIS

Evaluation Phase

Final report August 2003 pdf 7Mb download

Bishops Rise

The PWS is now switched off but continues to extract contaminated water from the aquifer, treating it with ferrous chloride, converting it to bromide and disposing it into special sewers (scavenge pumping).

The continued high concentrations of bromate and bromide observed within the monitoring network, the large volumes already permanently removed from the aquifer and the rapid increase in concentrations when the abstraction ceases, even for short periods, all indicate that there must be a significant source of both contaminants upstream of Hatfield.This remains a valid Interim Remediation Strategy but does not address the full pollution issue. The Appropriate Persons still need to develop and implement a full remediation strategy.

Bromate BrO3

Drinking Water Regulations limit the amount of bromate to 10µg/l in drinking water.Bromate is considered to be a probable human carcinogen linked to thyroid and renalcancer (WHO, 2005).The occurrence of bromate in the Hertfordshire Chalk aquifer presents a currentand future threat to groundwater resources.

EA (WIMS) ref Sampling dateSample date adjusted for chart

Bromate as BrO3 (ug/l) Bromide as Br (ug/l) Comments - all samples from the Chalk aquifer

12/01/2017 January 377.8 83211/04/2017 April 349.8 84019/07/2017 July 380.1 90414/09/2017 October 406.8 87110/01/2017 January 532 108011/04/2017 April 584.0 108011/07/2017 July 579.0 118009/10/2017 October 1030.0 105009/01/2017 January 1.0 69.810/04/2017 April 1.0 71.710/07/2017 July 1.0 58.909/10/2017 October 1.0 91.411/01/2017 January 1.0 72.912/04/2017 April 1.0 70.712/07/2017 July 1.0 68.311/10/2017 October 1.0 86.511/01/2017 January 65 132012/04/2017 April 65.7 128012/07/2017 July 65.3 125011/10/2017 October 78.2 127011/01/2017 January 669 143012/04/2017 April 668.0 137012/07/2017 July 644.0 134011/10/2017 October 808.0 139011/01/2017 January 1.0 57312/04/2017 April 1.0 61912/07/2017 July 1.0 60711/10/2017 October 1.0 59511/01/2017 January 928 185012/04/2017 April 954.0 179012/07/2017 July 895.0 174011/10/2017 October 1020.0 181009/01/2017 January 8.8 7410/04/2017 April 8.0 69.210/07/2017 July 7.8 64.509/10/2017 October 7.6 78.609/01/2017 January 1.0 11110/04/2017 April 1.0 11010/07/2017 July 1.0 10109/10/2017 October 1.0 10909/01/2017 January 52.1 14410/04/2017 April 65.1 15810/07/2017 July 61.6 14909/10/2017 October 58.4 16609/01/2017 January 657 134010/04/2017 April 636.0 131010/07/2017 July 579.0 121009/10/2017 October 569.0 1190

Pumped borehole. Different samplers. The dates shown are the closest available to the quarterly monitoring for the other sites.

PGWU1326

PGWU1656

PGWU1648

80163A01

Pumped borehole.

Pumped borehole. Bromate result below laboratory detection limit of 2 micro-grams per litre, so edited to show half detection limit for presentation on the graph (this is typical practice)Bromate result below laboratory detection l imit of 2 micro-grams per l itre, so edited to show half detection limit for presentation on the graph (this is typical practice)

80163A04

80163A05

PGWU2011

PGWU1718

80163A03

80163A23

PGWU1789

PGWU1720

Bromate result below laboratory detection l imit of 2 micro-grams per l itre, so edited to show half detection limit for presentation on the graph (this is typical practice)

Bromate result below laboratory detection l imit of 2 micro-grams per l itre, so edited to show half detection limit for presentation on the graph (this is typical practice)

Environment Agency Borehole data Some of these levels are in excess of 1000µg/l

Dr Bryan Lovell, OBE, CGeol

“The problem with the chalk aquifer is this: very quick pollution, very slow decontamination”“Monitoring of pollution as it takes place is not the main issue: pollution must be prevented from the word go”.

Bromate plume & Brett’s quarry site

The distance between proposed lagoons and bromate is only 400M

The Drawdown effect

This effect also applies to removal of water in the aquifer due to quarrying

When groundwater is pumped from a borehole, the water level is lowered in the surrounding area. A hydraulic gradient is created in the aquifer which allows water to flow towards the borehole. The difference between the original water level and the pumping level is the drawdown, which is equivalent to the head of water necessary to produce a flow through the aquifer to the borehole — the greater the yield from the borehole, the greater the drawdown. The drawdown decreases with increasing distance from the borehole until a point is reached where the water level is unaffected. The surface of the pumping level is in the form of an inverted cone and is referred to as a cone of depression.

Water flows into a borehole from all directions in response to pumping and, as it is flowing through a decreasing cylindrical area, the velocity increases as it converges towards the borehole

Brett Aggregate plan to quarry the Hatfield Aerodrome site for the next 32 years.

We can see from the above Drawdown effect that any excavation of the water in the lower mineral horizon and chalk aquifer will lower the piezometric line and cause contaminated water to migrate to the cell centre.

2.2.1 GeologyThe site is located within superficial Lowestoft formation which overlies the Lewes NodularChalk. Further details of the geology of the site are given in the ESID report and ES. Thesuperficial deposits comprise four primary deposits across the site; namely:• Overburden: comprising predominantly silts and clays (ranging from 0m – 2mthickness)• Upper Mineral Horizon (UMH): Silty sands and gravels (4m – 6m)• Inter-burden: Boulder clay (3m – 5m)• Lower Mineral Horizon (LMH): Sands and gravels (5m – 7m)These superficial deposits are underlain by the Chalk at a depth of between 15m and 18mbelow ground level. The proposed quarry will not fully work the superficial deposits and atleast 1m of in-situ LMH material will be retained at the base of the site.Lower Mineral Aquifer (LMA) (hydraulically connected with the underlying Chalk aquifer … SLR

The geology of the area suggest suggests a ridge or watershed exists between the N.E. of the quarry site and S.E flow of the pollution. If at any time this is breached, then bromate pollution could spread in a southerly direction. This would have a disastrous effect on Roestock PWS and then Tyttenhanger PWS.

Bromate pollution and the effects of quarrying

SLR Consulting Ltd, on behalf of Brett, have undertaken extensive site investigation at the proposed Hatfield Road Quarry. The presence of bromate (and bromide) pollution means that we require additional assessments compared to what is normally required for this type of activity. Our concerns were that the quarrying activity might cause migration of the contamination, either vertically or laterally, something which must be avoided. SLR’s investigations show that the proposed activities are unlikely to cause migration of the plume to the south and their activities are unlikely to impede the remediation of the groundwater. The northern boundary of the proposed scheme has been determined by the boundary of the bromate and bromide groundwater contamination. Brett have also adapted their proposed operations to reduce the risk of drawing the plume southwards.

 

In addition to the proposed measures to protect groundwater, monitoring throughout the life of the proposed development is imperative to confirm that SLR’s assessment is correct and there is no detriment to groundwater. If any movement of the boundary of the plume or increase in contaminant concentrations is detected, actions detailed in a Water Management Plan will be required to ensure there is no unacceptable risk to groundwater and the abstractions used for public water supply. Furthermore, Brett have told me that they do not want to cause the plume to move in order to avoid any question of liability with regard to the existing groundwater pollution.

 

Affinity confirmed to me that they are now satisfied that the risk to their groundwater abstractions can be adequately managed by measures they have agreed with Brett and through the planning regime. It is extremely important that the decision notice, if the proposed development is permitted, includes a Water Management Plan condition as was recommended by us in in our planning consultation response NE/2016/124652. A draft water management plan was submitted and responded to in NE/2018/128672. I also attach copies of these letters. Planning controls are the only means by which to adequately manage the risk from the pre-existing pollution. Our regulatory controls are not appropriate since both an environmental permit for the backfill of excavations and a water resources transfer licence can only be used to control the permitted activities themselves.

Environment Agency

 

Summary

Trying to predict the effect quarrying & pollution would do to the groundwater in the future is not a simple task. However, it is clear that working dry (UMH) on a quarry site will reduce the spread of pollution to a minimal level. Cemex quarry, adjacent to the plume, are only excavating the top gravel horizon.

There is a high risk that proposed quarry extraction work will disrupt the geology of the site to the effect of further contamination or spread of contamination of ground water.

The responsibility of minimising the risk of contaminating first the groundwater and then drinking water falls to the quarry operator and the water company. Failure to act quickly may result in closure of the quarry and closure of public water supplies.