DATASHEET: Nitrate vulnerable zone (NVZ) Eutrophic Waters...

Report for existing Polluted Water Truro, Tresillian and Fal

NVZ Name: Truro, Tresillian and Fal NVZ ID: ET5

DATASHEET:

Nitrate vulnerable zone (NVZ) designation 2017 – Eutrophic Waters (Estuaries and Coastal Waters)

Publication Date: June 2016


Form A (cover sheet) Page 2

Introduction

This document provides a summary of the evidence used in proposing an area of land as one which should be, or should continue to be, designated as a Nitrate Vulnerable Zone (NVZ) for the purposes of the Nitrate Pollution Prevention Regulations 2015.

A full description of the methods used in developing the NVZ proposals is set out in the detailed methodology for eutrophication-related NVZs, available via http://apps.environment-agency.gov.uk/wiyby/141443.aspx . These methods were developed under the guidance of a review group convened by the Defra for the last NVZ review (2011-2013), which included representatives from the farming and water industries as well as independent academic experts. Minor refinements to the methods have been made for the current review.

NVZs are areas of land that drain to polluted waters and which contribute to the pollution of those waters. Polluted waters include those which are eutrophic or may in the near future become so if the Regulations were not to apply there.

Eutrophication is defined as “the enrichment of water by nitrogen compounds, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned”.

For both freshwaters and saline waters, a weight-of-evidence based approach to assessing the risks and impacts of eutrophication was employed. The evidence for individual water bodies was assessed against a national suite of criteria for eutrophication in the different categories/ types of water for review. The criteria are both quantitative and qualitative and reflect scientific understanding of the process and effects of eutrophication. They are broken down in the same way for each water category as follows:-

Nutrients Plants/algae Secondary and other effects

For each designated or candidate water body which might meet the criteria for eutrophication, a datasheet such as this one was completed, bringing together information about the water body, its catchment, its uses, evidence of eutrophication and the sources of nitrogen input.

This document is a record of the evidence used in the designation process, including results from national monitoring and assessment programmes, and further information supplied by Area staff. The proposals for NVZ designation are made as a result of close working between Area and national Environment Agency teams, with further quality assurance for the eutrophication designations through the use of a national expert panel.

Some features of the maps within this report are based on digital spatial data licensed from the Centre for Ecology and Hydrology, ©.

Please note that any maps shown here have not used detailed field boundaries and therefore represent the indicative 'soft' boundary only. The definitive NVZ area can be seen on the “What’s in Your Backyard” (WIYBY) website ((http://apps.environment-agency.gov.uk/wiyby/141443.aspx).

http://apps.environment-agency.gov.uk/wiyby/141443.aspx






Ref. Code: ET5

EC Urban Waste Water Treatment and Nitrates Directives

Use these forms for existing designations under:

Urban Waste Water Treatment Regulations: Sensitive Areas (Eutrophic); Sensitive Areas

(Nitrate);

Nitrates Regulations: Polluted Waters (Eutrophic) leading to Nitrate Vulnerable Zone designation

Form A: Cover Sheet

Take information for questions 1 – 7 from original candidate reports (if available)

Existing Sensitive Area (Eutrophic) and/or (Nitrate)/ Polluted Waters (Eutrophic)

Sensitive Area coverage (highlight appropriate coverage):

England England &

Wales Wales

England & Scotland

1) Name of regulator

Environment Agency, South West Region, Devon & Cornwall

2) Designated Site name

(The name should be comprehensive, ie include the name of tributaries etc encompassed)

Truro, Tresillian and the Fal PW(E) and Lower Fal Estuary PW(E)

3) Main river catchment

River Fal

4) Location & extent of Designated Site (Map should be included)

The original designation extends from the tidal limits of the Truro, Tresilian and Fal Estuaries to the head of the Carrick Roads. The designated site was extended in a subsequent review period to the estuary mouth. The site boundaries are shown on Figure 3.1.

5) Type(s) of water body (Tick all boxes that apply)

Running freshwater

Still freshwater

Estuarine water

Coastal water



6) In previous reviews this site was designated as a: (Tick all that apply)

Sensitive Area (Eutrophic)

Polluted Water (Eutrophic)

Sensitive Area (Nitrate)

7) Summary of qualifying sewage treatment work discharges (i.e. greater than p.e. 10,000) which contribute to the pollution of the sensitive area.

Name of discharge Direct / Indirect

NGR

Approximate

Population equivalent

Current Treatment Planned Type of

TER (N, P, NP)

Level (PRIM, SEC, TER)

if TER enter Type (N, P, NP)

Newham STW Direct SW83374327 28,000 TER N

Falmouth STW Direct 39,000 TER N

Total PE 67,000

8) Executive summary of evidence of change in eutrophic status since designation:

Refer back to key indicators of eutrophication at the time of designation.

The designation of the Upper Fal (Truro, Tresillian, and Fal) PW(E) followed significant Alexandrium tamarense blooms in 1995 and 1996 (up to 3,000,000 cells/litre) that resulted in red tides and the toxin for paralytic shellfish poisoning (PSP) appearing in local shellfish beds. The toxin levels were of sufficient concentrations for the Port Health Authority to issue a prohibition notice on the collection of shellfish for the whole of the Fal Estuary from June to September 1995. There was considerable media attention and several public complaints linked to algal blooms.

Alexandrium species are still detected each year in samples from the Fal Estuary, but the blooms have not been on the same scale as those recorded in 1995 and 1996. A bloom in 2009 had a cell count of 16,200 cells/litre and temporary shellfish harvesting restrictions were imposed in August and September 2009 due to PSP (Form D, sections 9 and 11).

Control measures have been introduced at Newham STW and Falmouth STW with tertiary treatment for nitrogen reduction, and within the NVZs for both PW(E)s. The average concentration of DAIN in several of the main rivers discharging into the PW(E) has reduced since the period 2000 to 2005. The average DAIN concentration in the STW discharges has also reduced since the same period. Chlorophyll-a data indicates an improvement within the estuary with fewer significant blooms occurring (Form D, section 8).

The initially designated PW(E) and its later extension are within the Carrick Roads Inner and Carrick Roads Outer waterbodies, both of which fail the dissolved inorganic nitrogen standard under the Water Framework Directive. However phytoplankton is classified at present as being at good status.

On the basis of the evidence summarised in this document the NVZ should remain in place.

Now progress to the relevant form(s) for the Sensitive Area/Polluted Water



Form B – Running Freshwaters (information, data, evidence)

Form C – Still Freshwaters (information, data, evidence)

Form D – Estuarine (transitional) Waters (information, data, evidence)

Form E – Coastal Waters (information, data, evidence)

Form G – Actual effect of nutrient removal at qualifying discharge works


Form D (information, data, evidence) Page 6

Ref. Code: ET5


Form D: Estuarine Waters – Information, data, evidence

Existing Sensitive Area (Eutrophic) / Polluted Waters (Eutrophic)

1) SA(E)/PW(E) name: Truro, Tresilian & Fal (take name from Form A)

2) Define approximate area of estuarine water using grid references:

Truro, Tresillian and the Fal PW(E)

Start point Tidal limits of Truro, Tresilian & Fal NGR 1: SW82904465

NGR 2: SW82904465

NGR 3: SW88754217

End point Head of Carrick Roads NGR 4: SW88755217

Surface area (ha): 798 ha

Lower Fal Estuary PW(E)

Start point: Head of Carrick Roads NGR 1: SW 83003800

End point: Mouth of Fal Carrick Roads NGR 3: SW 83503150

Surface area (ha): ca. 20 km2

3) Attach map showing the SA(E)/PW(E), Water Framework Directive (WFD) waterbodies and locations of chemical sample points, biological sample points, any direct or indirect sewage treatment work discharges, direct or indirect discharges of nitrogen compounds from agricultural sources, and other significant discharges of nitrogen or phosphorus e.g. industrial. See Figure 3.1



Figure 3.1 Map showing the boundaries of the waterbodies and PW(E)/SA(E). The sampling points and STWs are listed in Tables 3.1 and 3.2.



Table 3.1 Key to sample points shown on Figure 3.1

Sample Point Code

Sample Point Name Chemical

sample point? Phytoplankton sample point?

81922283 Truro River At Truro Y

81940113 Tresillian Shellfish Water Site Y Y

81940103 Tresillian River Off Malpas Pt Y

H1922254 Truro River Off Lambe Creek Y

H1920225 Truro River Off Grimes Point Y

81922205 Truro River At Old Kea Y Y

H1920219 Truro River Off Ruan Point Y

81920177 River Fal At Tolverne Y Y

81920129 River Fal At King Harry Ferry Y Y

81911530 Restronguet Creek Mouth Y

81910170 River Fal Mid Channel Y Y

81910139 River Fal Vilt Buoy Y Y

81910627 Penryn River At Falmouth Road Y

81910535 Percuil River At Old Shellfish Water Y

81910116 River Fal At Black Rock Buoy Y Y

Table 3.2 Key to discharges shown on Figure 3.1

Discharge Name Approximate Population Equivalent (2015 data)

Ladock Valley STW 4,200

Newham STW 28,000

Tregony STW 950

Falmouth STW 39,000

St Mawes STW 1,300

St Just-in-Roseland STW 100

Mylor Bridge STW 1,350

Ponsanooth STW 2,800

Carnon Downs STW 2,900

4) Approximate retention/flushing time (days):

>10 days for Truro system to clear Carrick Roads completely.

5) Brief description of geo-morphological nature of estuary (e.g. broad and flat, deep and fjord-like, salinity regime, stratification etc)



The estuary is a ria – a deeply incised river valley ‘drowned’ by rising sea levels. It is a natural deep water harbour with the channel extending up to Malpas. There is some stratification under neap tides but the estuary is more well-mixed under spring tides.

6) Summary of main uses and designations: (Tick all boxes that apply)

Y Amenity Y Boating

Y Water sports Y OSPAR problem area

Y EC Bathing Water Y Angling

Y Commercial fishery Y* Designated EC Shellfish Water

Y Designated EC Shellfish Harvesting Area

Non - designated shellfish harvesting area

Other uses or designations:

1. passage of migratory fish 2. Conservation (see below)

3. 4.

* Very recently in December 2015, oysters harvested from the Fal Estuary using traditional fishing methods have gained protected designation of origin status. This is a significant development for the shellfishery, as the Fal River oyster fishery is the last oyster fishery in Europe harvested under sail.

7) If waterbody has conservation status provide details

The site is part of the Fal & Helford SAC, and is of European importance for the following marine interest features:

Sandbanks which are slightly covered by sea water all the time

Atlantic salt meadows (Glauco-Puccinellietalia maritimae)

Estuaries

Large shallow inlets and bays

Mudflats and sandflats not covered by seawater at low tide

Reefs

Key nature conservation designations (Natural England, 15th January 2016):

FAL & HELFORD Special Area of Conservation (SAC)(EC Habitats Directive)

MALPAS ESTUARY Site of Special Scientific Interest (Wildlife and Countryside Act 1981, as amended)

UPPER FAL ESTUARY AND WOODS Site of Special Scientific Interest (Wildlife and Countryside Act 1981, as amended)

LOWER FAL & HELFORD INTERTIDAL Site of Special Scientific Interest (Wildlife and Countryside Act 1981, as amended)

The Fal estuary is a complex system of drowned river valleys (rias), shallow inlets and bays in a sheltered position and with a low tidal range supporting a wide variety of substrates. The majority of the shores of the upper Fal and Helford are fringed by sheltered littoral sandflats and mudflats, transitioning to Atlantic salt meadows. Biologically rich sublittoral sandbanks are present throughout much of the ria system and eelgrass beds are found near the mouth of the both Fal and in some ria channels. In the lower Fal and Falmouth Bay extensive beds of the coralline maerl are present supporting a high diversity of flora and fauna. Littoral and



sublittoral rocky reef features are present in the SAC and include circalittoral reef in Falmouth Bay, kelp forest communities, estuarine reef and littoral rocky shore communities.

The SAC is a Protected Area under the EC Water Framework Directive and Marine Protected Area (MPA) under the EC Marine Strategy Framework Directive. The designated features are recognised as vulnerable to the adverse effects of eutrophication. Natural England advises that elevated nitrogen is a particular cause for concern in this context due to the sensitivity of interest features and the apparent susceptibility of the Fal system to toxic algal blooms. The reported MPA requirement is to ensure that deterioration in water quality due to elevated nitrogen is not allowed to occur. There is a need to ensure that nitrogen is maintained at a level where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features.

8) What chemical, biological, and observational data are available?(Tick boxes if evidence is supplied)

Y Dissolved available inorganic phosphorus (DAIP)

Y Dissolved available inorganic nitrogen (DAIN)

Y Chlorophyll-a

Y Cell counts

Y Dissolved Oxygen

9) What biological / observational data are available?

Angiosperms

Y Planktonic algal blooms

Macroalgae

Presence of foam / scum

Shellfish / invertebrate / fish mortality

Photographs



Chemical data: summary statistics of samples

Winter DAIN M/l (Nov-Feb surface samples)

Indicative Conditions

1. Significantly enhanced (>50%) relative to background concentrations for a defined geographical area based on salinity between Dec – Mar period;

2. Changing Winter nutrient ratios where elevations occur above: N:P >25, and N:Si >2;

3. Winter values of nutrient concentrations significantly exceed 12M/l DAIN in the presence of at least

0.2M/l DAIP (CSTT* standards).

Sampling Site Data

Included n

Mean

Salin

ity

Mean

DA

IN

StD

ev D

AIN

Min

DA

IN

Max D

AIN

n E

xc

eed

ing

Co

nd

itio

n 1

% E

xceed

ing

Co

nd

itio

n 1

n E

xc

eed

ing

Co

nd

itio

n 2

% E

xceed

ing

Co

nd

itio

n 2

n E

xc

eed

ing

Co

nd

itio

n 3

% E

xceed

ing

Co

nd

itio

n 3

Truro River At Truro 2005 - 2010 30 3.6 398 103 172 603 30 100 28 93 30 100

Tresillian Shellfish Water Site

2007 - 2015 23 22.5 227 123 57 494 23 100 23 100 23 100

Tresillian River Off Malpas Pt

2007 - 2010 26 21.2 203 125 23 432 26 100 25 96 26 100

Truro River Off Lambe Creek

2005 - 2011 33 20.0 199 104 40 419 33 100 30 91 33 100

Truro River Off Grimes Point

2005 - 2010 30 23.1 166 106 26 403 30 100 27 90 28 93

Truro River At Old Kea

2007 - 2015 17 27.8 116 72 39 286 17 100 17 100 17 100

Truro River Off Ruan Point

2005 - 2010 30 24.9 147 100 22 376 30 100 24 80 30 100

River Fal At Tolverne 2007 - 2015 23 25.7 125 86 38 346 23 100 22 96 22 96

River Fal At King Harry Ferry

2005 - 2015 45 28.2 104 68 14 252 44 98 39 87 42 93

Restronguet Creek Mouth

2005 - 2010 30 29.0 77 55 10 221 27 90 24 80 26 87

River Fal Mid Channel

2005 - 2015 46 32.1 41 27 9 116 43 93 35 76 41 89

River Fal Vilt Buoy 2005 - 2015 41 33.5 23 15 4 61 23 56 21 51 33 80

Penryn River At Falmouth Road

2005 - 2015 40 33.1 27 20 4 113 32 80 24 60 34 85

Percuil River At Old Shellfish Water

2007 - 2010 26 32.4 36 31 8 161 21 81 19 73 22 85

River Fal At Black Rock Buoy

2005 - 2015 41 34.2 15 8 4 42 16 39 9 22 24 59

Interpretation and discussion:

Winter DAIN levels in the Fal estuary system are significantly elevated relative to background waters in the western English Channel which are ~10 µM/l from Station E1 near the Eddystone Rocks.

A plot of all the DAIN data against salinity is given in Figure 8.1a for the period November to February. This



plot shows that there is a clear relationship between the DAIN levels and salinity during the winter months. This suggests that freshwater sources of DAIN are significant.

Under the Water Framework Directive, both the Carrick Roads Inner and Carrick Roads Outer waterbodies are classified as Moderate for Dissolved Inorganic Nitrogen (DIN). DIN and DAIN are exact equivalents, being the sum of ammonia and total oxidised nitrogen (nitrate and nitrite). Nitrate is the predominant nitrogen constituent of DAIN (and DIN) in coastal and freshwaters, being greater than 95% of the total.

DAIN data for all the sampling sites in the estuary are summarised above and presented in Figures 8.1a, b, and c. which show the relationship between the winter DAIN and salinity, mean winter DAIN presented spatially, and mean seasonal DAIN and salinity.

The Fal estuary system is hyper-nutrified, and both Carrick Roads Inner WFD transitional water and Carrick Roads Outer WFD coastal water are consistently reported as moderate status for DIN.



Figure 8.1a Winter DAIN Data (2005 to 2015)

Figure 8.1b Winter DAIN Means



Figure 8.1c Seasonal DAIN and Salinity Means



Winter DAIP M/l (Nov-Feb surface samples)

Indicative Conditions

1. Significantly enhanced (>50%) relative to background concentrations for a defined geographical area based on salinity between Dec – Mar period;

Sampling Site Data

Included n

Mean

Salin

ity

Mean

DA

IP

StD

ev D

AIP

Min

DA

IP

Max D

AIP

n

Exc

eed

ing

Co

nd

itio

n 1

%

Exc

eed

ing

Co

nd

itio

n 1

Truro River At Truro 2005 - 2010 30 3.6 1.47 1.33 0.61 6.13 17 57

Tresillian Shellfish Water Site 2007 - 2015 23 22.5 1.14 0.30 0.62 1.97 20 87

Tresillian River Off Malpas Pt 2007 - 2010 26 21.2 1.24 0.44 0.36 2.49 23 88

Truro River Off Lambe Creek 2005 - 2011 33 20.0 1.38 0.65 0.37 3.33 27 82

Truro River Off Grimes Point 2005 - 2010 30 23.1 1.19 0.47 0.16 2.42 27 90

Truro River At Old Kea 2007 - 2015 17 27.8 0.87 0.21 0.34 1.39 8 47

Truro River Off Ruan Point 2005 - 2010 30 24.9 1.06 0.33 0.33 1.61 23 77

River Fal At Tolverne 2007 - 2015 23 25.7 0.87 0.27 0.16 1.36 11 48

River Fal At King Harry Ferry 2005 - 2015 45 28.2 0.86 0.29 0.16 1.39 19 42

Restronguet Creek Mouth 2005 - 2010 30 29.0 0.73 0.29 0.16 1.07 11 37

River Fal Mid Channel 2005 - 2015 46 32.1 0.79 0.27 0.16 1.26 19 41

River Fal Vilt Buoy 2005 - 2015 41 33.5 0.72 0.28 0.16 1.13 13 32

Penryn River At Falmouth Road 2005 - 2015 40 33.1 0.74 0.28 0.16 1.19 13 33

Percuil River At Old Shellfish Water 2007 - 2010 26 32.4 0.76 0.21 0.16 1.03 6 23

River Fal At Black Rock Buoy 2005 - 2015 41 34.2 0.74 0.27 0.16 1.27 15 37


DAIP levels in the Estuary are elevated relative to background waters in the western English Channel, but not significantly, being less than 50 % elevated. Long term data from Station E1 near the Eddystone Rocks shows peak winter values for DAIP of about 0.6 µM/l. It is likely that the DAIP levels in the Estuary waters are buffered with phosphorus bound to the estuarine sediments, as there is no clear relationship between the DAIP levels and salinity, as shown in Figure 8.2a below.



Figure 8.2a Winter DAIP Data (2005 to 2015)

Figure 8.2b Winter DAIP Means



Chlorophyll-a (µg/l) during growing season (Mar-October) including surface and depth samples

Criteria

1. Concentrations of 10 mg/m3 (or µg/l) in algal blooms

2. More than 10% of samples exceeding 10 mg/m3

Sampling Site Data

Included n

Mean

Salin

ity

Mean

Ch

la

StD

ev C

hla

Min

Ch

la

Max C

hla

n

Exc

eed

ing

Co

nd

itio

n 1

n

Exc

eed

ing

Co

nd

itio

n 2

Truro River At Truro 2005 - 2009 69 8.0 14.8 22.6 2.0 163.0 25 36

Tresillian Shellfish Water Site 2007 - 2015 92 29.3 6.3 4.9 0.7 27.2 14 15

Tresillian River Off Malpas Pt 2007 - 2009 42 26.2 15.8 34.4 1.3 218.0 15 36

Truro River Off Lambe Creek 2005 - 2010 72 26.4 10.6 9.6 1.2 52.0 29 40

Truro River Off Grimes Point 2005 - 2009 68 27.6 11.0 19.2 0.9 128.0 19 28

Truro River At Old Kea 2007 - 2015 92 31.4 3.8 2.5 0.3 13.9 2 2

Truro River Off Ruan Point 2005 - 2009 68 29.4 6.1 5.7 0.8 35.0 11 16

River Fal At Tolverne 2007 - 2015 92 30.0 4.2 4.0 0.3 33.8 5 5

River Fal At King Harry Ferry 2005 - 2015 161 31.9 4.1 3.8 0.3 26.8 9 6

Restronguet Creek Mouth 2005 - 2009 68 30.2 6.6 6.6 1.1 49.3 9 13

River Fal Mid Channel 2005 - 2015 161 33.6 3.2 2.5 0.7 16.7 6 4

River Fal Vilt Buoy 2005 - 2013 101 34.1 2.9 2.2 0.5 14.3 2 2


2005 - 2013 101 34.0 4.6 3.5 0.6 18.1 8 8

Percuil River At Old Shellfish Water

2007 - 2009 42 33.8 8.1 16.7 1.0 109.0 6 14

River Fal At Black Rock Buoy 2005 - 2013 102 34.5 2.7 2.3 0.3 16.3 1 1


Discussion of chlorophyll and dissolved oxygen is included within Section 9: phytoplankton

Figure 8.3a Summer Chlorophyll Data



Figure 8.3b Seasonal Chlorophyll and Salinity Means

Figure 8.3c Summer Chlorophyll Means



Figure 8.3d Chlorophyll in the upper Fal estuary during the growing season for 2007 to 2015.



Figure 8.3e Chlorophyll in the upper Fal estuary during the growing season for 1995 to 2006.

Figure 8.3f Chlorophyll-a data) in the upper Fal Estuary PW(E) between 1995 to 2015 (2 values in 2002 have been excluded as outliers).



Figure 8.3g Salinity of the Chlorophyll samples in the upper Fal Estuary PW(E) from 1995 to 2015

9) Phytoplankton

Comparison of historic and recent chlorophyll and cell count data

The status of the Fal Estuary as a PW[E] relates to concerns about the occurrence of phytoplankton blooms, and in particular the significant blooms of the toxic algae, Alexandrium tamarense, that occurred in 1995 and 1996.

There is evidence that there has been some reduction in overall phytoplankton biomass since the site was designated. The concentration of chlorophyll is measured as an indicator of phytoplankton abundance. A salinity related chlorophyll standard was exceeded by approximately 14% of chlorophyll samples collected during the growing seasons between 1995 and the end of 2006 (Figure 8.3e above). In comparison only 2% of chlorophyll samples collected in the growing seasons from 2007 to 2015 exceed the standard (Figure 8.3d). Phytoplankton blooms are most frequent in the upper estuary, in the Truro River, and are less frequent in the middle and lower estuary (Figure 8.3b).

Some of the apparent improvement in chlorophyll may be explained by changes to the monitoring programme. WFD monitoring at Tresillian SFW, Tolverne and Old Kea began in 2007 and monitoring at Truro, Off Malpas, Ruan Point and Grimes Point stopped in 2010. This has increased the number of samples taken at high salinities and reduced the number of samples taken at lower salinities (Figure 8.3g). The average and maximum chlorophyll concentrations of the sample dataset reduce significantly after 2010 when fewer samples at low salinities were collected (Figure 8.3f).

Alexandrium blooms

In June and July 1995, blooms of A. tamarense developed during a long period of calm weather with bright sunshine. A maximum cell count of 3 x 106 per litre was observed coinciding with a neap tide (Table 9.4). In 1996, blooms of A. tamarense reappeared with a maximum cell count of 8 x 105 per litre. These cell counts exceed the WFD phytoplankton single taxa threshold.



Alexandrium species are still found in water samples collected from the Fal each year, but at much lower cell counts than the blooms of the mid 1990s (Table 9.5). Shellfish flesh samples containing levels of PSP above the Action (closure) level were collected from the Fal in 2006, 2009 and 2011 (Table 11.1 in section 11). The Fal was subject to approximately seven weeks of temporary harvesting restrictions, between early August and late September 2009 due to PSP in shellfish.

A. tamarense was found to overwinter in the sediments and therefore is likely to appear on an annual basis, and the extent of the proliferation and attainment of red tide conditions would appear to be very much dependent upon the inter relationship between climatic and physico-chemical determinands. The sampling in 1995 and 1996 found that the deeper areas of the estuary from Ruan to the Carrick Roads tended to hold blooms of A. tamarense for a longer duration than shallower areas. This may reflect the slower flushing ability of this area of the estuary.

Alexandrium species produce a non-motile cyst phase which can be incorporated into the sediments at the sea bed. These buried cysts remain viable, and can germinate when they are resuspended due to erosion of the bed sediments or through dredging. Recent work has shown that buried cysts of Alexandrium can remain viable for 60 years or longer (Feifel et al. 2015). This time span for the viability of cysts is a challenge for the management of sites where such toxic algae are present, as controls should be maintained or put in place to minimise those environmental conditions which favour or promote toxic algal blooms.

Monitoring of algal biotoxins in shellfish flesh and in water is carried out in the Fal by the Local Authority for the purposes of the Shellfish Hygiene Regulations. Some results of water samples collected by the Local Authority for the Shellfish Hygiene Directive are shown in Figure 9.5 below while Figure 9.6 shows the results of Environment Agency monitoring since 2007. The sites at Malpas and Turnaware Pontoon are within the Upper Fal PW(E). East Bank, Penryn and Percuil are within the Lower Fal PW(E). Further information is contained within biotoxin reports available on the CEFAS website (http://cefas.defra.gov.uk).

WFD phytoplankton status

The WFD status of phytoplankton is calculated using data on chlorophyll and counts of phytoplankton taxa cells collected over a six year period. The classification method is different for coastal and transitional waters.

The Carrick Roads Inner waterbody is a transitional water. The phytoplankton status of transitional waters is based on a measure that combines several chlorophyll summary statistics from the water body; and a measure that assesses the number of occasions that phytoplankton cell counts exceed thresholds for single taxa and total taxa. In Table 9.1 these measures are called “Chlorophyll” and “Elevated Counts”.

The Carrick Roads Outer waterbody is a coastal water. Measures to assess chlorophyll and elevated counts are used to assess coastal waters, along with a third measure that assesses the seasonal ratios of diatoms and dinoflagellates. In Table 9.1 this third measure is called “Seasonal Succession”. The 2015 phytoplankton classification results for the Carrick Roads Inner and Carrick Roads Outer are shown in Table 9.1. More information on the method used to classify phytoplankton is available on the UKTag website:

http://www.wfduk.org/resources/tags/transitional-coastal-water-159/tags/phytoplankton-68: Resources | wfd uktag

The WFD status of phytoplankton is at good status in both Carrick Roads Inner and Carrick Roads Outer. The breakdown of the results indicates that chlorophyll levels are generally low, but the phytoplankton cell counts in the Carrick Roads Inner often exceed thresholds for single taxa and total taxa (Table 9.3). The single taxa count threshold was exceeded in 41% of samples (Figure 9.3) and the total taxa count was exceeded in 27% of samples (Figure 9.1). This equates to moderate status for the elevated counts measure. The single taxa threshold is most frequently exceeded by Microflagellates. The highest cell counts since 2009 have been due to Phaeocystis and Chatoceros blooms.

http://www.wfduk.org/resources/tags/transitional-coastal-water-159/tags/phytoplankton-68

http://www.wfduk.org/resources/tags/transitional-coastal-water-159/tags/phytoplankton-68



Table 9.1 2015 Classification results for phytoplankton

The 2015 results are based on a 6 year dataset from 2009 to the end of 2014.

Water body Phytoplankton overall status

Chlorophyll result

Elevated Counts result

Seasonal Succession result

Carrick Roads Inner

Good High Moderate N/A

Carrick Roads Outer

Good High Good Good

Secondary effects from phytoplankton

Phytoplankton blooms can result in periods of oxygen deficiency. There is no evidence that phytoplankton blooms in the Fal Estuary are resulting in secondary dissolved oxygen (DO) problems, and DO is at High WFD status. However, DO is monitored in the Fal Estuary by collecting spot samples from near the surface of the water column at a few monitoring stations. The DO monitoring programme provides general surveillance data and is not designed to investigate the effects of phytoplankton blooms on DO. A targeted investigation would require higher frequency, or continuous, monitoring of DO at depth as well as surface at targeted sites where problems are most likely to occur.

Figure 9.1 Phytoplankton total taxa cell counts in the Carrick Roads Inner transitional water

11/Feb/14

6/Jun/13

27/Sep/12

23/Jan/12

10/Jun/11

16/Nov/10

25/Mar/10

30/Oct/09

12/Jun/09

15/Jan/09

12000000

10000000

8000000

6000000

4000000

2000000

0

Date

Ce

lls p

er

litre

1000000

151115

151116

151117

151118

151119

Station

Carrick Roads Inner: phytoplankton total taxa counts



Figure 9.2 Phytoplankton total taxa cell counts in the Carrick Roads Outer coastal water

18/Jul/13

5/Mar/13

23/Nov/12

13/Jun/12

15/Feb/12

3/Oct/11

8/Jun/11

8/Feb/11

14/Oct/10

16/Jun/10

6000000

5000000

4000000

3000000

2000000

1000000

0

Date

Ce

lls p

er

litre

1000000

155813

155814

155815

Station

Carrick Roads Outer: phytoplankton total taxa counts

Figure 9.3 Phytoplankton single taxa cell counts in the Carrick Roads Inner

The taxa with the highest count in each sample is shown

11/02/2014

06/06/2013

27/09/2012

23/01/2012

10/06/2011

16/11/2010

25/03/2010

30/10/2009

12/06/2009

15/01/2009

10000000

8000000

6000000

4000000

2000000

0

Date

Ce

lls p

er

litre

500000

151115

151116

151117

151118

151119

Station

Carrick Roads Inner: phytoplankton single taxa counts



Figure 9.4 Phytoplankton single taxa cell counts in the Carrick Roads Outer coastal water

Transitional and coastal waters have different single taxa thresholds.

18/07/2013

05/03/2013

23/11/2012

13/06/2012

15/02/2012

03/10/2011

08/06/2011

08/02/2011

14/10/2010

16/06/2010

2000000

1500000

1000000

500000

0

Date

Ce

lls p

er

litre

250000

155813

155814

155815

Station

Carrick Roads Outer: phytoplankton single taxa counts

Figure 9.5 Cell counts of Alexandrium species in samples collected by the Local Authority for the Shellfish Hygiene Regulations

The trigger level for Alexandrium species is presence.

0

5000

10000

15000

20000

25000

Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09

Ale

xan

dri

um

sp

ecie

s (

cells/lit

re)

Malpas Penryn Percuil Turnaware Pontoon East Bank



Figure 9.6 Cell counts of Alexandrium species in samples collected by the Environment Agency sampling programme

The trigger level for Alexandrium species is presence.

Figure 9.7 Cell counts of Dinophysis species in samples collected by the Local Authority for the Shellfish Hygiene Regulations

The trigger level for Dinophysis is 100 cells per litre, which was exceeded in 2005 and 2006.

0

100

200

300

400

500

600

700

Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08

Din

op

hysis

sp

ecie

s (

cells/lit

re)

Malpas Penryn Percuil Turnaware Pontoon



Figure 9.8 Cell counts of Dinophysis species in samples collected by the Environment Agency

The trigger level for Dinophysis is 100 cells per litre, which was exceeded in 2007, 2010, 2011 and 2012.

Figure 9.9 Cell counts of Pseudo-nitzschia species in samples collected by the Local Authority for the Shellfish Hygiene Regulations

The trigger level for Pseudo-nitzschia is 150,000 cells per litre, which was exceeded in July 2006.

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08

Pseu

do

-nit

zsch

ia s

pecie

s (

cells/lit

re)

East Bank Malpas Penryn Percuil Turnaware Pontoon



Figure 9.10 Cell counts of Pseudo-nitzschia species in samples collected by the Environment Agency

The trigger level for Pseudo-nitzschia is 150,000 cells per litre, which was exceeded in 2012 and 2013.



Table 9.3 Samples with a total taxa cell count greater than 5x105. Data from 2009 to 2014.

The cell counts given in the table are total taxa cell counts

Taxa are listed if they exceed WFD single taxa thresholds (250000 cells per litre in Carrick Roads Outer; 500000 cells per litre in Carrick Roads Inner)

Water body

Carrick Roads Outer Carrick Roads Inner

Sample Station Name



River Fal Vilt Buoy

King Harry Ferry

Mid Channel

Old Kea Shellfish Water

Tolverne

Station code

155815 155814 155813 151115 151117 151119 151118 151116

20/05/2009 1655000

Guinardia delicatula

1751000

Guinardia delicatula

1879000

Guinardia

1826000

Guinardia

1168000

Guinardia

13/08/2009 1019000

Dinophysiaceae

29/10/2009 908000

Heterocapsa niei

25/02/2010 3089000

Cylindrotheca closterium/Nitzschia longissima

20/05/2010 675000

Microflagellates

16/06/2010 546000

Skeletonema

2848000

Skeletonema

Heterocapsa triquetra

16/07/2010 2634000 1135000



Water body


Sample Station Name



River Fal Vilt Buoy

King Harry Ferry

Mid Channel


Tolverne

Station code

155815 155814 155813 151115 151117 151119 151118 151116

Skeletonema Skeletonema

04/08/2010 Karenia mikimotoi Chaetoceros

Leptocylindrus

600000

Microflagellates

15/03/2011 Skeletonema

13/04/2011 1113760

Phaeocystis

963831

Microflagellates

12/05/2011 Chaetoceros (Hyalochaetae)

Chaetoceros (Hyalochaetae)

585857


666571


08/06/2011 Leptocylindrus minimus

Microflagellates

Leptocylindrus minimus

749646

Microflagellates

20/07/2011 503334

Microflagellates

24/08/2011 Microflagellates Microflagellates Microflagellates 685391

Microflagellates

1004526

Microflagellates

985250

Microflagellates

07/09/2011 Microflagellates Microflagellates 514043

Microflagellates

05/10/2011 589008

Microflagellates

11/03/2012 540816.3

Microflagellates

29/05/2012 910285

Microflagellates

738937

Microflagellates

1101980

Microflagellates

792483

Microflagellates



Water body


Sample Station Name



River Fal Vilt Buoy

King Harry Ferry

Mid Channel


Tolverne

Station code

155815 155814 155813 151115 151117 151119 151118 151116

13/06/2012 899575.7

Leptocylindrus danicus


Microflagellates



631000


524752.5

Microflagellates

510000


2848656

Microflagellates

1368105

Microflagellates

14/08/2012 879047.6



Microflagellates

Pseudo-nitzschia

892661.2

Microflagellates

Pseudo-nitzschia

852209.4

Pseudo-nitzschia

5242744

Centric diatoms


Microflagellates

2181810

Microflagellates

Pseudo-nitzschia

826538.1

Microflagellates

Centric diatoms


3970894

Centric diatoms


Microflagellates

1613208

Centric diatoms


Microflagellates

27/09/2012 1032472

Microflagellates

24/10/2012 Microflagellates 1457152

Microflagellates

664442.9

Microflagellates

575850.6

Microflagellates

23/11/2012 Microflagellates 511998.1

Microflagellates

06/06/2013 3261961

Microflagellates

Phaeocystis

1410832

Microflagellates

Phaeocystis

5041100

Phaeocystis

10032676

Microflagellates

Phaeocystis

27/06/2013 834317.3


644853.3

Pseudo-nitzschia

626283.4

Phaeocystis

725330.6

Phaeocystis



Water body


Sample Station Name



River Fal Vilt Buoy

King Harry Ferry

Mid Channel


Tolverne

Station code

155815 155814 155813 151115 151117 151119 151118 151116

Phaeocystis

Pseudo-nitzschia

18/07/2013 2102140



Microflagellates

Phaeocystis

571386.9

Phaeocystis

2102140

Cerataulina pelagic


Microflagellates

Phaeocystis

1577137

Phaeocystis

2126325

Cerataulina pelagic


Phaeocystis

4314794


Microflagellates

Phaeocystis

1015799

Phaeocystis

09/08/2013 1211424

Phaeocystis

Skeletonema

2495173

Skeletonema

534818.8

Skeletonema

2406198

Phaeocystis

Skeletonema

3529318

Phaeocystis

Microflagellates

Skeletonema

2112939

Microflagellates

Skeletonema

02/10/2013 728612.6

Microflagellates

07/11/2013 913849.8

Microflagellates

07/04/2014 2879989

15/05/2014 3751097

Microflagellates

2191051

Microflagellates

3822208

Microflagellates

2156182

Microflagellates

18/06/2014 579549.1


1420349


1032775

Microflagellates



Water body


Sample Station Name



River Fal Vilt Buoy

King Harry Ferry

Mid Channel


Tolverne

Station code

155815 155814 155813 151115 151117 151119 151118 151116

Microflagellates

09/07/2014 8372345


Microflagellates

6480059


Microflagellates

5037021


7841416


Microflagellates

3498687


Microflagellates

Phaeocystis



Table 9.4 Alexandrium tamarense cell counts from 1995 and 1996, taken from the Upper Fal SA(E) candidate report, May 1997

Site Date sampled Cells per litre

1995

E19B9 (nr the sample point Truro River at Lamb Creek)

03/07/95 965000

07/07/95 167000

13/07/95 2400

Ruan Pontoon 13/07/95 14100

E19B2 (nr the King Harry Ferry)

03/07/95 1261000

07/07/95 3131000

1996

E19B9

24/06/96 1100

12/07/96 0

25/07/96 0

Ruan Pontoon

11/06/96 12000

17/06/96 800000

24/06/96 5000

29/07/96 9000

05/08/96 16000

12/08/96 0

19/08/96 0

09/09/96 0

17/09/96 0

30/09/96 0

E19B2 24/06/96 47500

12/07/96 7600

25/07/96 2000



Table 9.5 Details of samples containing Alexandrium species (cells per litre). Data from 2007 to 2014.

Date

Shellfish Water Old Kea Tolverne King Harry Ferry Mid Channel

Penryn at Falmouth

25/06/07 200 1400 80

10/04/08 40

24/04/08 40

22/07/08 200 200

05/08/08 200

10/09/08 200

20/07/09 600 600 200 800

12/08/09 2400 5800

13/08/09 16200 3000

05/05/10 300

16/06/10 1600 600

04/08/10 2400

24/08/11 800 19143 2429

07/09/11 429

11/04/12 71

27/06/13 333 2431 1459 71

18/07/13 972

09/08/13 6807 1945

06/09/13 972

02/10/13 1309 2356 38

15/05/14 167

10) Which of the methodology indicators are exceeded?

Y Nitrate concentrations (February nitrate/nitrogen concentrations significantly enhanced)

WFD phytoplankton classification of moderate ecological status or worse

Y Occurrence of unusual algal blooms

Oxygen deficiency (based on WFD and/or UWWT/Nitrate directive methods )

Macroalgae exceeds thresholds (UWWT and WFD)



11) Other evidence of adverse effects on uses and designations:

There is a potential loss of income to the commercial shellfishing industry from bed closures due to biotoxins in shellfish. The results of shellfish flesh samples which breached the statutory maximum level permitted for algal biotoxins are summarised in Table 11.1. These results would have led to or maintained a closure.



Table 11.1 Results of shellfish flesh samples which breached the statutory maximum level permitted for algal biotoxins

PSP Results exceeding the statutory maximum level

Sampling Point Date Sample Collected

Species Sampled

PSP HPLC Result

(PS/NG)

PSP High value ug/kg

PSP Average

MBA Result. ug/kg)

DSP Result

Positive/ Negative

Malpas 27 June 2006 Mussels 950 NEGATIVE

T Pontoon 02 July 2006 Mussels 920

T Pontoon 11 August 2009 Mussels PS 1170 NEGATIVE

T Pontoon 25 August 2009 Mussels PS 1050 NEGATIVE

R Pontoon/Tregothnan 01 September 2009 Mussels PS 1040

R Pontoon/Tregothnan 07 September 2009 Mussels PS 850

T Pontoon 07 September 2009 Mussels PS 830

R Pontoon/Tregothnan 28 June 2011 Mussels PS 2180

T Pontoon 28 June 2011 Mussels PS 1880

T Pontoon 05 July 2011 Mussels Detected 949

R Pontoon/Tregothnan 05 July 2011 Mussels Detected 926

T Pontoon 23 August 2011 Mussels Detected 848

Lipophilic toxin results exceeding the Statutory maximum level

Percuil 18 February 2002 Native

Oysters ND POSITIVE

T Pontoon 25 February 2003 Mussels ND POSITIVE

Penryn River - Meads 11 September 2006 Native

Oysters ND POSITIVE

T Pontoon 26 June 2007 Mussels PS ND POSITIVE

T Pontoon 02 March 2010 Mussels NG POSITIVE

Key

The action (closure) levels for toxins in shellfish flesh are as follows:

PSP >800µg STX eq. per kg shellfish flesh

Lipophilic toxins (DSP) by MBA - Positive

Toxin concentrations ≥ action level

PS = Positive

ND = Not Detected

NG = Negative

Test not applicable at this time



Comments in issues of Shellfish News and biotoxin monitoring reports which are published on the CEFAS website:

Issue no 30, Autumn Winter 2010

Five samples (all mussels) from the Fal breached the regulatory limit of 80 mg [saxitoxin di-HCl equivalent]/kg [shellfish tissue]. This area was subject to approximately seven weeks of temporary harvesting restrictions, between early August and late September 2009. Alexandrium species were detected at varying levels in samples from the Fal from mid July and throughout the PSP event described above.


Dinophysis spp. above 100 cells/L were recorded on 4 occasions (consistent with previous years) in samples from Fal: East Bank with the highest concentration (200 cells/L) recorded in July 2008.


As in recent years, Alexandrium spp. were detected frequently in samples from the Fal Estuary, where they occurred from April to September 2007, but generally at lower concentrations than seen in previous years.

Biotoxin Monitoring Programme for England and Wales, 1st June 2006 to 31st March 2007

As in recent years, Alexandrium spp. were found widely and regularly in samples from the Fal Estuary, where they occurred from early June to late September 2006. Unusually, these cells continued to be present in samples from Fal: Percuil collected in October and December 2006, and were also found in samples from both Percuil and Malpas in February 2007

Biotoxin Monitoring Programme for England and Wales, 1st April 2005 to 31st May 2006

As in recent years, Alexandrium spp. were found regularly in samples from the Fal: Turnaware Pontoon, where they occurred from early June to late September 2005.



12) List the current WFD status/potential for any WFD waterbodies within the SA(E)/PW(E)

Waterbody ID

Waterbody Name

Current overall status

Ecological status

Status of biological elements sensitive to nutrient enrichment

Status of Phys-chem supporting elements

Phytoplankt

on

Macroalgae

Angiosperms

Dissolved Inorganic Nitrogen

Dissolved Oxygen

GB

520804814400

Carrick Roads Inner

Moderate Moderate Good Good Good Moderate High

GB650806250000

Carrick Roads Outer

Moderate Moderate Good

Not assessed

Not assesse

d Moderate High

13) Is/are the WFD waterbody catchment/s in the SA(E)/PW(E) failing or at risk of failing the dissolved inorganic nitrogen standard for WFD?

Yes, Carrick Roads Inner transitional waterbody and the adjacent Carrick Roads Outer coastal water are failing the DIN standard for WFD.

14) Executive summary of the chemical, biological and other evidence illustrating eutrophication in the SA(E)/PW(E)

In the mid 1990s, when the Fal was a candidate PW(E), there were exceptional algal blooms of Alexandrium tamarense which were sustained through the summer months and resulted in the manifestation of PSP in local shellfish beds. The most exceptional bloom occurred in 1995 and coincided with a long period of warm calm weather.

Chlorophyll-a and phytoplankton data indicate that the eutrophic status of the estuary is now improving with fewer significant algal blooms occurring over the last 5 to 10 years.

15) Summary of eutrophication control measures (already in progress and/or already planned) if any, for the existing area.

Both the Upper and Lower Fal are also designated as Sensitive Areas (Eutrophic) under the Urban Waste Water Treatment Directive. Sewage effluents from STWs with population equivalents greater than 10,000 which discharge directly into these SA(E)s need to have nitrogen reduction measures. At Truro (Newham) STW, tertiary treatment for nitrogen reduction was installed by the 31st March 2004, but the STW was non-compliant with the annual average N reduction requirements in 2005 and 2006. A new process was installed in 2006. The STW is now compliant with the N reduction requirements.

Tertiary treatment for nitrogen reduction was installed at Falmouth STW in March 2010.

The catchments around the Fal are designated as an NVZ. This means that specific farming practices are controlled in the designated area to reduce nitrogen losses from agriculture to water.



The NVZ designation:

Requires farmers within the NVZ to reduce nitrate pollution.

The farmers must follow a set of mandatory rules, known as the Action Programme Measures.

The Action Programme Measures are based on Good Agricultural practice and require the careful management and recording of fertiliser and manure use.

A requirement for farms to be able to store slurry for 5 months has come into force in January 2012.

The catchments draining to the upper and lower Fal Estuary have also been priority catchments under the Catchment Sensitive Farming (CSF) Project until 2014.This Project which was formerly known as the England Catchment Sensitive Farming Delivery Initiative is an advice project in England designed to reduce the pollution of water caused by farming operations. Under the Project, advice on measures and practical solutions is provided to enable farmers and land managers to take action to reduce diffuse water pollution from agriculture. The Project began in 2006 and Phase 3 (2011-14) has recently been completed. However, since 2014 the catchments draining to the Upper and Lower Fal Estuary are now become medium priority catchments in the CSF Project.

The Environment Agency carried out an investigation into water quality in the Fal between 2009 and 2011 in response to poor shellfish flesh results. The investigations identified that pollution impacts and bacterial loadings to catchment streams were being caused by poor slurry management on farms, land use and run off and discharges from the sewage network at pumping stations and combined sewer overflows discharging to culverts beneath Truro.

Between January and March 2011 an Environment Officer visited all farm holdings, premises and company assets implicated in either causing pollution or at risk of causing pollution in the problem catchments.

In all cases, the sites visited were found to have pollution management issues of varying significance. In many cases the owners or operators of the sites visited were unaware that they were adding to the pollution loading of a stream.

The investigation also found significant faecal bacterial loadings emanating from the river culvert flowing beneath Truro. The city has a complex foul sewer system which includes some 30 combined sewer overflows (CSO) of different sizes. Many of the CSO’s discharge into the river culvert out of sight. The investigation suggested that many of these may well be discharging prematurely and not necessarily as a result of heavy rainfall.

Some of the outcomes of visits to farms and South West Water assets to date have been:

Satisfactory resolution of pump station raw sewage discharge Dirty water lagoons from farmyard run off increased in capacity to stop spillage Removal of blockages from 3 stage effluent tanks stopping discharge to stream Small capacity slurry lagoon discharge stopped to be replaced with indoor cattle facilities

thereby reducing volume of slurry produced. Meetings with key South West Water personnel to advise on the impacts of CSO

discharging under dry weather conditions as a driver for investment. Camera surveys promised to better understand how CSOs function and why they are discharging in dry conditions.

Site meetings with bulb growers to require better pesticide and sediment run off control. Poor quality silage clamps leaking effluent improved to SSAFO standards Alarm systems installed on dirty water and slurry lagoons to ensure overtopping is prevented Advanced notice to farmers in NVZ to ensure slurry storage facilities are compliant by

January 2012.

During these investigations and visits to farms, referrals were also made for CSF support for grants for farm infrastructure improvements, and grants were awarded for works to reduce the run off of slurry.

Following these investigations into the role of CSOs, extensive improvement works to the sewerage in Truro City centre were undertaken by South West Water during 2013 to 2015. These improvements have resulted in a significant reduction in the spillage of sewage into the Truro River during both wet and dry periods.

Report for existing Sensitive Area / Polluted Water Truro, Tresillian and Fal

Form G (effects of nutrient reduction) Page 41

Ref. Code: ET5


Form G: Effects of Nutrient Reduction

Existing Sensitive Area (Eutrophic) / Polluted Waters (Eutrophic)

1) SA(E)/PW(E) name: Truro, Tresillian and the Fal PW(E) and Lower Fal Estuary PW(E)

(take name from Form A)

2) Type(s) of SA(E)/PW(E): (take info from Form A)

Running freshwater

Still freshwater

Y Estuarine water

Y Coastal water

3) Summary of qualifying sewage treatment work discharges (copy info from Form A)

Name of discharge Direct / Indirect

NGR Population equivalent

Current Treatment Planned Type of

TER (N, P, NP)

Level (PRIM, SEC,

TER)

if TER enter Type (N, P, NP)

Newham STW Direct SW83374327 28,000 TER N

Falmouth STW Direct 39,000 TER N

Total PE 67,000

4) Summarise the comparative impact of the discharges (e.g.compare chemical and biological data upstream and downstream of the sewage discharge) in relation to pre-designation.

The past and present contribution of the 2 qualifying discharges, other discharges, and diffuse freshwater sources to the DAIN load to the Upper and Lower Fal PW(E)s are discussed in 5) below.

5) Where available provide estimates of nutrient loading for contributions for both qualifying sewage treatment work discharges and agricultural sources. Summarise how this has changed over time.

Nutrient loads to the Fal and Helford Special Area of Conservation were assessed in detail during the Review of Consents work (EA Technical Report dated November 2005). The assessment primarily used data from the period 2000 to 2005. It was estimated from this work that diffuse freshwater inputs contributed 3324.9 kg/day of the annual DAIN load from all discharges and freshwater sources



to the designated Upper and Lower Fal PW(E) sites. This was about 84% of the total DAIN load. The combined total of all discharges (both direct and indirect within the freshwater catchments) at the time was estimated to be 625.6 kg/day, which was about 16% of the total DAIN load. The 2 direct sewage discharges from Truro STW and Falmouth STW were the most significant discharges, being 158.9 kg/day and 175.7 kg/day respectively, and contributed about 8.5% of the total DAIN load.

The changes in DAIN concentrations in the in the 6 main freshwater inputs from the 1970s to the 2015 are shown in Figures 5.1 to 5.6. These rivers comprise about 75% of the freshwater DAIN load, and 78% of the freshwater flows to the Lower and Upper Fal designated sites.

Figure 5.1.



Figure 5.2.

Figure 5.3.



Figure 5.4.

Figure 5.5.



Figure 5.6.

These plots show that in several rivers there was a general increase in DAIN concentrations from the 1970s to the 1990s. During the 1990s and into the early 2000s, DAIN concentrations remained relatively unchanged. However, since 2000 to 2005, it is apparent that the DAIN concentrations have decreased in some rivers, particularly the Kennal, Tresillian, and Fal. The relative changes in DAIN concentrations between the periods 1995 to 1999, 2000 to 2005, and 2011 to 2015 are shown in Table 5.1 below. The relative reduction in concentrations used in the Review of Consents (RoC) work and those for the period 2011 to 2015 are also shown.

Table 5.1

River Mean DAIN Concentration for 1995 to 1999 mg/l

DAIN Concentration used in RoC work (2000 to 2005) mg/l

Mean DAIN Concentration for 2011 to 2015 mg/l

Relative change (2000 – 2005) to (2011 – 2015)

Fal 4.109 4.094 3.712 0.907

Carnon 3.160 3.104 3.050 0.983

Tresillian 6.908 6.698 5.722 0.854

Kennal 5.213 5.068 4.101 0.809

Allen 5.878 5.846 5.625 0.962

Kenwyn 5.610 5.550 5.803 1.046

Overall these relative changes between the periods 2000 to 2005 and 2011 to 2015 represent a reduction in DAIN load of about 9%, assuming that the river flows are constant between the 2 periods. If this percentage reduction in DAIN loads in the 6 main freshwater inputs is consistent over the whole catchment, then the diffuse freshwater inputs may now be 0.91 of 3324.9 kg/day which equates to 3,025.7 kg/day.



Estimates of the nitrate load as N from the freshwater catchments draining to the Upper and Lower Fal estuary have also been derived using the NEAP-N model. The NEAP-N model is used to represent the losses associated with agricultural land in the NVZ designations process. The NEAP-N model (Anthony et al., 1996; Lord and Anthony, 2000; Silgram et al., 2001) was developed under Defra Water Quality funding as a policy tool to allow estimation of nitrate loss from agricultural land, applicable to any catchment in England and Wales. It is acknowledged as the foremost national nitrate leaching model in the UK and is widely used throughout the UK and in pan-European studies. It has been an important part of the last three NVZ reviews.

Recent NEAP-N predictions for the Fal freshwater catchments using agricultural data from the 2014 census (ADAS 2015) indicated that the total agricultural losses of N equated to 3,336 kg/day, and that the sum of agricultural losses and that associated with atmospheric N deposition equated to 3,654 kg/day. This figure is greater than the estimated load from the freshwater inputs, but this is to be expected, as the NEAP-N output does not directly predict nitrate levels in surface waters, for a variety of reasons. However, the values are of a similar order.

There have also been reductions in the DAIN load from the Truro and Falmouth STWs, as the concentrations of DAIN have decreased since the RoC work. This is shown in the Figures 5.7 and 5.8 below.

Figure 5.7. DAIN and Total Nitrogen concentration measured in the final effluent at Newham (Truro) STW from 1990 to 2015. Nutrient removal was installed in 2004, but due to compliance issues, a new process was installed in 2006.



Figure 5.8. DAIN and Total Nitrogen concentration measured in the final effluent at Falmouth STW from 1990 to 2015. Nutrient removal was installed in March 2010.

The reductions and relative changes between the periods 1995 to 1999, 2000 to 2005, and 2011 to 2015 are shown in Table 5.2 below.

Table 5.2

Discharge Mean DAIN Concentration for 1995 to 1999 mg/l

DAIN Concentration used in RoC work (2000 to 2005) mg/l

Mean DAIN Concentration for 2011 to 2015 mg/l

Relative change (2000 – 2005) to (2011 – 2015)

Truro STW 22.376 18.103 8.706 0.481

Falmouth STW 34.430 14.792 9.884 0.668

These indicate that the load from Truro STW has roughly halved, while that from Falmouth STW has been reduced by a third.

These DAIN concentration data for the 2 discharges coupled with those for the 6 main freshwater inputs indicate that there has been a measurable reduction in DAIN load to the Lower and Upper Fal PW(E) sites over the past 10 years. This load reduction is considered to be reflected in the reduction in chlorophyll levels in both sites and in the less frequent occurrence of toxic algal blooms.

6) Give a summary of the eutrophication control measures (in progress and/or planned), for the SA(E)/PW(E).

See Form D, section 15.



7) If the SA(E)/PW(E) has previously been designated, is there any evidence to suggest that its status has changed (e.g. it is no longer eutrophic) and is this change a result of the control measures put in place, or due to a change in our methods/criteria, since the original designation?

The status of the Fal Estuary as a PW[E] relates to concerns about the occurrence of phytoplankton blooms, and in particular the significant blooms of the toxic algae, Alexandrium tamarense, that occurred in 1995 and 1996.

There is evidence that there has been some reduction in overall phytoplankton biomass since the site was designated. The concentration of chlorophyll is measured as an indicator of phytoplankton abundance. A salinity related chlorophyll standard was exceeded by approximately 14% of chlorophyll samples collected during the growing seasons between 1995 and the end of 2006 . In comparison only 2% of chlorophyll samples collected in the growing seasons from 2007 to 2015 exceed the standard. Phytoplankton blooms are most frequent in the upper estuary, in the Truro River, and are less frequent in the middle and lower estuary.

Both the Carrick Roads Inner Transitional water body and Carrick Roads Outer water body are currently classified as being at good status for phytoplankton.

The improvement in chlorophyll-a levels coincides with reductions in DAIN from the main river inputs and the 2 major sewage discharges from Newham STW and Falmouth STW.

The main concern when the estuary was designated was the occurrence of Alexandrium blooms resulting in PSP in shellfish. Alexandrium blooms in the estuary remain a concern and there is still a potential loss of income to the commercial shellfishing industry from temporary bed closures. Alexandrium species are still found in water samples collected from the Fal each year, but at much lower cell counts than the blooms of the mid 1990s. Shellfish flesh samples containing levels of PSP above the Action (closure) level were collected from the Fal in 2006, 2009 and 2011. The Fal was subject to approximately seven weeks of temporary harvesting restrictions, between early August and late September 2009 due to PSP in shellfish.

8) If control measures were removed, would the area be at risk of becoming eutrophic once more?

The exceptional algal blooms that occurred in 1995 demonstrate that algal blooms can become prolific in the Fal over an extended period when river flows are low and weather conditions are favourable. Algal blooms, some of which are toxic, have also occurred since then. It is considered that f nutrient control measures are removed there would be a risk that phytoplankton problems could become worse.

References

Anthony, S. Quinn, P., Lord, E.I.,1996. Catchment scale modelling of nitrate leaching. Aspects of Applied Biology 46, 23-32.

Feifel,K. et al., 2015. Alexandrium and Scrippsiella cyst viability and cytoplasmic fullness in a 60-cm sediment core from Sequim Bay, WA. Harmful Algae, 57, 56-65.

Lee, D et al. 2015 Neap-N Nitrate Leaching for 1970 and 2014. ADAS Report for Defra 26 pp.

Lord, E.I., Anthony, S., 2000. MAGPIE: a modelling framework for evaluating nitrate losses at national and catchment scales. Soil Use and Management 16, 167-174

Silgram,M., Waring, R., Anthony, S. & Webb, J. 2001. Intercomparison of national & IPCC methods for estimating N loss from agricultural land. Nutrient cycling agroecosystems 60, 189-195.

Report for existing Sensitive Area / Polluted Water Truro, Tresillian and Fal


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