Bathing Water Symposium

11th November 2015

Bathing Water Modelling to Improve Investment Decision Making

Andy Mortali (Scottish Water)

Elaine Hamilton (SEPA)

Scottish Designated Bathing Waters 2015 Classifications

SR10 Bathing Water Study Locations 2015 Classifications for SR10 Study areas

Collaborative Study Approach

SR10 Bathing Water Studies

Study area:

SEPA OPS Team:

Lead officer:

Report Type:

Report title:

Report section Page No Comment SW response SEPA feedback Actions following meeting on 05/06/2013 SEPA feedback v4 07/10/2013 SW response

Table 2.2 10

As with SEPA's comments on Table 6.2 of the NEEDS report is it necessary to

include all these assets in the table when many of them have either no bacterial

concentration or repeated bacterial concentrations associated with them?

These assets have been included in Table 6.2 for completeness

and will be included in Table 4.2 of the Needs report. No repeat

bacterial counting has been undertaken. See Needs comments

for further details.

From discussion on 05/06/2013 SEPA understands

that the network in Kirkcaldy is very complex ie

there are assets with multiple weir settings. To

accurately represent these in the DAS model all

weirs have been included as links in the model.

These have all been listed in Table 6.2 to ensure

this detail is not lost. SEPA notes that Table 4.2 of

the Needs report will be updated to reflect all the

assets listed in Table 2.2 (Options report) and Table

6.2 (Needs report).

This needs to be checked against the revised Needs

report when this is received.

Table 4.2 and table 6.2 amended in

the Kirkcaldy Needs report v4

Table 2.2 10

As with SEPA's comments on Table 6.2 of the NEEDS report there are a number of

assets listed in Table 2.2 of the OPTIONS report that do not appear in Table 4.2 of the

NEEDS Report. Please ensure there is consistency between the two reports and

between the tables within each report.

Table 2.2 will be updated for completeness as per table 4.2 in the

Needs report. To be confirmed when the Final report is issued

Can you expand out the assets under the Kinghorn

section to include all the assets. We understand they

may have been removed as they have no bacteriological

contribution but feel these should be included for

completeness. Previous comment that this table, table

2.2, should be consistent with per table 4.2 in the Needs

report still stands.

Kinghorn assets expanded in table

2.2 to cover all assets. Please note

that they all have no bacteriological

contribution to the overall bathing

water assessment.

Table 2.2 10

SEPA notes that the SW Asset Total includes the repeated bacterial concentrations

noted against the same assets. This could mean that the bacterial concentration from

some assets is double or even triple counted. Is this correct?

This is correct representation of the model and does not include

double counting. For example the output from the sewer model at

Lauder Road has three separate screens that lead to the outfall

and these are modelled as separate discharge hydrographs

within the sewer model and for direct comparison within the

marine model have been modelled as three separate

hydrographs, albeit discharging at the same location.

From discussion on 05/06/2013 SEPA understands

that the network in Kirkcaldy is complex and there

are assets with multiple weir settings. To

accurately represent these in the DAS model all

weirs have been included as links in the model.

SEPA notes the assurance that double/triple

counting has not occurred. Query closed. No response required

4. Modelled Solutions 16 v4

SEPA feels that footnotes 2 and 3 are fundamental to the

description of the modelled solution. and would like to see

these removed as footnotes and included in the main text

Footnotes two and three transferred

to the main text in section 4.1 and

removed from the footnotes.

4.1 14

SEPA notes that the removal of the blockage at Lauder Road catchment is considered

as an option. If the blockage is removed then the asset would operate as it should. Was

a scenario run to consider the 'as should' operation of the assets? If yes, what was the

outcome of this scenario?

As part of the optioneering stage the blockage at Lauder Road

was assessed. Removing the blockage results in a reduction in

spills at Lauder Road by approximately 30%. However, the asset

is still significantly impacting on the Bathing water quality at the

95%ile

From discussion on 05/06/2013 SEPA understands

that the DAS was altered to the 'as should' operate,

including the removal of Lauder Road siltation issue

and other issues relating to the WwTWs. SEPA

understands that this has been accepted by the

external auditor. SEPA appreciates that even under

the 'as should' operate scenario Lauder Road is still

impacting significantly on bathing water quality , at

the higher percentiles. No response required

4.1 14

SEPA notes the explanation in Footnote 2 and appreciates that a flow survey during the

bathing water season is required to confirm the base flow assumptions used in this

assessment. However, if the base flow is reduced (as detailed in Bullet Point 6) has the

bacterial concentration applied in the model been increased? It is SEPA's

understanding that the bacterial concentration for secondary treated effluent, as used in

the Needs assessment, was adjusted to take account of the dilution afforded by the

level of infiltration in the network. If this dilution is reduced by 50% but the bacterial

sources remain the same then should the bacterial concentration applied to the treated

effluent be revised upwards again? SEPA would like to discuss this further.

As part of the Needs assessment the full infiltration was included

within the modelling and this resulted in the reduction in

secondary WwTW values, however in the Option assessment

infiltration was reduced by 50% at the upper percentiles to

understand the impact that excessive infiltration would have on

the marine options. No increase in the bacterial load was

included in this option run where infiltration was reduced by 50%.

It might be anticipated that bacterial concentrations would

increase as infiltration decreases, but production rates based on

the population in the catchment were also considered and did not

indicate this was necessary. Furthermore, this makes up a very

small percentage of the total (only 6 FC/EC cfu at the 90th

percentile). For an investigation of options to meet the thresholds

at the 90th percentile the infiltration value has been returned to

100%.

From discussion at the meeting on 05/06/2013

SEPA understands that the reduced bacterial

concentrations were applied to the continuous final

effluent discharge in the Needs assessment, not

the intermittent CSO discharges (including the

WwTW CSOs).This enabled a better model

calibration to be achieved at the low percentiles in

the distribution. The reduction in bacterial

concentrations does not affect the higher

percentiles as these are influenced more by the

intermittent discharges, for which the bacterial

concentrations have not been adjusted. SEPA also

understands that in the Options assessment the

reduced default bacterial concentration for the final

effluent was not increased when inflitration was

reduced by 50% as this was shown to have little

impact, increasing the the bacterial level from 6

cfu/100ml to 12 cfu/100ml for the final effluent.

SEPA also notes that in the consideration of the

90%ile options the reduced bacterial concentrations

for the final effluent have not been applied. Query

closed. No response required

Figure 4.1 16

Please note that in the legend the bathing water area is referred to as Kirkcaldy Harbour

not Kirkcaldy Seafield as it should. Figure to be amended for the final report To be confirmed when the Final report is issued SEPA note this has been updated. Query Closed No response required

Figure 4.1 18 v4

SEPA thinks that the wrong map has been included and

that the map that needs to be included here is the

location map 4.1 as per the Kinghorn (Harbour) Bathing

Water Options Assessment v4, this map details the

locations of the new and revised long sea outfall locations.

Figure 4.1 included in this report does not show the

locations of the new and revised long sea outfall. In

addition the title for Figure 4.1 also appears incorrect,

there is no reference of location F instead it refers to

location G being an the location of an extension to the

current long sea outfall.

Figure 4.1 updated with proposed

outfall locations.

Table 4.2 18

The term 'compliance' is used in the column headings but the rBWD uses a

classification status assessment rather than compliance. Please amend this table

accordingly. This will be amended for the final report To be confirmed when the Final report is issued SEPA note this has been updated. Query Closed No response required

4.2 18

The report notes that Table 4.2 and Table 4.3 are the model results for the worst point in

the bathing water but the title of Table 4.2 indicates it is the node nearest the SEPA

monitoring point. Which is correct?

Table 4.2 is the SEPA monitoring point and 4.3 is the worst point

within the bathing water. This will be corrected in the final report To be confirmed when the Final report is issued SEPA note this has been updated. Query Closed No response required

Figure 4.2 18

Solution 3 on the graph does not seem to reduce the bacterial load by the 25%

indicated in Appendix B. SEPA would find it useful to have Figure 4.2 explained in more

detail.

Appendix B looks at the WwTW OCC discharge channel only

and the 28% reduction is noted for this alone (as noted in the first

reduction in the figure 4.2). The two other columns represent the

reduction by moving flows down the LSO at Charlotte Street (F)

and the extension of the WwTW LSO to G. Asset diversion to

each LSO is noted above Figure 4.2. Arrows can be added to

Figure 4.2 to highlight increase and decrease from the noted

bullet points above Figure 4.2.

SEPA notes this explanation. The arrows are not

required. Query closed. No response required

Section 4.3 28 v4

SEPA have not received the report as referenced: Atkins

2013 5110061.64.CO.020 Kirkcaldy Impact Assessment

report V4 Sent

Section 4.4 32 v4

SEPA feels that footnotes 5 and 6 are fundamental to the

description of the solution. and would like to see these

removed as footnotes and included in the main text.

Footnote 5 and 6 removed and

placed into the main body of the

text in section 4.4.

Table 4.5 33 v4

Table 4.4 details information for locations F and G (as per

the title) but the memo issued in June 2013 presents this

for locations A and G. Should this not be consistent or

should tables for A and G and F and G be presented, if

the solution likely to be between And F ?

This was amended following the

Options meeting held on the

05/06/2013, where SEPA stated

that location F gave them more

confidence in the options

assessment. Additional work is

required to locate the most suitable

point between location A and F, but

for this report it is location F that

has been selected as agreed with

SEPA.

Figure 4.6 28

The two plots appear to be very similar - is this correct? If the impact from diffuse

sources increases at higher percentiles SEPA would expect the plot for Combined Total

Assets to illustrate a higher bacterial concentration further down the coast compared to

the plot for SW assets only.

These plots were incorrect and have been amended in the report.

The figures now show the increase in diffuse pollution down the

coast. To be confirmed when the Final report is issued

Can you confirm that this has been updated. The plots

still seem to be incredibly similar. SEPA would expect

the plot for Combined Total Assets to illustrate a higher

bacterial concentration further down the coast compared

to the plot for SW assets only.

This figure has been updated, the

figures appear very similar due to

the upper boundary of the scale

used. Discharges from the fluvial

system match the discharges

locations for a number of SW

assets and at this upper percentile

(97.5) it is not possible to

distinguish the SW and diffuse

sources along the shoreline.

References v4

SEPA have not received the following two reports as

referenced: Atkins 2013 5110061.64.CO.020 Kirkcaldy

Impact Assessment report V4 AND Atkins 2013

5110061.64.CO.022 Kinghorn Impact Assessment report

v3

Version 4 reports are now available

for review - now sent

Appendix A 34

The totals for SW assets and diffuse sources appear to be incorrect. For example, the

totals for EC at 97.5th should 961 (SW assets) and 2061 (Diffuse sources). These are

different to those detailed in the table. Can you please check that the totals in the table

are correct?

The sum will not match the totals due to the statistical method

used to calculate the total impact. This is noted and explained in

the report.

SEPA appreciate that the the Totals for Diffuse and

SW asset contributions will not match the sum of

the data in the table due to statistical method used.

Query closed. No response required

Appendix B 36

Paragraph 3 explains the reduction in bacterial load expected if the base flow in the

network is reduced (i.e. infiltration is reduced). However, Paragraph 4 indicates that the

reduction in base flow for the 90%ile and 94%ile is probably not required as the total

SW asset contribution at these percentiles is significantly lower than 500cfu/ml. The

remaining part of the Appendix goes on to explain how infiltration will first be confirmed

and then reduced. However, if base flows are reduced by 50% should the bacterial

concentration applied, as part of the model, to the continuous flow from the WwTW

works be increased as there is less dilution in the influent. The original default bacterial

concentration was reduced due to issues with the model calibration. This was linked to

the significant level of infiltration into the system. SEPA would like to discuss this issue

further.

See row 14. We would be happy to discuss this further and it

should be noted that for an investigation of options to meet the

thresholds at the 90th percentile the infiltration value has been

returned to 100%.

See SEPA feedback in Row 14. SEPA is satisfied

this query is now closed. No response required

5110061_064_RW_CO_021 - Kirkcaldy Bathing Water Options Appraisal v4.pdf

Kirkcaldy (Seafield) BW

Fife

Steve Archibald

Revised BWD Options Report - Kirkcaldy (Seafield) Bathing Water

Target Objective, Extent of Bathing Water and Spatially Varying Performance

Source of Bacteria – Scottish Water / Other Sources

Investment Decision Tree

Key Principles

• Where SW intervention alone can

deliver an improvement in BW

classification then investment is

progressed.

• Where SW impacts alone do not

cause a poor classification then

investment should not be progressed

• Where a combination of sources are

impacting bathing water quality and

interventions are required to deliver

an improvement in class (or to

improve specific areas of the BW)

then SW investment should be

delayed until there is more certainty

on when other improvements will be

delivered.

Bathing Water Investment Decision Tree

Yes

No

No No

Yes Yes

Yes

No

Continued review and monitoring

Scottish Water SEPA

Update of Bathing Water

Profile to reflect model

outputs

SW Bathing Water Modelling

Are there diffuse pollution /

non SW sources impacting BW

quality

SEPA to undertake monitoring

to determine changes

resulting from improvement

at non SW sources

Are event and flow monitors

and reporting facilities in

place to monitor operation of

SW assets?

SW to provide operational

report to SEPA and update to

river and marine modelling

tools from reporting system.

Investment to deliver

monitoring and reporting

systems for SW assets

SW to maintain, improve and

update river and marine

modelling tools with new

data to refresh study outputs

Is there certainty that SW

intervention can deliver an

improvement in classification

at the Monitoring location?

Does SW asset impact Water

Quality anywhere in the BW? No further action

Agree revised CAR

licenses with SEPA

and implement

changes

SEPA to undertake catchment

management activities to try

and reduce diffuse pollution

level

SEPA to maintain and update

electronic signs and other

sources of public information.

SW Investment Requirements SR10 Bathing Water Study Locations

Conclusions

• The approach we have utilised has allowed SW to clarify an uncertain

investment requirement

• The development of the investment decision tree has generated a

consistent approach to decision making using a robust methodology,

signed off by all key stakeholders

• The approach has allowed us to understand more of the impacts on

Bathing Waters expected to be Poor and, by considering performance

across the entire BW, has improved our understanding of risk that

further bathing waters fail to achieve sufficient status.

• The approach has allowed Scottish Water to be confident that

investment will result in positive customer outcomes. It also allows

SEPA to understand where the focus on other sources is required.

THANK YOU

Andy Mortali (andy.mortali@scottishwater.co.uk)

Elaine Hamilton (elaine.hamilton@sepa.org.uk)