Offshore sediment monitoring survey of Region I, 2008 · ConocoPhillips, acting on behalf of the...

Offshore sediment monitoring survey of

Region I, 2008 English summary report

Akvaplan-niva AS Rapport: 4315.04

Front-page illustration: Field sampling onboard MS “Libas” during the Region I, 2008 monitoring survey.

Akvaplan-niva AS Rådgivning og forskning innen miljø og akvakultur Org.nr: NO 937 375 158 MVA Polarmiljøsenteret 9296 Tromsø Tlf: 77 75 03 00, Fax: 77 75 03 01 www.akvaplan.niva.no

Report title Offshore sediment monitoring survey of Region I, 2008, English summary report

Author(s) Sabine Cochrane Ingar H. Wasbotten Lars-Henrik Larsen

Akvaplan-niva report no 4315.04

Date 20.04.2009

No. of pages 55

Distribution restricted

Client ConocoPhillips

Client’s reference Contract no. NSBU-61990

Summary In 2008, Akvaplan-niva carried out a regional offshore sediment monitoring survey in Region I of the North Sea. This report presents chemical and biological analyses carried out on material from a total of 161 stations. Samples were collected at 13 individual fields (Ekofisk C & 2/4B&K, Eldfisk 2/7 B, Tor, Embla, Albuskjell, Ula, Valhall, Tambar, Hod, Valhall Nordflanken, Valhall Sørflanken, Gyda, Oselvar) and at 12 Regional stations.

Elevated barium levels in the sediment were found at all fields. THC contamination or disturbed fauna (where analysed) were not found at Valhall Nordflanken, Tambar and Oselvar. The remaining fields had various extents of impacts, but in general there has been a reduction in the area of impact since the previous survey in 2005.

This is the English summary report. The main report and a Norwegian summary report are issued separately. Project manager Quality controller

Lars-Henrik Larsen Hans Petter Mannvik / Gunhild Garte Nervold

© 2009 Akvaplan-niva AS. This report may only be copied as a whole. Copying of part of this report (sections of text, illustrations, tables, conclusions, etc.) and/or reproduction in other ways, is only permitted with written consent from Akvaplan-niva AS.

Offshore sediment monitoring survey of Region I, 2008 Akvaplan-niva AS Report 4315.04 1

Table of Contents

PREFACE ................................................................................................................................... 2

1 SUMMARY REGION I SURVEY, 2008 ............................................................................... 3

1.1 Executive summary .......................................................................................................... 3 1.2 Summary of results and regional status ............................................................................ 4

2 INTRODUCTION AND METHODS ................................................................................... 10

2.1 Background and scope .................................................................................................... 10 2.2 Sampling and methodology ............................................................................................ 12 2.3 Glossary and abbreviations ............................................................................................. 13

3 RESULTS .............................................................................................................................. 15

3.1 Regional stations ............................................................................................................ 15 3.2 Ekofisk C & 2/4 B&K .................................................................................................... 17 3.3 Eldfisk 2/7 B ................................................................................................................... 20 3.4 Embla .............................................................................................................................. 22 3.5 Tor .................................................................................................................................. 24 3.6 Albuskjell 1/6 A ............................................................................................................. 25 3.7 Valhall ............................................................................................................................ 29 3.8 Valhall Nordflanken ....................................................................................................... 32 3.9 Valhall Sørflanken .......................................................................................................... 35 3.10 Hod ............................................................................................................................... 37 3.11 Ula ................................................................................................................................ 39 3.12 Tambar .......................................................................................................................... 42 3.13 Oselvar .......................................................................................................................... 44 3.14 Gyda ............................................................................................................................. 46

4 RECOMMENDATIONS FOR NEXT SURVEY ................................................................. 50

5 REFERENCES ...................................................................................................................... 51

Akvaplan-niva AS, 9296 Tromsø 2 www.akvaplan.niva.no

Preface

This report gives a summary of the offshore sediment monitoring survey of Region I (Ekofisk) carried out in 2008. The results from the individual fields are presented in individual chapters, including comparisons to previous surveys, discharge and activity history at the individual field. A holistic evaluation of the environmental condition across the entire region (fields and Regional stations) is presented.

The 2008 sediment monitoring of Region I has been carried out on contract to ConocoPhillips, acting on behalf of the operators in the region. The following 13 fields are included in the survey:

Field: Operator:

Ekofisk C & 2/4B&K, Eldfisk 2/7 B, Tor, Embla, Albuskjell ConocoPhillips

Ula, Valhall, Tambar, Hod, Valhall Nordflanken, Valhall Sørflanken BP

Gyda Talisman Energy Norge

Oselvar DONG

In addition, the assignment included a survey of the cuttings pile at Albuskjell (operated by ConocoPhillips) and a survey at Loshavn (11 stations), operated by StatoilHydro. The results of these surveys are reported individually.

The project is carried out under the following accreditations:

Akvaplan-niva AS is accredited by Norsk Akkreditering for sampling of marine sediments, macrofaunal analyses and judgement and evaluations of results. Accreditation number is TEST 079. The accreditation is according to NS-EN ISO/IEC 17025.

Unilab Analyse AS is accredited by Norsk Akkreditering for analyses of THC, NPD, 16EPA-PAH and TOM, accreditation number is TEST 061. The accreditation is according to NS-EN ISO/IEC 17025. Analyses of grain size distribution.

NIVA is accredited by Norsk Akkreditering for analyses of heavy metals, accreditation number TEST 009. The accreditation is according to NS-EN ISO/IEC 17025.

NILU for analyses of perfluorinated compounds (PFCs).

Florida State University for analyses of radionuclides.

Tromsø, 20 April 2009

Lars-Henrik Larsen

Head of Marine Environmental Department


1 Summary Region I survey, 2008

1.1 Executive summary On behalf of the operators in Region I of the Norwegian North Sea, ConocoPhillips commissioned Akvaplan-niva AS to carry out the regional environmental offshore sediment monitoring in 2008 (contract agreement NSBU-61990). This is the summary report of the survey, which is fully presented in the main report by Cochrane et al. (2009).

The fields included in the survey are Ekofisk C & 2/4B&K, Eldfisk 2/7 B, Embla, Tor, Albuskjell, Valhall, Valhall Nordflanken, Valhall Sørflanken, Hod, Ula, Tambar, Oselvar and Gyda. In addition, samples from twelve Regional stations were collected. The fieldwork, comprising a total of 161 stations (149 field stations and 12 Regional stations) was carried out from 26.05 – 04.06 2008. Figure 1-1 shows the general location of the fields and Regional stations sampled during the present survey.

Figure 1-1:

Monitoring regions in the North Sea (Above). Region I (Ekofisk) is the southernmost region. Right: Location of sampling stations included in the 2008 Region I monitoring survey


The sediments throughout the Region I area consist of fine sand, with a relatively low pelite (silt+clay) content, and low levels of organic matter. The main current direction in Region I is east to south-easterly (Figure 2-1).

Most of the field stations up to 1 000 m from the field centres had elevated levels of barium. Elevated levels of THC were found out to 4 400 m at Ekofisk C field, out to 1 000 m at Ekofisk 2/4 B&K and Valhall fields and out to 500 m at Eldfisk 2/7B, Hod, Ula and Gyda. The sediments at Valhall Nordflanken, Tambar and Oselvar are not contaminated with THC.

Slightly disturbed fauna was found within 250 m of the field centres at the Eldfisk 2/7B, Ula and Gyda fields, out to 500 m at Valhall Sørflanken and Hod, out to 850 m at Ekofisk C and out to 1 000 m at Valhall. Distinctly disturbed fauna was found at a single station at the Gyda field, 250 m from the field centre. The greatest calculated total area of slightly disturbed fauna was seen at the Ekofisk C field. Faunal disturbance was not detected at Valhall Nordflanken and Oselvar.

Since the previous survey in 2005, the calculated area of THC disturbance has decreased at most fields (Ekofisk C & 2/4B&K, Eldfisk 2/7B, Tor, Valhall, Valhall Nordflanken, Ula, Gyda). This represents a further reduction in impacts since the survey in 2002.

1.2 Summary of results and regional status The topography and sediment composition throughout Region I area is relatively homogenous. The water depths are between 60 – 70 m and the sediments generally comprise fine sand, with low levels of pelite and organic matter. The main current direction is east to south-easterly. In general, the sediment composition has not changed notably since the previous surveys in 2005 and 2002. Table 1-1 shows the maximum and minimum values for the main parameters analysed, at both field stations and Regional stations during the present survey, compared with the previous survey in 2005.

Among the field stations, the minimum values for most contaminants generally reflected background values in both 2008 and 2005, with the exception of barium, which showed elevated levels at most field stations, relative to the Regional stations (in 2008, field stations contained 35 – 5383 mg/kg, relative to 11 – 83.4 mg/kg at the Reg. stations).


Table 1-1: Minimum and maximum values for the physical, chemical and biological parameters analysed at Region I, 2008 and the previous survey in 2005. The fields investigated in 2008 are Ekofisk C & 2/4B&K, Eldfisk 2/7 B, Embla*, Tor*, Albuskjell, Valhall, Valhall Nordflanken, Valhall Sørflanken, Hod. Ula, Tambar*, Oselvar and Gyda (* only chemical analyses). The 2005 data refer to the same fields, minus Albuskjell and Oselvar, which have not been sampled before.

Parameter Regional stations* Field-specific stations

2008 2005 2008 2005

Total number of stations* 12 (11)* 10 (10)* 161 (109) 108 (61)***

Depth (m) 62 - 70 69 - 76 61 - 69 68 - 78

% pelite 2.8 -5.2 0.3 - 4.2 4.4 - 10.5 0.3 - 35.5

% sand** 94.5 -96.9 85.1 - 98.3 88.2 - 97.5 65 - 100

% TOM 0.6 -1.0 0.7 - 1.1 0.6 - 5.9 0.6 - 1.5

Lead (mg/kg) 3.76 -7.0 4.0 - 7.2 4.6 - 17.4 5.3 - 24.0

Copper (mg/kg) 0.9 -2.4 n.d. - 0.5 0.7 - 15.4 n.d. - 21.0

Zinc (mg/kg) 4.13 -7.4 3.1 - 6.8 4.7 - 68.0 4.9 - 88.0

Chromium (mg/kg) 5.9 -7.6 5.8 - 9.1 5.3 - 33 4.8 - 24.0

Cadmium (mg/kg) 0.0 -0.0 n.d. - 0.2 0.0 - 0.2 n.d. - 0.09

Barium (mg/kg) 11 - 83.4 4.1 - 7.2 35 - 5383 28.0 - 5587.0

THC (mg/kg) 0.5 - 3.5 1.3 - 5.8 1.5 - 37.7 3.3 - 188.0

Olefin-based base fluid (mg/kg) n.a. n.a. 0.6 - 8.5 0.5 - 86.0

No. indiv. per station (0.5 m2) 374 - 2046 539 - 2154 380 - 9245 249 - 5193

No. taxa per station (0.5 m2) 48 - 69 56 - 89 33 - 87 20 - 97

Diversity H’ 2.3 - 5.0 2.5 - 4.4 0.9 - 4.9 1.3 - 4.5 * numbers in parentheses indicate stations analysed for physical and biological characteristics ** sand fractions (fine, medium and coarse sand) are determined in 2008, but not in 2005 (total sand only). Anomalous sediment at Hod-18 excluded (not sampled in 2008) *** figures only for fields that coincide with the 2008 survey; the total no. stations in 2005 is greater n.d. = not detected; n.a. = not analysed

The background level of THC in the sediments in Region I has decreased by approximately 2 mg/kg dry sediment for several of the Regional stations. The overall decrease in THC in undisturbed sediment has been checked to verify that the decrease is not due to differences in quantifying THC in sediments between different laboratories. The decrease in THC is also seen for undisturbed sediments at Valhall Sørflanken and Valhall Nordflanken. The average THC concentration in the sediments at all field-specific stations at Valhall Nordflanken is 3.2 ± 0.8 mg/kg, while in 2005 and 2001 (baseline survey) it was 6.1 ± 1.0 mg/kg and 7.6 ± 0.8 mg/kg, respectively. At Valhall Sørflanken, the average THC concentration in the sediment at all field-specific stations except the innermost station along the main current direction (VAS-01) in 2008 is 2.2 ± 0.5 mg/kg. In 2005 and 2001 (baseline survey) the average concentration of THC in sediments at the same stations was 4.4 ± 0.4 mg/kg and 6.2 ± 0.6 mg/kg, respectively. A decrease in THC level in undisturbed sediments could be caused by natural inter-annual variations. It is impossible to determine if the decrease in hydrocarbon discharges from the offshore installations in Region I also have influence on the THC level in the sediments at the Regional stations.

At the Regional stations, the range of numbers of macrofaunal individuals per station in 2008 was similar to that recorded in 2005, but there has been an increase in the numbers of individuals recorded at the field stations in 2008. The overall most abundant taxa recorded at the field-specific and Regional stations in 2008 are shown in Table 1-2.


The same four taxa are overall most abundant at both field-specific and Regional stations. The polychaete worm Galathowenia oculata is most abundant at both field-specific and Regional stations, but with higher average abundances at the field-specific stations. Extremely high densities of G. oculata tended to occur within 500 m of the field centres, and the highest abundances were found at the Ula field (more than 8000 individuals at one station). However, there are no consistent relationships between high abundances of G. oculata and THC or barium levels.

The polychaetes Paramphinome jeffreysii and Scoloplos armiger as well as the brittlestar Amphiura filiformis also tended to occur in higher abundances at field-specific relative to Regional stations. The polychaete Chaetozone sp., which is reputed to increase in abundance on organically enriched or otherwise disturbed sediments, was overall fifth most abundant at the field-specific stations, whereas it was 9th most abundant at the Regional stations. Similarly, the bivalve Thyasira flexuosa, which also may have show a positive response to disturbance, is 7th most abundant at the field-specific stations, but was not among the ten most abundant taxa at the Regional stations.

Further research is proposed to investigate this phenomenon of high abundances close to field centres, in relation to contaminant levels, or changes therein. Such a study will be carried out in an ecosystem context, taking into account factors such as fluctuations in water temperatures and fisheries activity in the region (biomass extraction, bottom trawling and exclusion zones around installations).

Table 1-2: The ten overall most abundant taxa recorded at the field-specific stations and the Regional stations in Region I, 2008. Values are average number of individuals per station. Abbreviations: B = Bivalvia, Ph= Phoronida, E = Echinodermata, P = Polychaeta, Cn = Cnidari,. Rh = Rhynchocoela.

Field stations Regional stations Taxon name Average

0.5 m2

Standard deviation

Taxon name Average

0.5 m2

Standard deviation

Galathowenia oculata (P) 1182 1229 Galathowenia oculata (P) 602 444 Paramphinome jeffreysii (P) 378 255 Amphiura filiformis (E) 96 44 Amphiura filiformis (E) 147 63 Paramphinome jeffreysii (P) 93 73 Scoloplos armiger (P) 85 107 Scoloplos armiger (P) 40 66 Chaetozone sp. (P) 60 54 Kurtia bidentata (B) 31 42 Kurtia bidentata (B) 48 63 Spiophanes bombyx (P) 23 12 Thyasira flexuosa (B) 42 41 Phoronis sp. (Ph) 21 11 Ophiuroidea indet. juv. (E) 36 13 Goniada maculata (P) 19 8 Cerianthus lloydi juv. (Cn) 34 17 Chaetozone sp. (P) 16 19 Spiophanes bombyx (P) 34 19 Nemertini indet. (Rh) 14 6 Phoronis sp.* (Ph) 28 10 Nemertini indet*. (Rh) 27 24

* additional taxa shown to compensate for abundant juveniles subsequently removed from statistical analyses

Through a consideration of the different analyses carried out on data from each field, the fauna at each station was classified into groups according to the level of faunal disturbance (see methods description for criteria). At three fields, Valhall Nordflanken, Hod and Oselvar, the fauna at all stations sampled is undisturbed (Fauna group A).

Slightly disturbed fauna (Fauna group B) was registered at seven fields; Ekofisk C & 2/4 B&K, Eldfisk 2/7 B, Albuskjell, Valhall, Valhall Sørflanken, Ula and Gyda. The largest


calculated minimum area of slightly disturbed fauna occurred at Ekofisk C & 2/4B&K (1.17 km2), followed by Valhall (0.88 km2). At the remaining fields, the area of slightly disturbed fauna was 0.2 km2 or less. In general, most of the Fauna group B conditions occurred within 500 m from the field centres in a generally SE direction, and within 250 m in the other directions. This is consistent with the general current directions in the area.

Distinctly disturbed fauna (Fauna group C) occurred only at the Gyda field, and was only registered at a single sampling station, located 250 m SE of the field centre. The calculated minimum area of distinctly disturbed fauna is 0.07 km2.

The total area of disturbed fauna (faunal group B in 2008 and general disturbed area in 2005) in Region I appear to have decreased from 12.6 km2 in 2005 to 2.64 km2 in the present survey in 2008. Most of this decrease has occurred at the Ekofisk C & 2/4B&K field. However, due to different calculation methods between the present and 2005 surveys, the exact figure should be treated with care. No instances of highly disturbed fauna (Fauna group D) were found during the present survey. The calculated minimum area of contaminated sediments and disturbed fauna in Region I, 2008 area is shown in Table 1-3.

Table 1-3: Calculated minimum area (km2) contaminated sediments and disturbed fauna in Region I, 2008 with an indication of changes since the previous survey in 2005. Note: Albuskjell and Oselvar were not surveyed in 2005.

Field THC Olefins Barium ** Other metals **

Faunal group B*

Faunal group C*

Faunal group D*

Ekofisk C & 2/4B&K 27.68 0.82 47.08 24.57 ** 1.17 0.0 0.0 Eldfisk 2/7 B 0.22 0.152

1.18 1.18 0.2 0.0 0.0

Embla 0.10 = n.a. 0.39 0.10 n.a. 0.0 0.0 Tor 0.11 0.12 1.18 1.18 n.a. 0.0 0.0 Albuskjell 0.02 12.57 7.85 0.59 0.05 0.0 0.0 Valhall 1.47 n.a. 12.57 1.18 0.88 0.0 0.0 Valhall Nordflanken 0.0 n.a. 4.71 0.00 0 0.0 0.0 Valhall Sørflanken 0.07 = n.a. 1.23 0.00 0.15 0.0 0.0 Hod 0.40 = 1.77 1.77 0.00 0 0.0 0.0 Ula 0.22 n.a. 1.47 0.49 0.07 0.0 0.0 Tambar 0.00 n.a. 0.49 0.18 n.a. 0.0 0.0 Oselvar 0.00 n.a. 0.55 0.00 0 0.0 0.0 Gyda 0.22 n.a. 2.36 0.11 0.2 0.07 0.0 Total area 2008 30.51 15.43 82.83 29.58 2.64 0.07 0.0 Total area 2005*** 40.38 2.78 ** ** 12.6* n.a. n.a. n.a. = not analysed * area not directly comparable between 2008 and 2005 (groups not used in 2005; also area often specified as < or >); estimate of change is made where possible. Total area for 2005 is given here by omitting the < / > signs ** not calculated in 2005 *** note – Albuskjell and Oselvar not sampled in 2005. A comparison between years for each field is given in the main report ( - increase in area, - reduction in area, = - similar or only slight variation)

Summary conclusions for each of the fields sampled at Region I, 2008 are given in Table 1-4 together with an estimate of changes in conditions since 2005.


Table 1-4: Summary results and conclusions for each field in Region I, 2008.

Field Summary results 2008 Change 2005 - 2008

Ekofisk C & 2/4B&K

Elevated levels of THC out to 4 400 m. 16 of 20 field stations are elevated with THC. Only 3 stations with THC level above 10 mg/kg.

All stations have elevated levels of barium and the highest concentration of barium is found at EKO-15, 5383 mg/kg.

Elevated levels of the other selected metals are found at almost all stations with exceptions of some of the outermost stations.

Slightly disturbed fauna found at four stations out to 800 - 850 m in an easterly/southeasterly direction from the field centre at Ekofisk C. No disturbed fauna was found around the 2/4 B&K installation.

Reduction in disturbed area (chemical and biological)

Eldfisk 2/7 B Elevated levels of THC are found out to 500 m E and 250 m S and N of field centre. The highest level of THC found is 29 mg/kg.

All field stations have elevated level of barium and the other metals.

All four stations located within 250 m of the field centre had slightly disturbed fauna. Only one 500 m station was sampled (south of centre), showing undisturbed fauna.

Reduction in disturbed area (chemical and biological; but only one common biological station)

Embla The stations 250 m E and S of Embla have elevated levels of THC.

All field stations have elevated levels of barium and the highest concentration is 5180 mg barium/kg (EMB-05).

The two stations 250 m E and S of the field have elevated levels of the other selected metals.

No biological analyses were carried out.

Unchanged area contaminated with total hydrocarbon concentration

Tor Elevated levels of THC out to 250 m E and N of the field centre.

Elevated levels of ethers are found out to 500 m S of field centre.

All field stations have elevated levels of barium and the other selected metals.

No biological analyses carried out.

Reduction in area contaminated with total hydrocarbon concentration

Albuskjell Elevated levels of THC out to 100 m SV, SE and NV of the field centre. All field stations are elevated with small amounts of olefins (< 2.2 mg/kg)

The stations out to 2000 m SV, SE and NE and out to 500 m NV of the field centre are elevated with barium.

Elevated levels of the selected metals are found out to 500 m in all directions from the installation.

Slightly disturbed fauna at all four stations located 100 m from the centre in all directions and at 250 m distance SE of the centre.

Not included in the monitoring programme in 2005

Valhall Elevated levels are found out to 1 000 m E/NE and S/SE and out to 500 m W/SW of the field centre. The highest concentration of THC in Region I in 2008 is found at VAL-08 with 55 mg/kg. In the 1-3 and 3-6 cm deep layer at VAL-08 the THC concentrations are 102 mg/kg and 95 mg/kg, respectively.

All field stations have elevated levels of barium. Other metals are elevated out to 1 000 m in one direction (E/NE) and out to 500 m in the 3 other directions.

Slightly disturbed fauna found at four stations; out to 1000 m in E/NE direction and 500 m in W/SW and S/SE directions.

A large reduction in area (~8 km2) contaminated with total hydrocarbon concentration

Reduction in area of faunal disturbance.


Field Summary results 2008 Change 2005 - 2008

Valhall Nordflanken

The sediments are not contaminated with THC.

Elevated levels of barium is found out to 2 000 m W/SW and out to 1 000 m in the other 3 directions.

All the stations sampled classified as having undisturbed fauna.

For the first time since production, the sediments are not contaminated with THC

Valhall Sørflanken

One station 250 m E/NE of the field centre has elevated THC level.

Elevated levels of barium are found out to 1 000 m E/NE and N/NW of the field centre and at the innermost station in the two other directions.

Slightly disturbed fauna found out to 250 m in a W/SW direction, and 500 m along the E/NE transect.


Hod The innermost station E/SE, W/SW and S/SE of the field centre has elevated levels of THC.

All field stations have elevated levels of olefins, barium and selected metals.

A single biological station, located 500 m SE of the centre, was included; this contained undisturbed fauna.


Ula Elevated levels of THC are found out to 250 m SE and SW and out to 500 m NE of the centre. At ULA-18 the concentration of THC is 35 mg/kg.

All field stations have elevated levels of barium and elevated levels of the other metals are found out to 500 m NE, SE and SW of the field centre.

Slightly disturbed fauna found out to 250 m SE of the centre. All other stations classified as undisturbed. Highest abundances of Galathowenia oculata of the entire Region I survey found 500 m SE of the centre.

Reduction in area contaminated with total hydrocarbon concentration

Tambar The sediments do not have elevated levels of THC.

Elevated levels of barium are found the two innermost stations NE, SE and SW of the field centre.

No biological analyses were carried out.

Not included in the monitoring programme in 2005

Oselvar The sediments do not have elevated levels of THC.

Elevated levels of barium are found out to 1 000 m NE and 500 m NW of the centre.

All the stations sampled classified as having undisturbed fauna. Generally low abundances of Galathowenia oculata.

First survey

Gyda Elevated levels of THC are found at the innermost station SE and SW and out to 500 m NE of the centre.

Elevated levels of barium is found out to 500 m NW and out to 1 000 m in the other directions.

Elevated levels of the other metals are found at the innermost station NE and SE of the field centre.

Slightly disturbed fauna found out to 250 m SW and NE of the centre, and distinctly disturbed fauna found out to 250 m SE of the centre.

Reduction in area contaminated with total hydrocarbon concentration.

Reduction in area of faunal disturbance.


2 Introduction and methods

2.1 Background and scope On behalf of the operators in Region I of the Norwegian North Sea, ConocoPhillips commissioned Akvaplan-niva AS to carry out the regional sediment monitoring in 2008. The survey was carried out by Akvaplan-niva in co-operation with Unilab Analyse and approved subcontractors. 13 fields are included:

Field: Operator:

Ekofisk C & 2/4B&K, Eldfisk 2/7 B, Tor, Embla, Albuskjell ConocoPhillips

Ula, Valhall, Tambar, Hod, Valhall Nordflanken, Valhall Sørflanken BP

Gyda Talisman Energy Norge

Oselvar DONG

Region I is located in the central part of the North Sea (Figure 2-1).

Region I

Figure 2-1: Left: The Norwegian offshore is divided into regions for monitoring of the petroleum activities. Region I (Ekofisk) is the southernmost region (www.sft.no). Right: Dominant surface water currents and water masses in the North Sea (Turrell 1992).


The topography and composition of the sea floor in the region is relatively homogenous, comprising predominantly fine sandy sediments lying between 60 – 70 m depth. The main current direction is east to south-easterly. The locations of the fields and Regional stations included in the 2008 survey are shown in Figure 2-2.

Figure 2-2: Location of the fields (with stations indicated; grey = chemical analyses only) and Regional stations (large black filled circles) included in the sediment survey of Region I, 2008.


Information on field history, drilling and discharge activities for the individual fields is given in the respective results chapters in the main report.

The present survey is the fifth regional monitoring survey carried out at Region I. The first was carried out in 1996 (Mannvik et al., 1997), the second in 1999 (Det Norske Veritas (DNV) 2000) and the third in 2002 (DNV, 2003) and the fourth in 2005 (DNV 2006). In Region I, 13 Regional stations are located in strategic locations to represent background conditions for the region as a whole. Twelve of these were sampled in the present survey (see below). Some of these Regional stations are continued from previous field-specific reference stations whereas others were newly established in 1999.

2.2 Sampling and methodology The sampling stations visited were for the most part in accordance with the approved sampling programme for Region I, 2008 (DNV 2008). However, sampling at the Eldfisk 2/7 A field was cancelled after sampling only ELDA-03, due to interference with moorings of an installation. Further, in agreement with SFT, the Regional station REG-10 was omitted, because the nearby Yme field has been shut down. The procedures for field work, laboratory analyses and reporting are carried out in accordance with Appendix 1 to the Activity Regulation. Samples were collected from a total of 149 field stations and 12 Regional stations.

The field survey was carried out onboard the vessel MS “Libas”, 26th May – 4th June, 2008. Station positions were located by GPS (Global Positioning System) and the vessel was held in position by use of DP (Dynamic Positioning). Station locations (distance from centre, and UTM coordinates) along with depth and sediment volume (for biological samples) per station within each field are presented in the individual result chapters. Sampling was carried out with a 0.1 m2 van Veen grab, with 5 and 3 replicate samples taken for biological and chemical analyses, respectively. The following analyses were carried out on the samples collected (not all parameters at all stations):

− grain size distribution − organic material content − hydrocarbon content − content of synthetic base oils: olefin and ester − metal content − faunal composition

Samples were analysed for the presence of the metals mercury, barium, cadmium, zinc, copper, chromium and lead. The sediment at the Regional stations is regarded as undisturbed by the petroleum activities. The background levels of hydrocarbons and metals are calculated across the whole region. By comparing the different background levels, a selection of suitable background values are used for calculation of limits of significant contamination (LSC). Synthetic base oils as esters, ethers and olefins that are included in synthetic drilling muds are not present in uncontaminated sediments. If these compounds are found in the sediments, the sediments are considered as contaminated.

A Principal Component Analysis (PCA) was carried out to determine whether the stations in Region I can be subdivided into sub-groups. No clear groupings were found, so the Region I stations are all treated as a whole. The results from statistical analyses of field stations,


compared with the relevant Regional stations, give an indication as to whether the environmental conditions around the installations are affected.

Where possible, results are compared with those from previous investigations. Relationships between measured environmental variables and the faunal composition are shown using Canonical Correspondence Analyses (CCA). Criteria for identifying faunal impacts are based on a combination of multivariate analyses (cluster analysis and MDS), CCA and a consideration of the general faunal composition (number of taxa and individuals, diversity indices, dominant and indicator taxa) at each station. A curious phenomenon exists within Region I, where extremely high abundances of a polychaete worm (Galathowenia oculata) occur in certain areas, and these high abundances fluctuate both in space and time. Where there are high densities of a few taxa, the diversity indices become lowered. For reasons explained in the main report (Chapter 18), we do not remove this taxon from the analyses, and therefore we also use diversity indices with caution. Four faunal groups (A – D) are defined (see Chapter 2.3).

The estimated area of contaminated sediments and disturbed fauna is based on a calculation of the area of an asymmetric ellipse. The radius varies from field to field and between transects within each field. In the calculation, the distance to contaminated/disturbed station is used. In cases where contamination is detected at some but not all transects, half the distance between the field centre and the first station along the ‘undisturbed’ transect is used as the minimum extent of disturbance at that transect.

2.3 Glossary and abbreviations The following terms and abbreviations are used throughout this report.

Diversity H’ Shannon-Wiener diversity index, a measure of faunal diversity. Populations where a few taxa are represented by many individuals will have a lowered diversity score.

ES100 Expected number of taxa per 100 individuals. A theoretical measure of species richness.

Evenness J Pielou’s index of evenness. Populations where taxa are not represented by large numbers of individuals will have a high J value.

Fauna group Specific term used in this report, assigning stations into groups based on faunal indicators of disturbance (see below).

Fauna grp. A Undisturbed fauna, usually with low dominance and containing a wide range of taxa from different taxonomic groups, including polychaetes, molluscs, echinoderms and crustacean. Taxa that characteristically appear in disturbed sediments are absent or occur in very low numbers.

Fauna grp. B Slightly disturbed fauna, generally with somewhat higher dominance, but still containing a wide range of taxa from different taxonomic groups. The faunal composition is slightly, but noticeably, changed in relation to adjacent and/or comparable stations with equivalent environmental conditions. Taxa that characteristically appear in disturbed sediments, including polychaetes and molluscs, show an increase in numbers, but are not usually dominant.

Fauna grp. C Distinctly disturbed fauna, generally with higher dominance and lower number of taxa. The faunal composition is distinctly changed. Taxa indicative of disturbed sediments, including polychaetes and molluscs, occur among the dominant taxa, and echinoderms are rare.

Fauna grp. D Highly disturbed fauna, totally dominated by small detritus-feeding polychaetes and particularly tolerant bivalves with symbiotic bacteria. Echinoderms and crustaceans are rare or absent. Low number of taxa.

Individuals (ind.)

Numbers of specimens of each taxon found in the samples. Unless otherwise stated, values are the sum of five replicate 0.1 m2 grab samples (0.5 m2 total).

Metals The following metals are analysed using ICP-MS and CVAAS: Barium (Ba), Cadmium (Cd), Cupper (Cu), Chromium (Cr),Lead (Pb), Zinc (Zn), Mercury (Hg)


NPDs Naphtalene Phenathren Dibenzothiophenes. Measured by Gas chromatography-mass spectrometry (GC-MS)

PAHs Polycyclic Aromatic Hydrocarbons, including NPD’s and 16 EPA-PAH. Measured by GC-MS

Pelite Sum of silt and clay fractions in the sediment. Defined as < 0.063 mm particle diameter.

Taxon/ taxa Recognised taxonomic unit for organisms. Can refer to both ‘species’ and higher groups.

THC Total Hydrocarbon Content. Measured by gas chromatography (GC)

TOM Total organic matter. Measured by loss during combustion.


3 Results

3.1 Regional stations Twelve Regional stations are included in the present 2008 survey of Region I, for physical, chemical and biological analyses. The Regional stations for Region I are located in similar depths to the field stations, ranging from 62 m (Reg-09) to 70 m (Reg-05). The sediments in the area are classified as fine sand, with a low content of both pelite (2.8 - 5.2 %) and TOM (1.1 - 11.2 %).

The concentrations of hydrocarbons and selected metals in the sediments at the Regional stations are low, and at a natural background level for these parameters. The levels of aromatics (NPDs and 16 EPA-PAH), barium and the other metals in the sediments are comparable with the levels found in the two last surveys (2005 and 2002).

THC in the sediments has decreased by approximately 2 mg/kg dry sediment at several of the Regional stations. A decrease in the natural background level for THC is also seen in undisturbed sediment at several fields in Region I. To verify the decrease in THC level at the Regional stations, the sediments has been reanalysed and the reference material has been rechecked; the response factor has been constant during the re-analysis of all the sediments.

Based on the small differences in background levels of chemical parameters in the sediments at Regional stations and the results of the PCA, we confirm that the surveyed part of Region I should not be divided into sub-regions, but be treated as a whole.

The number of individual animals at the Regional stations in the present survey varies from 374 to 2046 and the number of taxa from 48 to 69. The diversity index H’ varies from 2.3 to 5.0, the evenness index J from 0.38 to 0.84 while the ES100 varies from 17 to 37. Some changes have occurred in the abundances of the dominant taxa since the previous survey in 2005, particularly the polychaete Galathowenia oculata, with consequences for some of the diversity, evenness and faunal richness measures. However, this organism occurs in patchily high densities across the entire region, and these fluctuations are considered to reflect background variations.

The polychaetes Galathowenia oculata and Paramphinome jeffreysii and the brittlestar Amphiura filiformis are among the most dominant at all Regional stations. Of these, G. oculata alone comprises 49 % of the total number of individuals registered at the 11 stations.

On the basis of the results from the uni- and multivariate analyses, together with an assessment of community structure and presence of indicator taxa, Reg-03 is classified as having slightly disturbed fauna (Fauna group B). The cause of this disturbance is not known, but it is not considered a direct impact from the neighbouring petroleum fields. The remainder of the Regional stations represent background conditions for the area and are therefore classed as undisturbed (Fauna group A).

Results from the analyses carried out on samples from the Regional stations in Region I are shown in Table 3-1 to Table 3-4.


Table 3-1: Chemical data for the Regional stations at Region I, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).

St. no. UTM ED50, zone 31

N E

THC Ba Cd Cr Cu Hg Pb Zn

Reg-01 486429 486429 1.7 32.4 0.012 6.80 0.98 0.009 6.51 6.82

Reg-02 520295 520295 1.3 24.3 0.011 6.47 1.13 0.010 4.69 5.30

Reg-03 528070 528070 2.9 61.9 0.011 7.36 0.95 <0.005 6.29 6.98

Reg-04 551639 551639 3.0 83.4 0.010 7.16 1.23 0.016 7.04 6.36

Reg-05 469625 469625 2.7 52.3 0.012 6.90 1.55 0.010 6.72 7.29

Reg-06 479614 479614 3.4 38.4 0.010 7.62 1.30 0.016 6.32 6.85

Reg-07 484609 484609 2.9 37.1 0.010 7.51 1.25 0.023 6.97 6.44

Reg-09 510989 510989 2.2 41.6 0.006 6.67 0.79 <0.005 5.99 6.36

Reg-11 510005 510005 <1 11.0 0.008 5.91 0.90 0.009 3.75 4.13

Reg-12 499514 499514 2.2 61.7 0.008 7.42 2.38 0.018 7.00 7.41

Reg-13 476464 476464 1.0 41.7 0.009 6.52 0.98 0.009 5.65 6.57

Table 3-2: Background levels (mean ± st. dev.) and calculated Limits of Significant Contamination of hydrocarbons in sediments in Region I. All values in mg/kg dry sediment.

THC NPDs 16 EPA-PAH Backgr96-08 RegI 3.8 ± 1.5 0.015 ± 0.007 0.042 ± 0.013 LSC96-08 RegI

6.2 0.026 0.064

Table 3-3: Background levels (mean ± st. dev.) and calculated Limits of Significant Contamination of selected metals in sediments in Region I. All values in mg/kg dry sediment.

Ba Cd Cr Cu Hg Pb Zn Backgr96-08 RegI 41 ± 20 0.009 ±

7.0 ± 0.6 0.7 ± 0.4 0.010 ±

6.2 ± 1.0 5.4 ± 1.2

LSC96-08 RegI 74 0.015 8.0 1.5 0.020 7.9 7.5


Table 3-4: Biological data and amount (%) of TOM and pelite for the Regional stations (minimum- and maximum values in bold).

St. no. No. ind. No. taxa H’ J ES100 Pelite TOM

Reg-01 548 57 3.5 0.61 26 4.0 0.78 Reg-02 1301 54 3.0 0.53 18 3.4 0.83 Reg-03 2046 51 2.7 0.47 15 3.1 0.90 Reg-04 1052 59 2.8 0.47 19 3.8 0.84 Reg-05 374 65 5.0 0.84 37 4.5 0.92 Reg-06 1920 69 2.3 0.38 17 3.5 0.97 Reg-07 604 56 3.9 0.68 26 3.8 0.86 Reg-09 1540 52 2.4 0.42 18 2.8 0.63 Reg-11 1006 68 3.4 0.55 24 5.2 0.84 Reg-12 1596 48 2.5 0.45 17 3.3 0.82 Reg-13 433 64 4.5 0.74 31 4.0 0.86 Sum 12 420 - - - - Average 1129 58 3.3 0.56 23 3.8 0.84 St. dev. 598 7 0.9 0.14 7 0.7 0.09

- not applicable

3.2 Ekofisk C & 2/4 B&K The Ekofisk C & 2/4 B&K field is located in block 2/4 in Region I. Production at the field started in 1971. Ekofisk is operated by ConocoPhillips. During the 2008 survey, a total of 20 stations were sampled at the Ekofisk C & 2/4 B&K field, of which 13 were analysed for physical and biological parameters. This is an increase of 6 stations compared to the 2005 survey.

Results from the analyses carried out on the samples collected from the Ekofisk C & 2/4 B&K field, 2008 are shown in Table 3-5 and Table 3-6 The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Ekofisk C & 2/4 B&K is shown in Table 3-7 and illustrated in Figure 3-1.

The sediments at Ekofisk C & 2/4 B&K are classified as fine sand, with relatively low pelite contents (5.2 - 8.1 %). The TOM content varies from 0.90 % to 1.30 %.

In this survey, 16 of a total of 20 field stations at Ekofisk C and 2/4 B&K have sediments contaminated with respect to THC. Thirteen of 16 field stations with elevated concentrations of THC are slightly above the LSC limit. Three stations have THC levels above 10 mg/kg dry sediment, and the highest amount of THC is found at EKO-14 with 37 ± 5 mg/kg dry sediment. At EKO-14 the THC level in 2005 was 188 mg/kg dry sediment. At the other field stations the THC level is about the same as in 2005. The total minimum area contaminated with respect to THC is 27.7 km2 in 2008, which is a decrease from recalculated minimum area in 2005 (28.9 km2). There are reported accidental discharges of oil (~13 tonnes) and discharges of oil in produced water (~433 tonnes) during the last three years.

The barium level in the sediments is at a similar level or slightly higher compared to previous surveys. The minimum total area contaminated with barium is 47.1 km2 in the present survey.


In general, for the other selected metals the concentrations are comparable to levels in previous surveys and the minimum total area with concentrations of other metals is 24.6 km2.

The faunal assemblages at the Ekofisk C & B/K field stations generally follow similar spatial and temporal trends as are occurring across the entire area, as evaluated from the nearest Regional station. However, four of the stations closest to the field centre (500 − 850 m from the centre to the east and south) show signs of faunal disturbance. These stations are classed as Fauna group B; slightly disturbed. The spatial extent of biological disturbance is generally unchanged in relation to the previous surveys in 2005 and 2002.

Table 3-5: Chemical data for the stations at Ekofisk C & 2/4B&K, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).

St. no. Direction (deg.)

Distance (m)


EKO-07 74 3900 5.2 124 0.013 7.71 1.90 n.a. 7.28 8.95

EKO-08 84 1800 8.1 2437 0.025 6.94 1.51 n.a. 9.92 12.4

EKO-09 94 800 9.9 3377 0.038 7.86 2.88 n.a. 11.4 16.8

EKO-09A 70 500 7.4 5227 0.066 8.46 5.20 n.a. 15.6 29.5

EKO-11 144 4400 7.2 498 0.019 7.89 1.27 n.a. 8.46 9.27

EKO-12 148 2500 9.3 2103 0.024 8.55 2.07 n.a. 12.5 11.5

EKO-13 146 1300 7.9 1731 0.026 8.00 1.62 0.013 9.26 11.0

EKO-14 140 850 37.7 4037 0.048 7.82 3.67 0.019 16.1 22.4

EKO-15 175 500 29.7 5383 0.156 11.0 12.0 n.a. 31.4 68.0

EKO-18 208 2500 4.9 847 0.018 7.95 1.64 n.a. 11.2 9.22

EKO-19 200 1200 10.7 2213 0.030 8.44 2.09 n.a. 15.8 14.5

EKO-21 287 4000 6.8 267 0.012 7.52 1.60 n.a. 8.83 7.76

EKO-22 288 1900 8.1 1670 0.017 7.98 1.72 n.a. 11.9 9.11

EKO-23 290 1000 9.2 1381 0.019 7.41 1.30 n.a. 10.5 9.75

EKO-28 360 1000 6.5 1307 0.022 7.99 2.37 n.a. 13.8 9.55

EKO-29 360 2000 3.9 196 0.011 5.34 1.28 n.a. 4.61 6.15

EKO-32 180 500 8.6 4873 0.038 7.73 2.14 0.037 12.7 16.8

EKO-33 180 1000 9.5 2297 0.031 7.65 1.49 n.a. 11.3 12.0

EKO-34 270 1000 5.5 1149 0.018 7.85 1.20 n.a. 10.6 9.32

EKO-39 90 1000 8.1 1673 0.019 7.81 1.28 n.a. 10.6 9.89

Reg-03 2.9 61.9 0.011 7.36 0.95 <0.005 6.29 6.98

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5 n.a. = not analysed


Table 3-6: Biological data and amount (%) of TOM and pelite for the stations at Ekofisk C & 2/4B&K, 2008 (minimum- and maximum values in bold).


Distance (m)

No. ind. No. taxa H’ J ES100 Pelite TOM

EKO-08 84 1800 2023 73 3.1 0.51 19 8.1 1.15 EKO-09 94 800 3209 70 2.9 0.47 15 5.3 0.93 EKO-09A 70 500 3297 67 3.1 0.51 16 5.7 0.95 EKO-12 148 2500 1250 79 4.0 0.64 25 5.9 1.12 EKO-13 146 1300 1606 69 3.6 0.59 19 6.0 1.00 EKO-14 140 850 2377 72 3.3 0.53 18 7.8 1.13 EKO-15 175 500 4164 60 2.6 0.44 14 5.6 1.24 EKO-19 200 1200 1187 72 3.6 0.59 24 7.2 1.30 EKO-23 290 1000 1557 78 3.8 0.61 23 5.2 1.00 EKO-32 180 500 4663 73 1.7 0.27 11 7.1 1.04 EKO-33 180 1000 1436 69 3.7 0.61 22 6.5 1.12 EKO-34 270 1000 2469 69 2.6 0.42 17 5.7 0.90 EKO-39 90 1000 1917 72 3.3 0.54 20 5.5 1.06 Reg-03 - - 2046 51 2.7 0.47 15 3.1 0.90 Sum * 31 155 - - - - Average * 2397 71 3.2 0.52 19 3.4 1.07 St. dev. * 1123 5 0.6 0.10 4 1.0 0.12

* Excluding the Regional station.

Table 3-7: Distance along the transects (m) and calculated minimum area of contaminated sediments and disturbed fauna at Ekofisk C & 2/4 B&K, 2008 and the previous survey in 2005.

Ekofisk C SE SW NW NE Km2 (2008) Km2 (2005)

THC 1200 4400 4000 1800 25.32 27.14

Olefin 1300 125 125 500 0.70 0.83

Ba 2500 4400 4000 3900 42.37 ***

Other metals 2500 4400 1900 1800 21.43 ***

Fauna group B 850 600 500 500 1.17 *

Ekofisk 2/4 B&K E W S N Area km2

THC 1000 500 1000 1000 2.36 1.77

Olefin 125 125 500 125 0.12 0.12

Ba 1000 1000 1000 2000 4.71 ***

Other metals 1000 1000 1000 1000 3.14 ***

Fauna group B 0 0 0 0 0 *

Sum Ekofisk C and 2/4B&K

THC 27.68 28.91

Olefin 0.82 0.96

Ba 47.08 ***

Other metals 24.57 ***

Fauna group B 1.17 <7.5** * = not calculated individually ** = different calculation methods between 2005 and 2008; also impact intensity not estimated in 2005 *** = not calculated in 2005


Figure 3-1: Distribution of Fauna groups and amounts of THC and barium at Ekofisk C & 2/4 B&K, 2008.

3.3 Eldfisk 2/7 B A total of 9 stations were sampled for chemical analyses at Eldfisk 2/7 B in 2008, of which 6 also were sampled for physical and biological analyses. The sediments at Eldfisk 2/7 B are classified as medium sand with a relatively low amount of pelite (4.5 – 9 %) and TOM (0.81 – 0.97 %).

Elevated levels of THC are found out to 500 m east and 250 m south of the installation. In the sediments at these three stations, the level of olefins ranges from 1.2 ± 0.7 mg/kg to 4.2 ± 2.2 mg/kg dry sediment. The sediments at the two nearest stations east and south of the centre are both contaminated with NPDs. In general, high sediment concentrations of barium are found across the entire Eldfisk 2/7 B field. In addition, elevated levels of copper, zinc and lead are found in the sediments at all stations, and for cadmium at all stations located within 250 m of the field centre.

According to the biological analyses, combined with chemical parameters, all the stations located within 250 m in each direction of the field centre are classified as slightly disturbed (Fauna group B). All these stations had elevated abundance of the polychaete Chaetozone sp., which is an indicator of environmental disturbance. The station located at 500 m south of the centre (ELDB-06) is classed as undisturbed (Fauna group A), and had a faunal composition representative of background conditions for the area at large. Only ELDB-06 is common between the present and the previous survey, but an improvement in biological conditions is apparent at this station since 2005.

Results from the analyses carried out on the samples collected from the Eldfisk 2/7 B field, 2008 are shown in Table 3-8 and Table 3-9. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Eldfisk 2/7 B is shown in Table 3-10 and Figure 3-2. The minimum area contaminated with THC in the present survey is 0.22 km2, and this is a minor decrease since the previous survey in 2005 (0.29 km2). All the stations are contaminated with the selected metals and the minimum area contaminated with barium and


other metals is 1.18 km2. The area of faunal disturbance extends to at least 0.2 km2 (area not compared with 2005 due to only one common station).

Table 3-8: Chemical data for the stations at Eldfisk 2/7 B, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


ELDB-03 360 500 4.7 1197 0.012 7.17 2.38 n.a. 9.61 7.79

ELDB-04 360 250 5.2 4387 0.020 8.06 2.20 n.a. 15.3 11.9

ELDB-05 180 250 14.3 6383 0.038 6.24 5.08 0.021 20.3 23.8

ELDB-06 180 500 4.8 1500 0.007 5.89 2.05 n.a. 9.92 9.40

ELDB-11 270 500 4.8 1220 0.009 7.04 3.18 n.a. 10.6 7.82

ELDB-12 270 250 7.7 4853 0.021 8.20 3.58 n.a. 16.1 19.3

ELDB-13 90 250 29.0 5923 0.070 7.65 5.65 0.043 34.0 36.8

ELDB-14 90 500 8.4 4663 0.016 7.21 2.08 n.a. 14.6 11.6

ELDB-15 90 1000 5.8 1550 0.012 7.26 1.99 n.a. 10.4 7.77

Reg-03 2.9 61.9 0.011 7.36 0.95 <0.005 6.29 6.98

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed

Table 3-9: Biological data and amount (%) of TOM and pelite for the stations at Eldfisk 2/7 B, 2008 (minimum- and maximum values for field stations in bold).


Distance (m) No. ind. No. taxa H’ J ES100 Pelite TOM

ELDB-04 360 250 2333 61 2.8 0.47 15 5.9 0.88 ELDB-05 180 250 3547 74 2.7 0.43 16 9.0 0.97 ELDB-06 180 500 2019 79 3.3 0.52 21 5.4 0.81 ELDB-12 270 250 2024 55 2.8 0.49 15 4.5 0.93 ELDB-13 90 250 2314 52 3.0 0.52 15 8.7 0.97 Reg-03 - - 2046 51 2.7 0.47 15 3.1 0.90 Reg-07** - - 604 56 3.9 0.68 26 3.8 0.86 Reg-11** - - 1006 68 3.4 0.55 24 5.2 0.84 Sum * 12 237 - - - - Average* 2447 64 2.9 0.49 17 6.7 2.0 St. dev.* 633 12 0.2 0.04 3 0.91 0.07

- = not applicable * = not including Regional stations ** = additional Regional stations, near Eldfisk 2/7 B, included in biology table, to assess biological variation across a wider area.


Table 3-10: Distance along the transects (m) and calculated minimum area of contaminated sediments and disturbed fauna at Eldfisk 2/7 B, 2008 and the previous survey in 2005.

Eldfisk 2/7 B N E S W Km2 (2008) Km2 (2005)

Fauna group B 250 250 250 250 0.2 <0.8*

THC 125 500 250 250 0.22 0.29

Olefins 125 500 250 125 0.15 0.20

Ba 500 1000 500 500 1.18 **

Other metals 500 1000 500 500 1.18 **

* different calculation methods between 2005 and 2008; also impact intensity not estimated in 2005 ** not calculated in 2005

Figure 3-2: Distribution of faunal groups and amounts of THC and barium at Eldfisk 2/7 B, 2008.

3.4 Embla Samples were collected from 6 stations at Embla, for chemical analyses only. At Embla the sediments are contaminated with THC out to 250 m east and south of the centre. In general, the THC level in sediments at Embla has decreased compared to previous surveys. There are still olefins in the sediments at Embla, but the level is low and ranges between 0.6 and 0.7 mg/kg dry sediment.

In general, the sediments at Embla have elevated levels of barium, zinc (exception: EMB-06) and lead at all stations. The sediments are not contaminated with chromium, whereas for cadmium and copper, the 250 m station east of the centre is contaminated, while the sediment at station 250 m south has content at LSC or just above.

Results from the analyses carried out on the samples collected from the Embla field, 2008 are shown in Table 3-11. The calculated minimum area and spatial extent of contaminated sediments at Embla are shown in Table 3-12 and Figure 3-3


The minimum area contaminated with THC in the present survey is unchanged since 2005, 0.10 km2. The chemical results agree with the field history at Embla. No discharges have taken place at Embla since 1999, except for some small amounts of oil discharges/spills in 2002 and 2003.

Table 3-11: Chemical data for the stations at Embla 2/7D, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)

THC Ba Cd Cr Cu Pb Zn

EMB-04 360 250 3.9 2723 0.014 7.79 1.18 11.2 9.36

EMB-05 180 250 13.6 5180 0.015 7.81 1.69 15.8 13.9

EMB-06 180 500 4.0 612 0.010 7.64 1.04 11.0 7.29

EMB-12 270 250 4.4 2953 0.013 7.89 1.24 14.1 9.17

EMB-13 90 250 6.7 5123 0.017 7.23 3.70 14.0 12.5

EMB-14 90 500 5.7 796 0.012 7.23 1.32 10.6 7.69

Reg-03 2.9 61.9 0.011 7.36 0.95 <0.005 6.29

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9

Table 3-12: Distance along the transects (m) and calculated minimum area of contaminated sediments at Embla, 2008 and 2005.

Embla N E S W Km2 (2008) Km2 (2005)

THC 125 250 250 125 0.1 0.1

Ba 250 500 500 250 0.39 *

Other metals 125 250 250 125 0.1 *

* not calculated in 2005.

Figure 3-3: Distribution of the amounts of THC and barium at Embla, 2008.


3.5 Tor Samples were collected from 9 stations at Tor, for chemical analyses only. Sediments contaminated with THC are distributed up to 250 m east (TOR-13) and north (TOR-04) of the field centre. Both stations analysed for ethers (TOR-05 and TOR-06) were contaminated with ethers in all layers down to 6 cm.

With the exception of chromium the sediments are contaminated with barium and the other selected metals at all stations. Mercury contamination is found in the sediments at the 250 m station south of the centre.

Compared to previous surveys, the level of THC and barium has increased at the nearest field station along the main current direction. However, the total minimum area contaminated with THC has decreased from 0.22 km2 in 2005 to 0.11 km2 in 2008. This must be seen in relation to the field discharge history. Since 2005 there have been small amounts of discharges, and the discharge of oil in produced water is 5.9 tonnes and accidental oil discharges are ~2 tonnes.

Results from the analyses carried out on the samples collected from the Tor field, 2008 are shown in Table 3-13. The calculated minimum area and spatial extent of contaminated sediments at Tor are shown in Table 3-14 and Figure 3-4

Table 3-13: Chemical data for the stations at Tor, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


TOR-03 0 500 4.9 274 0.016 7.29 2.36 n.a. 7.53 7.89

TOR-04 0 250 6.4 575 0.019 7.67 2.46 n.a. 10.4 9.83

TOR-05 180 250 4.3 4283 0.041 7.85 5.04 0.024 21.5 27.9

TOR-06 180 500 2.5 276 0.019 7.88 2.64 0.006 10.2 9.3

TOR-07 180 1000 5.2 134 0.013 7.94 1.87 n.a. 7.69 6.90

TOR-11 270 500 4.5 455 0.017 7.99 2.05 n.a. 8.53 8.16

TOR-12 270 250 5.8 762 0.021 7.90 3.29 n.a. 9.80 9.91

TOR-13 90 250 16.9 1180 0.028 8.58 2.85 n.a. 17.2 20.5

TOR-14 90 500 5.6 339 0.012 7.82 1.58 n.a. 8.98 8.13

Reg-03 2.9 61.9 0.011 7.36 0.95 <0.005 6.29 6.98

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed


Table 3-14: Distance along the transects and calculated minimum area of contaminated sediments at Tor, 2008 and the previous survey in 2005.

Tor N E S W Km2 (2008) Km2 (2005)

THC 250 250 125 125 0.11 0.22

Ethers 125 125 500 125 0.12 0.29

Ba 500 500 1000 500 1.18 *

Other metals 500 500 1000 500 1.18 *

* = not calculated in 2005

Figure 3-4: Distribution of the amounts of THC and barium at Tor, 2008.

3.6 Albuskjell 1/6 A Samples were collected from 20 stations at Albuskjell 1/6 A, for physical, chemical and biological analyses. The sediments at Albuskjell 1/6 A are classified as fine sand with a relatively low amount of pelite (2.2 – 10.5 %) and TOM (0.61 – 0.95 %). With the exception of ALBU-04 (1000 m NW of the centre) with highest amount of pelite, and ALBU-11 (100 m SE of the centre) with the lowest amount of fine sand and highest amount of medium sand, the results at the other field stations are comparable with that found at the Regional stations.

In general the sediments at the 100 m stations have elevated levels of NPD’s at all four stations, while THC and 16 EPA-PAH have elevated levels at three (NW, SE and SW) and two stations (SE and SE), respectively. The sediments from samples collected at almost stations are contaminated with barium, cadmium and zinc. The sediments until 100 m from the platform are contaminated with all metals in all investigated layers.


There is a great variance in the number of individuals (648 – 7164), number of taxa (37 – 76), and diversity H’ (1.2 – 3.9) between the stations. The variance in the number of individuals and diversity is mainly caused by the unevenly distribution of the polychaete Galathowenia oculata in the area. The number of individuals of this species alone varies from 153 at ALBU-06 (100 m NW) to 6009 at ALBU-16 (100 m SW). As a result, the highest and lowest diversity is registered at these two stations.

Also at the 11 Regional stations in Region I the number of individuals (374 – 2046), number of taxa (48 – 69) and diversity H’ (2.3 – 5.0) varies. At these stations the number of individuals of G. oculata varies from 41 (Reg-05; H’ = 5.0) to 1305 (Reg-06; H’ = 2.3).

The fauna at the field is considered to be slightly disturbed at the four stations located at 100 m distance in all directions and at 250 m distance SE of the centre. At these stations, the brittlestar Amphiura filiformis occur in reduced densities compared to the other stations, including the Regional stations. This species is known to be sensitive to sediment contamination. The same tendency is seen for the bivalve Kurtia bidentata (= Mysella bidentata), although its reaction to organic enrichment/contamination is not known at the moment.

Other taxa, known to increase with increasing organic enrichment/sediment contamination, are the polychaetes Chaetozone sp. and Cirratulus cirratus and the bivalve Thyasira flexuosa and T. sarsi. The first of these taxa is registered with increased densities at two of the stations (ALBU-01 and ALBU-16), while the other three taxa show the same tendency only at ALBU-16. These five stations are separated from the other field stations and the Regional stations in the multivariate analyses, as well as in the correlation analysis. The correlation between the faunal distribution and the amount of Ba and Pb, and the other chemical parameters as co-variables, might indicate some influence from old discharges of drilling mud to the stations close to the platform. However, the correlation is weak, which indicates that the measured environmental variables do not have much effect on the faunal distribution in the area.

The fact that the Albuskjell 1/6 A was closed down in 1990 and that there has been no drilling or discharge activity at the field in almost 20 years, may explain the somewhat weak and unclear signals in the bottom faunal composition.

Results from the analyses carried out on the samples collected from the Albuskjell 1/6 A field, 2008 are shown in Table 3-15 and Table 3-16. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Albuskjell 1/6 A is shown in Table 3-17 and Figure 3-5.


Table 3-15: Chemical data for the stations at Albuskjell 1/6 A, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


ALBU-01 337 100 5.5 2163 0.036 9.87 15.4 0.033 47.4 46.7

ALBU-02 337 250 4.4 1162 0.030 6.81 1.08 n.a. 10.6 10.2

ALBU-03 337 500 2.8 350 0.016 6.85 0.89 n.a. 9.54 7.76

ALBU-04 337 1000 2.1 60.6 0.010 7.42 0.61 n.a. 7.02 6.65

ALBU-05 337 2000 1.8 48.1 0.013 7.49 1.91 n.a. 6.93 6.40

ALBU-06 67 100 9.0 2800 0.055 8.55 6.59 0.061 16.3 45.4

ALBU-07 67 250 3.3 977 0.025 7.83 2.26 n.a. 11.5 16.6

ALBU-08 67 500 2.7 181 0.011 7.68 0.74 n.a. 8.59 7.94

ALBU-09 67 1000 1.8 76.7 0.012 7.21 0.66 n.a. 6.69 6.31

ALBU-10 67 2000 2.1 83.5 0.010 7.56 0.55 n.a. 6.65 6.38

ALBU-11 157 100 14.5 3457 0.104 10.7 7.53 0.070 30.4 60.2

ALBU-12 157 250 1.8 452 0.031 5.55 1.43 n.a. 6.07 10.4

ALBU-13 157 500 2.5 268 0.019 7.23 0.85 n.a. 8.01 8.89

ALBU-14 157 1000 2.1 171 0.012 7.06 0.64 n.a. 6.50 7.04

ALBU-15 157 2000 2.5 194 0.019 7.36 0.60 n.a. 6.62 7.01

ALBU-16 247 100 10.5 4593 0.062 10.4 13.1 0.041 24.1 45.3

ALBU-17 247 250 2.3 990 0.033 8.27 1.72 n.a. 11.4 11.7

ALBU-18 247 500 4.9 454 0.023 7.67 0.95 n.a. 10.8 9.89

ALBU-19 247 1000 3.1 162 0.011 7.23 0.59 n.a. 7.96 6.89

ALBU-20 247 2000 2.2 75.9 0.007 7.05 0.49 n.a. 5.87 5.84

Reg-02 0.7 24.3 0.011 6.47 1.13 n.a. 4.69 5.30

Reg-06 3.4 38.4 0.010 7.62 1.30 n.a. 6.32 6.85

Reg-07 2.9 37.1 0.010 7.51 1.25 n.a. 6.97 6.44

Reg-12 0.9 41.7 0.009 6.52 0.98 0.009 5.65 6.57

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed


Table 3-16: Biological data and amount (%) of TOM and pelite for the stations at Albuskjell 1/6 A, 2008 (minimum- and maximum values for field stations in bold).



ALBU-01 337 100 2510 67 1.8 0.30 13 3.6 0.79 ALBU-02 337 250 1764 56 2.5 0.42 17 5.6 0.91 ALBU-03 337 500 1296 53 3.3 0.57 18 4.2 0.89 ALBU-04 337 1000 1585 52 2.6 0.45 17 10.5 0.89 ALBU-05 337 2000 1435 54 2.9 0.50 18 4.2 0.88 ALBU-06 67 100 719 56 3.9 0.68 25 2.2 0.84 ALBU-07 67 250 2276 65 2.7 0.44 15 3.9 0.90 ALBU-08 67 500 2433 63 2.6 0.43 15 4.2 0.89 ALBU-09 67 1000 2990 63 2.2 0.36 14 4.8 0.86 ALBU-10 67 2000 2222 66 2.5 0.41 17 4.7 0.87 ALBU-11 157 100 648 37 2.9 0.55 16 3.0 0.86 ALBU-12 157 250 866 51 3.4 0.60 20 2.8 0.61 ALBU-13 157 500 1334 66 3.3 0.54 20 3.7 0.87 ALBU-14 157 1000 1377 57 2.6 0.45 17 3.9 0.89 ALBU-15 157 2000 1498 70 3.1 0.51 21 4.8 0.95 ALBU-16 247 100 7164 76 1.2 0.20 9 6.4 0.90 ALBU-17 247 250 2378 63 2.6 0.44 15 3.7 0.87 ALBU-18 247 500 1747 63 2.7 0.44 17 3.1 0.87 ALBU-19 247 1000 1329 57 2.8 0.48 18 2.8 0.87 ALBU-20 247 2000 2144 55 2.3 0.40 15 2.6 0.84 Reg-02** - - 1301 54 3.0 0.53 18 3.4 0.83 Reg-06 - - 1920 69 2.3 0.38 17 3.5 0.79

- - 604 56 3.9 0.68 26 3.8 0.91 Reg-12 - - 1596 48 2.5 0.45 17 3.3 0.89 Sum* 39715 Average* 1986 60 2.7 0.46 17 4.1 0.86 St. dev.* 1372 8 0.6 0.11 3 1.8 0.07

- = not applicable * = not including Regional stations ** = additional Regional station included in biology table, to assess biological variation across a wider area

Table 3-17: Distance along the transects (m) and calculated minimum area of contaminated sediments and disturbed fauna at Albuskjell 1/6 A, 2008.

Albuskjell 1/6 A SE SW NW NE Area km2

(2008)

Fauna group B 250 100 100 100 0.05

THC 100 100 100 50 0.02

Olefins 2000 2000 2000 2000 12.57

Ba 2000 2000 500 1000 5.89

Other metals 250 500 500 500 0.59


Figure 3-5: Distribution of Fauna groups and amounts of THC and barium at Albuskjell 1/6 A, 2008.

3.7 Valhall Samples were collected from 12 stations at Valhall, for physical, chemical and biological analyses. The sediments at Valhall are classified as fine sand with generally low levels of pelite (2.8 - 6.3 %) and TOM levels between 0.71 % and 0.99 %. The results at the field stations are comparable with those found at the Regional stations.

In general the total hydrocarbon contents are above LSC in the sediments until 1000 m in two directions (south/southeast and east/northeast) and until 500 m in one direction (west/southwest). The highest level of THC is found at VAL-08 (54.9 ± 24.3 mg/kg dry sediment) and vertical core samples reveal THC up to 102 mg/kg in the 1-3 cm layer.

The sediment at Valhall contains elevated levels of barium at all stations, 10 field stations are contaminated with lead, 8 stations with copper and for the rest of the metals, elevated levels are found at less than half of the stations in the sediments. The highest levels of metals are found in the sediments at VAL-02.

According to the field history for the last three years, there have been 51 m3 of accidental oily discharges and discharges of 23 tonnes of oil in produced water. However, the level of THC has decreased in the sediments for more than half of the field stations since the last survey. The minimum recalculated area contaminated with THC has decreased from 9.4 km2 in 2005 to 1.5 km2 in 2008. The minimum area contaminated with barium and the remaining metals in 2008 is 12.6 km2 and 1.2 km2, respectively.

The biological analyses recorded a total of 14 781 individuals within 148 taxa (excluding juveniles) at the Valhall field stations. Polychaete worms dominate the fauna with 75 % of the individuals and 46 % of the taxa recorded. The overall most dominant taxa are the polychaetes Galathowenia oculata, Paramphinome jeffreysii, Chaetozone sp., Spiophanes bombyx and Scoloplos armiger, the ophiuroid brittlestar Amphiura filiformis and the bivalve


Kurtia bidentata. Of these, G. oculata, P. jeffreysii and A. filiformis are among the top dominants at all 20 stations. Most of these are typical for the area at large and, with the exception of Chaetozone sp., are not specifically associated with faunal disturbance.

The cluster analysis of the field stations separates VAL-02 (500 m ENE) alone at just over 40 % dissimilarity from the rest of the stations. Thereafter, two groups are formed, at approximately 35 % dissimilarity from each other; VAL-03 (1000 m ENE) and VAL-08 (500 m SSE) and VAL-15 (500 m WSW) appear in one group, and the rest of the stations in the other group. These four mentioned stations (VAL-02, VAL-03, VAL-08 and VAL-15) are classed as having a slightly disturbed fauna, and this agrees with the current and/or previous chemical content of the sediments, as well as observations of oily matter at most of these stations in 2005. Despite this, the chemical parameters analysed do not significantly explain the faunal variation across the stations. This is likely due to the fact that the overall most dominant taxa are common to all stations, regardless of contaminant levels. The minimum area of disturbed fauna at the Valhall field in 2008 is estimated at 0.88 km2.

Results from the analyses carried out on the samples collected from the Valhall field, 2008 are shown in Table 3-18 and Table 3-19. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Valhall is shown in Table 3-20 and Figure 3-6.

Table 3-18: Chemical data for the stations at Valhall, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


VAL-02 74 500 37.0 3943 0.065 8.77 6.13 n.a. 18.3 31.6

VAL-03 74 1000 10.0 1747 0.016 7.25 1.55 n.a. 10.1 9.62

VLA-04 74 2000 4.3 466 0.007 6.83 1.11 n.a. 8.44 6.48

VAL-08 164 500 54.9 3193 0.026 8.30 3.45 0.022 11.2 13.9

VAL-109 160 1000 7.8 887 0.012 6.27 1.41 0.017 7.14 6.82

VAL-110 160 2000 4.4 446 0.008 6.89 1.64 n.a. 9.51 6.94

VAL-15 254 500 13.6 1188 0.008 7.76 2.05 n.a. 9.37 9.61

VAL-116 254 1000 5.6 411 0.007 7.00 1.13 n.a. 8.78 6.81

VAL-16 254 2000 5.0 142 0.009 7.32 1.65 n.a. 7.38 6.41

VAL-21 344 500 5.0 578 0.009 7.26 2.01 n.a. 8.56 7.13

VAL-22 344 1000 4.2 416 0.008 7.31 1.39 n.a. 8.33 6.48

VAL-123 340 2000 4.7 1267 0.018 7.37 1.83 n.a. 11.4 8.97

Reg-11 2.2 61.7 0.008 7.42 2.38 n.a. 7.00 7.41

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed


Table 3-19: Biological data and amount (%) of TOM and pelite for the stations at Valhall, 2008 (minimum- and maximum values for field stations in bold).



VAL-02 74 500 1389 59 3.2 0.55 19 5.4 0.99 VAL-03 74 1000 832 63 3.7 0.62 24 4.4 0.76 VAL-04 74 2000 1311 73 3.4 0.55 23 3.8 0.71 VAL-08 164 500 777 63 4.2 0.70 27 6.3 0.98 VAL-109 160 1000 1010 66 3.7 0.61 25 4.9 0.89 VAL-110 160 2000 1196 58 3.3 0.57 21 5.1 0.77 VAL-15 254 500 1120 54 3.5 0.61 20 5.6 0.96 VAL-116 254 1000 916 66 3.7 0.61 24 5.9 0.78 VAL-16 254 2000 1531 76 2.6 0.42 18 6.0 0.84 VAL-21 344 500 972 68 3.8 0.62 25 2.8 0.83 VAL-22 344 1000 2150 77 2.8 0.45 19 4.4 0.82 VAL-123 340 2000 1577 69 3.1 0.52 22 5.9 0.84 Reg-04 1052 59 2.8 0.47 19 3.8 0.84 Reg-11** 1006 68 3.4 0.55 24 5.2 0.84 Sum * 14 781 Average. * 1232 66 3.4 0.57 22 5.1 0.8 St. dev. * 391 7 0.4 0.08 3 1.0 0.1

* = not including Regional stations ** = additional Regional station included in biology table, to assess biological variation across a wider area

Table 3-20: Distance along the transects and calculated minimum area of contaminated sediments and disturbed fauna at Valhall, 2008 and the previous survey in 2005.

Valhall E/NE S/SE W/SW N/NW Km2 (2008) Km2 (2005)

Fauna group B 1000 500 500 250 0.88 <2.4

THC 1000 1000 500 250 1.47 9.42

Ba 2000 2000 2000 2000 12.57

Other metals 1000 500 500 500 1.18


Figure 3-6: Distribution of faunal groups and amounts of THC and barium at Valhall, 2008.

3.8 Valhall Nordflanken Samples were collected from 9 stations at Valhall Nordflanken, for physical, chemical and biological analyses. The sediments at Valhall Nordflanken are classified as fine sand with relatively low pelite contents (1.5 - 4.9 %) and TOM values of between 0.74 - 0.85 %. The sediments are representative of the area at large.

In general, low total hydrocarbon contents are found in the sediments at Valhall Nordflanken and THC levels in the sediments are well below the LSC value. The sediments at Valhall Nordflanken have elevated levels of barium, but for the other selected metals the concentrations are low and the sediments are not contaminated with these metals. The level of hydrocarbons and metals is in general comparable to the survey in 2005, but there has been a significant decrease in the THC level in the sediments at almost all field stations. A similar decrease in the level of THC in sediments is also seen for Regional stations in Region I with natural background levels of THC. In 2006 there were discharges of water based drilling mud (11 608 tonnes), cuttings (1716 tonnes) and barite (26.33 tonnes). At Valhall Nordflanken, the sediments are only contaminated with barium, and the minimum barium contaminated area is 4.71 km2.

A total of 20 934 individuals within 133 taxa were registered in the present survey (excluding juveniles). The polychaetes dominate the fauna with 85 % of the individuals and 48 % of the taxa recorded.

The small, tube-dwelling polychaete worm, Galathowenia oculata is numerically most abundant at all the Valhall Nordflanken field stations, as well as at the nearest Regional stations Reg-04 and Reg-11. Second or third abundant at all field stations and Reg-11 are the polychaete Paramphinome jeffreysii and the brittlestar Amphiura filiformis. All three taxa occur amongst the dominants across the entire Region I area. At Reg-04, to the south-east of


the field, A. filiformis is less dominant, preceded by the polychaete Scoloplos armiger, members of Phoronis sp. and the bivalve Kurtia bidentata.

The faunal assemblages generally are representative of background conditions, and no stations are classified as having a disturbed fauna.

Results from the analyses carried out on the samples collected from the Valhall Nordflanken field, 2008 are shown in Table 3-21 and Table 3-22. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at the Valhall Nordflanken field is shown in Table 3-23 and Figure 3-7.

Table 3-21: Chemical data for the stations at Valhall Nordflanken, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


VAN-01 74 250 2.6 442 0.004 7.05 1.52 n.a. 7.17 6.45

VAN-02 74 500 2.2 265 0.009 6.93 1.37 n.a. 6.95 7.68

VAN-03 74 1000 2.0 134 0.009 7.17 0.85 n.a. 7.21 7.28

VAN-05 164 250 2.7 180 0.007 6.96 1.22 <0.005 6.51 6.31

VAN-08 155 500 2.6 125 0.008 7.67 0.93 n.a. 8.14 7.19

VAN-09 155 850 3.4 211 0.009 7.40 1.26 n.a. 7.06 6.69

VAN-10 164 2000 2.6 110 0.007 7.25 1.01 n.a. 7.18 6.46

VAN-106 254 250 3.3 146 0.006 6.63 1.01 n.a. 6.30 8.41

VAN-107 254 500 3.2 117 0.013 6.90 1.04 n.a. 6.38 7.37

VAN-11 254 1000 3.8 262 0.012 6.99 1.07 n.a. 7.39 8.81

VAN-13 344 250 3.7 131 0.006 7.39 1.11 n.a. 7.08 7.91

VAN-14 344 500 4.7 445 0.016 8.17 1.59 n.a. 7.88 7.91

VAN-15 344 1000 4.6 99.3 0.009 7.40 0.86 n.a. 7.29 6.97

Reg-11 2.2 61.7 0.008 7.42 2.38 n.a. 7.00 7.41

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed


Table 3-22: Biological data and amount (%) of TOM and pelite for the stations at Valhall Nordflanken, 2008 (minimum- and maximum values for field stations in bold).



VAN-01 74 250 4804 77 1.8 0.29 14 4.7 0.80

VAN-02 74 500 2444 72 2.3 0.37 17 4.9 0.76

VAN-05 164 250 2624 87 2.4 0.37 18 4.0 0.85

VAN-106 155 500 1996 62 2.4 0.40 18 1.5 0.80

VAN-09 254 250 2407 63 2.2 0.38 16 3.4 0.82

VAN-10 254 500 2037 59 2.5 0.42 17 2.9 0.78

VAN-11 254 1000 699 60 4.1 0.70 27 3.7 0.74

VAN-13 344 250 2599 70 2.1 0.35 16 4..2 0.77

VAN-14 344 500 1324 63 3.4 0.57 24 4.3 0.83

Reg-04 - - 1052 59 2.8 0.47 19 3.8 0.84 Reg-11 - - 1006 68 3.4 0.55 24 5.2 0.84

Sum * - - 20 934 - - - - - -

Average. * - - 2326 68 2.6 0.43 18 3.7 0.8

St. dev. * - - 1127 9 0.7 0.13 4 1.1 0.0

- not applicable * not including Regional stations

Table 3-23: Distance along the transects and calculated minimum area of contaminated sediments and disturbed fauna at Valhall Nordflanken, 2008 and the previous survey in 2005.

Valhall Nordflanken E/NE

(74º)

S/SE

(164/155º)

W/SW

(254º)

N/NW

(344º)

Km2 (2008) Km2 (2005)

Faunal group B 0 0 0 0 0 <0.2*

THC 0 0 0 0 0 0.11

Ba 1000 2000 1000 1000 4.71 **

* different calculation methods between 2005 and 2008; also impact intensity not estimated in 2005. ** not calculated in 2005 (see Chapter 3).

Figure 3-7: Distribution of barium levels at Valhall Nordflanken, 2008.


3.9 Valhall Sørflanken Samples were collected for chemical analyses from 12 stations at Valhall Sørflanken, of which 8 also were sampled for physical and biological analyses. The sediments at Valhall Sørflanken are classified as fine sand with a relatively low content of pelite (from 2.4 % to 4.4 %). The TOM content varies from 0.65 % to 0.95 %. There has been a notable decrease in pelite content at VAL-06 and VAL-113 since the previous survey in 2005, but otherwise, the granulometric composition is similar between surveys. The TOM content has increased slightly at only one station, VAS-01, located 250 m E/NE of the field centre.

In general, low total hydrocarbon contents are found in the sediments at Valhall Sørflanken. THC levels above LSC are found in sediments at one station, situated 250 m east/northeast of the field centre. Elevated level of barium in the sediment is found until 1000 m east/northeast and north/northwest directions relative to the centre at Valhall Sørflanken, and until 250 m south/southeast and west/southwest directions. For the other selected metals the concentration is low and none of the sediments are elevated with any of the other selected metals.

A total of 11 713 individuals within 121 taxa were registered at the eight stations in the present survey (excluding juveniles). The polychaetes dominate the fauna with 81.2 % of the individuals and 44.6 % of the taxa recorded. This is normal for the region.

The overall most abundant taxa at the Valhall Sørflanken field are the small tube-dwelling polychaete Galathowenia oculata, the filter-feeding polychaete Ditrupa arietina, the polychaete Paramphinome jeffreysii and the brittlestar Amphiura filiformis, most of which are common throughout the entire region. At VAS-01 and VAS-02, there are elevated abundances (> 100 individuals) of the polychaete Chaetozone sp., which is typical for environmental disturbance. This taxon appeared among the dominants at most of the other stations, but in far fewer numbers. In common with the 2005 survey VAS-01 and VAS-02 are classed as being mildly disturbed in terms of biological characteristics. Both stations also had elevated Ba levels.

Results from the analyses carried out on the samples collected from the Valhall Sørflanken field, 2008 are shown in Table 3-24 and Table 3-25. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Valhall Sørflanken is shown in Table 3-26 and Figure 3-8.


Table 3-24: Chemical data for the stations at Valhall Sørflanken, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


VAS-01 74 250 12.1 457 0.007 6.65 1.28 n.a. 6.65 6.89

VAS-02 74 500 2.9 288 0.007 6.35 0.95 n.a. 6.36 5.34

VAS-03 74 1000 1.3 128 0.005 6.23 0.78 n.a. 6.39 6.03

VAS-05 164 250 2.1 98.1 0.008 6.54 2.07 <0.005 6.38 6.16

VAS-06 164 500 1.9 52.9 0.005 6.05 1.47 n.a. 5.41 4.75

VAS-07 164 1000 1.6 35.1 0.003 5.55 0.67 n.a. 5.38 5.16

VAS-09 254 250 2.7 229 0.006 6.69 0.85 n.a. 6.69 5.84

VAS-10 254 500 2.0 50.1 0.004 6.40 0.82 n.a. 6.33 5.07

VAS-11 254 1000 1.8 66.4 0.009 6.86 0.77 n.a. 6.37 5.89

VAS-113 325 250 2.4 95.1 0.004 6.79 0.95 n.a. 6.18 5.61

VAS-14 344 500 2.2 99.3 0.007 6.99 1.13 n.a. 6.54 5.96

VAS-15 344 1000 2.9 104 0.007 7.01 0.78 n.a. 6.73 6.53

Reg-11 2.2 61.7 0.008 7.42 2.38 n.a. 7.00 7.41

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed

Table 3-25: Biological data and amount (%) of TOM and pelite for the stations at Valhall Sørflanken, 2008 (minimum- and maximum values for field stations in bold).


Distance (m)


VAS-01 74 250 4853 69 2.0 0.33 12 4,2 0,95 VAS-02 74 500 2179 65 3.1 0.52 19 4,0 0,70 VAS-05 164 250 1456 70 3.7 0.60 23 2,4 0,71 VAS-06 164 500 532 67 4.9 0.81 34 2,9 0,65 VAS-09 254 250 1196 62 3.3 0.56 23 3,2 0,72 VAS-10 254 500 504 51 4.4 0.78 28 3,3 0,68 VAS-113 325 250 613 47 3.7 0.66 24 3,2 0,73 VAS-14 344 500 380 45 4.5 0.82 28 4,4 0,83 Reg-04 - - 1052 59 2.8 0.47 19 3.8 0.84 Reg-11 - - 1006 68 3.4 0.55 24 5.2 0.84 Sum * - - 20 934 - - - - - - Average. * - - 2326 68 2.6 0.43 18 3.7 0.8 St. dev. * - - 1127 9 0.7 0.13 4 1.1 0.0

- = not applicable * = not including Regional stations


Table 3-26: Distance along the transects(m) and calculated minimum area of contaminated sediments and disturbed fauna (km2) at Valhall Sørflanken, 2008 and the previous survey.

Valhall Sørflanken E/NE

(74º)

S/SE

(164º)

W/SW

(254º)

N/NW

(325/344º)

Km2 (2008) Km2 (2005)

Group B 500 125 250 125 0.15

THC 250 125 125 125 0.07 0.00

Ba 1000 250 250 1000 1.23 *

Other metals 0 0 0 0 0.00 *

* not calculated in 2005

Figure 3-8: Distribution of Fauna groups and amounts of THC and barium at Valhall Sørflanken, 2008.

3.10 Hod Samples were collected at 8 stations at Hod, for chemical analyses, of which one station also was sampled for physical and biological analyses. The sediments at HOD-08 are classified as fine sand with a median value of 2.57 φ. The amount of pelite in the sediment is 4.9 %, the fine sand content is 91.9 % and the medium sand content is 2.9 %.

At Hod elevated levels of THC in sediments are found at three stations, and the highest level is found at the station nearest the centre along the main current direction, HOD-08 (10.3 ± 2.2 mg THC/kg dry sediment). The sediments at Hod are elevated with olefins and the level ranges from 1.6 ± 0.8 mg/kg to 8.5 ± 6.1 mg/kg dry sediment. Small amounts of olefins are also seen in the sediments at the nearest region station, Reg-08 (1.1 ± 0.6 mg/kg). The minimum area contaminated with THC and olefins at Hod is 0.40 km2 and 1.77 km2, respectively.


The highest levels of barium and lead are found at HOD-02 (Ba: 1004 ± 141mg/kg, Pb: 10.3 ± 0.5 mg/kg) and all field stations at Hod are contaminated with both barium and lead. The sediments at Hod are uncontaminated with respect to cadmium, chromium and copper. The minimum area contaminated with barium (and lead) is 1.77 km2. At HOD-09 (0.020 ± 0.013 mg/kg) the concentration of mercury is at the LSC-value.

Over the recent surveys, there has been a decline in THC and Ba levels at HOD-08. From the results of the 2005 survey, it was suggested that the faunal composition over time reflects these changes. In 2002, there was a marked increase in Galathowenia oculata at certain Hod stations, some, but not all, of which had experienced a marked decline in THC levels. G. oculata is notoriously patchy in its distribution over both time and space, and there does not seem to be a consistent pattern in relation to THC levels, or changes therein. Without a comprehensive statistical analysis of the phenomenon, we cannot attach any particular significance to fluctuating abundances in G. oculata. What is notable at HOD-08 is the appearance of the brittlestar Amphiura filiformis amongst the most abundant taxa in 2005 and 2008, whereas it was not among the most abundant in 2002. This also applies to HOD-02 in 2005 relative to 2002. Both these stations have had a high contaminant loading, which is decreased in 2008. A. filiformis tends to decrease in abundance in disturbed sediments.

On the basis of the results from the biological uni- and multivariate analyses, HOD-08 is classified as Fauna group A, undisturbed. The dominant taxa are similar to those at nearby Regional stations, and there are no signs of faunal disturbance. The polychaete Chaetozone sp., which increases in abundance with organic and/or general disturbance, occurs in similar abundances at HOD-08 and most of the Regional stations.

Results from the analyses carried out on the samples collected from the Hod field, 2008 are shown in Table 3-27 and Table 3-28. The calculated minimum area and spatial extent of contaminated sediments at Hod is shown in Table 3-29 and Figure 3-9.

Table 3-27: Chemical data for the stations at Hod, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


HOD-02 74 500 8.8 1004 0.013 6.72 1.24 n.a. 10.3 8.05

HOD-03 74 1000 4.2 183 0.009 6.53 0.99 n.a. 8.09 6.72

HOD-08 164 500 10.3 549 0.007 6.75 1.08 n.a. 8.92 6.94

HOD-09 164 1000 4.0 217 0.009 7.33 1.18 0.020 9.04 7.54

HOD-13 254 315 7.1 616 0.012 6.65 1.41 n.a. 9.27 7.91

HOD-14 254 500 4.5 278 0.012 6.36 1.14 n.a. 8.72 7.03

HOD-19 344 250 5.4 477 0.014 7.05 1.36 n.a. 8.44 7.67

HOD-20 344 500 5.7 244 0.011 6.84 1.10 n.a. 8.90 6.98

Reg-08 2.2 41.6 0.006 6.67 0.79 <0.005 5.99 6.36

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed


Table 3-28: Biological data and amount (%) of TOM and pelite for the stations at Hod, 2008.


Distance (m)


HOD-08 164 500 740 72 4.3 0.70 30 4.9 0.86 Reg-04 - - 1052 59 2.8 0.47 19 3.8 0.84 Reg-11 - - 1006 68 3.4 0.55 24 5.2 0.84

- = not applicable

Table 3-29: Distance along the transects and calculated minimum area of contaminated sediments and disturbed fauna at Hod, 2008 and the previous survey in 2005.

Hod NW

(344 º)

NE

(74º)

SE

(164º)

SW

(254º)

Km2 (2008) Km2 (2005)

Fauna group B 0 0 0 0 0 >0.5 THC 125 500 500 315 0.40 0.40 Olefin 500 1000 1000 500 1.77 1.33 Ba 500 1000 1000 500 1.77 * Other metals 0 0 0 0 0.00 *

* = not calculated

Figure 3-9: Distribution of amounts of THC and barium at Hod, 2008.

3.11 Ula Samples were collected from 9 stations at Ula, of which 7 also were sampled for physical and biological analyses. The sediments at Ula consist of fine sand with relatively low levels of pelite (2.2 - 4.8 %). The content of TOM varies from 0.67 % to 0.93 %.


In general, low total hydrocarbon contents are found in the sediments at the outermost field stations along the axes at Ula. However, THC levels above LSC are found in sediments at three innermost stations, situated northeast, southwest and southeast relative to the installation. In general, the level of THC in sediments at Ula has decreased since previous surveys. In 2005 four stations had THC contaminated sediment and because of that, the minimum area contaminated with THC has decreased from 0.37 km2 in 2005 to 0.22 km2 in 2008.

The highest level of metals and hydrocarbons in the sediments at Ula is found at ULA-18, and at this location the sediment is clearly contaminated. Except for one station, the sediments at Ula have elevated level of barium. In addition to ULA-18 the sediments at four stations have elevated levels of cadmium, copper, lead and zinc.

A total of 39 592 individuals within 129 taxa were registered at Ula in the present survey. The polychaetes dominate the fauna with 95 % of the individuals and 51 % of the taxa recorded. The small tube-dwelling polychaete Galathowenia oculata was overall most abundant at all the sampling stations at the Ula field, with the exception of ULA-116 (although this station was dominated by juvenile echinoids, which are not representative of the adult population). Highest abundances occurred at ULA-119 (8 529 ind.), located 500 m SE of the centre. All stations contained more than 3 000 ind. of this polychaete, except station ULA-116 (500 m NW of the centre), which had only 71 individuals.

On the basis of the results from the uni- and multivariate analyses, the stations at Ula are classified into two different Fauna groups. ULA-18 shows a typical pattern of faunal disturbance, with increased abundance of Chaetozone sp. (although not among the top ten most abundant taxa) and a lowered abundance of Amphiura filiformis. It has the lowest numbers of taxa of the field, and is classed as impact group B. The remaining stations are classed as impact group A. There is a remarkably high abundance of G. oculata at most of the innermost stations at the Ula field, in contrast to the 500 m NW station and most of the Regional stations. However, without a region-wide statistical study of its relationship with sediment contaminant levels, as well as other external factors such as fluctuations in water temperature, we find it unwise to make firm conclusions based on this phenomenon.

Results from the analyses carried out on the samples collected from the Ula field, 2008 are shown in Table 3-30 and Table 3-31. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Ula is shown in Table 3-32 and Figure 3-10.


Table 3-30: Chemical data for the stations at Ula, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


ULA-04 45 1000 3.1 341 0.010 6.68 1.72 n.a. 7.18 6.55

ULA-05 45 500 6.6 3247 0.017 6.94 1.73 n.a. 11.4 11.7

ULA-07 225 250 7.4 1636 0.012 6.21 1.56 n.a. 8.56 8.73

ULA-08 225 500 2.3 474 0.019 7.25 1.69 n.a. 8.44 8.69

ULA-116 330 500 2.0 65.9 0.011 5.54 1.21 n.a. 5.27 6.01

ULA-117 300 250 2.0 179 0.010 5.19 1.51 n.a. 5.93 6.50

ULA-119 135 250 6.2 5520 0.063 8.07 5.34 0.030 17.8 41.7

ULA-18 125 500 35.4 1375 0.016 5.86 2.01 0.014 8.57 11.8

ULA-20 135 1000 3.1 162 0.015 6.48 1.45 n.a. 6.55 6.65

Reg-01 1.7 32.4 0.012 6.80 0.98 0.009 6.51 6.82

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed

Table 3-31: Biological data and amount (%) of TOM and pelite for the stations at Ula, 2008 (minimum- and maximum values for field stations in bold).


Distance (m)


ULA-05 45 500 6395 72 1.0 0.17 9 4.2 0.84 ULA-07 225 250 7652 67 0.9 0.14 8 3.5 0.81 ULA-08 225 500 4063 66 1.4 0.23 11 4.8 0.83 ULA-116 330 500 463 54 4.4 0.77 28 2.2 0.67 ULA-117 300 250 7682 58 0.8 0.14 7 3.2 0.80 ULA-18 135 250 4092 49 1.1 0.20 9 4.1 0.93 ULA-119 125 500 9245 74 0.8 0.12 7 3.4 0.79 Reg-01 - - 548 57 3.5 0.61 26 3.8 0.84 Reg-09 - - 1540 52 2.4 0.42 18 5.2 0.84 Sum * - - 39592 - - - - - - Average. * - - 5656 63 1.5 0.25 11 3.7 0.8 St. dev. * - - 2985 9 1.3 0.23 8 1.1 0.0


Table 3-32: Distance along the transects (m) and calculated minimum area of contaminated sediments and disturbed fauna at Ula, 2008 and the previous survey in 2005.

Ula NE

(45º)

SE

(135/125º)

SW

(225º)

NW

(300/330 º) Km2 (2008) Km2 (2005)

Fauna group B - 250 - - 0.07 >0.4

THC 500 250 250 125 0.22 0.37

Ba 1000 1000 500 250 1.47 *

Other metals 500 500 500 125 0.49 *

* = not calculated in 2005


Figure 3-10: Distribution of Fauna groups and amounts of THC and barium at Ula, 2008.

3.12 Tambar Samples were collected at 8 stations at Tambar, for chemical analyses only. In general, low total hydrocarbon contents are found in the sediments at Tambar and the THC levels found in the sediments are below the LSC value at all field stations for the first time since production started at the field. According to the field history, there have only been small accidental discharges of oil based mud/oily discharge (~0.1 m3) at Tambar during the last three years, and this may explain why the THC level has decreased in the sediments at several of the field stations.

The sediment at Tambar is in general contaminated with barium and copper, and the highest levels for these parameters are found at the station nearest the centre along the main stream current, TAM-05. There has been a minor increase of some metals in the sediments at Tambar and this may be explained by the history of field discharges. In 2007 there were discharges of 3 675 tonnes of water based mud, 450 tonnes of cuttings and ~53 tonnes of barite.

Results from the analyses carried out on the samples collected from the Tambar field, 2008 are shown in Table 3-33. The calculated minimum area and spatial extent of contaminated sediments at Tambar are shown in Table 3-34 and Figure 3-11.


Table 3-33: Chemical data for the stations at Tambar, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


TAM-01 45 250 2.3 308 0.012 7.01 2.74 n.a. 7.61 7.57

TAM-02 45 500 1.9 87.8 0.011 6.63 3.24 n.a. 7.02 6.63

TAM-05 135 250 4.4 404 0.012 6.92 3.29 0.011 7.15 7.54

TAM-06 135 500 5.1 93.1 0.012 7.49 3.19 0.020 7.07 7.66

TAM-09 225 250 4.0 176 0.010 7.01 3.15 n.a. 6.97 7.95

TAM-10 225 500 1.9 122 0.012 7.10 1.80 n.a. 6.93 7.28

TAM-13 315 250 2.3 66.8 0.011 6.98 2.74 n.a. 5.89 7.15

TAM-14 315 500 2.1 90.1 0.009 7.03 1.92 n.a. 6.55 6.76

Reg-12 1.0 41.7 0.009 6.52 0.98 0.009 5.65 6.57

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed

Table 3-34: Distance along the transects and calculated minimum area of contaminated sediments at Tambar, 2008 and the previous survey in 2005.

Tambar NE

(45º)

SE

(135º)

SW

(225º)

NW

(315º)

Km2 (2008) Km2 (2005)

THC 0 0 0 0 0 0.07

Ba 500 500 500 125 0.49 *

Other metals 125 500 250 125 0.18 *

* not calculated in 2005

Figure 3-11: Distribution of THC and barium levels at Tambar, 2008.


3.13 Oselvar Samples were collected at 12 stations at Oselvar, for physical, chemical and biological analyses. The sediments at Oselvar are classified as fine sand with a relatively low pelite content (3.8 - 4.9 %), and the TOM content varies from 0.81- 1.00 %. With the exception of OS-01 having a higher medium sand content than the rest of the stations, the granulometric composition is similar across the Oselvar field, and values also are similar to those recorded at the nearest Regional stations Reg-13 and Reg-05.

In general low total hydrocarbon contents are found in the sediments at Oselvar. THC levels are well below LSC, and range from 1.7 mg/kg to 5.3 ± 1.0 mg/kg dry sediment. At Oselvar the levels of NPD’s and 16 EPA-PAH are below their respective LSC values, except for 16 EPA-PAH in the 3-6 cm deep sediment layers.

Also generally low sediment concentrations of metals are found at Oselvar. However, five field stations contain elevated levels of barium in the sediments at Oselvar. The level of the other metals is in general below their respective LSC’s. In two of six replicates at OS-04 and OS-05 the level of mercury range from 0.132 mg/kg to 0.183 mg/kg, while the concentrations in the other four replicates are ≤ 0.005 mg mercury/kg.

A total of 11 070 individuals within 130 taxa were registered in the present survey (excluding juveniles). The polychaetes dominate the fauna with 72 % of the individuals and 45 % of the taxa recorded. This is normal for the region. The small, tube-dwelling polychaete Galathowenia oculata is the most abundant taxa at all the stations, with abundances ranging from 249 individuals at OS-10 to 990 individuals at OS-07. The ophiuroid brittlestar Amphiura filiformis is either second or third most abundant at all the stations, followed by the polychaete Paramphinome jeffreysii, which is either fourth or fifth most abundant at all the stations.

The polychaete Chaetozone sp., which tends to increase in abundance in organically enriched sediments, is not among the dominant taxa at any of the Oselvar field stations, or at the two nearest Regional stations Reg-13 and Reg-05. The fauna at the Oselvar field stations is similar to all the Regional stations generally located in the western part of the region, and therefore is considered to be unaffected by the field operations (Fauna group A; undisturbed).

Results from the analyses carried out on the samples collected from the Oselvar field, 2008 are shown in Table 3-35 and Table 3-36. The calculated minimum area and spatial extent of contaminated sediments at Oselvar is shown in Table 3-37 and Figure 3-12.


Table 3-35: Chemical data for the stations at Oselvar, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


OS-01 45 250 1.9 165 0.019 7.65 1.15 n.a. 7.90 7.95

OS-02 45 500 1.7 109 0.012 7.20 1.09 n.a. 7.29 6.93

OS-03 45 1000 1.7 90.9 0.013 7.48 1.18 n.a. 6.93 7.19

OS-04 135 250 2.3 68.0 0.010 7.57 1.43 0.047 7.33 7.48

OS-05 135 500 2.8 70.7 0.010 7.50 1.11 0.064 7.15 7.20

OS-06 135 1000 2.9 60.5 0.009 7.12 1.12 n.a. 6.94 7.01

OS-07 225 250 2.4 53.2 0.009 7.46 1.10 n.a. 7.00 7.19

OS-08 225 500 2.8 46.6 0.009 7.43 1.17 n.a. 7.19 7.06

OS-09 225 1000 2.9 59.2 0.018 7.31 1.28 n.a. 7.34 7.90

OS-10 315 250 2.4 117 0.015 7.36 1.15 n.a. 6.91 7.34

OS-11 315 500 2.5 75.3 0.011 7.40 1.22 n.a. 7.17 7.68

OS-12 315 1000 5.3 57.3 0.011 7.41 1.36 n.a. 7.37 7.98

Reg-13 2.2 26.2 0.012 6.81 1.21 0.011 6.70 6.77

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. Not analysed

Table 3-36: Biological data and amount (%) of TOM and pelite for the stations at Ula, 2008 (minimum- and maximum values for field stations in bold).


Distance (m)


OS-01 45 250 798 55 3.2 0.55 21 4.9 0.87 OS-02 45 500 863 56 2.8 0.48 21 4.6 0.85 OS-03 45 1000 965 58 3.0 0.50 21 4.4 0.88 OS-04 135 250 752 50 3.3 0.58 21 4.3 0.91 OS-05 135 500 861 58 3.3 0.57 22 4.4 0.81 OS-06 135 1000 1000 63 3.1 0.51 22 4.4 1.00 OS-07 225 250 1460 69 2.4 0.39 18 4.7 0.81 OS-08 225 500 739 73 3.6 0.58 26 4.2 0.85 OS-09 225 1000 1285 51 2.6 0.46 19 4.3 0.85 OS-10 315 250 632 57 3.8 0.65 26 3.9 0.87 OS-11 315 500 904 64 3.3 0.56 24 3.8 0.87 OS-12 315 1000 811 64 3.6 0.60 27 4.2 0.91 Reg-05 - - 374 65 5.0 0.84 37 4.3 0.9 Reg-13 - - 433 64 4.5 0.74 31 0.3 0.1 Sum * - - 11 070 - - - - - - Average. * - - 923 60 3.2 0.54 22 3.7 0.8 St. dev. * - - 236 7 0.4 0.07 3 1.1 0.0 - not applicable * not including Regional stations


Table 3-37: Distance along the transects and calculated minimum area of contaminated sediments at Oselvar, 2008.

Oselvar NE SE SW NW Km2 (2008)

Ba 1000 125 125 500 0.55

Figure 3-12: Distribution of amounts of THC and barium at Oselvar, 2008.

3.14 Gyda Samples were collected at a total of 11 stations at Gyda, for physical, chemical and biological analyses. The sediments in Gyda field consist of fine sand with relatively low amounts of pelite (2.7 - 5.5 %), and the TOM content varies from 0.67 - 0.81 %. GYDA-18 has an anomalous fine “soupy” sediment, characterised in 2005 as silt-clay, but with no grain size analysis carried out in 2008. GYDA-18 had an elevated TOM content of 5.94 %.

The sediments at Gyda are contaminated with THC at four stations and the THC level at these stations ranges from 10 mg/kg to 23 mg/kg dry sediment. At station GYDA-19 the THC level is just below the LSC, but the sediment is contaminated with NPDs and 16 EPA-PAH. At the other field stations the THC level is well below the LSC for the region. The minimum area contaminated with THC has decreased from 0.49 km2 (recalculated) in 2005 to 0.22 km2 in 2008.

In general, low concentrations of heavy metals are found in the sediments at Gyda, but all stations are contaminated with barium. At GYDA-18, it was not possible to collect sufficient material for granulometric analyses. However, in 2005 the sediment at GYDA-18 contained almost only pelite, while the other stations contain about 3.6 % pelite. This difference in pelite amount may explain why the sediment at GYDA-18 has extremely high concentrations of the selected metals other than barium compared to the rest of the field stations.

A total of 40 650 benthic animals larger than 1 mm within 154 taxa were registered at the Gyda field in 2008 (excluding juveniles). The polychaetes dominate the fauna with 90 % of


the individuals and 42.8 % of the taxa recorded. At the nearest Regional stations, Reg-12 and Reg-02, polychaetes also dominated the fauna, with a similar proportion of taxa, but a lower proportion of the individuals.

The fauna at all the stations was dominated by the polychaetes Galathowenia oculata and Paramphinome jeffreysi as well as the brittlestar Amphiura filiformis, although the latter was almost absent at GYDA-18. At all the 250 m stations, members of the Nemertini were among the five most abundant taxa and at GYDA-06 and GYDA-07 (250 m NE and SW), there were elevated abundances of Chaetozone sp.

GYDA-18 has the lowest abundance of the overall top dominant organism, Galathowenia oculata (350 ind.), but no particular significance is attached to this, because also GYDA-09, located 2000 m from the field has low abundances of this polychaete (392 individuals). In 2005, GYDA-18 had a markedly atypical fauna. The two most abundant taxa (albeit present in low numbers) were the same as in the 2008 survey (G. oculata and P. jeffreysii). Thereafter, in 2005, taxa most often associated with the plankton or hyperbenthos rather than the benthos were recorded among the dominants, namely the pteropod Limacina retroversa, the shrimp Themisto sp. and arrow-worms belonging to the Chaetognatha. Also among the dominants, in both 2005 and 2008, was Chaetozone sp. (recorded as C. setosa in 2005), an indicator of disturbance. In 2008, GYDA-18 generally contains similar taxa to the other stations (although generally in lower abundances), but the almost absence of the brittlestar Amphiura filiformis, which is among the dominants across the entire region, indicates a disturbance to the fauna at this station.

On the basis of the results from the uni- and multivariate analyses, the stations at Gyda are classified into three different faunal groups. GYDA-18 is classed as distinctly disturbed (Fauna group C), with a markedly lowered faunal abundance and number of taxa. GYDA-06 and GYDA-07 are classed as slightly disturbed. The remaining stations are not considered notably impacted by the field activities and are classified as Fauna group A, undisturbed, although GYDA-17, located at 315º/250 m NW (upstream) of the field centre, has somewhat ‘borderline’ characteristics.

Results from the analyses carried out on the samples collected from the Gyda field, 2008 are shown in Table 3-38 and Table 3-39. The calculated minimum area and spatial extent of contaminated sediments and disturbed fauna at Gyda are shown in Table 3-40 and Figure 3-13.


Table 3-38: Chemical data for the stations at Gyda, 2008. Average THC and metal values for 3 replicates, expressed as mg/kg dry sediment (minimum- and maximum values in bold).


Distance (m)


GYDA-04 45 1000 2.6 118 0.009 6.66 1.01 n.a. 6.47 7.22

GYDA-05 45 500 10.5 399 0.009 6.04 1.64 n.a. 7.07 7.27

GYDA-06 45 250 23.4 2697 0.026 5.84 2.12 n.a. 8.52 11.5

GYDA-07 225 250 21.9 2280 0.013 6.03 1.75 n.a. 8.62 7.30

GYDA-08 225 500 2.9 437 0.010 5.99 1.29 n.a. 6.78 5.40

GYDA-09 225 1000 2.4 109 0.012 6.53 1.00 n.a. 6.19 5.48

GYDA-16 315 500 3.0 91.2 0.009 6.13 1.07 n.a. 6.32 5.10

GYDA-17 315 250 2.4 189 0.009 6.05 1.17 n.a. 6.95 5.57

GYDA-18 135 250 9.5 529 0.095 33.0 14.9 n.a. 17.4 67.8

GYDA-19 135 500 6.1 308 0.006 5.67 1.01 0.006 6.41 6.35

GYDA-20 135 1000 2.8 83.4 0.008 6.55 0.87 n.a. 6.22 6.13

Reg-12 3.8 41.7 0.009 6.52 0.98 0.009 5.65 6.57

LSC 6.2 74 0.015 8.0 1.5 0.020 7.9 7.5

n.a. = not analysed

Table 3-39: Biological data and amount (%) of TOM and pelite for the stations at Gyda, 2008 (minimum- and maximum values for field stations in bold).


Distance (m)


GYDA-04 45 1000 1267 72 3.3 0.54 22 3.2 0.71 GYDA-05 45 500 6069 77 1.2 0.20 10 3.2 0.77 GYDA-06 45 250 6370 60 1.2 0.20 8 5.5 0.67 GYDA-07 225 250 4220 57 1.5 0.25 11 3.4 0.71 GYDA-08 225 500 5469 78 1.6 0.25 12 4.0 0.73 GYDA-09 225 1000 1041 72 3.6 0.59 24 3.8 0.76 GYDA-16 315 500 2032 75 2.7 0.43 20 3.3 0.82 GYDA-17 315 250 4250 74 1.3 0.21 11 3.0 0.68 GYDA-18 135 250 600 33 2.3 0.45 13 n.a. 5.94 GYDA-19 135 500 6861 68 1.1 0.18 9 2.7 0.73 GYDA-20 135 1000 2471 69 2.3 0.37 17 3.5 0.79 Reg-02 - - 1301 54 3.0 0.53 18 3.4 0.83 Reg-12 - - 1596 48 2.5 0.45 17 3.3 0.82 Sum * - - 40 650 - - - - Average* - - 3695 67 2.0 0.33 14 3.6 1.21 St. dev.* - - 2309 13 0.9 0.15 5 0.8 1.57



Table 3-40: Distance along the transects (m) and calculated minimum area of contaminated sediments and disturbed fauna at Gyda, 2008 and the previous survey in 2005.

Gyda NE

(45º)

SE

(135 º)

SW

(225 º)

NW

(315 º)

Km2 (2008) Km2 (2005)

Fauna group B 250 250 250 125 0.15 >0.6

Fauna group C 125 250 125 125 0.07

THC 500 250 250 125 0.22 0.49

Ba 1000 1000 1000 500 2.36

Other metals 250 250 125 125 0.11

Figure 3-13: Distribution of fauna groups and amounts of THC and barium at Gyda, 2008.


4 Recommendations for next survey

Physical analyses In the previous survey of 2005, only total sand is measured, whereas in 2008, the sand fraction of the sediment is split into its fine, medium and coarse components (in accordance with Appendix I of the Activity Regulation). We recommend this also be done for the next survey.

Chemical analyses Concentrations of hydrocarbons and metals are analysed in vertical sections in sediment samples for four of the twelve Regional stations. The values in the deeper layers are not used in any calculations of any comparison with the field-specific stations. According to the Activity Regulation it is not a requirement to analyse the vertical sediment sections for chemical parameters at Regional stations. We therefore recommend that analyses in deeper sediment layers at Regional stations are excluded.

The new Regional station, Reg-13, is located close to Reg-05. The sediment characterisation and the chemical parameters at this station are very similar. It should therefore not be necessary to include Reg-13 in future surveys.

Biological analyses Biological analyses are more difficult to standardise between surveys and between different consultants, but in general the laboratory results are compatible between 2005 and 2008, despite different operators (DNV 2005, 2002, 1999 and Akvaplan-niva 2008, 1996). Comparing the data for the same stations between years allows a relatively accurate assessment of change. However, the interpretation approaches are different between 2005 and 2008.

In 2005, diversity indices were used to assess environmental quality, with and without the over-dominant polychaete Galathowenia oculata, whereas we do not endorse this practice (explained in the main report). Further, in 2005, a reduction in the dominance of G. oculata since the previous survey was considered to indicate an improvement in environmental conditions. In some cases, we agree that a reduction in impacts may have occurred in areas where there also was a reduction in G. oculata. However, there are as many incidences where no such relationship exists. It is clear that the high abundances are connected with proximity to the fields (within 500 m), but we recommend a further investigation of the Region I data combined with a wider set of environmental parameters before drawing conclusions about G. oculata and contaminant levels in the sediments.

In conclusion, we recommend an investigation of diversity indices and faunal abundances across the Region I area, resulting in a standardised approach to biological interpretation being used between different surveys and operators in the future.


5 References

Cochrane, S.K.J., Palerud, R., Wasbotten, I.H., Larsen, L-H. 2009. Offshore sediment survey of Region I, 2008. Main Report. Akvaplan-niva report 4315.02. 306 pp.

Det Norske Veritas. Innsamlingsprogram, Region I, 2008. vers. 01, 01.02.08.

Det Norske Veritas 2006. Environmental Monitoring Region I, 2005, Main report. DNV report 66110757. 335 sider.

Det Norske Veritas 2003. Environmental Monitoring 2002 Region I – Ekofisk. DNV report no. 2003-0338; revision no. 01.

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Offshore sediment monitoring survey of Region I, 2008 · ConocoPhillips, acting on behalf of the...

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