Policy support regarding PFAS in water, subsurface and sediments

With our knowledge of the water and subsurface system, and the distribution of substances in that system, we have been advising governments recently about their policies on PFAS contamination.

PFAS action framework

The PFAS Action Framework was published in late 2021. The amendments, and also the ‘non-amendments’, in the Action Framework with respect to the Provisional Framework are based in part on two Deltares studies:

– A study of the options for quality requirements for the application of soil and dredged material containing PFAS in fresh surface water.

– A study of the options for quality requirements relating to the distribution of saline dredged materials containing PFAS in coastal waters

Report on the application of soil and dredged material containing PFAS in fresh surface water

This report sets out options for the setting of quality requirements for PFAS in the application of soil and dredged material and the distribution of dredged material in fresh surface waters. It looks at two levels: the re-contamination level (HVN) and the upper limit for application.

The re-contamination level for nationally managed waters was derived in November 2019. In the most recent report for application in fresh surface water, more data have been used to determine the HVN for nationally managed waters again. It emerged that this resulted in almost the same numerical values. The HVN for nationally managed waters has therefore remained unchanged.

Several variants have been developed for the upper limit for application but these values have not been included in the Action Framework. The standard method for deriving an upper limit (the maximum value for class B in the Soil Quality Regulation) produces a value that is below the HVN. A number of pragmatic methods were therefore elaborated for an upper limit. Ultimately, however, there was a policy preference for using area-specific policy or a more detailed interpretation of the duty of care.

Report on the distribution of saline dredged material containing PFAS in coastal waters

In the Netherlands, large volumes of dredged material from ports and waterways are distributed at sea. This is a mixture of material that comes from the sea and material that is transported through the rivers. If the quality of the dredged material does not comply with the standards set out in the Saline Dredged Material Test (ZBT), it may not go to the sea and it is deposited on land, mainly in the Slufter area. Until now, it has been mandatory to measure PFAS levels in saline dredged material but testing is not required. The report looked at whether it is useful to include PFAS and, if so, which standards could be set.

It emerged from measurements that three substances occur regularly at levels exceeding 0.5 µg/kg: PFOS and two PFOS precursors, namely EtFOSAA and MeFOSAA. An initial global estimate has been made of the amount of PFAS introduced into the North Sea via dredged material and that estimate was compared with the amount that enters the sea through the New Waterway. The average contribution of dredged material to the total PFOS burden (dredged material plus river discharge through the dissolved fraction, plus the fraction bound to suspended matter) is limited to approximately 8%.

The next step was to examine which principles could be applied to quality limits: 1) environmental protection in line with the WFD standards for water, 2) standstill level of the receiving environment (the coastal zone) and 3) standstill level in the source environment (Dutch surface water).

Option 1 turned out to be close to the reporting limit. In that case, hardly any more dredged material can go to sea.
In the case of options 2 and 3, the effects on the quantity of dredged material that can be distributed have been calculated for a range of ports in the Netherlands.

This would lead to clear limitations except if a total standard for PFOS+EtFOSAA+MeFOSAA is applied at the level of the re-contamination level for rivers. In many samples, these three substances would seem to be ‘communicating vessels’ to some degree. A total standard provides some latitude in this respect but it is also preferable from an environmental-health perspective. A number of uncertainties have led to the continuation of the situation in the Temporary Action Framework, namely no testing on the basis of the standard. In the years to come, work will continue on the usefulness and necessity of PFAS standards for distribution at sea.

Earlier contributions to the PFAS Action Framework

Deltares has been involved with the Temporary Action Framework (THK) since September 2019. We support the policy for the application and distribution of soil and dredged material in the water system. It relates to: the application of soil and dredged material in deep lakes, in surface water, for examples parts of dikes located in the surface water, and the distribution of dredged material offshore.

PFAS re-contamination level in dredged material from regional waters

The HVN for nationally managed waters has been declared applicable to the whole of the Netherlands for many substances but this would allow too much latitude for the regional deep lakes in the case of PFAS. A re-contamination level for regional waters does more justice to the standstill principle in deep lakes.

A large database with measurements of aquatic soils in regional waters, rather than measurements of suspended matter, was used to derive the re-contamination level for regional waters. Seventeen of the twenty-one water authorities contributed to the database and the amount of data is large enough for a representative picture. However, the national database suffers from limitations: the Rhine West water authorities dominate the database because they have supplied much more data. In addition, the concentrations in this region are clearly higher than in the other catchment areas. That is why Deltares has elaborated two possible options in the memorandum: 1) one national value and 2) a separate value for the Rhine West region and the other catchment areas.
A single generic quality limit has been selected in the PFAS Action Framework. Because the database does not include a national uniform distribution, a conservative 80th percentile was chosen.

Provisional re-contamination levels for nationally managed waters 2019

In November 2019, Deltares, working with Rijkswaterstaat, derived the PFAS re-contamination levels (HVN) for aquatic soils in the nationally managed waters, and therefore set a standard for the reduction of the depth of lakes with direct connections to the nationally managed waters.

Data for the PFAS levels of suspended matter in water are used to derive an HVN for aquatic soils. The HVNs for the list of substances in the prevailing Dutch Soil Quality Decree (Bbk) have been derived on the basis of a 95th percentile for 10 years of suspended-matter-quality data at the Lobith monitoring location. That will not be possible for PFAS and the provisional HVN has been derived using the data about PFAS levels in the suspended matter in nationally managed waters (2018-2019). Because the database differs in that it covers a shorter period and other locations, a more conservative value – an 80th percentile – has been adopted on precautionary grounds. The historical data for PFOS showed that the 2018/2019 database that was used contained lower concentrations than a full database for the past ten years would contain. The HVN for PFOS is therefore not based on an 80th percentile but on a 95th percentile, as is usual for the normal derivation of an HVN.

Leaching of PFAS from soil and dredged material

For the purposes of the amendment in the summer of 2020, Deltares worked with the National Institute of Public Health and the Environment (RIVM) on the leaching of PFAS from soil from dry land, dredged material and floodplain soils. It was assumed that there could be more leaching from soil taken from dry land when it was used in surface water because soil is not continuously in equilibrium with water and because the sources of pollution in soil are not the same as those in dredged material. This study showed that, given the same total concentrations, leaching in batch tests was the same for soil from dry land, dredged material and floodplain soils. The research report, together with the data, can be downloaded from the RIVM website.

Recommendation for the distribution of dredged material containing PFAS in downstream water bodies

Dredged material containing PFAS may be applied/distributed downstream without testing on the basis of the standard. The assumption here is that this is consistent with the standstill situation: dredged material will only be distributed where it would go naturally. Deltares advised in November 2019 that this assumption is justified in ‘sediment-sharing’ systems. In a sediment-sharing system, sediment is freely exchanged by the dynamics (currents, winds, tides).

Advising regional authorities

PFAS recommendation for nature development projects outside the dikes in the Western Scheldt

The Provincial Authority of Zeeland has asked Deltares to prepare an overview of the available knowledge on the risks of PFAS in natural development projects outside the dikes on the Western Scheldt. In 2010, IMARES advised on the balance between the expansion of the area of nature in Western Scheldt projects and the risks of the contamination of the new nature by pollutants in the water and sludge from the Western Scheldt. IMARES concluded that a new nature area connected to the Western Scheldt will have the same nature quality and development potential (in terms of disturbance by pollutants) as the existing Western Scheldt area. The recent data on suspended matter and recently deposited material in and along the Western Scheldt do not indicate that there are any reasons to deviate from this conclusion.

Application of dredged material containing PFAS in the New Terneuzen Lock

The New Terneuzen Lock (NST) project wanted clearer answers to the question of whether the application of soil and dredged material from the Ghent to Terneuzen Canal was detrimental to the receiving surface water body. The basic thinking here was that the standstill principle should at least be met when applying dredged material in the surface water of the Western Scheldt (duty of care). It was expected that elevated PFAS concentrations also occur in the more sediment-rich parts of the bed of the Western Scheldt but it has not been possible to demonstrate this on the basis of the bed samples taken until now. This means that, for the time being, beneficial use will comply with the standstill principle only if it can be demonstrated that there is no PFAS in the dredged material to be applied. The availability of more soil data may result in the amendment of this conclusion.