DOI: 10.17026/dans-x89-6m9d
title: Offshore Route Survey, Hollandse Kust (noord), North Sea
title: Geophysical field survey using side scan sonar and magnetometer

description: &lt;p&gt;ADC ArcheoProjecten has performed an archaeological assessment of the geophysical survey data generated for the Tennet TSO Offshore Route Survey Hollandse Kust Noord (HKN) project. The seabed of a 1200 to 1600 m wide corridor has been surveyed from the beach just north of the coastal town Wijk aan Zee, via the planned HKN-platform location (approximately 30 km NW offshore), towards the planned HKNW-platform location (approximately 60 km offshore to the WNW). The surveyed route itself is just over 70 km in length.&lt;br&gt;The seabed will be disturbed when the cables are entrenched into the seabed. To prevent damage to possible archaeological remains present on the seabed or protruding from the seabed this assessment was executed with the aim of locating them within the survey area. The prehistoric landscape of the deeper subsoil is not subject of research within the assignment.&lt;br&gt;Based on the desk-based research six NCN contacts with an archaeological expectation were located within the survey area. It was expected that they might be discovered in the research area with side scan sonar. It appears that only two NCN contacts were detected and correlated with side scan sonar.&lt;br&gt;The archaeological assessment of the SSS data has resulted in nine contacts, which are classified in category 1. These locations have an archaeological expectation until the archaeological value of the objects is determined. This also applies to four possible archaeological NCN contacts that were not detected and of which their location could not be matched to the SSS sonar contacts from this study (table 9).&lt;br&gt;To prevent these possible archaeological remains from being damaged, their parent sites must be avoided in accordance with Dutch regulations for work involving soil disturbance in the North Sea.&lt;br&gt;They are defined by a 100-meter buffer zone around the archaeological remains. This zone may be reduced in size, when proof is obtained that the activity will not adversely affect the archaeological remains. A statement to that effect needs to be submitted to and be approved by Rijkswaterstaat as the Dutch licensing authority.&lt;br&gt;If damage to an archaeological contact can not be avoided, an underwater inspection is strongly recommended to determine its archaeological value in accordance with the Dutch Archaeological Quality Standard protocol 4103 (IVO Onderwater Verkennend or exploratory phase of underwater research). The underwater inspection may also be conducted with a remotely operated vehicle (ROV). For an underwater inspection and the possible deployment of an ROV, Terms of Reference must be drafted and be approved by the licensing authority.&lt;br&gt;In this study ferro-magnetic anomalies were assessed as well. It was found that 11 anomalies are related to category 1 SSS contacts and/or known NCN contacts listed as possible wreck in the hydrographical database. An additional 311 anomalies are not associated with known wrecks or category 1 SSS contacts, but have a signal strength of at least 50nT/m. They may represent an archaeological object, however in the limited scope of this survey the unidentified 311 anomalies may very well represent UXO or dredging obstacles. Therefore we recommend to include a maritime archaeologist in the UXO research prior to the cable laying operations. When, following the criteria and procedures from UXO standards, an anomaly is approached to ascertain possible UXO (pUXO) the archaeologist can assess the archaeological expectation of the approached object. This can be achieved remotely. If a completely covered shipwreck is missed by this approach, the passive archaeological supervision (mentioned below) will serve as a safeguard.&lt;br&gt;One exception to this advice is the large anomaly MAG_B_031 on the beach, which is associated with a known wreck (IJmuiden 5/Heemskerk) and considered (until valuation) to be an archaeological object (category 1 contact). For this location the same advice applies as for the category 1 SSS contacts: If this site including a 100 m buffer zone is threatened, it is recommended 6 to determine its archaeological value in accordance with the Dutch Archaeological Quality Standard, report VS06.1 The presence of archaeological remains outside the locations mentioned in these recommendations can not entirely be ruled out. Therefore we recommend a passive archaeological supervision during cable laying operations and the installation of the platform(s) as completely buried archaeological objects may be discovered. The supervision can be executed passively and serves as a precautionary measure in case unexpected archaeological remains are found. In practice, this means an archaeologist will be on call to assess the situation when this happens. The archaeological supervision needs to be executed in accordance with Dutch Archaeological Quality Standard, protocol 4107 and a Terms of Reference must be approved by the licensing authority.&lt;br&gt;Finally, the stakeholders of this project must be made aware that they have an obligation to report possible archaeological finds to the competent authority, as indicated in Article 5.10 of the Dutch Heritage Act.&lt;/p&gt;
description: Date Submitted: 2022-03-24