There is no such requirement under MARPOL Annex II for chemical cargoes. However, the International Safety Management Code (ISM) provides for all types of vessels to have on board procedures for key operations such as STS transfers. In this way, the ISM provides a link for chemical and LPG/LNG cargoes carriers to the STS transfer operations regulated under MARPOL Annex I.
The STS operations plan (the Plan) for each operation should be developed, taking into account the information detailed in the best practice guidelines for STS operations identified by such bodies as the International Maritime Organization (IMO), etc. These include:
The IMO Manual on Oil Pollution, Section I, Prevention, 2011 Edition (IMO Manual); and
The OCIMF Ship to Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases, First Edition, 2013 (the Guide)
ISGOTT (International Safety Guide for Oil Tankers and Terminals), 6th Edition 2020
The Tanker Safety Guide – Chemicals (fifth edition 2020 awaited)
Mooring Equipment Guidelines (MEG4) Fourth Edition 2018
The Ship Inspection Report (SIRE) Programme Vessel Inspection Questionnaires for Oil Tankers, Combination Carriers, Shuttle Tankers, Chemical Tankers and Gas Tankers, Seventh Edition (VIQ 7) and Chemical Distribution Institute (CDI) with their relevant sections and provisions.

The Guide sets out operational requirements for all types of tanker vessels. The additional considerations involving chemical tankers with MARPOL Annex II cargoes are outlined in Appendix B, while those for liquified petroleum gas cargoes are in Appendix C.

The STS Operations Plan is required to be in the working language of the ship and may also be incorporated into an existing Safety Management System (SMS).
According to Regulation 41, Paragraph 3 of MARPOL Annex I Chapter 8 “Any oil tanker subject to this chapter and engaged in STS operations shall comply with its STS operations Plan.”.
Ship-to-ship transfer while underway or at anchor
The following guidance has been prepared by reference to the IMO Manual and the Guide. It is not applicable to transfers associated with fixed or floating platforms, nor does it apply to STS operations necessary for securing the safety of a ship, life at sea or the environment. The reporting requirements may not apply to bunkering operations.
Person in charge

An STS transfer operation should be under the advisory control of one individual. Under MARPOL Annex I for oil cargoes, the role falls to the Person in Overall Advisory Control (POAC). In the case of MARPOL Annex II and LNG/LPG cargoes, the role falls to the STS Superintendent (STSSI). The roles could be performed either by the master of one of the involved vessels, typically of the mother (or constant heading) ship or an STS superintendent (or mooring master) from an STS service provider.
The appointment of the Person in Overall Advisory Control (POAC) or STS Superintendent (STSSI) should be a requirement of the STS operations plan.

The administration, cargo owners, tanker’s operators or charterers should agree and designate the POAC/STSSI. The POAC/STSSI should be qualified to perform all relevant duties relating to ship-handling and cargo operations, taking into consideration the qualifications detailed in Chapters 1.6 and 1.7 of the Guide and/or Paragraph No. 6.2.1.2 of the IMO Manual.
In the event that an STS service provider is utilised, they should be requested to provide documentary evidence of the intended POAC/STSSIs qualifications, experience and medical fitness.

It is worth considering two POAC/STSSIs to ensure continuous 24 hour supervision, if applicable.
The appointment of a POAC/STSSI does not in any way relieve the ships’ masters of any of their duties, requirements or responsibilities.
STS transfer area

The STS transfer area should be carefully assessed for risks and chosen for a safe operation, in co-ordination with the appropriate authorities. In selecting the area, the following considerations should be taken into account: sea room, traffic density, water depth and the availability of a safe anchorage. A more detailed account of the factors to be considered when selecting an area for STS transfer may be found at Paragraphs Nos. 2.3 and 2.4 of the Guide and Paragraph No. 6.2.2.1 of the IMO Manual.
Notification to authorities
Tankers subject to MARPOL Annex I Chapter 8, which plan STS operations within the territorial sea, or the exclusive economic zone (EEZ) of a party (i.e. signatory state) to the present MARPOL Convention are required to notify the relevant coastal state authority not less than 48 hours in advance of the scheduled STS operation. The notification shall comprise the information contained at Paragraphs No. 2.2 of the Guide and Paragraph No. 6.2.3.1 of the IMO Manual.
For STS operations involving other cargoes, the operators should check with local regulators to determine the level of approval required.
Where, in an exceptional case, STS operations are to take place within 48 hours, the oil tanker shall notify the coastal state authority at the earliest opportunity.
The responsibility for the notification to the coastal state authority rests with the masters of the tankers involved in the STS operation.
The masters should also ensure that they have a copy of any acknowledgment from the coastal state authority to carry out the STS operation.
When STS transfers are undertaken in international waters, a navigational warning (securité) should be broadcast to all ships, advising other traffic in the area of the names of the oil tankers; area and nature of operations; time and expected duration; and request a wide berth.
Equipment
Prior to the commencement of the STS operation, the masters of the two tankers should exchange information regarding the availability, readiness and compatibility of the equipment to be used in the operation. This should include the two ships themselves, having regard to their design and characteristics.

The tanker(s) should be provided with fenders, both primary and secondary. The former should ideally be floating pneumatic type complying with ISO 17357. The secondary can be foam filled type, light in weight and more easily hauled well above the water in positions with limited access to lifting gear. The fenders can be secured to either vessel, although landing on an unprotected section of the hull is less likely if the fenders are appropriately secured to the manoeuvring ship.
When smaller vessels (chemical tankers) of similar size are engaged, the accommodation superstructures will likely extend to the ships’ sides (not only the bridge wings). Fenders may need to be considered to protect the superstructures from contact during the operation as a result of rolling and listing of one or both of the vessels.
The master of the tanker to which the fenders are to be secured should request copies of the certificates demonstrating that the primary fenders have been tested in accordance with industry best practice, which is at intervals not exceeding two years. Secondary fenders do not require testing because they are not fitted with safety valves.