First of all, more information regarding the work is required and this information should be given to person qualified to do Ijtihad (juristic effort to infer expert legal rulings) so that he can get advice for his particular kind of work.
This answer covers, in general, the aspects of fasting while doing hard work according to scholars
The sawm (fasting) of Ramadan is an obligation upon every Mukallaf (person meeting the conditions to be held legally accountable for their actions). This is because Allah says in Qur'an:
شَهْرُ رَمَضَانَ الَّذِي أُنزِلَ فِيهِ الْقُرْآنُ هُدًى لِّلنَّاسِ
وَبَيِّنَاتٍ مِّنَ الْهُدَىٰ وَالْفُرْقَانِ ۚ فَمَن شَهِدَ مِنكُمُ
الشَّهْرَ فَلْيَصُمْهُ ۖ وَمَن كَانَ مَرِيضًا أَوْ عَلَىٰ سَفَرٍ
فَعِدَّةٌ مِّنْ أَيَّامٍ أُخَرَ ۗ يُرِيدُ اللَّـهُ بِكُمُ الْيُسْرَ
وَلَا يُرِيدُ بِكُمُ الْعُسْرَ وَلِتُكْمِلُوا الْعِدَّةَ
وَلِتُكَبِّرُوا اللَّـهَ عَلَىٰ مَا هَدَاكُمْ وَلَعَلَّكُمْ
The month of Ramadhan [is that] in which was revealed the Qur'an, a
guidance for the people and clear proofs of guidance and criterion. So
whoever sights [the new moon of] the month, let him fast it; and
whoever is ill or on a journey - then an equal number of other days.
Allah intends for you ease and does not intend for you hardship and
[wants] for you to complete the period and to glorify Allah for that
[to] which He has guided you; and perhaps you will be grateful. [Surah Al-Baqarah : 185]
As you can see above, the Lawgiver (Allah) has granted a concession to break fast to people who are sick, travelers, and those who come under those categories. However, those who do hard work do not come under these category (Sick or travelers and others) and they are obliged to fast. It is impermissible to break fast due to hard work. So, they have to form the intention to observe the fast of Ramadan from the night before and to start the day fasting.
Secondly, according to scholars, the person should analyze different other possibilities in order to ease the hardship for Ramadan for e.g. make his working hours during night or distribute the working hours in manner that he can both work and fast. In general, he should try to ease the hardship on him due to this work. Some scholars even have an opinion that if the person is unable to find other work without these hardships and they fear that they may suffer due to unfair laws that do not permit them to practice their religion, then it becomes obligatory on them to migrate from these countries to somewhere else where they can practice the obligations of their religion and their daily life, and interact with Muslims in righteousness and piety.
However (if all the above is not possible), if they are forced to break the fast (and this is after they start fasting), for example due to severe hunger, then it is permissible for him to break the fast only to the extent that wards off any harm or hardship and he must refrain from eating and drinking for the rest of the day (till maghrib) and later has to make up for that fast at the proper time.
This is what is indicated by the shar`i evidence from the Qur'an and Sunnah and it is what is indicated by the words of the scholars of all madh-habs.
And remember Allah says in Qur'an:
And whoever fears Allah - He will make for him a way out And will
provide for him from where he does not expect. And whoever relies upon
Allah - then He is sufficient for him. Indeed, Allah will accomplish
His purpose. Allah has already set for everything a [decreed] extent. [Surah At-Talaq : 2-3]
So, I ask the person in question to fear Allah regarding his affairs. Also, take a look at below rulings regarding fasting with hard work.
وبالله التوفيق وصلى الله على نبينا محمد وآله وصحبه وسلم.
Sawm while doing a hard job- Fatwas of the Permanent Committee
Breaking Sawm due to hard work- Abdullah ibn Muhammad ibn Humayd and Abdul-Aziz ibn Abdullah ibn Baz
Breaking Sawm due to hard work - Al´Allâmah Muḥummed Nâṣir ad-Dîn al-Albânî