The culvert runs underneath the site of the Grinkle Ironstone mine.
Internally the culvert is on the verge of total collapse, so I really wouldn’t recommend emulating my visit, a previous collapse in 1927 flooded the mine and trapped miners underground.
At the southern entrance of the culvert a large pool of water has backed up due to a collapse, here the tunnel seems to be cut into solid rock.
Interesting post. We walked through this site about a year ago (after visiting the Grinkle fanhouse) and saw the large collapse in what we thought was the old pit yard.
If anyone is interested a nice circular walk can be done in this area taking in the Boulby alum quarries and Grinkle ironstone mine remains, finishing with a pint in the Cod and Lobster at Staithes. Apparently there were considerable remnants of the Boulby ironstone mine standing until the potash mine was built…..