Blog Post: Porth Yr Ogof - Diving and Data. By Christine Grosart, Project Manager. 25th June 2016

     Porth Yr Ogof

An extremely busy year for both Rich and I meant that getting over to Porth this year was looking impossible, until I spotted a window of opportunity on a Saturday afternoon.

Of course, that means lining up the weather too and I kept a close eye on the Environment Agency River Levels Data website, which records the levels of the Mellte at regular intervals. Despite sporadic heavy showers, the water level in Tradesman's Entrance Station 3 was anecdotally low, the distance between the water surface and the top of the 'flat ledge' on the right being 64cm.

I decided to dive first and do the other data recordings at the other sites later. Kitting up in the car park, there were several mini buses of children going caving. I slid down to the water and to my horror, my go-pro 'pinged' from its string which had been tied to a bolt-snap and D-ring and vanished into the bubbling water.

Porth is notorious for eating dive gear, often dropped in the entrance and it is taken away by the fast flowing water, never to be seen again. I should have known better and put the go-pro in a pocket - but, furious with myself for not taking my own advice, continued with the dive in any case.

Standard photo of Tradesman's Entrance
Station 3

The flow in the entrance was moderate. I spotted 2 medium size trout which were pale in colour but not completely white, close to the first couple of tie-offs. I didn't have a helmet or helmet mounted lights, but used instead a Halcyon Focus hand held torch and back ups mounted on my harness. 

As I approached the Secci disc, I stopped so that I didn't disturb the visibility ahead.

The line is tagged with red cable ties at 50cm intervals so I put the focus onto a fairly tight beam and could just about make out the secci markings from exactly 5m away, counting the tags as I moved forward.

The depth of the Secci was 2.9m and the water temp was recorded as 13 degrees C.

I noted some detritus starting to form on the face of the secci, despite it facing downstream.

I continued upstream, noting some larger, whiter trout and 3 bullheads, one of which was grubbing around in the silt.

River Levels data. Standard image of Station 6.

There was a thick layer of silt on the normally clean washed passage floor and the viz seemed gloomy to me, with lots of particles in suspension.

I then approached the 'Pot' which has been neatly re-lined by Max Fisher, with a rope protector in situ, doing it's job to stop the line fraying over the edge of the pot.

This seems the way forward as I don't see much value in damaging the cave further by putting in a bolt for this purpose.

The flow seemed to get a little stronger as I continued upstream, possibly due to recent bursts of rain which may have started to make their way into the cave. As I got to the cobble slope which surfaces in Upper Cave Water Chamber, I was shoved quite violently down the tube and decided to turn around - which took some doing - as the flow was definitely getting stronger.

Children on their caving trips

I had the usual low viz roller coaster ride home and once de-kitted in the car park, headed back into the cave to look for my Go-Pro which I luckily found just behind the water entry spot, pinned to a rock by the high flow.

It was already past 4pm so I elected not to dive again but instead visit the other stations to take standard photos of each station and water temperature readings where I could.
It's a pleasant job to wander down to Main entrance (station 4) and sit in the tranquility once the cavers have gone home. I spotted a small brown fish darting around in the entrance pool - and one welly boot!
It's a short walk down to the resurgence where I took a temperature reading with my D-Timer and also up to Top entrance where there were some really pretty wild flowers growing. 
Back up the steps, a grey squirrel was busy running around the tree trunk. 

PB data sheets as an aide memoire

Depth gauge and reel, used for temperature data

Red Campion

Meadow Buttercup

Herb Robert

Data: Porth Yr Ogof. 25/06/2016. Christine Grosart. Dived.

Your name:	christine grosart	Observation date:	25/06/2016
Site Visited	Porth yr Ogof

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Church Sinks Observations
The river water was Flowing under the bridge
Church sinks flora: Not noted
Church sinks fauna: None seen
Church sinks water temperature: D-Timer would not record (too shallow)
General Church Sinks observations: Water partially flowing under the bridge, which was surprising given the initial low water levels in Porth. Wondering if the lunchtime rain had started to make it flow later on.

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Top Entrance Observations
Accessible by walking up the riverbed?: Yes
Top Entrance Flora: Red Campion Meadow Buttercup Herb Robert
Top Entrance fauna: None
Top Entrance water temperature: Not read but 13 degrees during dive
Top Entrance general observations: 1 intact plastic carrier bag (removed) in river bed.
Dives done into Top Entrance?: No

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Top Entrance Dive Log
Top Underwater Visibility:
Top Water flow:
Tope entrance underwater fauna:
Top Entrance other observations:

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Tradesman's Entrance Observations
Tradesman's flora: Hartstongue fern
Tradesman's fauna: Grey Squirrel in tree by car park, top of steps
Tradesman's water temperature: 13
Tradesman's water level: 64cm (25 inches)
Did you dive at Tradesman's Entrance?: Yes

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Tradesman's underwater visibility: 5.0 exactly with secci and tagged line, using Halcyon Focus on medium/tight beam. No helmet light.
Tradesman's water flow: Low in entrance, becoming higher beyond the pot and very high by Essers junction
Tradesman's underwater fauna: 2 medium size trout, pale but not completely white 2 large trout, mostly white 3 bullheads (white) throughout the cave and one seemed to be digging in the silt
Tradesman's general observations: Secci station depth: 2.9m Lots of particulate in the water, viz quite brown and poor. Lots of silt covering normally clean washed passages. Ladder had fallen down from first airbell so replaced it. New line in the pot looks very good and clean and rope protector doing a good job. Some snoopies have broken so a good job for a trainee to repair some. Silt screws on the sand banks before 4ways still totally solid. Lost go-pro in entrance so unable to shoot video or images (found post-dive but too late for a second dive.)

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Main Entrance Observations
Main Entrance flora: Usual moss and ferns
Main Entrance fauna: 1 small brown fish darting around in the main entrance pool
Main Entrance water temperature: 12 (at 2.2m depth)
Main Entrance general observations: 1 lager can and 1 welly boot

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Resurgence Observations
Resurgence flora: None noted
Resurgence fauna: None noted
Resurgence water temperature: 13 (at 1m depth)
General resurgence observations:

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Little Neath River Cave Observations
LNRC Observations:

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Final Observations
General Observations:

Data: Little Neath River Cave. 15/05/2016. Cristian Cristea. Dived

Your name:	Cristian Cristea	Observation date:	15th May 2016
Site Visited	Little Neath River Cave

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Church Sinks Observations
The river water was
Church sinks flora:
Church sinks fauna:
Church sinks water temperature:
General Church Sinks observations:

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Top Entrance Observations
Accessible by walking up the riverbed?:
Top Entrance Flora:
Top Entrance fauna:
Top Entrance water temperature:
Top Entrance general observations:
Dives done into Top Entrance?:

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Top Entrance Dive Log
Top Underwater Visibility:
Top Water flow:
Tope entrance underwater fauna:
Top Entrance other observations:

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Tradesman's Entrance Observations
Tradesman's flora:
Tradesman's fauna:
Tradesman's water temperature:
Tradesman's water level:
Did you dive at Tradesman's Entrance?:

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Tradesman's underwater visibility:
Tradesman's water flow:
Tradesman's underwater fauna:
Tradesman's general observations:

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Main Entrance Observations
Main Entrance flora:
Main Entrance fauna:
Main Entrance water temperature:
Main Entrance general observations:

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Resurgence Observations
Resurgence flora:
Resurgence fauna:
Resurgence water temperature:
General resurgence observations:

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Little Neath River Cave Observations
LNRC Observations: First trip down through Bridge Cave sump 1 to LNRC and some distance crawling in low water in The Canal before deciding to turn around. Sump 1 was pretty clear, at least 3-4m visibility, with a thick layer of brown foam on surface near entrance. There was also a strange smell, felt on the way back from the sump. Also spotted four big trouts in the sump1 and 2 other smaller ones in The Canal. No litter found in the cave, and the rescue drums were intact and sealed. Some footage taken on a gopro, will check it later.

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Final Observations
General Observations:

Data: Porth Yr Ogof. 14/05/2016. Rupert Massey. Dived

Your name:	Rupert Massey	Observation date:	14/05/16
Site Visited	Porth yr Ogof

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Church Sinks Observations
The river water was
Church sinks flora:
Church sinks fauna:
Church sinks water temperature:
General Church Sinks observations:

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Top Entrance Observations
Accessible by walking up the riverbed?: Yes
Top Entrance Flora:
Top Entrance fauna:
Top Entrance water temperature:
Top Entrance general observations: Nothing of note, the water level was low and the visibility was good.
Dives done into Top Entrance?: No

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Top Entrance Dive Log
Top Underwater Visibility:
Top Water flow:
Tope entrance underwater fauna:
Top Entrance other observations:

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Tradesman's Entrance Observations
Tradesman's flora:
Tradesman's fauna:
Tradesman's water temperature: 12 degrees C
Tradesman's water level: approx 50cm BELOW step
Did you dive at Tradesman's Entrance?: Yes

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Tradesman's underwater visibility: Medium
Tradesman's water flow: Medium
Tradesman's underwater fauna: 2 albino trout. Definitely fewer than I have seen before, possibly as a result of flow.
Tradesman's general observations:

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Main Entrance Observations
Main Entrance flora:
Main Entrance fauna:
Main Entrance water temperature:
Main Entrance general observations:

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Resurgence Observations
Resurgence flora:
Resurgence fauna:
Resurgence water temperature:
General resurgence observations:

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Little Neath River Cave Observations
LNRC Observations:

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Final Observations
General Observations:

Blog Post: by Maxwell Fisher. 19th & 26th April 2016

Tuesday the 19th saw me diving at Porth Yr Ogof for the first time in 2016.
I had been monitoring the weather forecasts and River Mellte gauge levels for some time, hoping to get in. Finally time off work and weather aligned and I was able to make a trip over.
The water level was approximately one fin length (Mares Quattro) below the step; steady progress was made along the passage in light to moderate flow. 

Line abrasion from flow in the 'Pot'

The first point of note was the abrasion partway down the first pot. The sheath of the line was worn through, exposing the core which showed some signs of wear. I decided it wasn’t about to break on me anytime soon and continued surfacing in the first airbell. 
A quick check on gas pressures was made before I continued onto the next airbell. Again a quick check on gas pressures was made before continuing onto the upper cave water chamber. 
About 10m before the junction to Esser’s passage, some loose line was billowing down the passage. I continued on and saw that it was coming from the pot leading down to the rest of the cave. I continued along the main line and surfaced in the upper cave water chamber, the boulder slope easily passed in a wetsuit and 7l cylinders. 

I crawled through to the chamber proper and removed my fins and one 7l cylinder, keeping one on to pass the next short sump. This sump is quite short, at 4m long I would estimate and had crystal clear waters. A cobble slope restricts entry to one point. Surfacing in a section of cave I had not visited before, I dumped my kit and began crawling to find the next sump. This part of the cave is a wide bedding with a cobble floor. 
The next sump soon presented itself and I spent a few moments floating in it trying to glimpse what was beyond. Retracing my route back through the cobbles, I was soon kitting up ready to pass the short sump back. 
I had ample gas reserves left so decided to tidy up the line billowing out of Esser’s passage on my exit. I pulled it in hand over hand, coiled and attached it to the bolt above the pot to keep it out of harms way. It was clear that the belay at the bottom of the pot was intact, however I decided to leave that task for another day, riding the gentle flow of the cave back to the tradesman entrance.

After a quick sandwich I decided to have a walk up the dry river to locate the other entrances which I had not looked at before, some pictures are shown below:

Cwmbran Entrance

Cwmbran Entrance

Top Entrance

Main Entrance

I decided to visit again on the 26th to make repairs to the line, I planned two dives: the first to repair the pot line, the second to repair the Esser’s line. I had been unable to get a good fill in my 7’s, so decided to dive with a part full 7 and a part full 12 to give me plenty of time to fix the line in the pot. The flow was slightly lower today, the gauge level having dropped from 0.26m to 0.23m since my visit the previous week. 

Easy progress was made to the pot where I spent a good 10 minutes assessing before I made any changes. I examined the roof, finding a small air bell but no natural anchors to create a deviation from. I noted a flake near the bottom of the pot which I thought to be useful for holding the line away from the pot wall. I tentatively cut the old line and began attaching the new one working upstream so as to always have contact with the exit line. In total this dive lasted 32 minutes, I was very chilled on exit. 

A diagram of the current situation in the pot is shown below (side view):

The carpark afforded no warmth during lunchtime with sleet and snow showers. A chilly diver re-entered the water with the intention of fixing the Esser’s passage section. 

Easy progress was made using just about 1/3 of one cylinder leaving 1/3 of the second cylinder to work with, I removed my coil from the S/s bolt I had made the previous week and descended the pot, new territory for me. 

To my surprise three belays at the bottom of the pot were intact, the break in the line having occurred much further into the cave. Once at the bottom of the pot the rock belay is intact, moving along the passage a little further a lead weight belay was intact and further again the final intact belay was a thread in the right hand wall opposite a cobbly slot in the floor which I believe is Esser’s passage itself (?)

I had a large amount of rope in my hand at this point, having added to the coil to this point rather than reducing it and was fairly cold so I decided to exit and come back again to further explore this section of the cave. I was glad to get back to the surface, ditch my wetsuit and drive home with the heating on full blast.

A plan view sketch has been drawn of the situation:

Data: Porth yr Ogof. 26/04/2016. Maxwell Fisher. Dived.

Your name:	Max	Observation date:	26/04/2016
Site Visited	Porth yr Ogof

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Church Sinks Observations
The river water was Flowing under the bridge
Church sinks flora:
Church sinks fauna:
Church sinks water temperature:
General Church Sinks observations: Small flow down river

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Top Entrance Observations
Accessible by walking up the riverbed?: Yes
Top Entrance Flora:
Top Entrance fauna:
Top Entrance water temperature:
Top Entrance general observations:
Dives done into Top Entrance?: No

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Top Entrance Dive Log
Top Underwater Visibility:
Top Water flow:
Tope entrance underwater fauna:
Top Entrance other observations:

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Tradesman's Entrance Observations
Tradesman's flora: The usual
Tradesman's fauna:
Tradesman's water temperature: 8 c
Tradesman's water level: fin lengthbelow
Did you dive at Tradesman's Entrance?: Yes

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Tradesman's underwater visibility: 5m
Tradesman's water flow: low for Porth
Tradesman's underwater fauna: Some fish seen, white ones with spots. Two mating frogs/ toads seen near exit on way out
Tradesman's general observations: Line repaired in first pot and bottom belay moved from rock at base of pot to flake which holds line away from the wall, tube used to protect line running over lip of pot. Not noticed before but is actually a small air bell above the pot. A plastic tub (sofonlime??) could be brought in flooded then filled/ sealed and used as a float belay above pot if further problems occur as an option instead of drilling a bolt. Second dive attempted to sort out Esser's line, descended pot and continued along passage, line was intact past lead weight belay to thread belay on right hand wall, then had been quite cold and I had a large amount of rope to deal with so tidied it and exited shivering all the way out.

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Main Entrance Observations
Main Entrance flora:
Main Entrance fauna:
Main Entrance water temperature:
Main Entrance general observations:

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Resurgence Observations
Resurgence flora:
Resurgence fauna:
Resurgence water temperature:
General resurgence observations:

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Little Neath River Cave Observations
LNRC Observations:

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Final Observations
General Observations: Hail stones/ snow in April !

Data: Porth Yr Ogof. 19/04/2016. Maxwell Fisher. Dived.

Your name:	Max Fisher	Observation date:	19/04/2016
Site Visited	Porth yr Ogof

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Church Sinks Observations
The river water was Flowing under the bridge
Church sinks flora:
Church sinks fauna:
Church sinks water temperature:
General Church Sinks observations: Very small flow under bridge

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Top Entrance Observations
Accessible by walking up the riverbed?: Yes
Top Entrance Flora:
Top Entrance fauna:
Top Entrance water temperature:
Top Entrance general observations: Top entrance clear, water well down inside below line, easy access to water
Dives done into Top Entrance?: No

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Top Entrance Dive Log
Top Underwater Visibility:
Top Water flow:
Tope entrance underwater fauna:
Top Entrance other observations:

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Tradesman's Entrance Observations
Tradesman's flora:
Tradesman's fauna:
Tradesman's water temperature: 8
Tradesman's water level: One fin length below step
Did you dive at Tradesman's Entrance?: Yes

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Tradesman's underwater visibility: 5
Tradesman's water flow: lowish
Tradesman's underwater fauna: some fish seen throughout cave
Tradesman's general observations: See: http://www.cavedivinggroup.org.uk/cgi-bin/CDG/BBS/threadall.html?Thread=4570

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Main Entrance Observations
Main Entrance flora:
Main Entrance fauna:
Main Entrance water temperature:
Main Entrance general observations:

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Resurgence Observations
Resurgence flora:
Resurgence fauna:
Resurgence water temperature:
General resurgence observations:

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Little Neath River Cave Observations
LNRC Observations:

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Final Observations
General Observations: