Anyone wanting to build ten homes or more in Llanelli or Burry Port would first have to find roughly 80 square metres of existing car park, yard or roof and take its rainwater out of the sewers, under planning rules going before Carmarthenshire’s cabinet on Monday.
The rule is there to protect the Burry Inlet. In heavy rain the towns’ combined sewers, which carry rainwater and sewage in the same pipes, overflow into the estuary, and the bacteria they carry threaten the cockle beds and the shellfish waters around them.
Every new home adds sewage to those pipes. Carmarthenshire County Council‘s answer, written into its revised development plan, is that big schemes must take more rainwater out of the system than the sewage they put in, leaving the sewers with more headroom than before.
The guidance does the sums. A home’s peak sewage flow, divided by the rate at which rain runs off a hard surface, doubled for good measure, comes to about eight square metres of existing hard surface per house that has to be disconnected from the sewer. The council calls the figure provisional, but on that basis a 100-home estate would need to find around 800 square metres.
Who it catches
The rule applies to anything counted as major development that drains to the Llanelli wastewater works: ten homes or more, a site of half a hectare, a building of 1,000 square metres, or mineral and waste schemes. That covers Llanelli and Burry Port.
There is a clause for the crafty. Split a site into phases to dip under the threshold and the council will add the pieces back together and apply the rule to the lot.
Developers must look for their rainwater in a fixed order: on their own site first, by swapping a car park or yard for permeable paving or sending existing downpipes into soakaways and rain gardens, then in the surrounding streets, then anywhere in the works catchment. Only when all three fail, and only with the council’s written say-so, can they ask Dŵr Cymru to build a scheme instead.
Drainage for the new homes themselves does not count. Only rainwater already lawfully flowing into the combined sewer, disconnected and confirmed with the water company, earns credit.
Where a scheme removes more than it needs, the surplus goes on a council register, the Betterment Bank, which later developments can draw on case by case.
The cockles, and a complication
The Burry Inlet is the most important cockle ground in Wales, and it is in trouble. Parsons Pickles mothballed its Burry Port factory in August after what it called the “most challenging season in living memory”, with eight jobs lost.
The complication is that Swansea University research has linked the beds’ decline to cleaner water, after the 1997 upgrade of sewage treatment stripped out the nutrients cockles feed on. The new rule targets something different: the bacteria in storm overflows, which the guidance calls the principal risk to whether the shellfish waters can be fished at all.
The council had already agreed to adopt an earlier version of the rule. It goes back out to consultation because Natural Resources Wales has published new interim guidance for protected marine sites, and because the examination of the development plan changed the policy it hangs off.
The estuary’s rules already bite on the Swansea side, where nutrient pollution concerns stalled Persimmon’s 216 homes at Gowerton and forced a full environmental study.
The Burry Inlet document is one of four pieces of guidance the cabinet is asked to send out for consultation, alongside biodiversity and nature recovery, trees, woodlands and hedgerows, and health impact assessments.
If the cabinet and then full council agree, the consultation runs for six weeks. The rule only takes effect once the revised development plan is adopted, which the council expects in the autumn or winter, under Cllr Carys Jones, the cabinet member for rural affairs, communities and the Welsh language.
Monday’s meeting also decides the county’s parking overhaul and the new school transport policy.
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