A Brief History of Newport Sewerage Print
Written by Robbie   
Monday, 10 May 2010 10:22

Newport Sewerage Network on Google Earth Overlay

 

The current sewerage system in Newport dates from principally the end of the 19th and the first two decades of the 20th Centuries. At that time the local authority with primary responsibility for its installation and maintenance was the Cemaes Rural District Council, whose acronym (CRDC) can still be seen on many SAPs (manholes) and other sewerage infrastructure places.


The system installed then, as now, is predominantly a "combined system" ; by which is meant that the same infrastructure is used for both the drainage of surface water run-off from buildings and street gutters, as is also used for the disposal of waste water and sewage from within buildings.


The result is that during, and in the immediate aftermath of, periods of severe rainfall events (i.e. storms) the system can become overloaded with a throughput or flow-rate demand greater than it can handle. For instance current computer modelling, done by DC/WW, for the town main is based on a calculated 'dry weather flow-rate' (DWF) of  5.4 l/s[1] ; whereas, the modelled 'Storm flow rate' (SFR) is set at 14 l/s[2]. In point of fact, storm condition readings have shown discharge rates in the system exceeding 24l/s, or more than x4 the dry flow rate.


In the early 1970s the Statutory Water Undertaker ("SWU") completed a 'so-called' Long Sea Outfall ("LSO") which stretched from a simple first stage maceration plant, located immediately to the west side of the Old Lifeboat Station at Y Cwm, out into the Bay to a point 380m off the coast at Pen Catman ("Cat Rock"). The process of discharging untreated sewage to immediate vicinity of coastal waters was said to be only a 'temporary' solution, as in due course the then anticipated European Legislation on bathing waters quality ("BWQ") would demand treatment of all sewage prior to coastal waters discharge. At this time there was no installation of any plant to 'treat' the sewage biologically, only a maceration and screening installation down at the Cwm.


In 1997 a detailed Study and Report[3] was done on the sources and levels of sewage contamination parameters, known as Faecal Indicator Organisms ("FIO"), in the whole of the Nyfer (“Nevern River”) Catchment, including also the waters of the Newport Estuary.


The findings indicated that whilst so-called farm run-off into the headwaters of Nyfer Catchment was a major source of faecal indicator organisms, during and after severe weather episodes (i.e. rain storms), generally a full 75% of the FIO budget load in the catchment came from sewer based discharges. This was at a time (summer 1997) when the record of bathing waters samples taken off Treath Mawr (the Big Beach), whilst passing the imperative or mandatory standards for FIO parameters, was never the less regularly failing the Guideline Standard of the 1976 EU BWQ Directive.


As a result of the findings in this Report, and at long last, the then Chairman of the Board of Welsh Water himself came to a meeting in the Memorial Hall (Oct 1998)and promised than within the next 5-year rolling programme of their Capitol Plant Improvement they would provide a full 3-stage Waste Water Treatment Works ("WwTW") for Newport, including third stage UV (Ultra violet) treatment for destruction of viruses left untouched by the bacteriophage treatment.


In the result, an engineering report was commission in 2001 for the installation but for only a 2-stage settlement and anti-bacterial sedimentation treatment works. However, rather than siting this down in the Cwm valley behind the Old Lifeboat House, which is the natural gravity base of the sewerage network, the Report placed the new WwTW up on 'Rhigian Farm' more than 800m (½ mile) to the east and up on top of the coastal cliffs more than 55m higher than the town main as it reaches Y Cwm behind the Old Lifeboat Station.


In order to supply this new Newport WwTW, DC/WW were then forced to install, at great water ratepayers expense, a continuous (24/7) duplex pumping station down at the Cwm instead, to pump the sewage up the significant height and over this considerable distance. Involving a full kilometre of sewers to supply and drain the WwTw. This was largely all done in order to cater to the concerns of, and indeed the access disputes between, the local landowners concerned. There was no community involvement in the consultations on this process, yet alone informed debate about its consequential effects whatsoever.


One such entirely predictable effect has of course been that during the heavy rainfall events (rain storms), precisely when the contamination of FIO parameters in the River system is at its greatest due to excessive farm run-off ; that is now also precisely when the pumping capacity down at the Cwm Sewage Pumping Station ("SPS") is unable to meet the demand, and a combined storm overflow ("CSO") comes into operation which simply by-passes the SPS, and therefore also the WwTW, entirely and instead simply discharges the 'combined' sewage run-off solution directly into the LSO. In effect, a simple re-iteration of the 'double whammy' effect previously identified in the Prof Kay study.


A couple of years later over the period 2002/3 DC/WW was, as reported to us, able to access grant aid funding to assist with a significant 'upgrade' to the Newport Sewer Main, by way of the laying of a larger diameter relief sewer, including across the Parrog, which would allow for compliance with the provisions of EU Waste Water Directive, given interal UK effect by Regs. in 1994. Including specifically as to the closure of the Combined Storm Overflows ("CSO") in the system, which it was considered would not then be needed once a relief sewer was installed. That was certainly the 'promise' made by DC/WW at the time as a benefit to be gained to the community from the works.


However, in the event, when the contractors came to install this relief sewer across the Parrog, they 'discovered' that a house built in the 1970s had been built directly over the top of the 'old' town main, against policy on such matters, and that consequently to comply with sewerage rules the 'old' Parrog Main would have to be capped and closed under this property, and consequently that the 'relief' sewer would have to become a 'replacement sewer' instead, across this part of the 'mid-Parrog' front.


NAEG is still left suspicious and concerned as to the extent to which this clearly unsatisfactory arrangement, creating in effect a two into one, choke point just before 'Ty Newydd', has contributed to a reduction in the flow-rate capacity of the new “relieved” system. What we know is that in the event the CSOs, both at the Parrog and next to the footbridge over the 'school stream' (known to DC/WW as 'The Elms' site), far from being closed, have been kept and are now due to be upgraded. The Parrog CSO has just this year been granted a brand new Discharge Consent by the EA(W) (for details see here).


Also it was found at the time the relief sewer was being completed in 2003 as far as the Cwm that, during and immediately after rain storms, sewage was 'backing-up' in the Lower Parrog area ('Bron Llys' and westward). In order to prevent the occurrence of sewage back-up into the domestic properties in the area (Bron-Llys to Bettws) non-return valves or rather flaps were installed. The need for these was self evident and obviously much welcomed by the residents concerned.


However, due to the ingress of sand sedimentation, seemingly blocking the LSO nearly entirely, at around the same time, a CSO was also “installed” under the slipway in front of the Old Lifeboat Station. This was arranged to operate from the manhole chamber, to the right of the Lifeboat House, where there had been some backup emerging, to discharge instead directly into the culvert carrying the Cwm stream waters under the coastal path to the left of the Lifeboat Station. This culvert itself then discharges directly on the open beach on the Cwm to the left of the slipway, which has been a traditional place for picnicking and for bathers using Cwm waters to change etc.

It was claimed by DC/WW again that this was only a temporary measure which might never or only rarely be needed. They claimed that it didn’t need a statutory discharge consent from the EA(W) because it was only an emergency measure, undertaken to protect human life and health in an unforeseeable emergency, as to which see an exceptional defence under the relevant legislation[4]. The NAEG position is that this is a palpably absurd position to take to excuse the creation of a permanent installation arrangement which has now been in ‘operation’ for years.

Originally the EA(W) appeared to us to accept this unacceptable position. However, since we have raised the matter with them, their position is now to have just recently refused a formal discharge consent application for this CSO, on the basis that it is an ‘unauthorised’ discharge for which only a temporary need has been established[5], as respects which they agree they’ll take criminal enforcement action, in the event of their having (or being given) evidence of its use. However, no monitoring equipment was ever installed and the EA(W)'s acceptance of the situation is based only on very intermittent inspections.

More recently still in the winter of 2006/2007 it was noticed that the concrete entablature surrounding the LSO, where that passed through the bottom of the tidal median, and therefore where the effect of the low tide surf is greatest, off the Lady's Bathing Beach (just beyond Y Cwm), had started to break up. Eventually it was determined by the following winter that the LSO had completely broken up. Consequently, in the spring of 2008 DC/WW installed a short (40m) length of re-placement outfall to the end of the broken section, and secured a dispersal discharger to the sea bed just 1m below mean low water depth.


However, once again it was declared at the time that this was accepted as only a 'temporary' solution. Fortunately the fulfilment of that commitment is now at last in sight. As the latest news is that DC/WW will be presenting an Exhibition in the Memorial Hall imminently, illustrating the replacement LSO which they have now scheduled for completed by Aug of next year (2011). So hopefully some good news to end on !



[1] Refer to para 6 of current Cwm SPS CSO storm discharge consent

The rationale for deciding on the ‘dry weather flow rate’ is set out at para 6 of the Treated Discharge Variation Consent as being derived from the following calculation, namely “the average daily flow to the treatment works during seven consecutive days without rain (excluding a period which includes public holidays) following seven days during which the rainfall did not exceed 0.25 millimeters on an one day”.

[2] More accurately 13,7 l/s (storn flow condition) per para 4 of same consent


[3] Faecal Indicator Organism , Sources and Budgets for the Nyfer Catchment, Pembrokeshire

June 1997 A Report to Dwr Cymru and the Environment Agency

By Dr Mark Wyer, Dr. John Crowther & Prof David Kay


[4] unlawful discharge of sewage into controlled waters was needed “in an emergency in order to avoid danger to life or health”, as to which see s.89(1)(b) of the Water Resources Act 1991.

 

[5] This on the basis that once the new replacement and larger diameter LSO is completed next year there’ll be no case any longer whatever for this CSO.

 

 

 

 

 

Last Updated on Wednesday, 09 April 2014 11:55