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Mark Adding lime will increase the pH to a level which will effectively stop gas generation. There has been a research project on this method of stabilising sewage sludge. Also the lime will reduce the moisture content which may make it suitable from a geotechnical point of view. The 5% limit on organic content for lime stabilisation is a value that is used when the end product is to be used a pavement structural layer and you are relying on chemical reactions between clay and the lime to achieve a certain strength. It may not be an appropriate limit if they just want to make the sludge less sloppy so they can build over it. Steve Wilson, Technical Director on behalf of EPG Tel 07971 277869 www.epg-ltd.co.uk -----( Disclaimer )----- > > Information contained in this e-mail is intended for the use of the addressee only, and is confidential and may contain commercially sensitive material. Any dissemination, distribution, copying or other use of this communication, other than for which it is explicitly intended, without the permission of the sender is strictly prohibited. If you have received this e-mail in error, please advise the sender immediately and delete it from your system. Whilst all e-mails are screened for known viruses, the company cannot accept responsibility for any which have been transmitted. -----Original Message----- From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Mark Henderson Sent: 31 August 2012 10:21 To: [log in to unmask] Subject: Re: Reclamation of former sewage works From an engineering perspective, lime stabilisation only works up to an organic matter content of about 5% which quite often puts sewage sludges beyond the realms of stabilisation. First thing to do is to determine organic content by representative sampling and testing. Then approach a friendly contractor (Kier, McLaren, etc) and see what he thinks - however sounds to me if it is gassing then OMC is high - and even if stabilisation was feasible it would still contain high organic levels prone to gassing (ie. stabilisation will not reduce organic content or bind it to prevent gassing). I'm looking at a similar site (also 7ha and ex-STW) and cost-wise though you are looking at about:- Mob/demob - £7000 Supervision - £2k/week Engineer - £2.25/week Site strip - £0.20/m2 Excavation - £1.20/m3 Spreading and compaction - £1.20/m3 Lime stabilisation - £3.30/m3 Haz waste - £180/m3 Nonhaz waste - £110/m3 If that is not feasible then you could consider one or a combination of alternatives:- - drying sludges and recycling off site (eg. there are companies that turn sewage cake into sintered pellets for re-use) - reusing organic material in soft landscaping - look into reducing organic content (eg. are there areas worse than others that could be segregated thereby treating smaller volumes, screening etc) There may also be dewatering issues. Good luck - treating these sites from a contam perspective is the easy part, overcoming the engineering and cost/volume issues are more difficult. As I said - speak to a contractor first. -----Original Message----- From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Paul Burns Sent: 30 August 2012 17:13 To: [log in to unmask] Subject: Reclamation of former sewage works I've been been involved in preliminary discussions about the feasibility of redeveloping a former sewage works for residential housing. The site is approximately 7.7 ha in area and is currently open space. Investigations have revealed that a layer of sewage sludge approximately 2-3 metres thick is present across the majority of the site which is generating significant amounts of gas. I'm aware that similar sites have been remediated by stabilising the sludge with lime cement, in order render it geotechnicaly suitable and to reduce gassing potential. I would be interested to know if anyone has experience of reclaiming such a site, whether stabilisation is feasible, and what ball park treatment costs would be. 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