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Suggestion For Determining Road Pavement Ages

  • 1.  Suggestion For Determining Road Pavement Ages

    Posted 18 August 2019 18:42
    Dear Huda

    Re your post of 7 August (from the Municipality of Chatham-Kent, Ontario), can I humbly suggest a different approach to take in assessing pavement age? It worked for me 20 years ago and may be worth considering for your situation.

    Until I retired at the end of 2016 I was the Director Technical Services (City Engineer) at Dubbo Regional Council in western NSW. I have been an active member of IPWEA for the last 40 years.

    Dubbo is a regional hub for much of northwest NSW with an urban centre of 40,000 population and various surrounding villages and rural localities making up the remainder of the Local Government Area. In the 1990’s Dubbo Council managed a road network on 250 kms of town streets (all sealed) and 900 kms of rural roads (50% sealed, 50% unsealed).

    Asset Management as a comprehensive discipline was introduced universally into Local Government in NSW in a rewrite of the Local Act in 1993. Councils were required to create asset registers for all asset classes as best they could over the three years 1993 to 1995. Dubbo was an early adopter of asset management best practice as then recognised.

    Putting a date on when road pavements were created is a key part of any road asset register. For recently built roads this is usually straightforward because modern Council records and the memories/knowledge of your own technical staff can be relied on. However beyond about 30 years these sources of information either dry up or become unreliable.

    My approach in 1996 was to make the identification of road segment construction dates a research project and employ an outside resource to undertake same. Expecting an existing staff member to do this sort of work in their “spare time” is unrealistic. We were able to identify a former teacher from Dubbo with a passion and the necessary research skills to delve into available historic resources, as suggested to him by us. We engaged him on a casual hourly rate and an upper limit fee was negotiated, and renegotiated as necessary, depending on progress.

    The results were excellent. Within 6 months he had determined when 90% of all road segments were initially built. From there another 5% could be inferred simply because of their physical location relative to known segments, and the remaining 5% of ages could be “guesstimated” to an acceptable level of accuracy based on best available assumptions in discussions between technical staff and our researcher.

    More sources of data are available than you might imagine. In the hands of a dedicated and intuitive researcher you will be surprised what can be found, and the important thing to remember is that you only need to do this work once.

    Most pavements proved to be less than 90 years old. A small handful of downtown streets could be dated to 1900-1910 when some sealing of streets took place using coal tar and slag from coal gas production. In general, however, it was the spread of cars and lorries after World War One which was the catalyst for construction of most of Dubbo’s “old” paved streets using natural gravels and tar macadam.

    The sources of data I suggest you might look for include:

    * Council files relating to land subdivision approvals. Road construction is normally closely related in time to such approvals. Records back to 1970 should be pretty good, but even if patchy before then, all you are really wanting to do is get an approximate date for when a good sample of your Streets were created. Being 20 years on from the time we did our research should also mean that you will have 45 to 50 years of good records to rely on rather than the 25 to 30 years we had.

    * Official Council Minutes (of Meetings). These exist back to the 1860’s and 1870’s in NSW for larger towns and from 1907 for rural Shire Councils. Minute books are a legal requirement for Councils to maintain, even today, and from experience here, both subdivision approvals and Council decisions to build or rebuild streets and roads are generally mentioned, however briefly, in these historic Minutes. Your researcher only needs to read through them once and take mobile phone photographs of relevant pages for later collation and study.

    * In NSW central registration of land subdivision plans began back in the 1860’s. For key subdivision dates which might help place a number of streets into temporal context you can always go to your provincial land titles office to view selected survey plans of subdivision. The cost of doing this can become an issue, however, so it may be that only important subdivisions should be followed up in this way.

    * For many years NSW Councils were also required by the Local Government Act to maintain paper based Registers of Streets and Roads. Although these “went out of fashion” during the 1970’s and 1980’s you may be lucky enough to find it’s equivalent still floating around in hard copy format somewhere within the Engineering Department’s design office or hard copy plan room. They generally recorded significant milestones for each road such as dates that gravelling and regravelling occurred, and when sections were sealed and resealed.

    * One technical register of value at Dubbo was the bitumen sealing register. This covered several decades and was very detailed as to locations, dates, bitumen and aggregate application rates. I suspect this was driven somewhat by the bitumen supply companies and what was considered to be best engineering practice amongst practitioners. Oftentimes, though, this register will be stored and maintained in the operations area of the Engineering Department so may need to be sought out by the asset management team to unlock its potential as a data source.

    * Aerial photography became available from the 1920’s onwards. Each Australian State had its own central mapping authority and in NSW the relevant Government authority maintains to this day a full set of vertical aerial photography undertaken periodically by them for mapping purposes. These are valuable for plotting town growth at the periphery in particular. The construction of particular streets can generally be bracketed between the dates of successive aerial photographs to at least narrow down the years in which that street was built or converted from unsealed to sealed.

    * Historic mapping is also a source of data on town growth and when streets were built. NSW had a major burst of orthophotomapping during the 1970’s and these are a valuable source of direct visual evidence of roads built at or before the date of the photography they were based on.

    * The Local Library and Local Museum also usually have sets of oblique photographs on file taken during random joyflights by local residents at different time periods. These can be valuable in determining where the edge of town was at a particular time or what the status of roads in the downtown area was, as this was often where people doing a joyflight focussed their attention.

    * Council budget records are valuable if they are detailed enough to record expenditures on particular road projects. Follow these back through Council’s records as far as you can, noting that sometimes even the official Council Minutes will record broad details where the more fulsome paper files have long since been disposed of out of the Council’s filing system. From experience you may also find some accounting staff are better at maintaining their own private records system of past budgets than the central records system.

    * Sewerage records can be a valuable source of detailed data. The experience here was that when Sewerage was extended through Dubbo in about 1930 it’s planning and design was preceded by very detailed mapping of existing streets and buildings. Surveyors went through the town collecting a complete topographic map view of “everything” that was present so that construction crews, when they arrived on site, would not be surprised by what was in their way, or in the worst case, find that some properties were simply not sewerable. I suggest that a detailed viewing of all Sewerage work-as-executed drawings held by the local Sewerage authority can be a very worthwhile exercise in putting detailed dates on when streets were built and of the status of streets when the detailed survey was done for the design of each sewer. Note that in Dubbo, Council is/was also the Sewerage authority so accessing records here was straightforward.

    * In a like vein, Councils in NSW were always responsible historically for recording and maintaining the internal sewer drainage details of each premise connected to town sewerage. As house construction often followed pretty closely upon completion of the streets in any new area, finding the date on the drainage diagrams for the first houses built in each new area is a good way of assessing quite accurately when the street outside was built.

    * In a similar fashion, design and WAE plans of Council’s stormwater drainage systems and extensions are good sources of dates for when roads were built, and often contain survey detail of relevance. As the old saying goes the three most important aspects of road design and construction are “drainage, drainage and drainage”, so one always goes with the other.

    * Copies of the local newspaper can be invaluable for putting dates on hard to find subdivision details and Council’s own road projects where internal records no longer exist. Any researcher who enjoys their work will happily troll through these records (usually kept at the Library or Museum) with an eye out for photographs, articles, land sale advertisements and the like relating to new streets, road constructions and reconstructions, summaries of early Council budgets, Government grant announcements - anything really which puts a date to when a Street or Road was first created or subsequently rebuilt. In these days of mobile phones and other devices it is now simple to record an image of a relevant section from an old newspaper, and then move on quickly without taking too much time over that process.

    * Books on Local History are usually available for most communities. These are worth skimming through to ascertain or check when different sections of town were developed and for photographs especially which might show when particular streets were built or upgraded.

    * Direct knowledge of older citizens. Always be on the lookout for “old timers” who may be able to clearly recall when certain streets were built or upgraded. If different record sources are pointing to different dates for a particular road segment, ask around - you never know what might come back to you via the six degrees of separation.

    The process we went through may sound “hard”, but in reality the right researcher can actually do it quite easily, effectively and efficiently without you or your staff having to spend much time on it at all. I only suggest it to you because in our case it did work well.

    All the best.

    Stewart McLeod
    Emeritus Member IPWEA
    Dubbo NSW
    +61 418 636 489

    Sent from my iPad

  • 2.  RE: Suggestion For Determining Road Pavement Ages

    Posted 19 August 2019 21:18
    Thanks Stewart great post and thanks for sharing your vast experience.

  • 3.  RE: Suggestion For Determining Road Pavement Ages

    Posted 06 September 2019 01:18
    Great work (as always) Stewart, thank you for sharing.

    You are correct in saying this is not 'hard', it just needs commitment to what is an important task for building (and hopefully maintaining) key knowledge for a variety of roles in local government.  Determining useful life, valuation, age profiling and reporting and predictive modelling comes to mind.

    Stephen Verity | IPWEA Australasia