DENY, DENY, DENY – The On-going Saga of Colliery Dams
Lawrence Rieper: June 28, 2013
DENY, DENY, DENY – The On-going Saga of Colliery Dams: More of what the City would like us to believe and what the citizens are discovering along the way.
I recently discovered the “Chase River Inundation Study -1963” at BC Archives (CM/B 2547 # 1247 –Sheet 1 & CM/C 2667 # 584 – Sheet 2). These maps (no report was available) were produced by BC department of Lands & Forests, Surveys & Mapping Board, Topography Division (scale 1” = 1000’). Since Harwood Improvement District relied on the province prior to its incorporation into the City of Nanaimo in 1975, this study was probably paid for and produced by the province. However, the City of Nanaimo has owned Westwood Lake since 1957, and the inundation shown almost reached the western boundary of the city. One might presume that they received a copy of the map in 1963 and certainly should have acquired the original from Harewood in 1975. Conversations with former emergency coordinators for the city reveal that they had no knowledge of this inundation study. What happened to it? Was it withheld by former Harewood officials and kept in a basement somewhere, like a lot of other documents, as some legends have it. Or was it simply discarded by city staff after amalgamation, as another legend has it. Maybe, it is still buried in the vault at City Hall.
The 1963 inundation map illustrates what I had long suspected, that water flows in a gully from Westwood Lake alongside the hydro line down stream into the Chase River. It shows a dotted line from the southeast corner of Westwood Lake to Power Line Dam (now known as Morrell Lake), then a solid line to Reservoir #2 (Upper Colliery Dam). Solid lines go from #1 and #2 Reservoirs to Howard #3 (Middle Colliery Dam) and thence to Howard #4 (Lower Colliery Dam), continuing on to the inundation boundary in Harewood below. Perhaps surprisingly, this boundary though similar to both the 2002 and 2012 studies actually covers a wider area. To the northeast, most of Robbins Park is flooded. In the southeast, the flood almost reaches Ninth Street, and it extends in the east well past Park Avenue. In the southwest, it runs south and west of a line between Bruce and Eighth and Howard and Seventh. In the northwest and north, it covers much less of Sixth Street, which is a bit incongruous. The outer boundary has a solid line while a slightly smaller inner boundary has a dotted line (related to 210 and 280 acres).
In the absence of an accompanying report, one has to make some assumptions from the notations on the map. The first is that all the dams mentioned have breached and the water flow is as shown, which is fairly obvious. The inundation area shows two values:
One – 28,000 cfs (cubic feet per second) flood yields 210 acres. The other – 36,000 cfs flood yields 280 acres. We don’t know whether or not some hypothetical major flood is included in this study or to what extent Westwood Lake might flood. We also have no comparable figures of the actual 2002 and 2012 flood areas to compare with. However, we are given some descriptions of the various dams:
Power Line – earthfill, 27 feet high, 176 acre feet (217,092 cubic metres), unlicensed;
#2 Reservoir – earthfill, 15 feet high, 45 acre feet (55,506 cubic metres);
#1 Reservoir – concrete gravity, 30 feet high, 67 acre feet (82,643 cubic metres);
Howard #3 – earthfill/concrete upstream, 35 feet high, 130 acre feet (160,352 cubic metres), unlicensed;
Howard #4 – earthfill, 75 feet high, 200 acre feet (246,695 cubic metres), unlicensed.
Total capacity = 618 acre feet (762,291 cubic metres). Compare this figure (762,291 cubic metres) with those extrapolated from the 2002 Chase River Dams Incremental Damage Assessment of all the Chase River dams breaching releasing a total of between 390,000 to 422,000 cubic metres (please see my “Is Nanaimo Safe” for details). Or compare the 762,291 cubic metres figure with those extrapolated from the 2012 Chase River Dams Breach Flood Inundation Study of the two Colliery dams breaching during a one-hundred year flood to a Probable Maximum Flood – 312,000 to 443,000 cubic metres (again, see “Is Nanaimo Safe”). Clearly, the 1963 study deals with a flood of a different magnitude – and even without a flood, almost twice the water considered in the 2002 and 2012 studies. Who remembers Morrell Lake being drained a few years ago and a new emergency outlet was installed? Somebody knew its significance downstream!
Despite the previous statement, another point of interest is that in 1963 like Morrell Lake, the two Colliery dams were unlicensed, perhaps indicating that these pools were considered of little importance because of their relatively small size. Now, comparing the relative size of the watersheds and stored water of the Chase River, Millstone River and Nanaimo River, the former is obviously considerably smaller than the other two, yet, unaccountably, has the highest possible Dam Failure Consequence Classification.
Besides the 1963 figure quoted previously, I have discovered a number of different water volumes for the two Colliery dams (those marked * are from bathymetric surveys)
27 Million Gallons = 122,740 cubic metres (assuming Imperial gallons) – 1910, Report on the properties of Western Fuel Company by Harry J. Lewis, A.F. Buckham Papers MS 0436, Volume 32, file 10. BC Archives (Lower Dam only in existence at this time)
*78.8 and 80.1 dam3 = 78,000 and 80,100 cubic metres – Middle and Lower Colliery Dams – April 1994, Chase To Nanoose, Water Allocation Plan, BC Ministry of Environment, Lands & Forests.
*92,600 and 173,000 cubic metres – Middle and Lower Colliery Dams – 2002, Middle & Lower Chase River Dams Spillway Hydrology Study and 2010, Seismic Hazard Assessment Middle & Lower Chase Dams.
*110,000 and 112,000 cubic metres – Middle and Lower Colliery Dams – 2012, Chase River Dams Breach Flood Inundation Study.
You can see that the highest assessment is about three times that of the lowest (Lower dam), putting the subsequent engineering conclusions into question. Also, not addressed in any of the inundation studies, is how much water might remain within the bowl of the lake, or the river bottom, particularly in the case of the Middle Colliery Dam.
So what was Chase River flood boundary within and beyond Harewood like in 1963? The closest city directory of Nanaimo available at the library is 1964. The following streets showed numbered houses as follows (and including a number of listed apartments within them): Bruce Avenue – 28; Carlisle Street – 5 + 1; Deering Street – 3; Eighth Street – 22 + 2; Haliburton Street – 1: Howard Avenue – 3 + 1; Jordon Avenue – 1; Murray Street -1; Nova Street – 23 + 1; Park Avenue -45 + 2; Seventh Street -40 + 1; Sixth Street – 2; Stirling Avenue – 27 +1; Victoria Road – 1; Winchester Avenue – 13 + 4.
Total – 215 houses plus 12 suites = 227 housing units. John Barsby School was built in the early 1950’s, so obviously was already in place with several hundred students/staff.
It is immediately apparent that certain roads existent today are missing: Aebig Street; Brookside Place (developed since about 1976); Gardasan Way; Georgia Avenue; Hewgate Street (developed since about 1967); Honey Drive, and some existing streets have been extended and built on since 1964. From the 1963 map the greatest concentration of houses is between Nova and Seventh, from Park to where Georgia is now. There appear to be some farms too. The following multiple dwellings have been added as shown: Country Gardens (Bruce Avenue – eventually 19 units) since about 1965; Ed’s Mobile Home Park (Honey Drive off Park Avenue – eventually 49 units) since about 1973; Willow Grove Apartments (Sixth Street at Bruce Avenue – 147 units) since about 1983; Rivergate Town Houses (Sixth Street near Bruce avenue – 31 units) since about 1994; Gardasan Way (principally four-plexes – 22 units since about 1995; Bruce Avenue at Eighth Street (four-plexes – 20 units) authorized in 2010 and currently still under construction.
Much of the building expansion in the inundation area has occurred since amalgamation in 1975, especially the multiple units, significantly increasing the permanent population.
Using 2.2 persons per housing unit, the nighttime population in 1963 can be estimated at about 500. The city estimates that the current nighttime population is almost 1900. From a number of independent sources, I estimate it between about 900 and 1100. If the present flooding danger has been present for the past fifty years, why has the population density been allowed to double or nearly quadruple in that time frame? Or, if that danger was not perceived in the intervening years, does it really exist now? The daytime population at risk includes perhaps 600 or 700 at Barsby School, as has been the case for sixty years.
We recognize that there was some concern for the stability of the Colliery dams in 1978 and rehabilitation work was completed by 1980. It was not until 2002/2003 that concern was again voiced by engineers hired to inspect the dams. We waited until 2010 for a seismic hazard assessment and 2012 for yet another dam breach inundation study. This time staff didn’t ignore it. Well actually, they rather kept it to themselves for three or four months. A draft copy was quietly released in June 2012, identical to that overtly released in September. City Council was not informed of the conclusions staff had made until late October. If the danger was as critical as staff expressed, was it not willfully negligent of them to have withheld the information from the public for four months? If it wasn’t so, from a safety perspective, aren’t we overreacting now?
Part of the problem lies with changes to the Dam Failure Consequence Classification. It changed in 1999 and again in 2011, making it harder and harder to fix the dams within the risk criteria. Fundamentally, as an engineer who has known the dams for some years admitted (in an exchange with Colliery Dam Preservation Society members), they have not really changed in condition – but the politics surrounding them has. Throughout the 1990’s and into the 2000’s, Dam Safety Branch cooperated with city staff to allow time to fix a serious problem with the Jump Creek Dam. Today, they appear to continue that cooperation with staff by ignoring all attempts from outsiders that want to preserve and repair the dams or change the Consequence Classification through mitigation. Unless we get permission to rebuild from all authorities (DSB, DFO, MOE etc.) before the dams are removed, it is most likely that such permission will be declined in the future.
It is my understanding, that the idea of removing the dams can be traced back to certain staff comments in 2009. This is about the time that the notion of a Harewood Neighbourhood Plan first appeared. I suspect that a desire to create more density within Harewood and appease the development community is the agenda pushing staff and perhaps the majority of Council in their decisions on the removal of the Colliery Dams. How else can one explain their obedience to staff direction, regardless of the issue or opposition from citizens. The wishes of the Harewood residents seem inconsequential within these decisions. Both senior staff and most of Council have ignored almost every presentation to consider an alternative to removal. Yes, they have agreed to replacement, but without prior permission this may be doomed. 2014 is an election year and some councilors may not be returning. They may simply change their minds or claim lack of funds, and there will be nothing that the rest of us can do about it. Such is the lack of trust. Conversely, I want to thank the minority of independent, thinking members of council for their support so far, and using their common sense.
It has been suggested that the dams be largely dewatered during the winter as a safety measure pending removal of the Middle dam next year and its subsequent replacement. I wonder if anyone has considered how long it would take to refill either one of the lakes. I suggest that, even in winter, the flow from upstream is less significant than one might suppose, without a major flood. The 2010 seismic hazard assessment made many assumptions and concluded that the Lower dam was probably not on bedrock, nor was there rebar in the concrete. A front page Nanaimo Free Press newspaper article from 10th November 1910 states clearly how the dam was built on bedrock. Furthermore, recent core sampling has shown the presence of rebar and mesh in the cement. All of this has been ignored by staff and minimized by their hired engineers. They simply will not contemplate an alternative to their conclusion – the dams are unsafe and have to go.
There is evidence from the aforementioned Ministry of Environment plan, that the dams control the water flow to the salmon fishery downstream. We don’t know what effect their removal might have. Due to the release of sediment, both taking the dams down as well as rebuilding them may have a negative effect on the fishery. If so, perhaps we need to reconsider both options. Were we to, for instance, dispense with the Middle dam and the water held back by it, accepting the limitations of whatever water may remain in a pool. The Lower dam could be reinforced by compounding considerable rock and earth fill into the basin below, but allowing the exit of Chase River downstream as well as increasing the capacity of the spillway somewhat. Maybe even including a relatively small concrete dam at the narrowest part of the river below. Despite what the latest engineering reports state, this may still be the best and most cost-effective solution.
I remain very suspicious of the 2012 Inundation study conclusions: it is the only one ever done in Nanaimo using two-dimensional computer modeling; with alarming results. It should be remodeled with more precise data and re-analyzed. The population at risk needs studying and revising and the fatality rate should be explained in considerably more detail. It is at the very root of the Consequence re-Classification and what followed.
Lawrence Rieper, June 2013
Posts and Comments on Nanaimo Governance 
Further Comment from Lawrence Rieper:
ADDITIONAL COMMENTS TO DENY, DENY, DENY.
Lawrence Rieper, June 2012
Since writing “Deny, Deny, Deny”, I have become aware of the work of two people who have independently concluded that the surface area within the Harewood evacuation area is about 180 acres. I would like to acknowledge these individuals but they seem to prefer anonymity. Both analyzed the City of Nanaimo Evacuation Area map distributed since October 2012. The pink colouring corresponds with the worst case scenario modeled within the 2012 Chase River Dams Breach Flood Inundation Study – breach of both dams at Probable Maximum Flood (PMF). I have done similar analysis but without arriving at an actual figure for the surface area.
The first person, working on the assumption that the surface areas of the Middle and Lower Colliery Dams were of roughly similar size, divided the lakes into the pink evacuation area, 24 times (12 each). On the understanding that the lakes were about 7.5 to 8 acres each this yielded approximately 180 acres within the Harewood inundation boundary. This is the lower figure. The higher figure is 192 acres.
The second, divided up a 1,000,000 square metres square block (roughly, Howard, 6th, Park, 8th) containing the pink shading and concluded that slightly less than three-quarters was the inundation boundary (728,460 square metres was deduced), representing 180 acres. (Three-quarters precisely would be 185 acres)
Adding the volumes of Middle and Lower dams (110,000 and 112,000 cubic metres) together yields 222,000 cubic metres. This represents 178 acre feet, an old way of measuring dam storage (that is still common in the USA), but useful in this case to illustrate that 180 acres divided into 178 acre feet gives a water depth of slightly less than 1 foot of water. One might drown in a wading pool or a bath, but they are generally considered safe for most of us.
However, the above example does not include the volume of any of the flood scenarios used in the 2012 study. The 100-year flood adds 90,000 cubic metres (= 73 acre feet); The 1000-year flood adds 141,000 cubic feet (= 114 acre feet) and the PMF adds 221,000 cubic metres (= 179 acre feet). Thus the totals become 251, 292 and 357 acre feet. Divided by 180 yields 1.4 feet, 1,6 feet and just under 2 feet. Of course, there would be some deeper and many much shallower areas, barely covered at all.
There is one more issue. The 180 acres do not purport to cover the inundation boundary within the Chase River gulley south and east of Park Avenue and Seventh Street, beyond Harewood into the South End and Nanaimo Harbour. This relatively narrow but deep channel can accommodate a large volume of water. It may add 20 or 30 acres to the inundation boundary/evacuation area for a total of 200 to 210 acres (it could be more). Re-dividing the various scenarios by 210 yields: 1.2 feet; 1.4 feet and 1.7 feet.
The 1963 Chase River Inundation Study map shows two inundation boundaries and two flow values associated with surface area: 28 feet per second (793 cubic metres per second) flood – 210 acres and 36 feet per second (1019 cubic metres per second) flood – 280 acres. For comparison, from the 2012 study, peak flows are as follows: 100-year flood = 537 cubic metres per second; 1000-year flood = 1140 cubic metres per second and PMF = 1168 metres per second. From the map, the smaller of the two inundation boundaries appears to be 210 acres and covers a very similar area to the 2012 evacuation area, thus reinforcing the 210 acres figure. The larger one is much greater, therefore presumably, 280 acres. There may be a copy of the 1963 study amongst the former Greater Nanaimo Water District (1952 – 2004) files to supply details.
Currently, the 2012 Flood Inundation Study is still available on the City website (as are the 2002 Spillway Hydrology Study and the 2010 Seismic Hazard Assessment). You will note that the sum of the volumes of the Middle and Lower dams (222,000 cubic metres) and the PMF (221,000 cubic metres) are almost identical, yet the scenarios for maximum flooding depth and extents differ somewhat. Scenario-6 (earthquake – dam break) is modelled much larger than Scenario-3 (PMF – no dam break). We can also note the coverage of 4 to 6 metres water depth in Scenario-6 (PMF with both dams breaching).
Regarding the actual size of Colliery dams, there are four or five different volumes (averages: Middle – 110,938 cubic metes, and Lower – 148,107 cubic metres) as previously noted. It is interesting that in their notice dated June 15th 2013 to replace works under the Water Act, the city quoted 75 and 140 acre feet for the Colliery Dams (92,500 and 172,700 cubic metres) instead of the most recent lower figure (2012 study).
Also, different surface areas have been recorded for the Colliery Dams. “An Ecological Survey of the Harewood Colliery Dam Park, Summer 1980, Harewood Recreation Advisory Council and the Government of Canada (Box 6, NCA”, states that the park is 68.4 acres and each reservoir is approximately 8 acres. The “BC Ministry of Environment, Lands & Parks, Water Allocation Plans: Nanaimo River – July 1993, show Colliery Dams #1 and #2 as 1.4 hectares (3.5 acres each), and Chase to Nanoose – April 1994, shows the surface area for Colliery Dams #1 and #2, as 1.43 and 1.42 hectares (= 3.5 acres each). The 2002 Middle and Lower Chase River Dam Spillway Hydrology Study shows Middle Lake as 27 hectares and Lower Lake as 25 hectares. Since most sources list Colliery Park as 28 hectares (69 acres) this is clearly a mistake of a factor of ten (one decimal point). Actually, 2.7 hectares = 6.7 acres, and 2.5 hectares = 6.1 acres. If one engineering study can make a mistake, so can another. Comparing the average depth of approximately 1.5 to 2 feet for the 200 or so acres within the evacuation area map with areas of 6 metres (20 feet) depth from the 2012 Inundation Study, one wonders if there wasn’t a similar mistake when the engineers used a two-dimensional computer model for the first time in Nanaimo. Reducing the water levels by a factor of ten would vastly reduce the potential damage. With a much lower (and accurate) Population At Risk, we might find that fatalities could shrink to less than 10.
A quote from the April 2002, Middle and Lower Chase River Spillway Hydrology Study, 5.1 Mitigation Options (to accommodate the PMF), states, “The following options could be considered to resolve this issue. (1) Decommission the dams. This would be costly and challenging. There would be environmental issues to overcome with draining the reservoirs and there could be loss of a valuable city amenity. However a seismic assessment may conclude that decommissioning the dams is a required remedial action (it didn’t!). (2) Carry out an incremental downstream damage assessment. To be classified as a high hazard dam the incremental damage over and above a PMF should be significant. In other words, the PMF would do considerable damage downstream anyway and the additional failure of the dams may not result in much more damage. The incremental damage is defined as the damage that would occur with a PMF plus dam failure minus the damage that would occur with a PMF without dam failure. However, if it were demonstrated that the incremental damage was minor, it would still be necessary to upgrade the spillway to at least the 1000-year flood. Otherwise, catastrophic failure could occur with a relatively frequent flood event. The Middle Chase River Dam is close to being able to pass the 1000-year flood.” In 2010, the Seismic Hazard Assessment, Middle and Lower Chase Dams referred to the December 2002, Chase River Dams, Phase 1 of Incremental Damage Assessment as, “….. a study that models breach of every dam on the Chase River system using the Probable Maximum Flood.” I must admit that previously I had missed the reference to PMF and drawn a lesser conclusion. The PMF reference is very significant as we shall see.
This study has never been released to the public. The question remains, did the incremental dam breaches significantly affect the PMF damage, or did they not? It is understood that the map from this study is used for emergency purposes (available on line – City of Nanaimo – Hazards – Chase River) and shows both Colliery dams plus the two reservoirs flowing into a flood inundation boundary within Harewood below. It is of similar shape to the 2012 map but slightly smaller in area. This is quite alarming, since the amount of water is significantly greater (two or three more dams). The volume figures for the Middle and Lower dams were 93,000 and 173,000 cubic metres. The volume of Reservoirs #1 and #2 were 60,000 and 30,000 cubic metres, totaling 356,000 cubic metres (higher values have also been quoted). It is unclear whether or not Harewood Dam (32,000 cubic metres) was included, but the PMF would have been at least as big as in the 2012 study if not much larger. One would expect a much larger flood footprint in 2002 than 2012. Perhaps this is another indication that the 2012 study is flawed.
As the 1963 inundation study shows, an unknown volume of water may flow out of Westwood Lake (which holds at least 2,300,000 cubic metres), though Morrell Lake (up to 217,092 cubic metres) and into the Chase River. It is currently unclear if Reservoir #1 (60,000 cubic metres) will be retained, and apparently #2 has been reduced to 20,000 cubic metres (however the spillway is unchanged, so probably not – it can potentially hold about 60,000 cubic metres), but Harewood still has 32,000 cubic metres. That totals more than 329,000 cubic metres flowing into Harewood before any PMF is added. The new 14,000 cubic metres reservoir will overflow too, probably into the river with treated water, notwithstanding a rupture of the supply lines adding 245,000 cubic metres per day. Even without the two Colliery dams, Harewood is still a potential flood risk. Surely this is obvious to the decision makers in the city. Any dam can fail.
In “Is Nanaimo Safe”, I stated that the 2004, Westwood Lake Dam Inundation Study, “recommended that mapping of the potential Westwood Lake Dam breach inundation in the Cat Stream and the Chase River be completed.” I have since seen references to the following studies: Cat Stream Drainage Study – May 1980; Chase River Drainage Basin Study -1981; Cat Stream Drainage Basin Study –December 1981; Millstone River Flooding Report, Ministry of Environment – 1986. These studies might provide some elucidation.
There is a presumption that the Colliery dams will collapse quickly in a serious flood or earthquake, allowing a massive wall of water to flow into Harewood. The more likely probability is of a series of stops and starts as debris collects and water pools behind blocks and slows the flow, then gives way and repeats. One way to mitigate the present perceived risk might be to remove the Middle Dam and reinforce the Lower Dam with compacted fill. Nobody has explained why the remedy used at Westwood Lake in 2008 is unsuitable for Colliery Dam, apart from the shape and size of the downstream valley. It would simply require more earth and rock fill, but still be a relatively cheap fix. Like Westwood Dam, it might slump in an earthquake but it would continue to control the flow. Also, the spillway still requires some modification. On the subject of spillways, if the city is planning to create a drainage ditch from Middle Lake instead of siphoning, then perhaps a proper spillway bypassing Lower Lake, should be considered as a permanent solution (if money is being spent on blasting anyway). But, because of the convoluted relationship between city staff and Dam Safety Branch, any alternative solution will require a lot more support from Council.
I believe that these comments, when combined with my observations about the Population At Risk should cause some to question the veracity of the 2012 inundation study. Instead of blindly accepting the risk and panicking, the City ought to revisit all the data connected with it, and have open discussions with all concerned parties. Is the risk really what staff insists it is? Perhaps the 1963 and 2002 inundation studies were ignored because they didn’t show enough cause for alarm, except some wet basements.
Readers are also directed to two previous posts by Mr. Rieper on this blog: i.e. “Some Observations……” on Dec. 1, 2012 and “Westwood Lake Dam Inundation Study…” March 29, 2013.
Any chance of uploading the maps?
Lawrence another example of superb investigation……. would it be at all possible to condense some of this into a ‘Dam Inundation Studies for Dummies’?
Cheers
Jim
Fire all involved (with cause), and recall the “infamous” 5. Especially Nanaimo’s self proclaimed Oracle. what a mess.
We bought our property in large part because it borders on the lovely Chase River. Every time I go down to the bank I think how privileged we are to have this marvellous piece of property. So, if they destroy the dam and the river, can we sue the city for destroying much of the value of our home??