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HomeMy WebLinkAbout04-04-2017 Item 2, SchmidtCOUNCIL MEETING:_ 4 41 ftlwCE1VED 1 � �� ITEM NO.: . 2 __ I APR 0 3 2017 From: Richard Schmidt < Sent: Sunday, April 2, 2017 9:23 PM Subject: Agenda Item 2, Inflow and Infiltration To: E-mail Council Website <emailcouncil4slocity.org> Dear Mayor and Council Members, Please see my comments on this item attached. Richard Schmidt April 2, 2017 Re: Item 2, "Inflow and Infiltration" Dear Mayor and Council Members: So staff wants you to require every homeowner to pay $8,000 to create sewer capacity sufficient for infill development like 71 Palomar! R U kidding? That would be political suicide and get those who vote for it thrown out of office. The fuss over the rental ordinance would be Muppet play by comparison. I have much respect for our Utilities staff — especially for figuring how to do things like the neighborhood notification pollution alerts — but I do think they're off base with this proposal. So let's look at this issue through a different lens. Staff states that overloading of sewer lines comes from rainwater entering private sewer laterals, decrepit city sewer lines, and illegal connections. But the proposal before you focuses almost exclusively on private sewer laterals and recommends truly draconian steps. Why do they put such emphasis on imperfect private sewer laterals, which even if guilty as accused (and I believe evidence and analysis will both show they are not demonstrably guilty) would contribute much less volume than the other two culprits? This makes no sense, unless the object of this program is to punish homeowners as a class. So, here are some thoughts about how this situation might be viewed differently. Sewer Deficiency Areas of City The city has several districts identified as having inadequate sewage capacity. I live in one of them, and both 22 Chorro and 71 Palomar are within or feed into that inadequate -capacity area. (If capacity is inadequate, why are such high-intensity developments still being approved? Instead of increasing neighborhood sewage spill frequency by increasing sewage flows with such intense projects, you could declare a localized sewer hookup moratorium until you are able to correct your capacity problems. That you don't suggests you don't really believe you have capacity problems, i.e., that you don't believe staff who keep telling you that you do have problems.) So the proposal before you would require homeowners in these inadequate -capacity areas to be the first to be forced to spend $8,000 to replace their laterals. What sense does this make? The capacity problem is in city sewer lines. Reducing any small amount of infiltration from private laterals would not solve a capacity problem in city sewer mains. If the city lacks sewer capacity, that's a problem the city must solve. Being financially punitive to homeowners doesn't do anything to solve the recognized city sewer capacity problems. So the suggested "solution" of replacing private lateral isn't a solution at all. Problem With Laterals Not Defined The proposal would require homeowners to hire a private contractor (who would have a built-in conflict of interest since said contractor would also do lucrative lateral replacements) to survey the homeowner's lateral and see if there are deficiencies. What does that mean? What exactly is a deficiency? One gets the impression it could be something as minor as a few tree roots, which, in my experience, find their way into all sewer lines, including city lines. Anyway, when a deficiency — whatever that may be - - is noted, replacement of the line would be required. In other words, the whole issue of what constitutes a problem lateral remains undefined and open to abuse. Is an undefined problem fair justification for hitting homeowners with an $8,000 bill? Sticking Homeowners With the Bill For Infill Since the announced justification for these punitive measures is to create more sewer capacity for infill, is it fair to stick homeowners with that bill? Think of this goal as "sewage conservation." Harken back to how we achieved water conservation sufficient to allow new development. The developer had to retrofit enough inefficient water fixtures to produce the water needed for the new development. Why shouldn't the same be done for sewage conservation once truly offending laterals are identified? The bill to homeowners would actually be much higher than the technical work's $8,000. What about having to dig up patios, walkways, driveways, disturb mature vegetation, and the like? This is no simple feat. Who pays for that? It's another cost the homeowner gets stuck with. Lessons From Broad Street Z, ,;x. ..� ::•�.+�1.3�.'�.: Overflowing sewer Broad/Murray 1/22/17 The two January overflows — listed in the chart on Page 1 of your staff report -- at Broad and Murray both occurred during huge storms. Clearly storm water was the cause. But where did that storm water come from? Staff apparently has no idea, but it's pretty certain it didn't come from infiltration into private laterals. I say that because in both instances, Jan. 20 and Jan. 22, there were huge downpours, and the sewers overflowed within an hour of when the peak of those downpours happened. When the heavy rain stopped, the overflow also quickly stopped. In other words, the sewers responded practically instantaneously to the heavy rain. This has been the past pattern as well. There's only one way I can visualize this happening. Someplace up -line there's one or more direct connections to a city sewer through which large quantifies of storm water are being directed. This means the overflow occurs quickly, and when the intense runoff stops, the overflow stops. This means Inflow is the causative problem. Could this sewer overflow be caused by Infiltration from private laterals? In short, no, and here's why. Laterals are buried in the ground — for argument's sake, let's say 4 feet deep, which is probably a typical depth. For infiltration into laterals to explain the overflow of our Broad Street sewers, water from current rain would have to seep into the ground to the depth of the lateral, then enter it, and flow into the sewage system. As we saw above, the response of the overloaded city sewer was nearly instantaneous with heavy rain. Could infiltration into laterals happen this fast? The short answer again is no. Perhaps oversimplifying a bit will make this point clear. To reach the 4 -foot deep lateral rain falling on the soil surface would have to infiltrate the soil to a depth of 4 feet. Such infiltration happens at various rates, depending upon the physical makeup of the soil — gravel faster, clay slower. Our dominant soils are heavy clay, the type of soil with the slowest infiltration rate. How long would it take water to infiltrate 4 feet of heavy clay? The USDA rule of thumb is that infiltration into a level surface with heavy clay soil occurs at the rate of .13 inch per hour. To reach a 4 -foot depth at that rate would take 15 days. Infiltration is even slower on sloping surfaces, of which there are many in our city. For example, on a 16% slope, infiltration occurs at .03 inch per hour, and to reach 4 feet deep takes 67 days. Clearly then, infiltration has nothing whatsoever to do with the overflowing sewers on Broad Street during heavy storms. The recommended solution of replacing private laterals is thus not a solution at all. The evidence, in fact, suggests Inflow, not Infiltration, is the culprit, and the proposal before you barely deals with Inflow. Lessons From Sewer Plant Inflows The staff report also blames Infiltration for winter spikes in inflow to the sewage treatment plant, and the chart on Page 2 of the staff report shows a dramatic representation of those spikes. In that chart there are sharp spikes that then quickly recede into routine background levels of inflow. But again, where's the evidence ANY of this has to do with infiltration from private laterals? Staff offers assertions, not evidence. This is one of those moments when I'm happy I have a rain gauge and keep records. Looking at the dates of the huge spikes on the sewage plant inflow chart, almost every one of them corresponds to a day with a huge rain storm. In other words, the same story as at Broad Street — there's a very fast uptick in plant inflow immediately after a large storm, then it quickly drops back towards normal. When it doesn't, it appears the cause is on-going rain which kept inflows elevated a bit longer. So, these huge spot inflows to the sewage treatment plant at the time of large rain storms couldn't possibly be due to slow infiltration from private laterals. But there's even more evidence. If infiltration were to blame, the flow would be gentle over a period of time. If accumulated infiltration were overpowering the sewage treatment plant, we'd see flows rising slowly and elevated for weeks at a time, and not spiking at the times of rain storms. Remember, for infiltration to happen, the lateral must be sitting in water, and given our dominant clay soils that takes many days after a storm to begin. The chart shows no general or prolonged elevation of flow rates such as would happen if the cause were private lateral infiltration. After each peak, flows into the plant settle back into the normal range. This is very strong corroborating evidence that infiltration from private laterals isn't a sufficient problem to merit the draconian recommendations being made. Are Imperfect Laterals Actually A "Problem" or Are They An Environmental Good? This is more of a philosophical quandary, but it needs to be posed because there may be undesirable impacts of tightening up our private laterals to the proposed standards. We are being told by staff that imperfect private laterals are some sort of evil that must be exorcised. But is that true? One can make some very simple contrary arguments, that somewhat leaky laterals — since our evidence indicates low level inward leakage plays no worrisome part in overpowering the sewer system — are in fact an environmental benefit and even a civic benefit. Those tree roots in your lateral? The trees, in our semi -desert climate, have found a reliable source of water and nutrients. This makes for robust trees that enhance our visual pleasure, cool our yards thus increasing comfort and reducing the need for air conditioning, purify urban air of pollutants, and sequester greenhouse gases that cause climate change. Is this an evil thing for our sewer lines to accomplish? If such gentle outward "leakage" is taking place, that means the sewage plant has somewhat less work to do, which saves the city money, but also saves the planet since sewage treatment is arguably the most energy -intensive city operation. (Are you aware that the unmitigated energy impact of the 1990s plant upgrade would have taken planting of 5,000 acres of new forest to sequester the plant's increased greenhouse gas emissions? And what about the latest upgrade?) But isn't lateral leakage a health hazard? Probably not, if it's a small amount, and never rises to the soil surface. In fact, a bit of leakage can be considered a bit of recharge to soil moisture and perhaps even to an aquifer. (A potential hazard would result, however, if the lateral were within a water table and not in dry ground.) In fact, such discharge is an accepted and safe manner of dealing with sewage — it's called a septic system. My point being, one can get hysterical over such things, or one can analyze them and figure out the "problem" isn't much of a problem after all, and might actually have its beneficial features. Conclusion. Clearly the city has sewer main capacity inadequacies in parts of the city and needs to fix them. Clearly the city has major Inflow problems it needs to locate and fix or require perpetrators to fix. And clearly an unconvincing case has been made that infiltration into private laterals is a sufficient problem to merit the draconian anti -homeowner and politically -foolish measures being proposed. urge you to drop the Infiltration measures being proposed, and focus on the big stuff that will actually make a substantial difference to the public health and welfare — fixing the Inflow and Capacity Inadequacies which keep neighborhoods like mine flowing in sewage. Sincerely, Richard Schmidt