and then you have your actuator which is physically in the analog domain and plant analog domain. Sensors may be analog to digital depending upon whatever is a sensor interface and then you typically have this setup for any megatron system and you may have feedback in some cases like you may be missing the feedback also. The sensor feedback may not be there some systems are like that but in general you have this feedback control happening in especially high fidelity megatron scan of the system. And then we saw some basics of what happens when the signal is sampled especially when you take the sensor signal which is an analog domain and you sample it and like you want kind of represent it in the digital domain. And now we are looking at how the signal is thankfully representing what it is supposed to be. The contents of the signal in some sense are preserved when you sample it. That is what we are discussing and for that the main theorem is about the Shannon sampling theorem. So a couple of these questions you should be keeping in mind and seek answers for. How do we kind of say that the samples are true representation of the original signal? Or how do you recover the signal back from the samples? Are there any method? Is there any method or under what conditions we can do this complete recovery back? And how is it applicable to our case? Like say this PWM is going to the motor as a sampled signal. So now you may have a little bit of a clarity here. See this PWM is itself has this switching signal. It is quite positive and 0 at very high frequency. When we say sampled so for all our practical purposes what we consider this PWM signal when like you know implemented on a motor is that it is giving some average voltage to your motor. And that average voltage is now given as a sampled form. So this average is one value and after some time sampling time it is changing its value. That is how we can visualize this or look at this. Otherwise if you say okay oh my see PWM signal itself is sampled but it is at high frequency and if I want to consider that also into into accounting analysis then it is a different story okay. What we are assuming here is especially for PWM signal. See otherwise if there is an analog interface to control motor then absolutely no problem there to clear analog signal is at some value. During the sampling instant it remains constant okay and then like in the next sampling instant it is a different value. So what is this effect of this kind of a way of you know actually receiving these signals in this kind of a stepped form okay. Every sampling time the step value changes. So we will be looking at that in in new course. Okay so we started off with these fundamentals of sampling and this is analogy one can use our physical thinking can be done based on this. All the concepts that we see later can be you know easily understood if we connect it to this kind of analogy. Because this gives you some kind of a visual kind of a way to to think about stuff and we will see formally as we go mathematically how things work out but we will not derive the equation we kind of use some of these sampling theorems and the reconstruction part and things like that. So as we saw if you sample when this arrow is at a point before the 180 degree position okay. So if arrow is here and the next arrow position if it is before 180 degree position we can see that okay we can carefully kind of see the the field direction and velocity at that. Now you can see that you know see if I sample it here and it completes one rotation and goes beyond and again I take a second sample that is also a possibility okay. But that will indicate you speed which is not reality okay although the direction is same okay. You can see that you know the arrow is pointing here it completes one rotation and comes here and I take that as a sample. So even in that case the direction is is is proper but the speed is speed information is not proper. Further if I say okay oh it completes from starts from here completes one rotation complete second rotation and again comes to the same that position that is also one possibility. So so but that that will give you like the same speed when it is reproduced but actual speed has happened like with the two rotations in between. So this is information that is getting in some way okay. So how to see that in the frequency domain is slowly that we will look at that. So the frequency domain representation would like give you some all these kind of possibilities that that are there for for such a such a sample signal okay. So how that happens like we will see in a while okay. So so same thing extended now to actual signal and its time samples here okay. So you can see that here some models kind of a frequency sign wave is coming up okay. So you have original sign wave which is going at very high frequency and then when you are sampling it your like low frequency sign wave is coming up in the in the signal okay. So if you if you see this problem is similar to like you know this wheel kind of a problem okay. So the frequency at which you are observing the wheel to be moving is much slower okay and in the opposite direction for this particular kind of a case. So like that you will have this frequency of the sinusoid is much lower and its phase is also you know in not in line with the phase of this original kind of a signal okay. So that is how one can kind of connect these two things to kind of think physically what what might happen to your signal. Okay now this is like more kind of a formal mathematical kind of a representation of what we are talking now generalized to a signal okay. So this is a signal f of t which is in general like like you know evolving signal with some frequency content and what we are interested in is is a signal for which the frequency contents are typically of center signal. So so frequency contents are obtained by using like another Fourier transform of the signal and the numerical way of doing that is is past Fourier transforms and those past Fourier transforms would give you this kind of a plot of we saw some example signal here this signal okay. So this is the original signal and this is a past Fourier transform okay and in the in the f of t you can see that the signal has a content which is like know some frequency here and like know some small frequency at at at one end of here okay. So beyond that there are hardly any frequency content. So this signal is kind of bad limited to frequency of about like say 35 or that kind of a value okay. So so like that we can say that this signal typically is represented this triangle as or this is kind of a straight line has no really great meaning here I mean it just to signify that the signal has some content in this in this domain it may be like one kind of a single line or like multiple lines we don't know what the contents are but typically the signal is generally represented in this kind of a form okay. So so actually if you want to really see what is this then you need to take f of t but to us to kind of like know this for the purpose of the discussions people would represent the signal like saying okay it has some content here they represent these contents are in this kind of form and now the the question arises is that okay suppose I sample this signal and get these white dots these are the samples which are recorded in my computer okay this is coming up as a vector array in my in my computer then what is the frequency content of such a such a signal okay. So so this frequencies can have a multiple kind of values here okay how that is happening is is based on some mathematics of Fourier transform so this this signal is represented for the mathematical kind of a transforms the Fourier transform for sample signal the sample signal needs to be represented in in terms of some kind of a math and that is a mathematical representation of the sample signal direct data and then when you take a Fourier transform of this signal and do some kind of mathematical manipulations you end up with this sample signal Fourier transform okay. Now for this sample signal Fourier transform you can see that you can you can see that this this f is a Fourier transform of original signal in the analog program okay so so this sample Fourier transform is is represented in in in terms of some kind of a form of original signal Fourier transform so f of t is original signal and its its Fourier transform is f of j omega so this is f here okay so f of j omega is the Fourier transform but now when it is sampled there is some kind of a scaling that is happening here 1 over t some kind of a scaling factor coming and then there is a summation of multiple of multiple copies of this f of j omega which are replicated at frequency k omega s okay. So for example if k is equal to 0 value you can see that this is nothing but f of j omega here okay so that is one part one so k is equal to 1 then like no it is a shifted by frequency omega s and as omega s is the sampling frequency 2 pi over t okay so so that's how one can interpret these and with these if I want to plot it here say for k is equal to 0 this this will simply replicate here as as the signal f of j omega is this value and this will simply replicate here at f of for k is equal to 0 okay and then for k is equal to 1 it will be replicated at omega s value so you I need to kind of find where omega s s here and at that axis I need to again replicate the signal as it is from here to f of where k is equal to 1 where omega is equal to omega s value so this is what will come like this here okay so when the signal is like this its sampled form will look something of this sort here there is one time there is a replication then there is a second replication here then there is a third replication at the minus so so you see if it is it is minus infinity to infinity k value so it is keeping on replicating everywhere that's is that is the main crux of this sampling theorem that it says that your signal in the frequency domain will get like a mirror mirror itself at multiple omega s values okay and that has some sense I was talking about like you know even after like you know rotation of one complete rotation you'll have you know this the frequency can be same okay some kind of a sense of that information is coming here here your signal is getting replicated at multiple omega s values and and that's how your samples can be visualized so so your samples are just discrete data points okay if I see the frequency contents of those discrete data points they'll be represented in this type of form okay so so now if I start changing this omega zero so my frequency content of omega s okay I decrease the sampling frequency okay so I what you can imagine now this sample is first replica is coming here you can see the scaling also one what is scale scaling is happening here and now this part is going to come more closer to these okay as I start decreasing omega omega s okay as omega s decreases this will start shifting okay in omega s omega axis here and keeping omega zero same if I decreasing omega s then at some point like you know this omega s over two then these two will start touching each other okay so when omega zero becomes omega s over two I still have these two samples that these these signals they are touching each other so if you see there are these signals here still have the same kind of a form like a triangle form that it was there for the analog signal okay it is still preserved here but once you see that my omega s decreases below a certain value okay which is two times omega zero kind of a value then my signals will start interacting with each other and you see that there is a summation of these things okay so when they start overlapping you need to actually sum them up in the frequency domain is the frequency of the sample you you you sum them up in the frequency domain and like you know they they start now missing the information so this earlier signal was something of this sort and the new signal has now lost that information here okay new signal has beyond this frequency lost some some part of the information is getting lost okay so that is what is is is called aliasing and that is why the signal has to have a sampling enough frequency enough so that you know we don't see this loss of a signal okay so any question so far this is what is a crux of like no seven something one part which is you know that the signal should be sampled at least twice its largest frequency content so that it is represented like no in its full form in in in its in samples okay so in the strain gauge for your transfer there weren't any repeating triangles right right so so would it transform would give you a signal let's see which is only up to the first like no first part of the frequency contents okay only up to the the limit here see okay these are done like a digital Fourier transforms okay so this is done in a way that your maximum frequency here depends upon what is the sampling frequency so you you you assume that the signal has whatever aliasing that had happened already and beyond that like you know whatever is the signal content it is produced only up to omega s over 2 omega s over 2 will be the frequency here so if you have sampled the signal at frequency I think in this case to be sampled it at a frequency of 1 millisecond or 1 millisecond what kilohertz so this maximum value here on this frequency axis can go only up to 500 and beyond that it will be we cannot represent because it's going to be a replica of the same thing is is assume it will not come as a part of the numerical you know a 50 method of like no getting a Fourier transform so so this understanding is implied here that okay this part is going to get repeated you know beyond this point and we hurts frequency that is there for the omega s over 2 value perfect god yeah I mean one can kind of set up your plots in a way that you want to kind of see them as plotted like that but a 50 algorithm does not by itself really do that okay so this is the main main part here so so you you see that you know when we take samples you know although these samples are looking as as these kind of points here as something possess in the frequency domain they are not seen as an emphasis okay that is the main thing that you should not confuse about okay they are seen as a continuous signal here okay okay when we do numerically some stuff there is a different story don't worry about that part but because it is sampled here it produces samples here also no that is not correct okay it produces this actually this this is like an analog kind of a signal here in some sense like you know this is analog means like it's a continuous signal here okay is in the frequency domain so see these are different domains of thinking okay so so frequency domain thinking like no easy is different from time domain thinking there is a transform that is happening in between okay so once you say okay this is the samples that I am representing here in the time domain that doesn't mean the frequency domain also I have only the samples no that is not correct that is not main thing one should not fall in that trap okay so clear this part like okay this is how like you know these signals get mingled up or mixed up and gets messed up okay when we start you know sampling it with a lower sampling frequency and now one can see that okay see if if I have my my signal in the form of that rotation suppose we take the field rotation example then omega zero value is what is of my interest so there is one kind of a say what omega zero is a frequency of order or the speed of rotation okay so that value will be represented here as omega zero signal and now if I sample it at multiple kind of you know different frequencies one can see that if the sampling is is not fast enough then then I will see that this omega zero coming up here if I measure from here see this this part is fs here or fs of fs replicated at you know so this is my zero basically okay so when k is equal to zero okay and now this is omega s value of here now omega s it will get replicated here again and omega zero from this side will come up here okay so this frequency is what I am going to see as a first frequency when I start replaying that signal okay and this frequency is now you can see that it is less than omega s over two okay so this is a much lesser frequency than original frequency omega zero that I had here okay that is what is going to be seen in this signal which is you know not sampled enough actually that's how one can start thinking about this and okay so so like that one can see whatever that rotation way of doing things can be seen now in the formal you know mathematical representations yeah okay now Shannon has proposed for the reconstruction now the question is okay you said okay if I sample it you know faster than twice the frequency contents of the signal the signal can be completely decreased I mean the signal can signal contents are preserved so now the question is how do I reconstruct this signal back okay and there is this other derivation mathematical derivation is more than the derivation like now there's how this formula comes up from from basic you know Fourier transforms and like how this expression comes up by considering the filtered version of of that signal okay so you filter this signal by by using so your your sampled signal is like having now many such kind of replicas here we want only for first replica which is at zero the frequency replica that value that that is what we need to kind of preserve and so we filter this signal using this ideal filter which is a flat filter here with the with the scaling t so that we cancel out this one over t by this scaling factor and then we can produce this signal back okay that is how one can think of reproduction of the signal in the frequency domain and by using that those kind of fundamentals one can work out the the what is what is happening correspondingly in time domain and that's where like you get this you know formula for time domain representation of the signal now so this is how like you know the signal can be reconstructed from the samples now let's understand what what is it this this part is doing here okay these are the samples this is FSKT is a is a is a samples of this sample sample of the signal and then each of the sample is multiplied by some kind of a function here okay and then they are all added up together is what gives you this reconstructed signal back okay so and then this particular function is of the form sin theta upon theta okay so we'll see what is this function looks like okay let's kind of see that now so reconstruction part is having this kind of a formula what we have seen and and now we will see how one can construct the the samples back the signal back from the samples okay so say these are the samples here okay so these are different color kind of you know things have been sending samples at T2, T3, T4 things like that now this function as as saying that it's sin theta upon theta kind of a function and if you know from your like mathematics this function will have a if you see sin theta upon theta limit as theta tends to zero its limit is actually one okay so so this function is is is called sometimes sin function sin theta okay and it has some representation of this kind okay so if you plot it against theta when theta takes value of pi then this this function is going to go to zero okay so at zero value all this sin theta upon theta and the limit as theta tends to zero is one and when sin theta is equal to pi this will take value zero and so on and so forth for like no integer multiple of pi values okay that's what is going to happen here okay and and this is a way that the amplitude will go on reducing because as theta increases like the overall value of this coming at one over theta so the amplitude is one over theta which gets reduced for a sin function okay so this is how like now this function evolves in in in theta okay now theta in our case here is actually pi for pi t minus kt upon t okay now what is what does it mean supposed t supposed to say k is equal to zero then this is like pi t over t okay okay and then like this this theta will take this value pi t over t and this this function will will have now variation coming in time okay so now instead of theta it will be coming as a time function here okay and when the time becomes equal to capital T okay this pi t then theta becomes equal to pi this value it will be equal to capital T okay you can see that right like no say k is equal to zero okay so this term is not there and now your t becomes like a capital T value then theta becomes pi and we know that theta is equal to pi this function takes value zero okay so when it gets kind of you know multiplied to this this has the scaling factor here additional scaling factor is f of kt so if this sample will scale this this signal okay so so this suppose this is a sample so instead of this one value at whatever like this value okay other thing okay let us let see when what happens when theta is equal to zero when theta is equal to zero part here this is the theta equal to zero position okay which is this y axis for this function plot at that point t becomes equal to kt that means like for each sample like no this function is going to get placed here okay at a sample value such that this one matches or lengths get scaled by by the sample value itself okay so I will have this say for for say k is equal to one if I want to put this here then t will be equal to capital T here so so at that point my theta is going to be zero so this this value one will get scaled by this f of kt factor and then it will come here so this is signal if I start now drawing and I know from here if I go one t apart I will hit theta is equal to pi value okay so this signal is going to come first as like this okay so for k is equal to one value this function is going to look like here okay and it will have some kind of propagation okay is this this is part clear any questions about this so we are just considering one case k is equal to one and then like no seeing the how this mathematical form or this function it's represented as for k is equal to one okay and then we need to consider there now that for k is equal to like minus infinity to infinity actually but we don't have samples before zero so we consider like a sample starting from zero and for sample here is maybe zero then how this signal is is is dependent okay how this construction is is seen okay so yeah not clear why did you choose this form of function because there will be interference between the consecutive sample reconstruction right right right so it's not it's not interference but this this so say if I now do it for k is equal to two I'll get another kind of a signal which is cached up here like that okay so this is two signal so this is still an approximation of original signal right so so I'm just kind of passing now k is equal to one k is equal to two only I have to consider k is equal to minus infinity to infinity then it is giving me complete signal it's not an approximation it is say if I limit myself to like you know some few values of k alone then it will be approximation if I consider all the values of k okay all the samples that are like you know possible possible for the signal to be considered then it is not an approximation but essentially you're still fitting it between the points right it's just that if you have a lot of points then it might look like an original signal no no it's it's not that so so look so it's not that you need to have in between points also no no but that's not what I'm talking about I'm talking about that it has all the samples are there okay so so right now I'm talking a little bit of a you know from the mathematical perspective saying that okay if I have all the samples known okay from from t is equal to zero to t is equal to infinity or k is equal to zero to k is equal to infinity all the samples I have I have available or beyond certain point I have my signal is zero for example and I know that okay all the samples are there then I'll be able to kind of reproduce my signal back completely so my doubt is if you evaluate this function at suppose t by 2 somewhere in the middle point more or less there will be a slight error right no that's what I'm saying like so so we'll come to that right say say for example between these two values okay t p and 2t like you know you have this signal coming up right now and this signal coming up right now so they are getting added and they'll produce some kind of form here okay then if you see if I consider next sample k is equal to 2 sample or k is equal to 3 sample okay I have this signal coming up so this is also contributing to this part is also contributing to something between t and 2t okay like that every sample okay say I consider this blue part okay blue part has also something to contribute between t to 2t then I consider next part okay like that if I consider all these parts they'll have something to contribute between this t to 2t and that's what is a beauty and problem both for I'll tell you why beauty and my problem okay so this the Shannon reconstruction considers all the samples and like you know every sample has some representation between these two values okay so if I go to 2t to 3t again like you know I can see that you know the previous samples also are contributing something and future samples are also contributing something okay ideally k is going from minus infinity to infinity but if I put it in a numerical software then it depends on how many samples I'm choosing for the summation right that's why you will have if you're doing the numerics anything anytime you'll have some approximation but it will be much better construction than like you know saying that okay I'm just holding this sample here and like you know I'm meeting till the next sample to happen and again I'm changing that value and holding it here again like that it's much better approximation than that okay so or if you have this some kind of some linear kind of interpolation between the two samples that is other kind of a construction that can be possible but that is not still a Shannon reconstruction because the signal is not smooth like it's not getting it feels exactly what it was but if I even if I use like say for this sample I use two future two future values and two past values okay and reconstruct that that itself with the Shannon kind of a formula it will give you give me much better kind of approximation it's a smooth function that is going to come up like that okay your signal is actually in some sense getting reproduced you know in a very smooth manner and if k is equal to infinity then it will be like exactly but now the problem is that for any reconstruction here I need a future values all the future values and in our mechatronics system or real-time control system is impossible to get future values beforehand right because your feedback is happening because based on the feedback the future values will come okay so so you cannot have the channel reconstruction possibility in the mechatronics control systems at all so this is a very important aspect of these that okay whatever reconstruction that we need to have they need to be causal in nature they should be using only the previous samples values okay they should not be using the future values which we don't know okay so this standard reconstruction is not a causal reconstruction it is using all the future values to construct the signal fact that's where like the problem is okay so that's why you cannot use the standard reconstruction or it's ideal kind of a reproduction of the signal for mechatronics or control kind of a domain system okay but then the question is where it is useful can you anybody knows where this standard reconstruction could be useful in some way okay this is useful for for for the cases of like you have heard about like you know you're digitally representing the sound okay so your sounds or like you know any anything sound representation in the digital way if it is done you're only here future and past samples are available right for any kind of you know the sound to be played back played back again okay so this high high fidelity sound systems they would use this kind of a you know future information about the samples to do some kind of reconstruction based on the future value the future values of the samples to get you know the quality of sound produced in the same way as it was recorded okay it's not analog recording it's like a digital recording of a signal and you want to produce really to the very close extend to the analog kind of reproduce that sound again you you you can use these kind of concepts okay so communication industry would use this in some way okay so your digital high fidelity sound representation that they are reproduction of the sound again they can use this standard reconstruction but for our control systems this is not not feasible to do okay so what we do is we hold the values in the register you remember you have this duty register in which like you know once you put the value it will it will not change by itself till the time you put other value there and you will have a chance to put other value only when you kind of like a complete once happening time instance and come back again and I can put other value there so till that time the value with the head constant okay so so the way you are like you know reconstructing the signal is basically holding this signal constant from here to the t to the 2t value okay then it is changed to this value and again that value will be head constant then it's changed to this red value and again that red value will be head constant and again then it will change to blue value it will be head constant is how like you know in some kind of a step form you you you represent that signal as a reconstructed signal okay especially for it for implementation on the on a motor or actuator so so so this is how like you might can think of Shannon sampling theorem and make use of that for for you know sampling the the signals in the in a way to make sure that the contents are preserved to work with best form it's just to think about like you know how what should be the function here which when multiplied by this f of kt and this should be function of t minus kt so that i now produce my you know the stepi function stepi form player so first the stepi function we can use the rectangle yes yes so this is what we're talking about is stepi function here okay and this is already here okay so so this is a frequency domain oh sorry don't not confuse here it is a frequency domain kind of a representation okay so maybe maybe am i am i like you know some writing here is is yes so this is called zero order word i just correct this and and it goes to slides again probably this is called zero order or you may note down like with this ideal reconstruction written here is not a correct thing okay just just delete this part ideal because this is not ideal reconstruction at all okay ideal reconstruction will be this part where you have this p and rectangular window coming out here is a ideal reconstruction this is a different part this is a this is like that rectangle function that that was talking about so instead of this this same function here will this rectangular function will be coming out here okay so this this function when like now you represented in the same form f of kt like you know this function t minus kt what it would give you actually this reconstruction which is called zero order word so the zero order word you'll find in matlab some places people have used this in the in the digital domain to a to d or t to a conversion okay so so the systems we want to transform from from another domain to digital domain like here you'll be asked okay whether they should use binary transforms or they should use zero order word kind of a form or what kind of a form that is to use that time like when you you understand that okay zero order form means like with zero order word means like i'm holding this value uh till the next time so if this is happening and under this scenario if i want to see what my system is responding then like for that that digital system conversion from another digital domain is what is based on this zero order word kind of a form okay so if i reconstruct the signal back like this okay so so we are not yet coming to the system so we are just kind of talking about only the signal how the signal is is represented and reconstructed back from the samples okay please so what we saw so far is like the signal getting uh sampled like this and once this is sampled um what is the happen with frequency contents and uh after that like you know if i want to reproduce the signal what are the different ways i can reproduce the signal and one of the ways is this channel reconstruction reproduce it back like you know completely but that is the completely ideal case we will not do that in the in the in the control system domain we'll rather do it this kind of okay so now this is the way we are kind of reconstructing uh the signal uh into into the sample so so if you see the same sensor signals also when they are sampled and and like let me go to that slide when they are sampled this is the first slide that we are talking about when they are seeing see since the signals are sampled and like you know put in the digital domain their their value is held constant till the next sample comes for the sensor the way it happens for your duty cycle the same way it will happen for the sensor value also the sensor value will be held constant till the next time sensor sample comes okay again that value will be held constant till the next time sensor sample comes all this kind of reconstruction that is happening inside the the the domain although we are kind of representing these values as a discrete time values only and persisting them for what our purpose is they are actually if you see they are held constant or over the samples okay and then that holding constant over the two samples has much more kind of a effect when when it is implemented on the actuator okay it's it doesn't matter too much when you kind of just to persist those values here but it has much more implication than it is implemented on the actuator and how that happens that we can see in a minute


It's Wednesday, and we're here at the mall.  Five days later, it's still there. And funnily enough, everyone around me is starting to get sick now, so my sister went back to Alice for the cold. The chick I've been staying with has a cold.  But either way, beautiful day here in Christchurch. Honestly, the weather has been amazing.  I can't complain with that. But yeah, hopefully by Monday, when I have to go back to reality, my sickness is gone and I'm feeling all right. But Anna went back to Alice today. So she had a 5.30 flight. Had to be at the airport at like 3 o'clock, so I'm sure she had fun doing that.  Man, I've basically been using intermittent fasting to get me through this holiday without too much damage.  So I don't know, man. It's hard. It's definitely hard being on holiday sticking to a diet, especially like I don't have a show this time. If I had a show date that was in a few weeks, man, I'd be miserable because I wouldn't be able to or basically if I did give in on the diet I'd be just waking up feeling miserable and it would be consuming and without having a show date in place, I've been able to just cruise, just eat what I want, obviously hit my protein amount and just try and keep calories under a certain amount. So at the end of the day we'll see what the damage is. There definitely has been some damage done but not as much as could have been done. That's all good. I'm just here chilling, relaxing. I'm actually going to get a haircut. It's going a bit crazy. I'll just get the sides and back done. I'm going to keep the top. So we'll go do that. But first I'm going to start my day off, well, my first meal because I've had one basically black coffee and now I'm going to have another one which is a vanilla chiller which you might have seen me get one in Alice. Well, since then I've been addicted to them. My sister told me she was addicted. I can now tell why. So you can basically up the coffee amount as to how many shots you want to have. So I have a regular which has two shots in it already plus an extra shot on soy milk. Tastes absolutely amazing. Gloria Jeans is right behind me. So I'm going to go to that now. She first, I'm going to go and see an old friend. See if she's here. Surprised her. Apparently she works at Barker's. So Barker's, Barker's, Barker's. Alright, so she's officially not at work today. I have to surprise her tomorrow. So I'm just around to go get a haircut. I've heard a lot about these guys. My father's barber. Apparently it's a really great barber here in Christchurch. So I'll give them some business. See what they can do for me. So it looks like my day tomorrow has already sorted for me. Got the haircut booked. Going to go see Holly here tomorrow.  Might go shopping. Who knows? You know, it's funny.  It's funny, like, the one I put up yesterday is it's got footage in it that's a month old. And so I can't really remember what I was saying back then. You know what I mean? So if anyone does pull me up for saying things that I've contradicted myself since then. Man, pull me up because, you know, that's, I guess that's just what you're going to run into when you're putting a series up that's a month behind. But it's funny in my last episode, someone noticed that I was watching a Frisma video. So I was obviously vlogging and watching that at the same time. And he told me that Frisma, who's, you know, an inspiration to me, he's an inspiration to many. I mean, he's younger than me, but he's still an inspiration to me. I'm not going to, you know, I'm not going to deny that. I'm not going to try and act cool and say that no one younger than me can inspire me because of course they can. So anyway, apparently he, oh fuck, there's someone beside me. I still lose my call in front of people on the camera, but apparently Frisma has gone, deleted all of his journey back to aesthetic videos and they had like 10,000 views each and heaps of likes and everything.  And I'm just thinking, well, why on earth would someone do that?  Like, I'm better than that or I don't need it or I don't need people's validation for me to feel good about myself. And you know, some people sort of do take this whole social media thing that way and it's all about making themselves feel good.  At the end of the day, I was looking forward to the next journey back to aesthetics episode, man. I want to see him, I can get back to aesthetics.  Maybe. Oh, yep. I'll tell you what, one thing you learn when you grow up is that coffee's good. And I'll tell you one thing about these coffees, they do the trick every damn time. They really do give you a kick. It's probably because of the fact that I've got three shots in there.  Haven't had any pre-workout.  I have still been having caffeine, but nothing from, you know, the supplements. It's all been from coffee, so it'd be good to get back on that when I get back.


We should be good to go all right. We'll call the meeting to order and I'll recognize that myself and councilmember Fleming are here to establish a quorum. Mayor Rogers is not able to join today. We'll go to public comment for non agenda items. If there's anybody who has a comment on something that falls within the jurisdiction of our subcommittee, but isn't on today's agenda. Happy to hear from anyone. We have anybody online. We have no hands raised on zoom. All right, then we'll start with department reports. Chair Rogers, may I ask if we could do the approval minutes please. Oh, can I please skip over them. I did. Faceshoot. Yep. Did you have any amendments to the minutes? Okay. Let's do public comment. Anybody have any changes to the minutes? Any hands on zoom. No hands on zoom. Great. We'll show those approved as presented without objection. And now we'll go to Tasha for the department reports. And I do not have any department reports this time. All right. You want to just jump on in on item 5.1 then you got it. Okay. So item 5.1 downtown parking study presented by Chad hedge manager of the parking division. Just park yourself right over there. Okay. I need to write that one down. I'll be good. And that's important. Do that for you. If you want me to. Okay. It'd be parallel. Sure. That's coming up. I feel like there's a meter joke you could throw in there. I'm sure there. We're trying to figure this out here. We're trying to figure this out here. Yeah. Yeah. We're trying to figure this out here. Okay. Bring the expert in. For me, it's operator error. It's not the IT. Yeah. Perfect. All right. Good afternoon, everybody. We're, my name's Chad hedge on the parking division manager. This is Tanya. She is our, our new analyst. And we were brought here today to talk about the, the climate action subcommittee. I think you were on the, the board. Kind of talk about what we're going to use these funds for. And how it's going to help the downtown, the railroad square, how it's going to impact parking. And so I threw a whole bunch of extra information into these slides. Just so I can make sure I cover it all. But on June, June 28th, the MTC approved the plan Bay Area 2050 implementation. We're going to look at, we're going to look at, we're going to look at the grant award of the grant award. The city of Santa Rosa city of their parking will receive $207,000. That'll go towards a curb management and access plan grant. That study will include, we'll evaluate our existing occupancy. We will utilize and compare best practices from local agencies. We're going to look at San Diego, Santa fell. I mean, the city of Santa Rosa is going to be in the, in the city of Santa. Purchase of the grant, evaluate future demand impacts from the state's elimination of the parking minimums. And approving the approval of multiple housing developments in the downtown and railroad square area. We're going to establish goals and visions for the future of the downtown of railroad square, analyze current revenues with future needs. And importantly, evaluate the EV capacity and needs with the increase in multi developments in the downtown impacts on the grid and then the infrastructure availability through numerous meetings with PG&E. We're gonna develop numerous presentations that we can outline the progress as we go forward and answer questions and have multiple community meetings to try to solicit information questions or highlight anything that we may have missed. So the background for us going forward with this study, you know, it's all come from the downtown station areas plan, the climate action plan, the climate vulnerability and adaptation report, as well as the multiple Walker report studies we've done over the past few years that showed us what our occupancy was, what it is currently and considering what we need it for in the future. And then incorporating the different housing units that are coming into Santa Rosa and how that's gonna impact what we currently have when it comes to garages, lots, but also commercial loading zones, ADA spaces, passenger loading zones and everything throughout Santa Rosa. And these are a few clips I took out of the climate action plan that will show that in order to reach our climate goals, reduce the GHGs and reduce the VMTs, there's things that we have to do through the climate action plan they're gonna help us get to that point, right? In conjunction with our changes in order to make things work better in the future for the city of Santa Rosa. A couple of the important items on 3.4, eliminating the amount of free parking in high traffic areas, free parking is gonna make people wanna drive around and circle and circle and we wanna eliminate circling around too much. Price on street parking relative to congestion, I believe the city did that in 2017 when we pushed forward to the progressive parking policies. Implement the city's residential parking permit program near high traffic areas. This has been going on for years and we're actively doing it and we have meetings and this really does help out a lot of the current residents and then evaluate the zoning code for amendments to reduce parking requirements where alternative transportation is available or planned. We've been working really hard on developing a really good relationship with transit. Whatever we do, I think can affect transit parking-wise and whatever transit does, I think can help benefit parking. So working together with Rachel and her crew, I think it would go a long way. And then of course the goal five, the electric and hybrid vehicles, in order to make these things work, we need to have the EV infrastructure in place, we need to have the chargers ready to go and that takes months, if not a year plus of planning. So we're gonna work on that as well. Some of the intended outcomes for the MTC funded study, better utilization of existing spaces, reduce the GHGs and the BMTs, ensure the implementation of EV chargers for public and fleet use, utilize technology to have a real-time data collection so we can be as fluid as the band changes, support the city's partnership with PG and Tesla, install EV chargers in the carriages, right? I think that's what we wanna do is try to get folks to use the garage more and to lower rates and more availability for the EV chargers, better utilize what we have for the benefit of the businesses and the visitors, stream operations for improvements to aging facilities, better wayfinding and equipment, additional oversight facilities, provide a safe and enjoyable experience. We want people to be able to know where to park before they show up in Santa Rosa. We want people to know they can park anywhere and they can be safe, they can visit businesses, they can visit residents, they can come to the markets and do anything they want. So we need more outreach and more communication on our end. Community outreach with stakeholders identified changes that would benefit all those impacted by parking. We go out daily downtown and I meet with business owners or I meet with guests, just I love talking to people, so I'm down there all the time trying to get feedback from folks. The only thing I'm trying to figure out as I go forward to make sure I do this study correctly and then the right way and I check all the boxes is find out what do you guys see as a concern regarding parking? What discussions have you had with guests and business owners of downtown that could impact parking and where do you rank the need to install more EV chargers and infrastructure upgrades along with parking? And there's my contact information if anybody has any questions going forward and I think we're good. All right, thank you. So before we answer those questions for you and get into a discussion, do you have any questions on the presentation? One question which went back to action item 3.4.1 parking on street relative to congestion is that are you looking to bring back some version of progressive parking? I can't, I don't know what I'm looking for and I only say that just because I don't know what this study is gonna show me as far as where I'm deficient or where I'm in surplus of. I don't know what's gonna happen with the sale of the properties. I'm not certain on how many developments are coming in. So there's gonna be holistic changes. I just don't know what they are yet. And when you get $207,000, does that buy you additional staff time? Does it get you consultants? How does this money get deployed?  So I've been speaking a lot with the MTC. This is a unique situation to where we won't see a dime of that money. The MTC will do the request. They will identify the contractor. They will hire the contractor based on meetings with us and what we need. And they'll pay everything. They'll have the quantifiable. So we won't have to do anything on that. So we don't process any of the moneys. We just receive that service. Yeah. It's unique, unique. Yeah. Thank you. Thank you. Does that mean that they manage the contract also? Correct. Okay. Correct. I understand and we're still in the beginning stage to this is that when they start identifying multiple vendors and start to make their choices, then we'll be brought into these conversations based on what these people are offering. So when you do the analysis for downtown, you have cited in there, I think it was 900 housing units with 500 and some change parking spaces planned within those developments. Are you planning based on projects that have been proposed or are you planning based on zoning and potential? Proposed. Okay. Proposed and or approved developments right now and based on what I can get from city. Yeah. Everybody knows that sometimes things will come in, they'll be proposed and then they'll just fall away and not be billed, yeah. But yeah, I would encourage you, it's more a comment than a question, but I'd encourage you to also work with Jill Scott and other folks, Claire, Raisa, because there are, I know of a number of developments that are at least talking to the city that have not been formally proposed yet. I like, for instance, we just finished some of the surplus lands acts, some of the first steps of the surplus and lands act on multiple city-owned properties that I know is not accounted for in that analysis. Correct. But if we're gonna be doing a study, there might be some placeholder numbers that we can put in based on some assumptions so that by the time the study is complete, it's more accurate than it might be otherwise. I agree. We've had some great conversations, all city staff's been great, with Raisa, with Jill, with Claire. I've also had folks, like I say, one Santa Rosa Avenue or a different developers who will call me when they haven't even filed for an application and they'll say, if I wanna do this, could I get permits here? And of course I'll say, yeah, no problem, let's work here. So there's a lot of what-ifs that we don't have factual right now that will be a part of this. It's gonna be six to, probably six to eight months is how long this study will take. Yeah, yeah. Let's go to public comment. Do we have any hands for public comment on Zoom? We do not. Anybody wanna provide comment? Peter, anyone? All right, do you wanna put back up the slide with the feedback that'd be helpful from the committee? Do you wanna kick it off? Sure, you know, it's always interesting to me when it gets to parking, you know, because it's so important. It's one of our greatest assets that we don't have more. You think that people would be beaten down our doors to talk about parking, so. What do I see as a concern regarding parking? You know, we wanna, you know, it's all about balancing this asset that we have and making sure that we don't encourage people to not use transit bike and pedestrian, we want people to use active transportation. We wanna make sure we're funneling as many people into the downtown as possible without, you know, having things made confusing for people. So, you know, one of the things you bring up is having the EV, I'm gonna bounce around because none of these are really distinct. I see that, you know, the idea of having EV charters in the garages is one of the best ways to get people off the street into the garages and it also targets one of the populations that is most challenging to get to use their garages. And so if we can partner, say with economic development and art in public places to continue to beautify and make the garages lighter, brighter and feel safer, if there's a great amenity that you cannot be gotten on the street. Okay. But can be gotten in the garage. We're gonna solve a couple of our problems over time in my prediction. One of the things that I hear from residents who live in these parking districts downtown, particularly Cherry. Yes, residential. Yes. Is significant frustration with a new system. And you and I have been in communication. Yes, yes, yes, yes. And so I think that, you know, working to figure out a way to incentivize them to have their guests use garages where there are garages proximal to their residences for guest use. Having some sort of program for limited amount of guest use for them might be a way to ease some of the consternation that they have over the new system. I'm thinking about a particular around the garage behind Russian River. And then, you know, one of the things I always think about with parking is, you know, we don't want to dissuade people from coming downtown. And at the same time, we don't want to encourage them to use their vehicles. And so what other solutions do we have besides charging for parking? I mean, we can charge for parking, but you kind of nailed it on the head about working with transit. And how can we work with transit to make sure that there's less incentive. And I'd be interested to have a back and forth with the chair about some of the ideas that as he sees them in order, but the number one tool I think is to not place EV charters on the street. That makes sense. Place them in the garages. But I'm curious to know, I should ask this during the questions period. Have we looked at partners outside of Tesla and PG&E partners that might be a little bit more palatable to our public? No, those are all great questions. Let me start first on the EV question about the garages. We're actively working on getting fingers crossed, 13 EV chargers starting the process to install 13 EV chargers in garage nine. And if things go well, we could install somewhere upwards of 30 chargers. Is nine the one behind Corression River? I'm sorry. This one right here. This one, okay. And then garage 12, the one right behind Roxy. We're working on possibly getting 30 plus EV chargers installed in there. So we're definitely focusing on garages with the chargers. Are you focusing on the underutilized garages or the well utilized garages? Right now, well, I guess everything's underutilized right now, just because of our occupancy. I know what you mean what I'm saying. I'm hoping that focusing on these that are kind of used to be our good ones, these chargers will make them become more utilized and push more people out towards the house. They used to be the good ones. Is it okay if we used to have good ones? Like as in they used to be well utilized compared to some of the other ones? I'm sorry. This garage right here used to have a lot more occupancy with the state and the federal employees downtown. And they just haven't came back.  Yeah. And the same with 12, the one behind the Roxy. We used to have more folks. I assume it'll come down to the events. Barbie didn't fix that. Well, I haven't checked today. I parked there when I saw Barbie. In fact, we paid a whole dollar for it. I parked at City Hall and walked over. Sorry. But at any rate, so I mean, I think that, and the only time we'll tell, I think that's really interesting because what you're kind of banking on is that these two types of businesses that have really not had a good pandemic recovery, you're banking on moreing people back to office and movie theater usage. And what we're seeing people come back in droves to is services like restaurants and salons. Yeah. And so, you know, I would have probably gone, if it had been me, like the garages on the north side of Forest Street rather than the south side. I'm not telling you to change. I'm just saying it is an interesting bet and I might've split it up between the two to see, for the test to see which side of Forest Street got the fastest uptick in return. But also to see which kinds of economic uses we want to most encourage and see what Bryce and her team think, you know, are most official in the city to encourage. I agree 100%. I think going forward, I am assuming that how can I maintain parking if occupancy does not increase? I'm expecting the worst, figuring out a way I can kind of continue to go through and still do my job and that if it improves, then we can spend on other projects. But right now I'm trying to figure out how to maintain. The second one, the permit thing, maybe offline, you and I can talk. We've made some, based on our conversations, some significant changes to that program that will greatly benefit everybody. I've been getting complaints lately. So whatever you're doing is helpful. Okay, good. I think we reached out to them. So that's very, very good. And then the third question you were asking as far as, I jumped right past it, the last one. Or did I get them all? You might. Oh, partners. I've met with Sonoma Clean Power. I've got a pretty good relationship with the brand Arthur down there. I've been working a lot with Tesla just because they've got a lot of new things. The changes in EV technology is gonna be a universal NACP plug that even if it's a Tesla charger, it'll work on 90% of the automobile manufacturers out there. And I think that that'll be beneficial. Different city departments, Rice's department, Gabe's department just, I can't do any of this in a bubble. So I've been trying to reach out to everybody and we're all trying to come up with a grand plan on how we can go forward. The transit, like I mentioned, we've been working a lot with them. We've actually introduced a couple of months back but now we offer a commuter permit and the lots right under the freeway, a discounted commuter permit because we want people to use smart. We want people to use transit and hopefully that commuter permit will encourage more people. Right, and that's an example of a place where I wouldn't necessarily be opposed to putting chargers. When I say like, don't put them on the streets, I mean, don't put them in super valuable parking places. Put them in places where people are less inclined to go. I agree, I agree. Where they can stay for long, three, four hours if they needed to, no issues. Yeah, I mean, just that's about it. Good points, very good points. Yeah, so on the flip side of that, what I was gonna mention is to me, the amount of electric vehicle charge stations we put in is almost secondary to what type. If you look at sort of the demographic of why people are coming downtown, doesn't really make sense for them to leave their car there for three or four hours to charge on a lower level charger. But if you had fewer chargers but more fast chargers where somebody can plug in and have their car charged by the time they're done having a beer or having a meal, I think that that actually would be a better fit for the economic profile of why people are in downtown. I actually, I'm glad you brought up the lot for smart because I was gonna mention what I think is really key is to decentralize sort of the parking from and make it accessible for all of our public transit because we do know people are gonna drive and park and get on the smart train or drive. And if we have the proposed circulator coming back to downtown potentially, like what smart is now doing with the airport, that's an opportunity where you could have people who are pushed towards the outer parking structures and then still take the circulator where they need to if they're not willing to walk or bike or do whatever. So I think looking at sort of those options as well, I'm not ready to agree on, let's put the chargers in the garages solely, but I do like the idea of creating an amenity there for people to be able to come in. And in fact, we have snubba clean power meetings, for instance, we've got somebody from Cloverdale who drives down for those meetings, drives our electric vehicle and finds a charger and plug into every single time. I know people on the North Coast that when they're heading either to Sacramento or to San Francisco for meetings, they intentionally stop in Santa Rosa because of our charging infrastructure is better than some of the places around us. And I've noticed the same thing for me. I think we were remarking, I drove my wife's electric mini Cooper over to city hall today. Nothing only gets a hundred miles on a charge. So when I'm going to Sacramento, for instance, every single time, I'll stop in Vacaville where they've set up an intentional charging. And of course, while I'm charging, even if it's only for 20 minutes, half hour on a fast charge, I'm walking around to those businesses that are there, right? And so I think a lot of times with climate and I think charging infrastructure is one of them. First movers in the space create their own economic incentive and then it'll diminish over time. But we have a really good incentive to create an atmosphere in downtown for people to stop and to charge. You mentioned your partnership with the Sonoma Clean Power. Sonoma Clean Power's office itself right now is sort of a test case on charging infrastructure. And so talking with them about, there's potential to make money off of the charging based on where we place it with businesses and access that we have to businesses. And they're doing a couple of interesting pilot things. Some of it is related to the bi-directional nature that we would need in cars. Some are able, some are not. But having the infrastructure that prepares for that kind of a future, like I know Senator Skinner right now has legislation that would require in the future, all electric vehicles to have bi-directional charging where they can both get charged by the grid but then also be used as an essential battery pack in a time of emergency or to sell back to the grid. And so I just wanna make sure that we don't install the technology of today by the time we get there, there's new technology and new rules. So it might be worth having a conversation with Sonoma Clean Power about what does the next five years look like? What does the next 10 years look like in terms of capacity and building? Okay. I too, between the two of us, we represent every historic district in Santa Rosa and complete around the downtown. I hear the same things that Victoria's hearing about the residential parking permit program. And it's at a time where people are more interested in it because they're concerned about the impact of housing projects that are nearby. So for instance, love the Canary project that's coming in but the neighbors on the other side on Pearson right behind it are concerned about the spillover of traffic into their neighborhood, right? And so I do hear that quite a bit from residents.  So I don't think that's helpful to you, but that's the thing I guess it is. Sometimes it's just a miscommunication. Maybe they don't know enough or what really goes on. And to that point, I think that as soon as some other jurisdictions start charging. It's very Petalema, Sonoma. Any of them. Yeah. You know something in Sonoma you can imagine. I'm not gonna get involved in that and all that. So for some of our regional partners would start turning to parking. I think it will make us look less like the bad guys. When it comes to that, I think that people just don't get that we have a parking district. So I think as much education as this reasonable and something you didn't ask me what I thought, but here we are five years later. So one of the things that I noticed is that you have someone on your team, a parking enforcement officer I don't know if that's your technical term for those workers who comes in. I'll be at like one of the shops on Forrest Street and Railroad Square and he'll say, hey, come check your leaders. And I think that those kinds of things build really good will. They just build education and an opportunity for people not to feel burned by overstaying a little bit of enjoyment time. I think that's really helpful. I'd be interested to ask you Chris, why you think what the logic is about not suggesting putting the EV charters in the most undesirable places near economic opportunities? And I'm not sure I'm against it. I would need to think about it a little bit more. I'm also a little bit on kind of the equity framework because I was driving through the East Bay earlier and I realized how much I hate the paid HOV lanes where like if you're poor, you have to sit in traffic, but if you're not, you don't have to. And kind of the idea of we're trying to incentivize people to be more climate friendly. And that means that you're gonna drive a car that's gonna be less polluting and then you're gonna have to park further away and potentially walk than somebody who's driving a car that's polluting and can park right on the square or right on Forrest Street because they don't need a charger, right? I'm not saying I hate it, but that's immediately where my head went of that you're essentially saving the prime parking spots for the non-electric vehicles and pushing the electric vehicles away from those spots. Again, I'm not sure I hate it, but that's the first thing that I've triggered. I have to think about it a little bit more. And the logic for me is that if you can afford the electric vehicle and you can afford to charge it, one is that's the demographics that I hear and not super willing to come to downtown all the time. So I was trying to think of an incentive to get them to come downtown without giving them the prime parking spots. I think we need to move away from the assumption that people who are driving an electric vehicle are more well off. Well, it's just a fact at this point in time. It's not gonna be true forever, but it is true now. I disagree that it's a fact now because many electric vehicles are still getting incentives from the state and federal government that are making them cost competitive with internal combustion engines. And at the same time, because they have less fuel costs, less upkeep, it's a first cost barrier. If you can get into one, it's way cheaper and depending on how you get into them, what your loan looks like has absolutely nothing to do with what your economics, your economic is versus somebody else's. I'd say in general, you're probably right, but I think we're moving away from that where they're becoming more accessible. There's more on the secondary market. And so I don't wanna make an assumption on a long-term infrastructure plan based on an assumption that may or may not be true today, but probably won't be true. I completely agree that it probably won't be true down the road regardless of what it is now, but I do think that a long-term goal of mine has been to move parking to the garages and to have higher utilization of them. And I agree with that entirely. And so I think that seeing if it makes sense over time, I'm not trying to ram it down your throat today, but I'm just curious though of over time adding amenities to those garages and not over incentivizing the curbside parking may be something that we consider. And again, I'd have to think more through it, but you can very easily accomplish the same thing by flipping that on its head and saying only EV parking in downtown. And then it pushes people who are not driving an electric vehicle into the lots anyway. There's ways to talk about it if that's what the intended goal is. Again, not making any distinctions on it today, but... There's a lot of different things to do. I just wanna encourage garages. It's really like that. I think it's that, yeah. And if I can, you guys are hitting exactly what's so confusing about EV is that how can it be beneficial to everybody? And then how can we afford it, whether you're talking about the city or just parking? Lot 10, I'm sure you guys saw, or maybe not. Were we doing the lot 10? I'm sorry. Which one? The car lot? Yeah, the one right behind... Lot four. The Russian River. Oh no, lot 10, yeah. That's one of the things that I'm seven years in and I have still never figured out which lot is which lot unless I'm looking at a map or... I just thought it was like the fifth and D. The one right behind Russian River. We've got this huge project coming up. We're gonna redo the entire lot. Once all's said and done, we're gonna have 12 EV chargers in that lot. So as we talk right now about where we wanna put the chargers, the big hinge pin for us is when we do this application through PG&E and we wait months to get a response, we have to give them an exact amount of how much power we're gonna need, right? But as we get to the point where we can afford chargers more, whether we're talking about downtown, if we can put a DC fast charger downtown, like you were saying, as opposed to a level two charger, well, now people can come downtown shop, get nearly a full charge on their car in 20, 25 minutes, as opposed to using one of the level twos downtown and having to wait three, four hours and then put the level twos maybe in the garages for people who are gonna be in the garages for hours. So the technology's gonna change and cause change. I will say with the council member's idea around putting them in the garage, one thing that you could use it as an incentive for is to change people's charging behavior that for the people who have permits to park while they're at work and park in the garages, if they had a charger that they could plug into, you're actually helping to lower the demand curve because then they're charging during the day as opposed to the evening when energy usage is higher. And so you could look at it from a feasibility standpoint of putting those where we have business permits being held. And then if you were looking at something on the square or something on 4th Street, the DC fast charger just makes a lot more sense. If you're at work for three or four hours, it makes sense to charge your car so long as it's cost competitive with the rate you'd be paying at home. That's a good point, a really good point. Cool. Two thumbs up. That is good. Thank you. Thank you. Chair? Yeah. Let's go on then to item 5.2. 5.2 is the overview of low carbon concrete and that will be presented by Andrew Pazelle, leaders of materials but associate for transportation and public works and Rob Sprinkle, deputy director of traffic engineering. And I'll tell you, Victoria's been waiting for this one for a while. She keeps telling me over the last couple of years, we need concrete solutions. We need concrete solutions. I got it. Thanks. I got it. I can be permeable. I mean, flexible. Oh. Ah. I can share. I can share. Yes. Just don't be hard as me. See? We've got a good mix of jumps here. I liked it. No, no, no, no. Skipping it. We have projects on my street and the time period for some of us. Getting there. It's literally. Okay. There we go. All right. So thanks for having us today. I'm Rob Sprinkle, deputy director of traffic engineering and this is Andrew Pazelle. He's our materials associate. He runs our materials lab. Our materials lab is kind of a gem in Santa Rosa. They do all our compliance testing for concrete asphalt aggregate for all of the stuff that goes into our streets, which is one of the reasons why our streets last as long as they do. Because we're one of the only agencies that actually can monitor the quality of the asphalt concrete and aggregate that go into our streets. So it's helping our streets last longer than they do. But today we're here to talk about low carbon concrete. So as we get into that, first go over what concrete is in general. So concrete's a mixture of gravel, sand, cement and water. And it's typically in the proportions of three parts gravel, two parts sand and one part cement. So, and then the water is what hydrates it in which starts the chemical reaction to harden the concrete. And it mixes with the cement and the cement is the binder and that's what gives concrete its strength. So, and the process to make cement not concrete itself, but just the cement portion of concrete is what is really the GHG hog. I guess if you want to call it in this instance and it does produce about 8% of the world's greenhouse gases. So as kind of a carbon footprint, one ton of cement creates one ton of CO2. So it's a lot. And at the bottom? Yeah, it's a ton. So I have a little couple of pictures here at the bottom of the slide here just for educational reasons. So the two photos of our trucks on the left, those are cement trucks. Those carry a dry product of cement. The truck on the right is a concrete truck. So that's just what, so we hear cement trucks a lot and then maybe it's just a pet peeve of mine because we work with it all the time, but the cement trucks are the ones on the left. Okay. Where's that one? Okay, so what is low carbon concrete? So I'm not going to read the entire definition, but I'm basically just going to summarize it. Low carbon concrete is concrete that uses other products other than cement in it to help offset the cement GHGs. So two typical elements that we see around here are slag from blast furnace, a byproduct from blast furnace and flash, which is from cold fire power plants. So those are both products that can be supplemented in for cement, which then help lower the use of cement, which lowers the greenhouse gas. And that's kind of the key to using, to what low carbon concrete is. And Andrew can jump in anytime he wants to interrupt me. So two, three, two. You're impressive. Okay, good. So then in another aspect of, so I will read the last part. So potential advancements in carbon reduction in concrete manufacturing are being studied in prefabricated concrete construction materials such as pavers, bricks and center blocks that it's currently limited to these prefabrication facilities. So on site when they're building those particular items and it's they're not available yet for doing field right next concrete. So that's where they inject the CO2 to help cure the concrete and use CO2 that way. They're forming the pavers, the bricks of the center blocks bringing them into effectively a curing oven and then injecting high concentrations of CO2 into the oven to speed up the curing process. So the situation on the industrial side. Exactly, just no water in it. It's just pure CO2 in the room. So two examples of projects that we've used concrete recently. The one on the left is the Fulton-Lewainey project from Gervild Piner. And then the one that we've finished back in 2019 is the Fulton Reconstruction Project between Occidental and West 3rd Street. So both of those projects used a structural section of eight inches where we took out eight inches of the existing street section, the structural section of the road and replaced it with concrete. So we're using RCC, which is roller-competitive concrete on the Fulton-Wideing project on the one on the left. And we used PCC, which is Portland Cement concrete on the project on the right for the project that we've already completed. The differences between those two is the Portland Cement concrete is basically concrete you see coming out of a truck that's wet. It can flow, it gets vibrated in the place and screed it off. The roller-competitive concrete actually is put into a paver. It's very dry and it gets actually compacted with rollers and you can't put a roller on the wet concrete, they'll just sink. This is so dry that it's actually being compacted in place with steel drum rollers. So in the Fulton-Wideing project, we're using 50% Portland Cement and 50% slag in the cementus cementus, yeah, I can't say that word. Material touches, thank you, composition. And in the Fulton-Wideing, we used 100% Portland cement. So with the mixed designs that we have with both of these products, the cylinder strengths or the compressive strength of the cylinders were the same. So you can meet the same strength requirements that we need to meet. But the roller-competitive concrete had much less CO2 output. So basically we used half as much cement and we saw a reduction of about 46% in the CO2 output and we used a lot less water. In addition to that, we used a lot less structural section than we would with asphalt and we'll get into that in a little bit and a couple more slides here. So some of the benefits that we see from using concrete roads in general is the carbonation of the pavement or the concrete itself. So when concrete undergoes carbonation, it actually captures CO2 from the atmosphere and uses some of that CO2 up that it actually was being produced in the making of the cement portion of that product of the Portland cement. Also there's a high albedo, which is the reflective property of concrete is higher. It's about four times higher than that of asphalt. There's other issues with that that can happen where Andrew's looking at some studies relating to concrete streets in Phoenix and where they had concrete streets and not a lot of street trees, they did see a lot of reflectivity and a lot less temperature on the ground but it was reflected back into the buildings and then the buildings had a lot higher energy use than the buildings that had asphalt streets next to them because of the reflectivity property of the roadway. Concrete streets also offer less maintenance in the future. There are higher life cycle costs or higher life cycle than asphalt streets and I'll get into that in the next slide. And there's less excavation which means for the same structural section that you get with an asphalt street, you might see say a foot and a half of asphalt would do the same amount of structural section or same amount of work for bus loading and truck loading than about eight inches of concrete. So a lot less material, a lot less stress on the natural materials and everything that go into each of the products. So this graph shows the life cycle costs on an arterial street with a traffic index of 11. So that's a street similar to Fulton which has a lot of the truck traffic, bus traffic, has bus routes on it and sees a high volume of traffic throughout the day. The bottom line is the roller compacted concrete or PCC, those are very similar in their performances for initial cost over at the left at the zero, it's just under $700,000 for a per lane mile that's calculated for construction. While the two lines that are above it, one is a full depth HMA which is asphalt. So if you just take the full depth of the structural section and make an asphalt, it's about a foot and a half. That's a little bit under a million dollars. And then if you use actually AB2 as a base which is the aggregate base rock and then a smaller section of HMA or asphalt, it's a little bit higher cost. And this shows different treatments over the years of the product. So at year eight, you would see for the asphalt you would want to do to maintain it properly, you would want to do a high traffic slurry seal on the product. Then again, in another 10 years or a year 18, you'd want to do another slurry and then another 10 years of slurry and then eventually year 36, about 35, you'd want to do an actual overlay of that product. So if we move down and that continues over until you have a reconstruction in the years in the future. If you look down at the concrete, there's a much lower maintenance cost. You can wait until year 25 before you do your first diamond grind which is where you go back and you basically smooth everything out, smooth all the bumps out. And then at year 40, you go back and you'd replace 10% of the slabs that have cracks or failed or are rocking and then at year 60, you would do a 5% slab and then diamond grind again. So this just shows the maintenance costs over the lifecycle of the product and cost savings you have potentially with concrete over asphalt. Now this does vary dependent on the type of street you would be applying this to. So in a neighborhood street, these lines really start out almost identically at the same point. It's almost exact same cost to do a concrete street as it would be to do an asphalt street. It's just that the maintenance is a lot better for the concrete street. But there's other issues that I'm going to concerns with the concrete roads. So concrete roads are a lot more difficult to cut through for utility maintenance. And then when you have a trench you have to either repair or say you want a new water service or something. It takes a lot longer to trench and to have the concrete set up and do traffic control for that over that trench while you're trying to repair or asphalt you can typically put down, roll it and it's ready to go. So there's a time factor there and convenience factor for the public. Also there's difficulty in leak detections. And I mentioned this before, but our local streets don't have the same, they have about the same initial cost and then they do show longer maintenance benefit from that. So with that, I think I talked fast and I'm ready for questions. Want to start us off? Yeah, I'll admit that my knowledge of material science is somewhat limited. So please forgive me for asking what might seem bone edge questions. When we get to talking about on slide three, fly ash byproduct from coal-fired power plants, sounds like great climate solution, or steel slide byproduct brought up from steel mill blast furnaces. Walk me through why these options are better for the environment. Like I understand that cement takes a lot of, produces a lot of greenhouse gases. Are these products going to be made anyway and is that why they're better or is it just, are we going to count on something that's like terrible to continue to be produced and where does we need the byproduct and is that what we're doing with this? I'll jump in. Okay, I was going to say on you go or you can go and follow. So fly ash is historically been what we've been using in the city. We have specs dating back to 1982 that's called out for using fly ash. We've seen fly ash be phased out by many of our producers in our local area because coal power plants are becoming less and less common. With that said, with continued development, both here in the US and we import some slag into the area, steel mills will always continue to be a thing and it's a byproduct. So either way, it's going to be made so we might as well throw it in the cement. Right, I guess what I'm trying to get at is like, let's say we have a really dirty steel mill in China and we're like, hey guys, cool job on making all that nasty like byproduct. Can you ship it over here across the ocean and you're also not very efficient freighter. How do we know that the overall, I'm not just talking about like in Santa Rosa, but the overall effect on the environment is better from using this product. Yeah, so from the studies that we can find online, these recycled materials cost less even upfront CO2-wise to produce than Portland cement. Okay, and I suppose we'll be looking for some better solution than relying on use in the future. Yeah, I'm sure there will be other things that we're looking at that will continue to try to reduce the use of cement products. The other thing around the high albedo, is that what you're saying? Albedo, yes. Albedo, great. So one of the things that I noticed in areas of Santa Rosa where we do have the concrete streets is that they also are concurrent with mature street trees in a lot of events. I thought that the lower temperatures was mostly result of concrete streets. It sounds like that may not be the case. So I just wanna highlight that I'm curious if we're starting to think about how to pair concrete streets or lighter colored streets with more incentives around street trees so that we don't have like a high heat areas or we do have high heat areas in our city and they do correspond with lower income census tracks. And I just wanna be curious about how we're looking to mitigate that. So that's kind of more of a planning development kind of question, because they do the street trees as part of the development process. But we could definitely look at when we're, so we look at each project, I guess, on its own merit, depending on how are we gonna use a concrete street or are we gonna use asphalt? And we basically look at the best fit that we think for the taxpayers and the use of that location. So, and we have had locations where we do a slurry and it's a lighter color, like Marlowe Road, for example, is a much lighter slurry than we've had than some of the other slurries that have been done. And so we do get that reflective property, but we don't always have that choice on the product where it comes from it's a little bit. So, I'm getting a little bit off track, but I'm trying to refocus. Some of it's not all on you. But it's not, yeah, it's not, it's not always our choice to, it's not always our choice, I guess, it's, so. Yes. Well, there's a lot of solutions that we can bring for it that are not within the scope of this here conversation. Yeah. Any other questions? All right, let's go to public comment. Any hands on Zoom? No hands on Zoom. Cool, I'll bring it back for some discussion then. So, first of all, thank you. I'd actually be really interested in checking out the lab. I've never actually seen it. Absolutely. So I think that'd be really cool to go and check out how we determine and all of that. Cause I do get asked about that frequently from people about road failures and materials. And so if we could set that up, that'd be great. I know Marin County passed a low carbon pavement program or preference, I'm not quite sure how to put it. I'd be really interested to see, bring back in the future a discussion about what exactly does that policy look like? What are the best practices that other jurisdictions are doing? When I was at COP 27, they actually had an entire area that was dedicated to new materials that were emerging. And many of them that were related to roads kind of fit within this bucket, but saw even greater than that 46% reduction in carbon, but also didn't see the same cost savings that you potentially get with concrete. So I would be interested to see how do we incentivize the folks who are bidding on our projects to be up on new technologies that might meet both of those goals for us. I'm actually really encouraged to see how one of the big questions I had was about how the upkeep would be, whether materials would fail faster if you'd have to spend the money on the backend. And I actually was really encouraged to see sort of your chart there on maintenance. I think that's pretty incredible actually. And so it doesn't, for me, doesn't need to be pushing forward with our requirement that we use this type of materials, but maybe looking at it through the lens of how do we create an incentive for people bidding on our projects to be looking through a climate lens as they do their bidding in their worksheets as well. Yeah, we're actually really excited about our Roller Compacted Concrete project. It's the first in Santa Rosa and not a lot of people are doing it. It's really not really great. So the first thing I hear from people every time is it sounds different. That when they're driving on it, it sounds different than the asphalt bid for them. And I just always think it'll get quieter too after we've done and grind it. So that's probably a little noisy right now. Yeah, well, they don't even mean it in a negative way. They just mean it just sounds different than what they're used to. So it's funny how we pick up on those. Yeah, this is good stuff. I think it's gonna be an interesting, the decades to come, these technologies are gonna get more and more interesting, more complex. I think it's gonna be fun to watch. Yeah, and I mean, quite frankly, it has to be right. The built environment, they're expecting a 70% increase in the built environment by 2050, especially as you've got other nations that are building out their infrastructure. And if you have materials that are representing right now, 8% of global emissions to hit our climate goals, you can't not touch the built environment. And I think we've had plenty of conversations about how do we design the built environment so that people can reduce their carbon impact. But I think Santa Rosa could be a leader in talking about not just how we design it, but what we build it with to be a part of a solution. So. Great. Cool. All right, thank you. Thank you. Thank you. All right, future agenda items. Let's go ahead and go to public comment to see if anybody in the public has any suggestions for future agenda items that they'd like to see. No hands raised on Zoom. Nope. Anything on your end? I'm curious to know if you think that this was covered by our last item or our last meeting around cooling and general initiatives to actively cool. I know that I'm starting to hear some inquiries, press inquiries around what the city is trying to do to produce a cooling effect and not be a heat sink. Don't know if you think that that would follow then that this committee would look at. Nope, I love it. I love that as a discussion. And I know some cities are doing cool roofs and some are doing materials and to your point about trees. I think there's a lot of areas that staff can kind of take that and bring back some information for us. Well, nothing is not cool. That's right. Yeah. My colleague does not blow hot air. Poor Morgan's not coming back. He's like, I'm done. He has. With that, we'll adjourn. Thanks, everybody. Thank you. That was quick.