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Site Development Strategies

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In the previous lecture, we have seen what are the broad aspects which we should keep inmind while selecting a site for sustainable development, sustainable architecture. In thislecture today, we will look at what are the strategies which should be employed forsustainable site development. We are largely talking about the design and constructionphase when we are developing the site.(Refer Slide Time: 01:10)So, while starting with the sustainable site development, we have to first assess the siteconditions based upon different parameters. So, the first and foremost parameter istopography. Here we have to look at what is the contour map of the site, what are theunique topographic features; for example, there might be a rock outcrop, there might be awater body, there might be a thick dense forest. So, what are the unique topographic features which are there, and we will also do an estimation of the slope stability and therisks associated with it.Now this topography is important, because it affects a lot of other parameters, otherfactors. One very important is how the storm water runs through the site. So, if there is asteep slope, the storm water runs very fast; and when we are talking about storm water,simultaneously soil is getting eroded along with the storm water.So, how the slope should be utilized, how the construction activity on this topographythis variation shall be done will be dependent upon how, what is the contour map andwhat is the topography. So, it is important to assess topography.(Refer Slide Time: 02:37).The next is hydrology: we have to understand the hydrology of the site. Now thatincludes flood hazard areas; we have to see where the nearest water body is and howmuch is the flood hazard. That is what we were talking in the previous lecture, where wetalked about the flood plains; we have to ensure that the site does not come in floodplain. Even when it is not coming under the flood plains, we have to see what are theflood hazards for the given site.We have to understand whether where are the delineated wetlands is our site or part ofthe site is part of that wetland or lake or any other water body, what are the shorelines ifwe are talking about the coastal areas, what are the shorelines, what are the rainwater collection and reuse opportunities depending upon the topography analysis assessmentthat we have done. So, topography and then hydrology is very important to beunderstood before we go on to design and develop the site.(Refer Slide Time: 03:42)The next is climate. So, we have already done a detailed understanding of how theclimate of a place we understood, what are the different parameters, what are thedifferent factors which are used to understand the climate of a place. Now that was themacro level study. Here when we are talking about climate, we are doing it specific tothe site; here we are talking about the solar exposure.So, for example, there are there may be a lot of buildings around the site and they mayactually block all the sun which is coming onto the site; or there might be buildings onone side of the exhibit the site under consideration and the other side might be free, howmuch of the hard surfaces are there around and all that, that will also come in climate.Also when we are talking about the site, specific climate issues and assessment we aretalking about prevailing winds; because the direction of winds may change inside thecity, once they are inside the city. Because the built mass, the skyscrapers and high risebuildings they divert; they deflect the wind when it passes through the city. So, it mightbe a different experience, it might be a different direction altogether.And besides that the overall macro factors which define the climate of a place. (Refer Slide Time: 05:06)After this we also have to understand, we all also have to assess the vegetation which ispresent; because we are talking about sustainable site development and at no given pointof time should we be compromising on or exploiting the natural resources which arepresent. And vegetation is one very important resource.So, we have to know what are the different types of vegetation which is present, howmuch of the Greenfield area is there. We have to do that, we have to properly map whatall trees are there, where they are, what are the different species which are there, and ifany of these species is a threatened or endangered species. Even plants have endangeredspecies, some plants are on the verge of extinction; because they have been overused andthere is no replantation or regrowth of them. And if it is the site is a unique habitat tocertain plants and animals that is what we have to see.We also have to understand if there are any other invasive plant species. If youremember our initial lectures we talked about alien invaders; now alien invaders are notjust animals, they may also be plants. So, certain plant species may be invasive and theymay just take over the entire area. So, we have to identify those, all this has to be donewhen we are assessing the site for its vegetation resource. (Refer Slide Time: 06:32)Besides this we also have to look at the soil characteristic.So, what are, what is the type of soil, what is its retention capacity, what is its bearingcapacity; besides all those, we also have to see whether it has been previously developed,whether there is a potential for redevelopment, the kind of plantation that can be grownin the soil, is there any disturbance which has been caused to the soil. So, all that willcome within the discussion on soils.(Refer Slide Time: 07:06) Now, besides these physical and tangible aspects of resources which are already present;we should also look at how the humans have been using the site or what are thepossibilities in which the humans can use. Now here this we would do on the basis ofsome factors; few of these are views. Now what kind of views and vistas are available tohumans, to occupants from this site and at what height.Now, this may be view and vista to natural scenery which is available around or it mayalso be some iconic structure which may be available, which may be there in the vicinity,it may be something else also. So, the views to that; then we have to look at how thetransportation, adjacent transportation is there. So, in case of large sites, there are severalsuch cases where on one side there is a metro line coming and on the other hand theremight be a public transportation. Now where would the entry to the site be has to keep inmind, where would largely the people be coming from, what kind of transport mode theywould be using.We have to look at the adjacent properties, how humans would be using those adjacentproperties. So, suppose there is a commercial building which is being developed, andthere is a commercial build a huge mall, shopping area which is right next on the site.Now it is absolutely human that the people will be using the adjacent site. So, how, whatkind of connections should be provided, so that it is easy for people to use. Now for thatthe assessment of adjacent properties has to be done.Besides this the kind of construction materials which can be used for their recyclabilityand reuse potential, may also be assessed at this stage. This is also the stage where weare looking at what kind of uses are going to be there, when we are talking aboutoccupants, human. So, suppose we are developing a school for differently abled children;now what kind of materials shall be preferred when we are talking about differentlyabled children and their school?So, this is not based upon any other factor; like local availability of the material or itsdurability or any other property, but we are primarily looking at the human use aspect ofit. So, this is the social aspect of site assessment. (Refer Slide Time: 09:55)Once we have assessed the site for all of these, we would then go ahead with designingthe site for a sustainable development. So, couple of aspects that we would keep in ourmind while designing and also developing. So, it is design and construction bothtogether, when we are talking about sustainable site development.So, there are certain aspects which we would keep in mind; the first and the mostimportant we being we have to minimize the disturbances to the site. The natural systemsto the soil, to the vegetation, to the open area, to habitat if it is of any other species, to thestormwater pattern; so there was a natural stormwater drainage pattern, which wasexisting before the development would take place. We have to minimize the disturbancesto each of these; to hydrology, to topography, to vegetation, to everything this is whatour main aim should be. (Refer Slide Time: 11:04)Now to do that, we have to limit the construction. So, one the design should bedeveloped in such a manner that it respects the topography and hydrology of the site, andensures the retention of maximum amount of vegetation which was already present there.In order to do that, we will have to limit the construction. So, suppose a building hasbeen planned, a building block has been planned; now when the construction goes on alot of spillover because of excavation and construction material being brought in, a lot ofspillover is there.So, though the building may be restricted limited only to this much area, but the spilloverof this construction may be even wider; we have to limit that. So, if you look at differentrating systems; there are different guidelines which are prescriptions that the disturbanceto the site may be limited within 1 meter, 2 meter, 3 meter of the building boundarydepending upon what kind of construction it is.So, suppose it is a walkway, it is just a paved walkway; the allowable limit is smaller.So, it may just be half a meter from the side of the walkway; when it is a larger buildinga huge full-fledged building, this limit may exceed, the increase to around 1.5 to 2 metersdepending upon the type of building structure which is coming up, depending upon it isheight. But the overall impact of this construction shall be limited to certain areas andthis will happen if it is being done; the construction activity is being done in a preplanned manner. So, there has to be a planning of construction which has to be done. So, constructionplanning and management has to happen.(Refer Slide Time: 13:08)So, we are talking about; when we are talking about limiting the construction, we aretalking about, also talking about development footprint. So, it is not just the totalbuilding area which is being developed, it is the overall site which is being developed.So, many are times; even though the building footprint is small, the developmentfootprint is quite large.So, there are roads, there are walkways, there are some play areas. So, there is hardly anysite which is left which is not developed or which is undisturbed. Now these are twodifferent things; so we talking about building footprint and we talking aboutdevelopment footprint here. We have to reduce the development footprint. (Refer Slide Time: 13:50)The next aspect would be spill prevention and control; now often the constructionmaterial which is used on site is spilled over almost everywhere on the site. For example,say we are using bricks very simple, it is a very common building material in ourcountry.So, if bricks are being used, now those bricks will be brought from somewhere, they willbe stacked on your site, they will be soaked in water, they will be then taken to the actualconstruction where the building is getting constructed. Now in that process there is a lotof spilling of this material. So, not just, now brick is relatively a safe material and it canalso be picked up cleaned; and the soil can be the original characteristic of it may beretained. But there are other materials; for example, there may be chemicals, there maybe adhesives, additives which might be used on the construction site and they are.Now, spilling of that may actually change the characteristic of the site forever the soil, itmay not have the same characteristics. (Refer Slide Time: 15:03)So, we have to ensure that there is no spilling which is happening and that will comewith proper barricading and alienating of areas, where such materials will be stored,proper handling of these materials. So, chemicals on a proper sheet of metal plate, propercubicles being made, areas being delineated categories to sort different categories ofwaste.So, all that who will come as part of the construction management plan, which will helpin reducing and preventing the spilling on site.(Refer Slide Time: 15:39) The next aspect is soil erosion and it is control. Now often during the construction a lotof soil is eroded, because of rains and also wind; that has to be absolutely controlled,minimized and brought close to zero. So, no soil should be eroded during the process ofconstruction. Now there are multiple strategies and practices which are which will comewhen we are talking about soil erosion; the first and foremost is protecting the topmostsoil topsoil from erosion.Now, topsoil is the most fertile soil all of us know that, that is also the soil which is mostneglected and abused, misused during building constructions. We excavate and that soilis either dumped used back for refilling is not properly taken care of, dumped for someother purpose dumped somewhere else. Now that topsoil should be stored properly inproper manner, so that it can be reused in landscaping because it is a fertile soil.In addition to just reusing the soil, it should be we should try our level best to bring thesame soil back to the same place; because a lot of bacteria are there in the soil which isthe characteristic of that soil. So, if the soil which was excavated from say site A isbrought back to the site A it will be beneficial and the overall site will be healthier moresustainable.(Refer Slide Time: 17:32)So, two different strategies and these practices for soil erosion control are also mentionedin NBC 2016 in chapter 11 and chapter 12, where protection of landscape duringconstruction and soil and water conservation are being addressed. (Refer Slide Time: 17:44).There are many strategies which are given as part of NBC and which are also beingpracticed. I am just mentioning few here, but there are many more; it is not acomprehensive list of strategies which can be used for soil erosion control. One isinfiltration trenches; if you can see here, this is an infiltration trench. Now this isnothing, but just a little depressed area which is filled up with rocks and boulders and itallows water to stay to hold.So, it one we have to reduce the speed with which the stormwater flows. Once we areable to reduce the speed, we are able to reduce the amount of soil it carries. So, reducingthe speed and then holding it in one place where the soil is settled. So, if the water whichis flowing comes here settles, all this soil will be retained within this trench and therewill be no soil erosion which will be taking place. (Refer Slide Time: 18:46)Besides infiltration trench, we have bio filtration swale or grass swale.So, in infiltration trench rocks and boulders are used as a lining, they just filled up. So,the water percolates down and the soil is retained. In a bio filtration swale, instead ofrocks and boulders, we use vegetation. So, this is an example where they have justcreated a trench, a kind of depressed channel; and gradually the vegetation has come up.Now the roots of the vegetation, the plants which come up in this swale, bio filtrationswale; they keep the earth porous, and they help the water to percolate down and toretain the soil.So, it helps both in stormwater management as well as the soil erosion control. So, it is astrategy. (Refer Slide Time: 19:45)The other is a sand filter. So, sand filters are devices that filter stormwater runoff througha sand layer into an underground drain system. Now here what we are doing is, we aremainly lining the entire channel of this stormwater with sand, which will help to filter,which will help to reduce the speed, and also help in percolation of water down to theground; and during the process of this filtration, the soil is held back by the sand.So, this is another very effective strategy. There are sedimentation tanks.(Refer Slide Time: 20:25) Now, sedimentation tank; the previous three strategies which we just discussed, requireless of space; they are just channels. So, depending upon how much area do you haveavailable, smaller channels can be created; they can be created at regular intervals and allof that; however, sedimentation tank requires larger area.(Refer Slide Time: 20:49)We need huge areas where the water can be, the entire water from the site during a stormcan be brought; it will be allowed to stay there, retain. It helps in charging recharging thegroundwater, because the water will percolate down and it will control the soil erosion.So, a lot of water bodies in villages and all actually acted; the ponds which we normallysee in villages are actually serving the purpose of a sedimentation tank. So, all the, andthese will be created in the low lying parts of the site, where the contours are low. So,that all the water comes together there, there is no additional means additional channelwhich is created to bring water to these. Naturally through the natural slope, the watergets collected to these into these sedimentation tanks. The soil is held and the water ispercolated down to the ground.So, these are some of the examples. Now these tanks may require lining; like this onewhich we see here, this is also a sedimentation tank, or properly done lining, or it couldjust be a loose lining; it may not be lined at all, it may just be very naturally occurring. (Refer Slide Time: 22:16)But sedimentation tanks will again help in both; reducing the stormwater flow out of thesite, and holding the soil back.Besides sedimentation tanks, we are we can also look at trenching. So, instead of aregular slope, this slope can be broken. So, smaller trenches are created. Now once thewater comes instead of running directly, water comes here collects. So, the speed isbroken. And then once it overfills, it is further flowing, again the speed is broken andlike that. So, there would hardly be any water which is flowing through the slope, andthere will be more percolation down to the ground. So, we are allowing for morepercolation to the ground and at the same time we are reducing the speed of thestormwater, so that no soil is carried along with the water, stormwater.The other methods are seeding. So, the slopes will then be seeded. So, there will bevegetation which will be there. So, lose and not a very manicured planned manner; butjust seeding the entire slope, will help in reducing the flow of water and percolation of itdown to the ground and reducing soil erosion. Others are using gabion wall, the verythick gabion wall which is loosely filled wall with gravel and boulders and sandbags;sandbags like these, they may be placed to stabilize the soil wherever there are slopes.So, these may be used to reduce the sliding of the soil, carrying of the soil with water orwind with the help of these. (Refer Slide Time: 24:02)There are strategies where the entire patch of the slope has been covered withgeomembrane or other kind of fabrics. This one is a particular strategy and a productwhich is called Bhoomi Vastra. Now here the entire soil is covered with that, it isbiodegradable, it is organic; but by the time the slope stabilizes this material decomposesitself. The slope has stabilized, because the vegetation has grown. So, there are roots andthis will eventually degrade, because it is organic.So, this is again another strategy of soil stabilization.(Refer Slide Time: 24:42) Temporary seeding and mulching we have already seen, not just for slopes, but also forplain areas. The soil which is tagged, which is coming out of the excavation for largebuilding product projects, it may be seeded and mulched temporarily; but it will help incontrolling the soil erosion.And then proper stacking of materials; many a times because the material is not properlystacked, it disturbs the compactness of the soil, it makes it loose and that is what alsoincreases the soil erosion. So, besides soil erosion, another very important factor aspectis preserving the vegetation which is existing on the site.(Refer Slide Time: 25:28)Now, majority of the times this will happen; because it is not just the building footprint,it is the development footprint. So, once we limit the development footprint, there arelarger chances where we will be able to preserve the existing vegetation; but if wedeliberately want to preserve existing vegetation, we have to design the buildings in sucha manner that trees are not being cut.The buildings may be chamfered; the buildings may be slightly shifted, so that a treewhich is existing is preserved. And once through design, we have arranged to preservethese trees; during construction we have to actually physically preserve. So, there will bebarricading, there will be cover which will be provided to the trees during theconstruction activity and we have to ensure that this root of the tree is not gettingdisturbed. In case there is a tree which needs to be cut while the development, while theconstruction of the building has to be commissioned for different rating programs, greenbuilding rating programs, different numbers are there; but around 3 to 4 times more treesare supposed to be planted. In one of the rating systems, you can see that as high as 10times the number of trees cut is to be planted on the site; it is not elsewhere, but it is onthe site that those trees have to be planted.So, if one tree is cut say, four trees need to be planted and provisions need to be made.But the best strategy is to preserve the existing vegetation through design first, and thenthrough construction like this, proper covering of these trees.(Refer Slide Time: 27:29)In case we cannot preserve the tree for some reason, tree transplantation could also bedone. Now it is not a very easy thing to do, because the tree has to be excavated alongwith it is root. So, for all the fully grown mature trees, they have a huge large rootstructure as large as their foliage above on top.So, this entire root has to be taken out. So, it becomes quite a challenging engineeringexercise to transplant a tree; and at times the tree may not survive because of the changein the soil condition and moisture and a lot of other things. But in case there is nopossibility of preserving the tree, tree transplantation can also be done. (Refer Slide Time: 28:11)Another very important aspect is dust prevention and control. So, often when buildingdevelopment is taking place, the construction takes is taking place; the soil becomes veryloose and it creates dust all around the construction area, all around the construction site.And it is a major cause of air pollution in cities; because a lot of construction activityalmost keeps going on, and these suspended particles of soil which is dust, very fineparticles they create air pollution.To control that dust, there are certain measures which need to be taken into account,which need to be practiced during construction. This is largely during construction. So,we have to barricade the site. Now you would find that, in India earlier there was nobarricading which was happening; but now almost all large projects are barricading. So,the entire site would be barricaded with at least 3 meter high barricades and thesebarricades may go up. So, this will contain the air pollution to the construction site only.In addition to that washing the wheels of all the vehicles which are exiting the site;because this soil is loose and it is taken by the vehicles and through their wheels. So,wheel washing. So, this is a water body, a water tank a very shallow tank which iscreated full of water.So, every time any vehicle goes out of the site, the wheels are automatically washed. (Refer Slide Time: 29:55)So, there are different strategies which are used for wheel washing, this is for dustprevention. In addition to that coverage of fine aggregate; here we can see that the fineaggregate and also the soil which is excavated and it is available on the site is properlycovered. Not just what is there on site; but all the vehicles which exit the site and theycarry a lot of construction materials, they need to be properly covered too, so that they donot carry dust with them.In addition to that, what is sprinkling on the fine aggregate and excavated earth; so waterwill control the dust from rising up and creating problems. (Refer Slide Time: 30:34)For all the diesel generator sets on site which are to be used, they should have properchimneys with their outlet us facing away from the site. And in case of large tallbuildings, the use of dust barrier; so these geomembranes should be covering the entiresite, not.So, this is just one portion which is there, but actually the entire building has to be cladusing these geo membranes, so that no dust during the construction of the building comesout.(Refer Slide Time: 31:10) So, this is what I was talking about, where the vehicles have to be properly covered, thevehicles which are carrying loose materials.(Refer Slide Time: 31:17)Now, to implement all these strategies, to practice all these strategies; a proper sitemanagement plan has to be created, where would the vehicles enter and exit from, wherewould that wheel washing happen, where would the different materials be stacked, wherewould the earth which is excavated that will be stabbed.So, all that has to be developed in the form of a site management plan; how in a phasewise manner the construction activity will go on, so that the transportation of materialsthrough the site is not happening as much the development footprint is contained. So, forall of that, proper site management plan will be created; there will be dedicated activityspaces, there will be dedicated roles and responsibilities for people and different phasesof development will be identified and planned. (Refer Slide Time: 32:16)In addition to these construction related strategies and practices, we also have to payattention to provision of open spaces; whether they are we are developing commercialbuilding or residential area or any other type of building, because that is the basic humanneed. Humans need to go out and interact with nature, with five different elements of thenature and for that we need open spaces. We are not talking whether these spaces have tobe vegetated, they can be hard or not, which we will come to in the later slides; but hereit is just about having enough open areas in the site.(Refer Slide Time: 32:57) Now, one more aspect which is of great concern in cities is the parking footprint. Theaim is to promote people to use public transportation and not come using their ownvehicles; that can be done if we provide only the amount, the number of parking’s whichare prescribed as per bylaws, not providing anything more than that. So, people will bediscouraged; if they do not find enough of parking inside the office building, they will bediscouraged to bring in their cars that is the whole intent. So, the parking footprint has tobe reduced; and to reduce the building footprint of the parking mechanical parking,basement or stilt parking they have to be used.So, these are new technologies which are available where the parking’s require muchlesser amount of space. Separate though, it does not mean that visitor parking will not beprovided.(Refer Slide Time: 33:55)Separate visitor parking has to be provided