Orange County NC Website
Browse       Search
26 <br /> 1 Eric Lappala: That's the purpose of the modeling analysis I did was to demonstrate that that's not the case.There's not <br /> 2 really an aquifer underneath this. What this site is underlain by bedrock which weathers gradually up until you basically get <br /> 3 the clay rich soils at the top. And so you have this material and the rock is actually fractured. There's a lot of the water <br /> 4 supply wells in these kind of geologic environments, including this neighborhood,the private water supply wells get their <br /> 5 water out of the fractures. So that's why the wells have to go so deep. The weathering zone is only about 30 to 50 feet <br /> 6 deep. And the water in the shallow zone is just not very reliable. So that's why all the water supply wells typically go deep. <br /> 7 <br /> 8 Beth Bronson:And you're professional recommendation with this would be deeper well? <br /> 9 <br /> 10 Eric Lappala: Oh yes. They're going to have <br /> 11 <br /> 12 Beth Bronson: At 300 plus? <br /> 13 <br /> 14 Eric Lappala: Yes, in order to get the yield they need to supply the water demand you're going to have to go somewhere, <br /> 15 again based off on this study that the USGS did of the whole county and similar studies that I've done in Orange County <br /> 16 and in Chatham County and so forth, the wells are going to have to be anywhere from 200 to perhaps 300 feet deep to get <br /> 17 intercept enough fractures to get the water supply. <br /> 18 <br /> 19 Beth Bronson:And considering that most of these single-family homes surrounding it probably on average do or do not <br /> 20 have that same type of well? <br /> 21 <br /> 22 Eric Lappala: If they have a well it's to get the yield that they need for a two-bedroom house,they're going to have to have <br /> 23 that. You need somewhere between, to supply a single family home you need somewhere between, it's not very much, 1 <br /> 24 to 4 gallons a minute out of the well. But again a lot of homes don't have a storage facility so you're waiting for the,you <br /> 25 turn on the faucet,the pump has to go into the pressure tank to give you the pressure in your house. <br /> 26 <br /> 27 Beth Bronson: That's why you have the pressure tank? <br /> 28 <br /> 29 Eric Lappala: Right. Pressure tank provides you the pressures so you can take a shower. <br /> 30 <br /> 31 Beth Bronson: And of that first couple hundred gallons that the rest of it being down there? <br /> 32 <br /> 33 Eric Lappala: Yes. <br /> 34 <br /> 35 Beth Bronson: I'm just trying to understand the average age of these homes surrounding it are not necessarily up to date <br /> 36 with the well depth technology. When these houses were built,these houses were built in the 70s. These homes were <br /> 37 built in the 70s. And if they're well, you were saying something about it was at 30 feet, right? So anywhere from 30 feet to <br /> 38 300 feet you could achieve a well depth? <br /> 39 <br /> 40 Eric Lappala: Well, I did not do an inventory of the houses in the neighborhood that have wells. I wouldn't know that <br /> 41 answer. It's that, if somebody wants to find that out you can do that. The homeowners would have to agree. The well <br /> 42 driller typically puts a tag on the well when he installs it that says who he was and how deep it was,when he drilled it. <br /> 43 Whether, the other thing in this fractured rock aquifer like we have here,you only put casing down to where this weather <br /> 44 material is so it doesn't cave in the hole. But anything under it is an open hole. So you don't put a typical well screen and <br /> 45 sand pack and so forth to complete a well in these kind of environments. It's basically surface casting that's cemented off <br /> 46 to protect the well from any surface pollution.And then it's an open hole over that. <br /> 47 <br /> 48 Beth Bronson: Okay. And again, I'm trying to understand that proportion of water usage at the depth what kind of effect <br /> 49 that might have on somebody who has,on shower or wells in the surrounding area. <br /> 50 <br /> 51 Eric Lappala: The effect, the radius of influence of these wells is typically, there's a reason there's a 100-foot buffer around <br /> 52 water wells. Public water supply wells. In general,that's the area from which that well receives recharge from rainfall to <br /> 53 replenish it. It's also a reasonably good guide as to how far,when that well is pumping, it's going to affect things. They're <br /> 54 kind of apples and oranges. So the radius of influence of these wells pumping anywhere from between 1 to 4 gallons a <br /> 55 minute, not 24/7 but enough to provide enough water supply when it's needed, is somewhere maximum maybe going to be <br />