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Thread: Alley design: best practice

  1. #1

    Alley design: best practice

    We have gravel alleys for the most part. We have residents that want their alley paved, and we are exploring paving 2 "wheel paths" rather than paving the whole width of the alley. The 2 paths would slightly pitch toward the middle of the alley to minimize runoff due to the new impermeable surface (either asphalt or concrete). I am proposing that grass be planted between these two paved paths to help absorb the runoff. I think this is responsible, economical design. It should cost about half as much as paving the full width of the alley. Also it will (nearly) eliminate the need for costly structures like catch basins or manholes or storm sewers for that matter. I would anticipate minimal runoff to the adjacent properties rear yards, unless the "trench" overfills. Has anyone done/seen this, and what are your experiences/feelings/thoughts about it???
    Who's gonna re-invent the wheel today?

  2. #2
    Unfrozen Caveman Planner mendelman's avatar
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    The grass strip in the middle...will it be regularly maintained? Because I see the grass getting destroyed quickly and the area becoming hard packed dirt and effectively imprevious at that point.

    In my muni. (a streetcar suburb of Chicago with almost every lot serviced by an active alley), they fully pave all alleys and pitch it to the middle then grind out a 1/2 inch deep by 3-4 inch wide "trench" down the center to send the runoff to the streets and/or a catch basin in the center of the block.

    Seems to work fine for us.
    I'm sorry. Is my bias showing?

    The ends can justify the means.

  3. #3
    Quote Originally posted by mendelman View post
    The grass strip in the middle...will it be regularly maintained? Because I see the grass getting destroyed quickly and the area becoming hard packed dirt and effectively imprevious at that point.

    In my muni. (a streetcar suburb of Chicago with almost every lot serviced by an active alley), they fully pave all alleys and pitch it to the middle then grind out a 1/2 inch deep by 3-4 inch wide "trench" down the center to send the runoff to the streets and/or a catch basin in the center of the block.

    Seems to work fine for us.
    By Ordinance they are "supposed" to maintain to the middle of the alley. I don't think we have enough fall (very flat area) to get drainage from the middle of the block to adjacent streets......We would have to do alot of shaping and then it may not match existing garages/driveways just off the alley.
    Who's gonna re-invent the wheel today?

  4. #4
    Cyburbian wahday's avatar
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    Check out this link to an example of what Vancouver BC is doing with some alleys:

    http://www.city.vancouver.bc.ca/grea...et&storyid=332

    I realize your physical environment is quite a bit different, but it is a good example of using the two paved tire strips while engineering the rest as permeable (they use geoweb and structural soil to address problems of absorbtion rates and settling). Its also worth noting the degree to which the city got the local residennts involved - you see them out there laying the pavers for access to their individual properties.

    In your environment (which I am guessing is a bit like Albuquerque), paving the bugger will only create more runoff that must be dealt with. Better to let is recharge the soil near the houses than shoo it away in storm sewers...
    The purpose of life is a life of purpose

  5. #5
    Cyburbian boilerplater's avatar
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    they fully pave all alleys and pitch it to the middle then grind out a 1/2 inch deep by 3-4 inch wide "trench" down the center to send the runoff to the streets and/or a catch basin in the center of the block.
    So they've been doing that for a long time? To me it sounds like a recipe for short-life-span asphalt. Doesn't some water stay in the channel and freeze in the winter? Do they use some kind if steel in the channel to keep the edge from crumbling?
    Adrift in a sea of beige

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    Quote Originally posted by boilerplater View post
    So they've been doing that for a long time? To me it sounds like a recipe for short-life-span asphalt. Doesn't some water stay in the channel and freeze in the winter? Do they use some kind if steel in the channel to keep the edge from crumbling?
    Well they've been doing this seemingly forever within the city and some suburbs, but I've only seen it done with concrete,

  7. #7
    Unfrozen Caveman Planner mendelman's avatar
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    Quote Originally posted by KissAndRide View post
    Well they've been doing this seemingly forever within the city and some suburbs, but I've only seen it done with concrete,
    Exactly.

    As for the crumblings edges...it's must really not be must of a concern...these are very low volume residential alleys and it's only 1/2 inch, I'm talking about. Freezing shouldn't be a concern either, because it can just expand up.
    I'm sorry. Is my bias showing?

    The ends can justify the means.

  8. #8
    Cyburbian
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    I suggest paving the whole thing. To help with the drainage issue, look into permeable asphlat or concrete. Google portland green streets and you can see how permeable asphalt has been used. Don't know what your soil makeup is like, or even what the freeze/thaw cycle is like where you are, but this type of thing has been used in winter climates with some success.

  9. #9
    Quote Originally posted by cololi View post
    I suggest paving the whole thing. To help with the drainage issue, look into permeable asphlat or concrete. Google portland green streets and you can see how permeable asphalt has been used. Don't know what your soil makeup is like, or even what the freeze/thaw cycle is like where you are, but this type of thing has been used in winter climates with some success.
    I think that is more $ than paving asphalt or concrete though because it is very labor intesive - at least from everything I have seen. I was looking for an economical solution that would minimize rear yard runoff. We don't plow alleys. One alley would be 3" asphalt or 4" concrete because it is only driven by cars. The other one I am looking at would be 4" asphalt or 6" concrete because it gets dumpster trucks.
    Who's gonna re-invent the wheel today?

  10. #10
    Cyburbian
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    Quote Originally posted by ssnyderjr View post
    One alley would be 3" asphalt or 4" concrete because it is only driven by cars. The other one I am looking at would be 4" asphalt or 6" concrete because it gets dumpster trucks.
    That is WAY under designed. Garbage trucks till tear that up.

  11. #11
    NIMBY asshatterer Plus Richmond Jake's avatar
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    Quote Originally posted by savemattoon View post
    That is WAY under designed. Garbage trucks till tear that up.
    Not necessarily. In temperate California climates the standard local street cross section specified 3-1/2" of asphalt over 6" of compacted base rock.
    Of course, here in Florida, nobody seems to know what base rock is so the asphalt is applied thicker and during the summer heat the pavement develops ruts.

  12. #12
    Quote Originally posted by savemattoon View post
    That is WAY under designed. Garbage trucks till tear that up.
    Keep in mind we already have 12"+ of aggregate base from buildup of the alley over the years. The trucks don't turn on the pavement either, they drive straight thru - the alley is too narrow.
    We have had loaded semi's driving on 8" (unreinforced) and not doing any damage, so I think 6" will be sufficient for trash trucks. There would only be 2-3 trash trucks per week, so it is not like they would use it as a street.
    We also have a 4" asphalt parking lot I designed that successfully sees 2-3 dumpster trucks/week and has held up really well, even with turning on it. It's all in the Base - if you use enough base, you don't need to use as much asphalt, and can save $ on the overall design too. Especially in parking/low volume areas.
    Who's gonna re-invent the wheel today?

  13. #13
    Cyburbian
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    Quote Originally posted by ssnyderjr View post
    Keep in mind we already have 12"+ of aggregate base from buildup of the alley over the years. The trucks don't turn on the pavement either, they drive straight thru - the alley is too narrow.
    Ah...that makes the cheese a little more binding When you said dumpster trucks, I imagined a lot of backing and turning, etc.

  14. #14
    Cyburbian zman's avatar
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    As people redevelop in our alley-accessed areas, they are responsible for paving the alley if they want to use it exclusively.

    Of course, we have alleys, but our transportation division is damned if they'll let anyone have exclusive access...
    You get all squeezed up inside/Like the days were carved in stone/You get all wired up inside/And it's bad to be alone

    You can go out, you can take a ride/And when you get out on your own/You get all smoothed out inside/And it's good to be alone
    -Peart

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