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<br /> _ The Designers' Notebook—VI
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<br /> Many large commercial parking areas, such as shopping wl 1-&'1-0.39.--- ..,-- ,;.r;;;:,.-::,,,.. Atr- .
<br /> center parking lots, are designed to provide parking spaces e .tii",�
<br /> for 2 to 3 times the average daily automotive traffic level in �' -�" '�
<br /> the commercial center. In addition to parking, the lots may ',.".;% '
<br /> - ,+' .", ` 'l,
<br /> help to satisfy open space and stormwater detention require •,. .',,f.:,'.;:r.. ��- -
<br /> ments. As a result, significant paved areas with low parking ;;,.:'t" -
<br /> occupancy are created. Incorporating a properly designed • /
<br /> grass paver system into these low use areas, which may
<br /> comprise as much as 50 to 60 percent of the total parking f
<br /> area,will add to the"green"space,allow for occasional park-
<br /> ing and improve the stormwater detention function of the — ,• .,r '.
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<br /> parking area. ,,4-,;r�''
<br /> Grass pavers are normally placed on a 3 to 6 inch base •
<br /> of sand,fine stone,or gravel which has been spread uniformly -•e
<br /> �'v
<br /> over a smooth, cleared subgrade. The voids in the blocks . 4%p®
<br /> are filled with soil in which has been planted a suitable grass ,, ,, ;41) 7-;' ��
<br /> or groundcover. A properly chosen grass or groundcover must • '
<br /> withstand occasional vehicular traffic, mature quickly,and be •.
<br /> suitable for the light and moisture conditions of the area in r',
<br /> which it is planted.Where plantings are not desired,the voids fi • P.,
<br /> can be filled with sand or gravel. ''~ .7 A '• -•A
<br /> Benefits of the perforated paving block system are nu- ..
<br /> merous. When the grass or groundcover is established, the Typical Paved Lot
<br /> area incorporating grass pavers will resemble the appear- yp
<br /> ance of a well maintained lawn or field.The area can be used
<br /> for parking while satisfying some open space requirements F ",411 - -• ...'..•_ i i'�"' .,, kr,��, .,..A.-
<br /> in an innovative manner. These benefits are particularly at- �„y -• 1,-....• '• y;:,;,,,r15,. t..c
<br /> �'0w > �-
<br /> tractive to owners and occupants of commercial centers. ~Y :•
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<br /> The velocity of water flow over perforated paving blocks r : 'F„�
<br /> is about half of that on a comparable paved area. Because ` }
<br /> of this, runoff water will soak into the soil and subgrade of
<br /> the system, adding to the volume of water that can be stored
<br /> when the parking area is also designed to provide stormwater
<br /> detention. The "captured” storm runoff then provides mois-
<br /> ture necessary for growth of the groundcover, reducing or
<br /> eliminating the need for periodic watering. The remainder of
<br /> the runoff water will percolate through the soil into the ground V r a
<br /> water system.
<br /> However, certain precautions must be taken when•using r ^
<br /> grass pavers. Oil and gas dripping from cars and trucks, and
<br /> the constant running of tires over the plants, will kill the grass 4y ?
<br /> or groundcover and may clog the soil and prevent the flow
<br /> of water to the subgrade. If the subgrade of the perforated
<br /> paving blocks does not absorb runoff water quickly, ponding . ' ;1 ".. 'Q, ''
<br /> may occur on the surface. While this may not be detrimental �.,
<br /> to users of the area,the grass or groundcover may be harmed
<br /> by the high moisture conditions. In addition, if there is in Bloc
<br /> sufficient drainage, in northern climates freezing and thawing Perforated Paving. o4iF .
<br /> may cause heaving of the blocks. Parking' Lot • "7
<br /> NatureScape July 1982
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