Do you like the idea of pervious, or porous, pavement throughout Key Biscayne, allowing rainwater to drain through?<\/p>\n
There are a lot of benefits, but there are also higher initial costs, in addition to regular maintenance expenses.<\/p>\n
Stefano Viola, Vice President at engineering planner and consultant Kimley-Horn and Associates, Inc., in Plantation, recently spoke at a Village Council meeting, where he compared permeable and non-permeable materials and why the penetrable concrete or pavers would not be effective in some areas.<\/p>\n
Viola not only spoke about pavement performance, but also its impact on stormwater, life-cycle costs and environmental compliance.<\/p>\n
Basically, pervious (permeable) materials absorb water, he said. Those include pervious concrete, pervious asphalt, permeable aggregate pavement, and grid\/cellular pervious systems, all allowing some infiltration into the aquifer and into the soils.<\/p>\n
Non-pervious materials include conventional, or traditional, pavers and asphalt, where water bounces off the top and must run off to a swale system or stormwater system.<\/p>\n
“It needs drainage infrastructure,” Viola said. “Aesthetically looking, you really can’t tell (much of a) difference. Pervious can become impervious if not maintained properly,”<\/p>\n
Non-pervious materials also need regular maintenance with crack-sealing and the associated drainage systems.<\/p>\n
Viola said he didn’t want to scare anyone, but with Key Biscayne’s water table being so high, voids will create underneath at high tides, for example, allowing seepage from below in all cases.<\/p>\n
Comes down to costs<\/p>\n
Viola showed a couple of charts referring to the expected costs between permeable and non-permeable materials, with initial installation costs higher for the permeable materials.<\/p>\n
For example:<\/p>\n
Initial startup costs<\/p>\n
\u2022 Permeable asphalt: $7-$15 sq. foot (non-permeable $4-$12)<\/p>\n
\u2022\u00a0Permeable concrete: $8-$20 sq. foot (non-permeable $4-$15)<\/p>\n
\u2022\u00a0Permeable aggregate pavement: $8-$15 (composite pavement $11-$17)<\/p>\n
\u2022\u00a0Permeable gravel grids: $4-$12 (no permeable alternative)<\/p>\n
Note: Permeable surfaces require periodic (annual) vacuuming or pressure washing ($0.25-$0.50 sq. foot to prevent clogging).<\/p>\n
In contrast, non-permeable asphalt often requires resealing or patch work after 5-10 years.<\/p>\n
Expected costs to maintain<\/p>\n
\u2022 Permeable asphalt: 20-30 years; $0.70 sq. foot (non-permeable 20-30 years, $0.60 sq. foot)<\/p>\n
\u2022\u00a0Permeable concrete: 25-40 years; $0.50 sq. foot (non permeable 30-50 years, $0.42 sq. foot)<\/p>\n
\u2022\u00a0Permeable aggregate pavement: indefinite lifespan; $0.80 sq. foot (non-permeable 40-60 years, $0.90 sq. foot)<\/p>\n
\u2022\u00a0Permeable gravel grids: 20-40 years; $0.60 sq. foot (no non-permeable alternative)<\/p>\n
Case study of parking lot<\/p>\n
Viola also brought out a case study from Kimley-Horn looking at the Village Hall parking lot of 16,000 square feet with the expected 30-year maintenance cost.<\/p>\n
Here’s what they found:<\/p>\n
Initial startup costs<\/p>\n
\u2022 Permeable asphalt: $160,000-$280,000 (non-permeable $95,000-$180,000)<\/p>\n
\u2022\u00a0Permeable concrete: $190,000-$380,000 (non-permeable $120,000-$260,000)<\/p>\n
Expected costs to maintain<\/p>\n
\u2022\u00a0Permeable asphalt: $336,000 over 30 years (non-permeable $288,000)<\/p>\n
\u2022\u00a0Permeable concrete: $240,000 over 30 years (non-permeable $201,000)<\/p>\n
(all costs include the sub base)<\/p>\n
Value analysis (based on 30-year life-cycle)<\/p>\n
\u2022\u00a0Permeable pavement: $400,000-$716,000<\/p>\n
\u2022\u00a0Non-permeable pavement: $300,000-$470,000<\/p>\n
\u2022\u00a0Life-cycle cost premium: $100,000-$246,000 over 30 years<\/p>\n
Note: Non-pervious materials would need stormwater management costs; pervious would not.<\/p>\n
Viola noted that the break-even threshold in this case study, must offset $3,000-$8,000 per year in avoided stormwater infrastructure or operations and maintenance costs on sites where pervious pavement can replace drainage structures, underground conveyance, or satisfy stormwater treatment requirements that would otherwise require separate practices.<\/p>\n
Where pervious works best<\/p>\n
More appropriate applications for permeable surfaces for Key Biscayne would be small to medium parking lots, long stretches of sidewalks, plazas and shared-use paths, Viola said.<\/p>\n
Lower traffic areas work best with pervious materials.<\/p>\n
Viola said his company is seeing large vehicles leading to the deterioration of the lower sub-surface areas and failures begin, for both concrete and asphalt layers, introducing water into the underlay.<\/p>\n
Councilman Michael Bracken asked if the Harbor Drive re-milling project could be a place where pervious material could be used, Viola did not recommend it. First of all, the asphalt would have to be cut down to the sub base before starting. Secondly, the traffic on that road with the larger trucks, would greatly less the lifespan of the material used.<\/p>\n
“I’d recommend maybe a cul-de-sac with four homes,” Viola said, “but even then we’re seeing signs of failures with trucks turning (in that small space). I would not recommend it in drive-able surface areas. Private driveways make a lot of sense.<\/p>\n
“Just need the right material for the right place.”<\/p>\n","protected":false},"excerpt":{"rendered":"Do you like the idea of pervious, or porous, pavement throughout Key Biscayne, allowing rainwater to drain through?…\n","protected":false},"author":2,"featured_media":225136,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[126,123,125,124,11262,101710,101712,101711,127],"class_list":["post-225135","post","type-post","status-publish","format-standard","has-post-thumbnail","category-miami","tag-key-biscayne","tag-miami","tag-miami-headlines","tag-miami-news","tag-pavement","tag-pervious-material","tag-porous-material","tag-rainwater","tag-village-council"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/posts\/225135","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/comments?post=225135"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/posts\/225135\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/media\/225136"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/media?parent=225135"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/categories?post=225135"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-fl\/wp-json\/wp\/v2\/tags?post=225135"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}