Mi­ami sep­tic tanks fail­ing due to sea rise

Lodi News-Sentinel - - LOCAL/NATION - By Alex Har­ris

MI­AMI — Mi­ami-Dade has tens of thou­sands of sep­tic tanks, and a new re­port re­veals most are al­ready mal­func­tion­ing — the smelly and un­healthy ev­i­dence of which often ends up in peo­ple’s yards and homes. It’s a bil­lion-dol­lar prob­lem that cli­mate change is mak­ing worse.

As sea level rise en­croaches on South Florida, the Mi­amiDade County study shows that thou­sands more res­i­dents may be at risk — and soon. By 2040, 64 per­cent of county sep­tic tanks (more than 67,000) could have is­sues every year, af­fect­ing not only the peo­ple who rely on them for sewage treat­ment, but the re­gion’s wa­ter sup­ply and the health of any­one who wades through flood­wa­ters.

“That’s a huge deal for a de­vel­oped coun­try in 2019 to have half of the sep­tic tanks not func­tion­ing for part of the year,” said Mi­ami Water­keeper Ex­ec­u­tive Di­rec­tor Rachel Sil­ver­stein. “That is not ac­cept­able.”

Sep­tic tanks re­quire a layer of dirt un­der­neath to do the fi­nal fil­tra­tion work and re­turn the liq­uid waste back to the aquifer. Older rules re­quired one foot of soil, but newer reg­u­la­tions call for dou­ble that. In South Florida, there’s not that much dirt be­tween the homes above ground and the wa­ter be­low.

“All those reg­u­la­tions were based on the premise the el­e­va­tion of ground­wa­ter was go­ing to be stable over time, which we now know is not cor­rect,” said Doug Yoder, deputy di­rec­tor of Mi­ami-Dade County’s Wa­ter and Sewer De­part­ment. “Now we find our­selves in a sit­u­a­tion where we know sea level has risen and con­tin­ues to rise.”

Sea level rise is push­ing the ground­wa­ter even higher, eat­ing up pre­cious space and leav­ing the once dry dirt soggy. Waste wa­ter doesn’t fil­ter like it’s sup­posed to in soggy soil. In some cases, it comes back out, turn­ing a front yard into a poopy swamp.

High tides or heavy rains can push fe­ces-filled wa­ter else­where, in­clud­ing King Tide flood­wa­ters — as pointed out in a 2016 study from Florida In­ter­na­tional Uni­ver­sity and NOAA — or pos­si­bly the re­gion’s drink­ing sup­ply.

In to­tal, there are about 108,000 prop­er­ties within the county that still use sep­tic, about 105,000 of which are res­i­den­tial. The vast ma­jor­ity (more than 65,000) of the sep­tic sys­tems are in un­in­cor­po­rated Mi­ami-Dade.

Mi­ami Gar­dens, North Mi­ami Beach, Pal­metto Bay and Pinecrest have the most of any city, at about 5,000 each.

Some of those cities will see hun­dreds more sep­tic tanks ex­pe­ri­enc­ing yearly fail­ures within the decade, like North Mi­ami Beach, which has 2,780 homes with sep­tic tanks with pe­ri­odic is­sues now. By 2030, that is ex­pected to jump to 3,751.

The re­port did not fore­cast past 2040, when the re­gion is ex­pect­ing around 15 inches of sea rise, a num­ber that is pre­dicted to creep ex­po­nen­tially up­ward over the decades.

“The best re­sponse is sewer ex­ten­sion, but ob­vi­ously that in­fra­struc­ture takes quite a bit of plan­ning and time,” said Kather­ine Hag­gman, the county’s re­silience pro­gram man­ager.

JOEY FLECHAS/MI­AMI HER­ALD

King tide brought high wa­ters that flooded sev­eral low-ly­ing streets on Nor­mandy Isle in North Beach in Mi­ami on Oct. 5, 2017.

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