유수 측량 및 조절 제품 전문 업체인 Badger Meter 사는 최근 2012년 11월 만들어진 밀워키 본사의 10,000 평방 피트 크기의 녹색지붕의 새로운 개량사업을 완료하였다고 발표했다. 본 개량 사업은 연간 유수의 우수 시스템으로의 유입을 90% 가량 감소시키고 최고 유수 시간대를 제외한 나머지 시간에 남은 10%의 양을 지연시키는 기능을 할 것으로 알려졌다.

녹색지붕은 완전 건조시의 6000 갤런까지 강수량의 전부를 응집할 수 있는 것으로 드러났다. 만약 양이 포화되거나 동파의 위험이 있을 경우, 응집된 물의 일부는 흘려 보내진다. 하수도의 위험한 표면, 주차장, 지붕등에서 발생된 과잉수들을 응집·보존함으로써 위 회사는 하수도 과잉 유출 및 지하 침투 등의 위험을 최소화하려는 것으로 보인다. Badger 사와 같은 녹색지붕은 또한 미국 내에 가장 큰 수생태계 위협요인으로 손꼽히는 강수와 오염된 우수 유량과의 섞임을 방지는 기능을 한다.

MILWAUKEE, WI, Aug. 20, 2013 -- Badger Meter, a specialist in flow measurement and control products, completed a new 10,000 square-foot green roof at their headquarters in Milwaukee, Wis., in November of 2012. The renovation is expected to reduce the annual runoff into the stormwater system (an estimated 249,000 gallons) by as much as 90 percent and delay the remaining 10 percent to a time past peak flows.

For every one inch of rainfall, the green roof collects just under 6,000 gallons of water if it is dry. If it is saturated or frozen, some of the water will run off. By keeping excess water from roofs, parking lots and impervious surfaces out of the sewer system, the company is helping reduce the risk of basement backups and sewer overflows. Green roofs like Badger's also help prevent rain from becoming polluted stormwater runoff, the biggest remaining threat to our rivers and lakes in the United States.

When it was time to replace the roof, Badger Meter thoroughly reviewed available options to find the most effective solution. According to Brian Rogers, the company's facilities manager, after several months of in-depth research, he and his team determined a green roof was the best option. A key benefit of a green roof is water retention. During a rainstorm, green rooftops collect and store water that would otherwise run off into the sewer. "We wanted a solution that would be innovative, efficient and all-around better for the company," says Rogers. "The green roof not only makes sense from an environmental standpoint, it was a sound economic choice."

Since 2003, the Milwaukee Metropolitan Sewerage District (MMSD) has been awarding green roof incentive funding to building owners to help reduce the volume and number of sewer overflows to waterways. Badger Meter was awarded $48,135 through MMSD’s Regional Green Roof initiative program to pay for part of its green roof project.

Rogers says the company is using its own metering technology to measure the water absorption. Badger Meter installed two of its 2-inch M-Series® Electromagnetic (mag) Flow Meters and a controller, so it can measure the outflow from each of two roof drains. It also mounted a weather station on the rooftop to measure rainfall.

"With the possibility of rocks, sticks and debris coming down the drains from the roof, our mag meters are perfect for this application because of their open flow tube design and high accuracy," explains Rogers. "Once the weather stations are fully integrated into our software system, we’ll be able to determine how much rain the roof is absorbing on a per event basis. We’ll also be able to measure how fast it recovers after a rainfall."

Other sustainability benefits of the green roof include energy efficiency, noise mitigation and air scrubbing. The insulation properties of the soil and plant material generate both heating and cooling system savings estimated at $3,100 per year or $62,000 over 20 years, the typical lifespan of a conventional roof. Plants, soil and the air trapped in the soil provide acoustic insulation, reducing indoor sound by as much as 40 decibels. The green roof buffers acid rain and helps remove nitrate pollution, while at the same time slowing air movement, allowing pollution to settle and detoxify. Plus, the plant material guards the roof membrane from the damaging effects of weather, so the expected lifespan of a green roof is 35 to 40 years; double that of a conventional roof.

The green roof consists of a 3-inch layer of insulating materials, a layer of hard board, a sealing membrane, a leak-detection material and a 4-inch layer of green material. Langer Roofing and Sheet Metal, Inc. handled the design, tear-off of the old roof and installation of the conventional portions of the new roof. LiveRoof® supplied the green material. Green material is custom grown for each green roof project off site in modules for about 12 weeks. Because the LiveRoof plants are mature, there is no costly establishment period.

The vegetation is primarily sedum, which is selected, developed and tested specifically for rooftop cultivation. The plants require very little maintenance and are resistant to disease, insects and drought. Several varieties that are green and red in color are arranged in a design that mimics the Badger Meter logo symbol and is visible from above.

[출처: Waterworld / 2013년 8월 20일]