# Hamilton West Apartments Ecoroof 1212 SW Clay Street, Portland, OR

Project Summary

Projec t T y pe : M u l t i -fam i l y resi dent i a l – de m onst r at i on pr oject
Technol ogies : Ecoroof

Ma j o r Bene fit s : • Inc r ease d roof longevity – T h e ecoroof s h o u l d d o ubl e t h e l i fe of t h e ro of

. • St orm w at er m a nagem e nt – Th ere i s a su bst a n t i a l reduct i o n i n ru n o f f f

r o m m o re t h an 8, 40 0 s q

. ft

. o f ro of

. • Ov er t h e co urse of a typ i cal y ear, t h e stormwat er facilities m a n a g e abo u t 7 6 8

, 00 0 g a llons of pote n tial storm w ater as sum i ng a n a v era g e re ten tion rate of 53.5% a n d an avera g e a n nual rain fall o f 37 i n ch es.

• 5, 14 0 s q

. ft

. o f l a ndsca pi n g w a s ad de d, i m provi ng t h e u r ba n e nvi ro nm ent and t h e ae st het i c ap p eal of th e pr op er ty. Cos t: $ 127 ,5 00 (u n it co st o f $1 5 p e r sq

. f t

. of i m pervi o us a r ea m a naged )

. En vi r o n m ent a l Servi c e s g r an ted $90 ,0 00 f o r th e pro j ect.
Constr ucted : Sep t em b e r 1999

Background In fall 1999, an ecoroof wa s installed on the newly constructed Ha m ilton West Apar tm ents build ing. This was a joint p r oje c t between the H ousing Authority of Portland (HAP), the City of Portland Bureau of Environmental Services (BES), and the Po rtland Developm ent Comm ission (PDC). It was the City’s fi rst ecoroof de m onstration and testing facility. At Ham ilton, th e City m easures stormwater capture and water quality a nd com p ares the success of planting m e thods, soil type and depth, and vegetation selection.

Ha m ilton and other ecoroofs represent an im portant sustainable storm w ater (low i m pact developm ent) strategy. They m a nage storm w ater at the source, using natural system s that hav e po sitiv e im pacts for storm w ater runoff volum e and quality. Associated benefits su ch as energy cost reduction, air pollution and heat reduction, bird a n d i n s e c t h a b i t a t , e roof lifespan, and urban b eautificatio n, m a k e e c o r o o f s a valuable urban asset. x t e n d e d

The 8,700 square foot roof is divided into an el evator vestibule (not vegetated), a 1,000 square foot concrete paver terrace with seating and tables, and a 5,140 square foot ecoroof containing succulents, grasses and flowers. The Ha m ilton Apartm ents ecoroof show cases opportunities for partnerships by public and private organizations and has served as a catalyst for other groups to pursue this m e thod of st ormwater runoff reduction. The building and roof terrace are an exam ple

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, 2 005 Pag e 1of how to maxim i ze density on an u r ban inf ill site while prov iding outdoo r am enities f o r tenan t s. Based on monitoring results, the ecoroof pr ovides excellent storm w ater m a nage m e nt

.

Overview of the Stormw ater System In order to test the stormwater capacity of different types and depths of soil, the ecoroof was divided into east and west sections. E ach side was planted using identical m e thods and types of vegetation. The east side consists of 2,620 square feet of vegetated cover w ith initia l s ubstra t e depth of 3 inches. Saturated wei ght is 10 pounds per square foot. The west side consists of 2,520 square feet of vegetated cover with initia l soil substrate depth of 5 inches. Saturated weight is 25 pounds per square foot. There are tw o roof drains one in the west section and one in the east section. Each section slopes toward its roof drain.

The vegetated portion o f the roof receives p r ec ipitation directly. Runoff from the sto n e terrace infiltrates through the pa vers to the sand bed below and into the ecoroof substrate. Air conditioning condensate and runoff fr om the elevator vestibule is pi ped directly to the roof drain so that it does not skew st orm w ater m easurem ent data.



### Stormw ater Capacity and System Components

Stormw ater Management Goals The ecoroof is a dem onstration project in stor m w a t er m a nagem e nt. It was designed to m eet multiple go a l s and objectives th at ben e f it tenan t s, partne rs, an d the la rger community. Goals include reducing peak flows and volum e of st ormwater, which helps alleviate Portland’s

com b ined sewer overflow (CSO) problem ; a nd providing opportunitie s for research and education in developm ent of ecoroof technol ogy specific to the Pacific N o rthwest.

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, 2 005 Pag e 2System Co mponents

Ecoroof Catchment a r ea : 7,800 square feet Facility foo t print: 5,140 square feet Overflow : D r ains to sto r m sewers Additiona l information :

• The roof is built in lay e rs. From the bottom up, they are:

o A waterproofing m e m b r a ne over the roof structure

o Root-res i sta n t barrie r made from 6 mm polyethylene

o A drainage layer m a de from a geotextile drainage fabric

o 1 cm thick Poly-sc r im root re inf o rce m ent m a terial

o Soil substrate (organ ic and coarse ag gregate)

o Irrigation sy stem

o Plants and w a lkway stones

Each side of the roof drains into a gravel filt ering area then into a drainpipe inside the building that then co nnects to the City storm drain sys t em . A s m all, 60 degree, V-trapezoidal flum e is installed imm e diately upstream of each prim ary roof drain. A bubbler-type flow m e ter m e asures the water level at each flum e. The prim ary roof dr ain is sealed and iso l at ed to direct all flow through the flum e prior to entering the drain. The possibility exists that during very large storm s , som e water m a y flow out the secondary drain and not flow through the flum e.

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, 2 005 Pag e 3Emergency Overflow

The prim ary roof drains are plum bed directly to the City storm sewer system . The secondary drains function as em ergency overflow drains if the prim ary drains become plugged. S i nce the secondary drains are fitted with a tw o-inch exte nsion collar, water enters the secondary drains only if the p ooled water level around the drai ns exceeds th e collar. The secondary drains discharge directly off th e side of the building.

Landscaping Each side of the roof was divided into three s ections and planted identic ally using the following three m e thods. Plants include a m i x of natives and hardy ornam e ntals.

• NE and NW sections planted with 11 x 22-inch (1.8 square foot) m a ts of pre-germ inated seedlings an d root cu ttin gs

• West and east sections plan ted with plugs and containers of sedum s, succ ulents, and perennials

• SE and SW sections planted with hand-broa dcast m i x of sedum sp rigs, and hydro-seed

m a trix of perennial flowers and grasses. A sm all area of the south section was planted with native grasses and wildflow ers such as lupine and yarrow.

Soil or substrate The roof uses two types of substrate, one for the east side, and one for the west.

• The east s i d e was insta l led with th re e inch es of very lightweight m i xture with a

m a xi m u m s a turated weight of 10 pounds per square foot.

• The west sid e was installed with five inch es of lightweight m i xture with a m a xi m u m saturated weight of 25 pounds per square foot.

• Lightweight soils erode easily. Because of soil loss due to w i nd, red pum ice stone was added to the NE section. This treatm e nt is now being m easured to test its ability to
contro l erosion, provide m i neral content a nd pore space for plant roo t s, an d suppress weeds.

Irrigation The roof uses an autom a tic irrigation system w ith spray heads on 12-inch risers. Irrigation is applied each summer. In summer 2001, about 6 in ches was ap plied to the east side and 4 inches to the west. After the initial plant establishm ent period, irrigation am ounts were reduced. During the very dry summer of 2002, 3 inch es of irrigation was applied to the east side and 2 inches to the west side.

Typically, irrigation is only used on the roof in lim ited a m ounts and when plants show effects from prolonged periods of dry, hot weather.

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### Budget

The final project budg et subm itted by the HAP was $127,485 includ ing m a nage m e nt , design,

m a terials and construction. The budget breaks down as shown below.

Budget Elements

Activity Cost % of Total Cost D e s i g n $ 1 7
, 9 0 0 1 4

. 0 % Perm i t t i n g $ 2

, 2 9 2 1

. 8 % Roof Construction $43,620 34.2 % P l a n t i n g s $ 9

, 7 4 0 7

. 6 % Soil and waterproof m e mbrane $41,483 32.5 % I r r i g a t i o n $ 2

, 5 0 0 2

. 0 % M i s c e l l a n e o u s $ 7
, 9 5 0 6

. 2 % Total $127, 485 100 %

Cost Comparisons Because roo f scaping cov e rs and pro t ects the wate rproofing and structural com ponents of a roof, ecoroofs typically last tw ice as long as conventio nal roofs. This m eans that in the long-term

, higher construction costs are offset by lower repair and replacem e nt costs.

The Ham ilto n W e st Apartm ents roof is desi gned a s a build ing am enity and include s extra features not required for storm w ater m a nage m e nt . These include a terrace with tables, planters and seating, a fence separating this from the vege tated po rtion of the roof, and elevator access to the te rra ce. Additiona lly , the pro j ect was the f i rs t of its kind in Portla nd and required special attention.

This roof tested the effectiveness of different t ypes of plant establishm ent. Techniques that were tested included installing grass sod and non- grassy sod, hydroseeding annuals and installing

sm all plants by hand. A typical ecoroof would not include this research component and could choose the most cost-effective way of establishing the plants, rather than testing m e thods with a higher initia l cost.



### Maintenance and Monitoring

The City is r e quired to monito r the ef fectivenes s of stormwat er best m a nagem e nt practices (BMP) per the City’s Na tiona l Pollu tant Discha rg e Elim inatio n System (NPDES) Stormwater Discharge perm it. Flow monitoring and wate r quality sam p ling at the Ham ilton ecoroof evaluates th e storm w ater m a nagem e nt characteris tics of this type of BMP and com p ares the rela tive ef f

ectiven ess of the two dif f

e rent e c or oof soil types and depths. Monitoring for flow control, water quantity and wate r quality has been ongoing since 2000.

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, 2 005 Pag e 5H a m i l t on W est E c or oo f St or m w at er Ret e n t i on by M ont h

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0% 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 1 00%% Retention M ont hl y R a i n f a l l ( i n. ) M ont hl y % S t or m w a t e r R e t e nt i o n

* R a i n / F l o w dat a m i s s i ng f r o m N o v e m ber 2 7

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, 2 002

* * * I n c l u des d a t a f r om M a r c h 1 - 19, 200 4

The chart ab ove shows the seasonal variation in the percentage a nd am ounts of storm w ater that the ecoroof is able to m a nage. The colum n s show the am ount of rainfall received during each month. The connecting line shows th e percent of that rainfall that the ecoroof retains. As you can see from the rainfall columns, Portland has pronounced wet and dry seasons, which affects
storm w ater perform a nce.
During dry months, the ecoroof retains and m a na ges nearly all of the sto r mwater. This is im portant because runoff from a conventional roof during summ er storm s t e nds to contain m o re pollutants a nd will en ter waterways at a high er tem p erature. During the r a iny m onths, the ecoroof m a nages m u ch higher volumes of water than the conv entional roo f . It eventually becom e s saturated bu t e v en when it does not re ta in all of the water, it slo w s and f ilter s the f l ow.
BES data show that the perform a nce of the ecoroof is im proving as th e plants m a ture. During the first 16 m o nths of m onitoring, th e ecoroof retained an average of 52.5% of all the rainfall it received. In the following 12 m onths, the roof retained 55.6% of the total rainfall, an im prove m e nt of 3%.

The next graph shows the perform a nce of the ecoroof during a typi cal winter storm

. You can see that the ra inf a ll oc curs in jagged sp ik es of di f f

e ring intens ity. Traditional roof s with drainp ipe system s would disch a rg e alm o st all of that water direc tly.

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, 2 005 Pag e 6The sm oother line on th e chart rep r esents th e run o ff from the ecoroof, as m e asured by the flow

m e ters at the roof drains. As you can see, the sh arp surges in rainfall are moderated. More than a third of the rain never flows out. The soil and the plants retain it. The rest of the runoff is delayed and slowly leaves the ecoroof even several hours later.

The City also evaluated the perform a nce of th e construction, soil, and plants installed on the roof. As of 2004, approxim a tely one inch of soil had been lost on both sides of the roof due to wind erosion and soil decom position. In late spri ng 2004, lightweight red pum i ce of less than 3⁄4 inch size was applied to sparsely vegetated area s. This should prevent further wind erosion and allow an opportunity to observe any benefits to plant health fro m added mineral content and pore space for ro ot growth.

Regular m a intenance activities in clu d e the follo wing com p onents:

• About 1 inch of irrigation has been applied each summer during prolonged dry periods (typically ten or more days of no rain).

• The roof uses no fertilizers or herbicides. Hand weeding of the ecor oof occurs at least once a year in late spring.

• The owner of the property m a nages the terrace an d accepts res ponsibility f o r all

m a intenance activ ities f o r the se ating areas , planters, pavers, trash and the fence around the ecoroof. Periodic dam a ge, prim arily to the irrigation system , occurs from various hum an activities.

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### Successes and Lessons Learn ed

The Ham ilto n W e st Apartm ents ecor oof was one of the earlie s t ecoroof pr ojects in th e City of Portland. It has provided data on st ormwater retention, plant cover establishm ent, cost factors, and substrate perform a nce. Ongoing m onitoring at the site continues to refine our knowledge of the perform a nce and capabi lities of the ecoroof.

After five years, the roof is beautiful and plant coverage has increased substantially from planting. Som e species originally planted have died away, while others have spread rapidly. Certain plants that thrive on one side of the roof do less well o n the othe r, highligh ting the im portance of selecting plants ad apted to the conditions and dept h of the soil. This d a ta is helping the City develo p a lis t of recommended ecoroof plan t spec ies an d their growth requirem e nts. The plants highlighted at the e nd of this section have proved particularly successful, and continue to spread and thrive on the roof habitat.

Bef o re f u ll plant cov e rag e wa s established, wind erosion of soil occurred to a m u ch greater degree than expected. About an inch of soil was los t f r om both sides of the roof. Care must be taken to protect the lightweight ecoroof soil from wind erosion or exposure. Early in 2004, lightweight
pum i ce grav el was used to cover areas where soil was exposed in order to reduce further soil erosion. This technique seem s to be succe ssful. Plants are spreading through the gravel and birds do not expose underlying soil when they dig for insects. Plants growin g thr o ugh re d pumice

Water quality contro l tes t s reveal that elevated le v e ls of certain m e tals are leach ing from one of the two types of soils. T h is is one of the earliest studies of ecor oof water quality considerations, and these unexpected results show the value of experim e ntation and m oni toring. Depending on water quality concerns in the area an d the type of soil substrate used, it m a y prove useful to test the soil levels of m a terials of concern before installation.

The volum e of water that the roof controls has in creased as the plants on the roof have m a tured. Summ er stormwater retention now reaches 100% and wet-season retention rates continue to increase. In a typical winter rain ev ent, storm surges are elim inat ed and runoff release is delayed by about 4 hours. Delaying runoff that the roof cannot hold helps m oderate flooding and

com b ined sewer overflo w events.

Other known benefits from the roof that have not been specifically quantified are reductions in

am bient air tem p erature and build ing energy cos t s, increased urban habitat values for birds and other wildlif e, and an open-space venue for the building tenants.

Residents frequent the roof terrace , particularly in sunny summer weat her. It is an attractive and pleasan t place and a con s iderab le am enity to th e building in a dense urban environm ent. This dem onstration projec t h a s also show n the f easib ility of th is type of stormwater m a nagem e nt practice, and m a ny other projects in P o rtland have followed its exam ple.

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, 2 005 Pag e 8Soil m onitoring shows that both very shallow and slightly deeper roof soils can support thriving plant communities. Ver y shallow so ils a r e m o st favorable to sedum species and showed m o re bare areas th an the deep er soil on the west side. C a re m u st be take n in preventing wind erosion in very shallow soils, as erosion can easily expose the underlying drai nage layers in areas without plant coverage.

The sligh tly deeper so il o n the W e st side of th e roof shows greater plan t coverage, but also has greater prob lem s with weeds. W eedy plants su ch as vetch and red clover each cover up to 30% of the roof’s west side. Most of the roof plants are low growing and these plants can grow right over them . Areas where taller g r asses are es ta blished seem more able to resist weed s.
More than 40 types of plants grow on the Ha m ilton ecoroof. Som e plan ts clearly prefer the deeper soil on the west side of the roof, and som e do better on the thinne r soil on the east side. These lists s how currently predom inant plan ts on each sid e of the roof , in order of the i r prevalence. Many other plants are also presen t in trace am ounts. You can find a m o re com p lete discussion of ecoroof ve getation in the docum ent Plant Survival Findings in the Pacific Northwest , published by the City of Portland Bureau of Environm ental Services in summ er 2005.

West side d o minants (d eeper soil) Ea st side dominants (shallow soil) Blue Fescue ( Festuca glauca ) Spanish stonecrop ( Sedum hispanicum ) Cascade sto n ecrop ( Se dum di v e r ge ns ) K i r i n

- s o ( Sedum kamtschaticum ) Iceplant ( Delosperma cooperii ) I c e p l a n t ( Delosperma cooperii ) Spanish stonecrop ( Sedum hispanicum ) Redstem f

ilaree ( Erod iu m cicutar i u m ) Common thym e ( Thymus vulgaris ) Dragon’s blood ( Sedum spurium ) Dragon’s blood ( Sedum spurium ) Oregon stonecrop ( Sedum oreganum )

The following sam p ling of species have spread a nd thriv e d p a rticula r ly w e ll. They rep r esent a

m i x of native and ornam e ntal plants. These plants are very hardy and should do well in most roof garden settings. Monitor plants closely imm e diately after planti ng, as the initial establishm ent period is the m o st difficult tim e for the plant.

Kir in-so: S e dum kamtschaticum T h is type of stonecrop was included in the vegetated mats placed o n the North s ections of the roof during initial planting. This is a perennial plant. B r i ght green leaves turn red in October before going dorm a nt. New growth be gins in March. Growing habit is

com p act, upright and spreading. Kirin- so has yellow flowers from June through early Nove m b er and reach es less th an 6 inches in height.

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, 2 005 Pag e 9Iceplant: D e losperma cooperii Both red and purple varieties of this

ornam e ntal plant grow on the Ham ilt on ecoroof. Most of the red variety died back during a prolonged cold spell in January 2004. These plants are noted for thriving particularly well n e a r a i r e x h a u s t v e n t s , w h i c h c ordinarily be a very stressful envi ronm ent for plants. They form l o w , creeping m a ts around six inches in he i g h t , w i t h b r i g h t g r e e n v e g e t and conspicuous flowers. Flowers begin in sum m e r a n d p e r s i s t t h r o u

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. Spanish stonecrop: Sedum hispanicum var. minus This stonecrop species is m o st prevalen t on the so uth portions of the ecoroof, where it was covered with the hydro-seed m i x of the initial planting. Spanish stonecrop has a spreading habit, a nd for m s a dense, creeping m a t of gray-green leaves. Pale pink flower s bloom from July through August. Spanish ston ecrop reaches between 4 and 6 inches in heigh t

.

Blue fescue: Festuca glauca Blue fescue is a pere nnial grass that was included in the vegetated m a ts from t h e o r i g i n a l p l a n t i n g

. B l u e f e s c u e a persistent spreader and grows a bout 14 inches high. It is located prim arily in the nor th sec tions, esp ecially on the west side w h ere th e soil is deeper (5 inches deep rather t h a n 3 )

. T h e g r a s s g r o w s i n b u n c h e s of fine, bluish-green leaves. Som e outer leaves brown out in the fall. Bloom s o b s e r

Common thyme: Thymus vulgaris Common thym e has an upright, bushy growing habit and reaches abo u t 8 to 10 in ches in heig ht. This plant showed stress immediatel y af te r the initial planting and experienced som e dieback, but those pl ants that s u rvived the first y ear are now vigorous and spreading slowly.

Environm ental Services Sustainable Storm w ater Managem e nt www.portlandonline.com / bes

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