anc 1c presentation-kalorama park plaza-dec 3 2014

KALORAMA PARK

Presentation to ANC 1Cby

Belinda Reeder & Cynthia Polson the

Proposed DPR/DGS Re-design of the Plaza

Dec. 3, 2014

DPR/DGS’S PROPOSAL TO DEMOLISH & REPLACE

KALORAMA PARK’S PLAZA:

THE ORIGINAL NATIONAL PARK SERVICE DESIGN & WHY IT SHOULD

BE PRESERVED

THE NATIONAL PARK SERVICE’S 1947 PLANS FOR KALORAMA PARK

Overall Plans

Close-up of Plans for Plaza Area

THE NATIONAL PARK SERVICE CAREFULLY ADHERED TO THE 1947 PLANS AS IT BUILT THE PLAZA

SATELLITE VIEWS OF THE PLAZA OVER THE YEARS SHOW THE SYMMETRY & BALANCE OF THIS DESIGN & ITS CONSISTENCY WITH THE 1947 PLANS

1999 Satellite View of the Plaza Area

EXCEPT FOR THE INTERPLAY WITH NATURE (THE LOSS OF TREES IN THE PLAZA & THE ADDITION OF TREES IN THE PLAYGROUND), THE 1947 DESIGN OF THE PLAZA & THE OTHER “ROOMS” IN THE UPPER AREA OF THE PARK HAS REMAINED INTACT FOR SOME 50 - 60 YEARS

WE SUDDENLY FIND OURSELVES FACED WITH DPR/DGS’S PROPOSAL TO DEMOLISH THE PLAZA IN ITS ENTIRETY & REPLACE IT WITH A NEW PLAZA THAT WILL NOT HAVE THE STRUCTURE & SYMMETRY OF THE EXISTING PLAZA AS ESTABLISHED BY THE 1947 NPS DESIGN

DPR/DGS “Final” Redesign Plans (Nov 18, 2014)

TO PUT THE DPR/DGS PROPOSED CHANGES IN CONTEXT, IT IS HELPFUL TO LOOK AT THE PLAZA IN VARIOUS WEATHER CONDITIONS & SEASONS

NOTE THAT THE SYMMETRY & BALANCE OF THE PLAZA’S DESIGN SHINE THROUGH REGARDLESS OF THE CONDITIONS

Aerial View of Plaza (winter of 2009)

Aerial View of Plaza (2010)

Aerial View of Plaza (early 2011)

Aerial View of Plaza (spring of 2011)

Aerial View of Plaza (summer of 2011)

Aerial View of Plaza (July of 2014)

IT IS ALSO IMPORTANT TO KEEP IN MIND THAT THE PLAZA, IN ITS CURRENT FORM, ACCOMMODATES A WIDE RANGE OF USES & ACTIVITIES & IS MUCH MORE THAN AN EXTENSION OF THE NEARBY PLAYGROUND

People Using the Plaza (2005)

People in the Plaza (2008?)

People in the Plaza (2009)

THE PLAZA, IN ITS CURRENT FORM, PROVIDES A WONDERFUL PUBLIC SPOT WHERE NATURE & DESIGN COME TOGETHER IN HARMONY

Hawthorn-Northeast Corner of Plaza (fall of 1993)

Hawthorn in Bloom in the Plaza (undated)

Eastern Side of Plaza (2008)

Western Side of Plaza (p re-erosion) (spring of 2003)

Western Side of Plaza (pre-erosion) (spring of 2003)

View of Plaza from the Oval (2008?)

View of Plaza in Winter (2009)

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DPR/DGS PROPOSAL FOR A PERMEABLE PAVEMENT SYSTEM FOR THE PLAZA:

QUESTIONS & CONCERNS ABOUT THE VIABILITY OF THE PROPOSED SYSTEM

The bad history of the 2009 anti-erosion project requires extra vigilance

• Following DPR’s 2009 implementation of an anti-erosion project, erosion worsened

• That 2009 project involved tearing apart the park to install 3 “bioswales,” modify 3 catch basins, install 1 new catch basin, remove 2 catch basins, & install a new play area for children

• Some 5 years later, the 2009 project remains unfinished & caused damage to the park in many areas


• The 2009 anti-erosion project did not include improvements or repairs to the trench drain system in the plaza– The trench drain system had worked well for some 50

- 60 years– It was damaged in recent years either by DPR

contractors for the 2009 anti-erosion project or by some other occurrence like root intrusion

– It has not been repaired in spite of its central importance

– DGS confirmed in July of 2014 that the trench drain’s main drain pipe was damaged


• DPR commissioned a report in 2012 by an engineering firm (Volkert) to assess the 2009 anti-erosion project

• Volkert found numerous flaws in the implementation of the 2009 anti-erosion project, including that the 3 catch basins associated with the bioswales were not working properly

• DPR failed to develop proper contracts in 2009 for the anti-erosion project or to oversee the contractors


• The fix proposed by DPR/DGS in 2014 for the mess created by the 2009 anti-erosion project is a complex, engineered permeable pavement system

• Based on history, it is not wise to automatically assume that the planners have it right

• Given history, it is reasonable to question whether DPR/DGS will implement the aggressive maintenance plan required to keep the proposed system in operation

How the proposed permeable pavement system would work

• It captures & temporarily stores water in a stone reservoir directly below the pavement’s surface

• The system is designed to collect water & return it to the stormwater system or filter it into the soil within 48 hours

• If working properly, it provides some control of water run-off

• It can also slow down the speed at which surface water is released into the stormwater system

How the proposed permeable pavement system would work

What are key design issues as per DC’s Stormwater Management

Guidebook (SWMG)?

• The depth of the stone reservoir – typically in the 2’- 4’ range – is determined by several factors, including:

- Water flow into the reservoir from direct precipitation on the surface

- Water flow into the reservoir from adjacent areas

- Permeability of the soil beneath the reservoir


Guidebook (SWMG)?

• The below-surface drainage system for slowly emptying the reservoir:

- This system may consist of: drainage pipes (over & under drains – typically 4” – 6” in diameter & with 3/8” perforations); & the “infiltration sump”or a second stone reservoir below the under drain pipes

- Other factors: number of drainage pipes in the reservoir; space between drainage pipes


Guidebook (SWMG)?

• Connections to the stormwater system to drain the water out of the reservoir

• Geotextile & other walls between the stone reservoir & adjacent areas to prevent clogging of the pavement & drainage system

• Distance from nearby buildings and utility lines (DC’s SWMG recommends at least 10’)

Possible problems with permeable pavement systems?

• The reservoir has insufficient storage capacity

• Due to design deficiencies, the water retained below the pavement surface in the reservoir cannot drain within the requisite 48 hours

• Some or all of the drains in the reservoir become clogged over time

Possible problems with permeable pavement systems?

• The surface pavements clog up over time, blocking water from filtering into the reservoir

• The geotextiles used to create walls between the reservoir & nearby landscaped areas break down over time, allowing soil to migrate into the reservoir

Main problems with a permeable pavement system in the plaza area?

• The soil beneath the plaza has limited ability to absorb water: - A DGS subcontractor found the soil to be close to not

permeable – it can absorb only about ¼” inch of water in 48 hours (0.005 inches/hour)

- The subsurface reservoir must be engineered to both retain virtually all the water & to gradually release it into the stormwater system over 48 hours

- The stone reservoir must be deep (likely at least 4’) & equipped with multiple drains

- The system must be linked to the stormwater system


DGS tested the water infiltration rate at 8 points in the park in July of 2014

- The plaza testing points are shown on the map in the next slide (B-2 is the main testing point for the plaza; tests were also conducted at B-1)

- The results of the tests at all 8 points are shown in the slide after that


• Nearby areas drain into the plaza area (the roof of the rec center, the 2 playgrounds, & the Oval), compounding the problems associated with the soil’s limited permeability:- Additional issues are implicated by unformed plans to

reconstruct the adjacent playgrounds- The surface of the adjacent playground already poses a threat to

a permeable pavement system – it is 6” above the plaza & consists of mulch & similar loose materials

- DPR/DGS plans to upgrade the playgrounds but does not plan to install permeable surface (DGS Nov. 5 announcement)

- DPR/DGS plans to replace the existing surface with wood chips (likely incompatible with the proposed permeable pavement system as loose materials could clog the system)


• The plaza directly abuts the rec center – under the SWMG, the 10-foot strip in front of the rec center should not be part of the permeable pavement system

• DPR/DGS plans to plant new trees & landscaping in the plaza (a source of loose materials)

• Unanswered questions include who will vacuum & maintain the permeable pavement system– This is a baseline question

– DC does not have an established track record of maintaining the park (trimming trees & hedges, repairing the trench drain)

THE BOTTOM LINE

• A permeable pavement system is a complex, engineered system, with numerous points of possible failure, and requires regular, systematic maintenance

• The plaza area has many features which are highly problematic for a permeable pavement system (mulch, organic materials, a building, trees, shrubs, grass)

• Permeable pavement is best suited to less environmentally complex areas (like parking lots with limited vegetation)

• Given the small surface area involved & the high cost, it is an ineffective way to manage stormwater

SUGGESTED APPROACH

• Defer finalizing plans for plaza improvements until plans for playground improvements are finalized

• Restore & augment the trench drain system & remediate erosion

• In developing plans for plaza improvements, preserve the 1947 NPS plaza design by steps like replacing the Hawthorn trees with similar trees, restoring the plaza’s privets, & planting compatible bushes or plants in the 2 oblong planters

• If it is conclusively determined that the permeable pavement system is technically & environmentally superior to the trench drain system & that maintenance questions can be resolved, consider deployment of permeable pavement in areas of the park where it will not require modification of the existing plaza design

anc 1c presentation-kalorama park plaza-dec 3 2014

Environment

plaza area

new plaza

existing plaza

plaza satellite views

aerial view of plaza

aerial view of plaza

kalorama parks plaza

plaza undated hawthorn