July 9, 2015

NCPC File No. 7326

Preliminary Submission_______________

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Project Information

Project summary:The United States Army Corps of Engineers (USACE), acting on behalf of the Defense Intelligence Agency, has submittedpreliminary site and building plans for the Intelligence Community Campus – Bethesda, Master Site Design project. TheIntelligence Community Campus – Bethesda (ICC-B), former National Geospatial Agency Headquarters, is located inBethesda, Maryland. The Campus is bound by a local park and private school to the north, undeveloped property to thesouth, retail and residential to the east, and National Park Service land to the west. A small amount of residential is alsolocated to the west of the site. The Campus is in the process of being redeveloped into a modern, state-of-the art facilitythat will serve the Intelligence Community, a coalition of 17 agencies and organizations within the executive branch thatwork to gather the intelligence necessary to conduct foreign relations and national security activities.

In 2012, the Commission approved the ICC-B Master Plan which separated the redevelopment of the site into two phases(North Campus and South Campus). The first phase, North Campus, includes the construction of a new parking garage inthe northwest corner of the site, a visitor control center, and a vehicle inspection facility. The Commission approved theNorth Campus redevelopment at its July 2012 meeting.

Phase two, South Campus, entailed the full redevelopment of the existing buildings on the site to meet modern office andtechnology requirements, to provide the requisite level of security. Phase two also included significant site improvementsthat substantially eliminated the amount of impervious surface that currently exists on the site.

Commission meeting date: June 4, 2015

NCPC review authority: Federal Projects in the Environs (40 U.S.C. §8722(b)(1))

Applicant request: Preliminary approval of site and building plans

Delegated / consent / open / executive session: Open session

NCPC Review Officer: Lee

NCPC File number: 7326

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Project Information

Project summary continued:

The current proposalMaster Site Design develops an integrated design for the 30-acre campus, binding the three campus redevelopmentinitiatives previously reviewed by NCPC including the North Campus, Centrum, and the Roberdeau/Erskine Hall façaderenovation projects into an integrated site concept. The MSD follows the overall campus vision and extensive communitydialogue that has transpired since 2010.

Key elements of the MSD include coordinating site demolition and building construction; utilities and infrastructureconnections; significant improvements to the site storm drainage systems; erosion control measures; site security andlandscape architecture connecting elements that are outside the limits of previous redevelopment work and integratingthe primary site entry features with the North Campus development program.

The development of the preliminary MSD included a series of local community coordination meetings facilitated by theICC-B project team, these meetings included specific sessions on addressing landscape architecture, site setting,community aesthetics, and final stormwater management planning. This outreach has been instrumental in balancingsite needs with community perspectives and has helped the design team formulate context sensitive solutions incollaborative manner with the surrounding community.

The preliminary MSD stormwater management concept is focused on an integrated campus design that achievescompliance with MDE regulations, EISA implementation guidance, and community concerns for the entire redevelopmentarea of the campus. The preliminary MSD integrated concept significantly improves the hydrologic profile of the campusfrom the 2008 era preconstruction conditions. Incorporating a blend of green infrastructure and low impact developmentpractices across the campus, including elimination of over seven acres of existing impervious cover on site. The MSDapproach also reduces peak runoff rates and overall runoff volumes significantly, using green infrastructure practices totreat, absorb and infiltrate significant quantities of precipitation on site, replicating pre-development hydrology to themaximum extent practical.

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Project Location

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2008 Existing Conditions

Erskine Hall Maury HallRoberdeau HallAbert Hall

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2008 Existing Conditions

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Master Site Design Project Area

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Limits of Work – North Campus and Centrum Project

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Stormwater Drainage Planning Area

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1945 Natural Drainage Areas

Comparison of Site Drainage Areas

Natural Site Conditions

• Area 1 flowed to northwest channel, alongside Wapakoneta Road and to the C&O Canal.

• Area 2 flowed from the central area of the site to a channel which also flows west to the C&O canal.

• Area 3 flowed to the southeast to Sangamore Road and Brooke’s Lane.

• Area 4 lacked a defined drainage way, indicating runoff was minor and primarily confined to sheet flow across the hillside leading to MacArthur Boulevard.

• Native soils are predominantly Type B soils which drain well. Site C soils were found along the south east portions of the site.

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2008 Pre-development Drainage Areas

Comparison of Site Drainage Areas

Pre-Development Site Conditions

• Area 1 continued to drain to the Northwest channel via two independent stormwater outfalls.

• Area 2 continued to the mid-site channel, but the upper portions of the drainage area were filled in to accommodate the construction of Maury Hall and the stromwaterdetention behind it.

• Area 3 was piped to the municipal stromwater systems installed along Sangamore Road.

• Area 4 was captured and piped in, creating the southwest channel as a direct result of campus discharge .

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Proposed Conditions Preliminary MSD Drainage Boundaries

Comparison of Site Drainage Areas

MSD Proposed Conditions

• Impervious surfaces throughout the site have been significantly reduced

• Rooftop runoff from Erskine and Roberdau Halls has been consolidated and rerouted to be managed onsite

• Drainage Area 4 has been consolidated with Drainage Area 3 in accordance with the recommendation provided by the USACE’s 2011 Storm Water Drainage Engineering Study, eliminating the problematic off-campus outfall southwest of Erskine Hall

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MDE Requirements

MDE ESD Target Volumes (Proposed Conditions)

Compliance with MDE, EISA, and community commitments to detain and treat the 25-year design storm

• Combination of impervious reduction and environmental site design (ESD).

• ESD targets include evaluation of the rooftop runoff volumes from Erskine, Roberdau and Maury Halls, even though these areas is not required by MDE or EISA. (these rooftop areas are not considered part of redevelopment activity by MDE standards as the rooftop impervious footprint is not changing)

• Areas 1 and 2 require small amounts of additional ESD volume.

• Area 3A will not required additional ESD volume due to significant reductions in impervious surface (over 50% of the existing impervious area is removed).

• Area 3B will require management of an additional ESD volume to enable closure of the existing outfall behind Erskine Hall. This re-routing of existing DA-4 (approx. 2 acres) required application of MDE new development design standards, requiring treatment of a target precipitation of 2.2 inches.

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EISA Requirements

EISA Regulations

• The EISA requirements are greater than the MDE requirements as EISA does not distinguish between new development and redevelopment, focusing on achieving the METF criteria for the entire campus footprint.

• Retention of the 95% rainfall event (1.7 inches of rainfall over a 24-hour period), this equates to infiltrating and retaining approximately 53% of the entire 2-year, 24-hour storm event (3.18 inches of rainfall) within the campus

EISA GI/LID Volume Targets (Proposed Conditions)

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MDE/EISA Compliance Summary

Stormwater Concept Compliance Summary (Proposed Conditions)

• The MSD stormwater concept slightly exceeds EISA compliance across the entire campus

• The MSD design significantly exceeds minimum standards of the MDE regulations, providing almost three times the required treatment volume

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MDE/EISA Compliance

Stormwater Concept Compliance Summary (Proposed Conditions)

Drainage Area 1:

• The North Campus project achieved EISA compliance within Drainage Area 1 by meeting the METF requirements, as permitted and approved by MDE Permit #11-SF-0359

• Although Area 1 was unable to meet regulatory standards for on-site infiltration credit due to limiting natural soil conditions, an open bottom underground detention structure was utilized in the North Campus design to maximize any available infiltration potential

• Development of the pedestrian/bridge/walkway was integrated with the original North Campus strormwater drainage design approved by MDE as an amendment to the Centrum project in 2014

• Additional compensatory on-site infiltration in the south campus campus area (area 3)

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MDE/EISA Compliance

Stormwater Concept Compliance Summary (Proposed Conditions)

Drainage Area 2 ESD/GI/LID strategies:

• Removal of extensive impervious hardscape surfaces resulting in a min. required treatment of 255 cubic feet.

• On-site bio-retention as part of the North Campus.• Installation of several bio retention ponds, a green roof, and rooftop rainwater harvesting system as part

of the Centrum Project.• Additional bioretention structures treating the rooftop runoff from Roberdeau Hall and the new

serpentine entrance road serving the North Campus area fulfill the additional EISA requirements (13,510 cubic feet)

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MDE/EISA Compliance

Stormwater Concept Compliance Summary (Proposed Conditions)

Drainage Area 3 ESD/GI/LID strategies:

• Consolidation of existing outfalls from Drainage Areas 3 and 4 to enable closure of the existing campus outfall location behind Erskine Hall

• Re-routing of runoff from pre-development Drainage Area 4 to the existing outfall in Drainage Area 3 which discharges o the Montgomery County stormwater system which drains across Brooke’s Lane and Sangamore Road, ultimately discharging to Little Falls Branch just above the Capital Crescent Trail

• Removal of impervious parking areas east of Roberdau• Removal of the Emory building and associated parking• Re-routing of runoff from the Erskine Hall loading dock to the on-site bioretention areas via a grass swale• Treatment of Erskine Hall rooftop runoff through additional bioretention and underground infiltration

chambers

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Proposed Master Site Development

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Landscape Design Concept

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Integrated Landscape Design Concept

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Integrated Landscape Design Concept

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Landscape Zonal Plan

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View from Sangamore Road

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View from Sangamore Road

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Bioretention Planting