Gate 7 Garage_65 Narrative.pdf

DEPARTMENT OF

HOMELAND SECURITY

GARAGE

CONTROLLED UNCLASSIFIED

INFORMATION (CUI) PROPERTY OF

THE UNITED STATES GOVERNMENT

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NARRATIVE

9.4.2026

CONTROLLED UNCLASSIFIED INFORMATION (CUI)

PROPERTY OF THE UNITED STATES GOVERNMENT

FOR OFFICIAL USE ONLY

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DEPARTMENT OF HOMELAND SECURITY

GATE 7 GARAGE

Building No. DC0253

TABLE OF CONTENTS

1 PROJECT OVERVIEW

Site Background

Natural Site Features

Geotechnical Analysis & Recommendations8

Existing Utility Analysis & Description

Utility Distribution Planning

Stormwater Management Planning

2 CODE ANALYSIS

Life Safety

Accessibility

3 ARCHITECTURE

Site

Garage

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Project Overview

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PROJECT OVERVIEW

SITE BACKGROUND

HISTORY & HISTORICAL SIGNIFICANCE

The new Gate 7 Garage will be built on the St. Elizabeths Hospital West campus in southeast Washington, DC. Opened in 1855, the hospital was the first federally operated psychiatric hospital in the United States.

Existing landscape elements include man-made features such as roads, walkways, water elements, railings, steps, walls, garden structures, and a cemetery. Developed as an arboretum on its flatter hilltop or plateau, the grounds included a wide variety of specimen trees, along with generous lawns and curved drives and pedestrian paths. The trees provide critical shade, clean air, seasonal interest, and frame key views and vistas from the campus to the north and west towards the Anacostia and Potomac Rivers and downtown Washington DC. On the steep slopes to the north and west, the landscape has historically been managed as meadow and woodlands. All these elements contribute to the character of the campus as a verdant place of respite.

Designated as a National Historic Landmark in 1990, several of the existing, older buildings on site have been renovated and repurposed for use by the Department of Homeland Security. In addition, a new building, the Douglas A. Munro Building, home to the headquarters of the United States Coast Guard a DHS agency, was completed in 2013. Construction is underway for another new building to house the future headquarters of another DHS agency.

CONTEXT

The St. Elizabeths West Campus, located in Ward 8 in the District of Columbia, is bordered by the Barry Farm housing development to the north, Martin Luther King Jr.

Avenue and the East Campus of St. Elizabeths to the east, the Congress Heights residential neighborhood to the south, and I-295 and Naval Support Facility Anacostia to the west.

The St. Elizabeths West Campus sits on the southern portion of the Anacostia Hills which comprise part of the topographic bowl surrounding Washington, DC and the floodplain of the Potomac and Anacostia Rivers. The topographic bowl refers to the wooded ridge surrounding the core of the city, an important terrain feature. Its ridgelines are distributed along highlands and lowlands and provide unique views and vistas of the Capital including the Washington Monument, the dome of the Capitol Building and the National Cathedral in the distance. The Federal Elements of the Comprehensive Plan for the National Capital emphasizes the importance of preserving this natural feature due to its historic and symbolic character and relationship to the identity of the Capitol’s setting.

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CAMPUS ORGANIZATION & SITE CIRCULATION

The campus buildings and elements are connected via a network of curvilinear paths laid out and built in the early 1900s as the hospital expanded. Paths were originally built to accommodate carriages and eventually widened to accommodate cars. Today these drives connect the campus though various entrance gates to the adjacent streets, highways, and neighborhoods. Other, more narrow paths connect elements throughout the site for pedestrians. No pedestrian pathways are proposed connecting the parking garage to the rest of campus.

HISTORIC STATUS

Saint Elizabeths Hospital was listed in the National Register of Historic Places in 1979 and designated a National Historic Landmark (NHL) in 1990. As such, it is subject to Section 106 and Section 110 of the National Historic Preservation Act of 1966, as amended. The NHL has a period of significance that stretches from 1853 to 1943 and has eighty-two contributing structures and seventeen noncontributing structures. As a federal agency, the General Services Administration (GSA) must take into consideration potential adverse effects to contributing elements within the NHL. This includes potential demolition of resources and compatibility with new construction. GSA is in continual consultation with the Advisory Council on Historic Preservation, DC State Historic Preservation Office, and other Consulting Parties regarding these historic resources.

CONSTRUCTION

A new garage will be constructed at the northwest corner of the St. Elizabeths campus.

Following guidance from the Secretary of the Interior’s Standards for Rehabilitation – Standard 9 in particular – and the Guidelines for Rehabilitating Historic Buildings, it is intended that the proposed new construction for the garage will be designed and built in a manner that protects the integrity of the historic buildings and St Elizabeths historic setting.

Location of Topographic Bowl in Relationship to St. Elizabeths West Campus

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The proposed new construction including landscape improvements will not alter the historic character of the St. Elizabeths campus. Other guidelines to be followed include the following directives:

• The historic setting and context of the West Campus will be protected, including the degree of open space and building density. This includes the formal and informal arrangements of buildings at St Elizabeths.

• The historic relationship between St Elizabeths buildings will be protected.

Contributing buildings will not be isolated by inserting the new parking garage at Gate 7.

• The historic landscapes and significant viewsheds to and from St Elizabeths will be preserved.

The proposed concept design for the parking garage will, per the SOI Guidance, be deferential and compatible with the historic resources within the NHL campus. The bulk of the mass of the garage will be built into the existing steep hillside, so as not to affect any views or vistas throughout the NHL. Plantings and landscape around the garage will preserve the cultural landscape of the grounds. The garage’s presence will be further softened by a layer of vertical Corten steel fins and a series of planters throughout the length of the facade. The proposed façade pulls from the existing campus material palette & color tones to remain contextually respectful without compromising the performance-oriented design and remaining subservient to the civic buildings on campus which should remain as the primary focus. In addition, the St. Elizabeths West Campus Preservation, Design & Development Guidelines will be followed to ensure that the construction will be compatible with the context of the existing historic buildings, their design, setting, materials, workmanship, feeling, and association.

NATURAL SITE FEATURES

LANDFORM & TOPOGRAPHY

The topography of the St. Elizabeths West Campus is a plateau landform characterized by a generally flat area at the higher elevations with adjacent steep slopes and ravines to the north and west. The West Campus Plateau elevations range from approximately 150 feet above mean sea level (msl) to approximately 170 feet above msl. Steep slopes between 8% and 40% are found west, northwest, and southwest of the Plateau and extend to the historic floodplain of the Anacostia River, which is now bounded by I-295.

Most of these slopes are greater than 15%, and the campus has a topographic low point of approximately 10 feet above msl.

The Gate 7 Garage site sits in the northwest corner of the campus in a low-lying area below the plateau. The plantings in this area are currently comprised of meadows and woodlands. The site is bounded by an ephemeral stream and Sweetgum Lane to the south which leads to the Gate 6 entrance to campus. Gate 6 is currently used for truck access with the Truck Screening Facility and other service buildings nearby. The site is bounded to the north by the Barry Farms neighborhood. A proposed new housing development is planned for the land immediately north of the garage site. To the west, the site is connected to St. Elizabeths Road SE which is where the Gate 7 entrance will be accessed. East of the site lies a steep hill that leads up to the Point, the promontory that overlooks downtown Washington, DC with views of the US Capitol.

Historic land use has affected the natural resources of the campus and the Gate 7 Garage site. Once an orchard, then wheat fields, the site has undergone many transformations. Most recently it was used as an infill area from the excavation required

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4 Building No. DC0253 for the construction of the Munro Building. Since that time the area has been left untended so that it’s now overgrown with invasive shrubs and grasses. Some trees remain at the perimeter of the area but appear to be in poor condition or overtaken by invasive species.

HABITAT, VEGETATION, & WILDLIFE

Landscaped areas are present on the plateau, while naturally vegetated areas exist to the west, northwest, and southwest on steeply sloping hillsides that are incised by ravines.

The wooded areas contain a mix of mature native species with patches of smaller areas dominated by nonnative species to varying degrees. Historically significant trees are found throughout the plateau.

The natural vegetation on the West Campus of St. Elizabeths is primarily composed of succession growth on abandoned land areas which were previously farmed. A few larger trees exist along the stream systems on the north and west borders of the property.

Prevalent tree species include tulip poplar, white oak, green ash, red maple, black walnut, and black locust. Typical understory species include pawpaw, sassafras, and spicebush.

Native herbaceous vegetation includes Virginia creeper, eastern poison ivy, pokeweed, goldenrods, and false nettle. Many nonnative invasive species occur throughout the disturbed regrowth areas of the site. These include princess tree, multiflora rose, tree of heaven, English ivy, and Asiatic tearthumb. The areas on site previously used for agriculture have been primarily planted with lawns.

Bird species observed at St. Elizabeths West Campus included typical songbirds such as the northern mockingbird, carolina wren, american robin, and blue jay. Notable bird species found on the site include Red-tailed hawk in the woods along the northwestern portion of the site and evidence of wild turkey roosting in the large trees within the cemetery. A bald eagle nest is located in the mature woods just off the southwest property line, the eagles nest has been active since 2017. The bald eagle is protected under the bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act. It is

St. Elizabeths West Campus areas

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5 Building No. DC0253 expected that the project will adhere to the 2007 National Bald Eagle Management Guidelines, which provides recommendations for avoiding disturbance at nest sites.

Nonnative species observed were the typical urban species including the european starling and the pigeon or rock dove.

Several species of mammals are common on the campus including woodchuck, northern raccoon, white-tailed deer, gray squirrel and fox. Other mammal species likely present include the Virginia opossum, shrews, and eastern cottontail rabbits.

The proposed landscape plan for the Gate 7 Garage building seeks to employ the approach delineated in the approved Master Plan by enhancing the arboretum setting in the woodland through protection of existing specimen trees and planting of a wide diversity of new trees to replace trees that have been lost over the years thereby increasing canopy cover onsite. This includes planting areas immediately adjacent to the parking garage to provide shade and screening of the building and expanding the wooded areas at the perimeter of the site by planting new groupings of trees where woodland has been lost or removed.

HYDROLOGY

The St. Elizabeths West Campus site drains generally in a northwest direction and is divided into two primary northern and southern watersheds. The northern watershed drains into a surface swale that discharges to a storm drain inlet at the northwest site limit. This swale collects runoff from the westerly slopes. A majority of the southern watershed drains to an existing storm drain inlet near the southwest site limit. This watershed collects surface water from most of the developed areas of the site. In addition to these two primary watersheds, there are other small sub-watersheds, including some that parallel Martin Luther King Jr. Avenue and drain to the street. There is also a small watershed on the northeastern edge of the site which flows offsite to the north. The existing ravines which line the western edge of the site are an integral part of the site drainage pattern. Stream and wetland systems on site have been identified and mapped through natural resource field investigations. Wetlands are in the vicinity of the Cemetery, the Gate 7 Parking Garage site, and the Pumping Station. Intermittent streams are located along drainages on the southern and western boundaries of the campus.

A significant result of site development is the effects it has on the watershed, site hydrology, and downstream waterways. The goal for stormwater management on the St.

Elizabeths campus is to minimize the impact of new development, and to also mitigate problems caused by past development. As a site mitigating factor, these efforts should aim to return the site to as close as the natural hydrologic condition as possible. This can be accomplished while maintaining the historic context of the site.

The St. Elizabeths West campus is located directly adjacent to the tidal Anacostia River and flooding of waterways downstream of the site are not a major concern. However, improving water quality is important in altering the degraded condition of the Anacostia and Potomac Rivers, and the Chesapeake Bay as well as on-site water courses.

Changes to site hydrology can improve water quality by filtering runoff through plants and increasing infiltration. Increased infiltration of rainwater will help recharge groundwater and provide a steadier flow of water for on-site springs, seeps, and streams, thus improving stream hydrology and ecology. This will also reduce flash flows in these streams, reducing erosion and sedimentation. As per the principles set forth in the approved Master Plan, new development must include restoring site hydrology through best practices for stormwater mitigation such as maximizing pervious surfaces and managing rainfall where it falls via increased localized retention. The landscape proposed for the Gate 7 Garage incorporates many of these strategies to reduce runoff and planting of areas of groundcover and trees to increase retention and absorption

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GEOTECHNICAL ANALYSIS & RECOMMENDATIONS

GENERAL

Subsurface investigations for the proposed Gate 7 Garage have been performed and will be shared in a report as part of the IFC documents.

details of the subsurface exploration and geotechnical laboratory testing programs.

SUBSURFACE CONDITIONS

Soil Subsurface conditions at the Site generally consist of man-placed fill consisting of loose to very dense silty/clayey sands and soft to very stiff clays. The man-paced fill overlies the natural Potomac Group, which are Cretaceous age sands, silts, and clays with occasional gravel. The silts and clays of the Potomac Group are often referred to as “marine clays” and typically have high plasticity characteristics and significant shrink-swell potential. The Potomac Group soils are highly over-consolidated and fissured and contain pre-existing failure planes referred to as “slickensides”.

Based on the recent borings, the fill thickness is significant in the west and highly variable, ranging from only a few feet thick at the northern and more upland areas of the garage and up to about 40 ft thick at areas further to the west (i.e., closer to St.

Elizabeth’s Road SE and the Gate 7 site entrance, within the general limits of the proposed surface parking to the west of the Gate 6 Garage). Specific to the area within or in the immediate vicinity of the proposed Gate 6 Garage footprint, the available test borings identified the top of the natural Potomac Group soils between El. 53 and El. 84, corresponding to approximately 2 to 22 ft below existing site grades and 3 to 34 ft above the proposed finished floor elevation (El. 50 +/-).

Groundwater Existing hydrogeologic data near the Site shows variable piezometric head levels.

Measurements from vibrating wire piezometers installed within the Fill and Potomac Group (refer to borings HA24-WH-03, HA24-WH-05, and HA24-G-03) indicate piezometric heads ranging from approximately El. 60 towards the southwestern (rear) site limits (as measured within boring HA24-G-03) down to approximately El. 14 at the northwestern site limits (as measured within boring HA24-WH-05). Available groundwater/piezometer monitoring data is provided in the Geotechnical and Environmental Data Transmittal.

GEOTECHNICAL DESIGN RECOMMENDATIONS

Seismic Design Criteria Based on anticipated subsurface conditions at the site, and in accordance with Section 1613 of the IBC, the site can be classified as Site Class D for seismic design purposes.

The soils at the site are not considered to be liquefaction susceptible during the design earthquake event.

Following IBC 2024/ASCE 7-22, for Site Class D, the design acceleration are:

SDS = 0.13 g

SD1 = 0.059 g

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The design accelerations provided above combine with the Risk Category (I, II, III, or IV) for the building to determine the Seismic Design Category (SDC) which governs the structural design and construction requirements for the building.

Design Groundwater Level In consideration of the piezometric variability across the garage footprint, two design groundwater elevations are to be considered for the building footprint. The southeast half of the building should be assigned a design groundwater corresponding to El. 65, and the northwest half of the footprint should be assigned a design groundwater of El. 45.

Building Foundations The lowest level floor slab for the garage is planned to be finished at about El. 50, corresponding to up to about 40 ft below existing site grades and is anticipated to be entirely within the Potomac Group clay soils. We note that areas to the west of the garage footprint (such as within the proposed surface parking area and drive lane areas) may have Fill soils which extend below their subgrade elevation.

Lowest Level Floors The lowest level floor slab may be designed and constructed as a soil supported concrete slab-on-grade, bearing on a minimum 12-in. thickness of compacted granular fill (or layer of sub-slab pressure relief material) placed over a properly prepared subgrade.

Waterproofing & Resistance to Hydrostatic Pressures Hydrostatic uplift pressures will act on the bottom of the lowest level slab if the slab is set below the design groundwater level. To address hydrostatic uplift pressures (and as an alternative to waterproofing and designing for hydrostatic uplift), we recommend that the lowest level floor slab be fully relieved using a subslab pressure relief system. The subslab pressure relief system should consist of 4-in. diameter slotted or perforated drainpipe embedded in a minimum 12-in. thick layer of crushed stone (drainage layer) placed below the floor slab and vapor barrier and underlain by a geotextile filter.

The pressure relief plumbing (slotted or perforated drain pipe) should outfall to the downstream storm system. The elevations of phase 1 proposed building will allow for the gravity system to be efficient, and the slopes will minimize any perceived tailwater concerns.

Below-grade walls should be waterproofed and insulated in accordance with the Building Code. Evaluations of the need to control humidity to prevent formation of mold or other organisms within the structure were not within the scope of work of this evaluation.

Lateral Earth Pressures It is anticipated that permanent lateral earth pressures will be supported by a permanent retaining structure positioned along the north, south, and east sides of the site, as well as the parking structure itself. Retaining wall types are noted under Support of Excavation below. Recommended earth pressure coefficients and lateral earth pressures will be provided within the forthcoming Geotechnical Report.

GEOTECHNICAL CONSTRUCTION CONSIDERATIONS

Excavation & Soil Management Construction of the proposed structure will require excavation through topsoil, existing unsuitable fill soils containing granular (sands, silts, and gravels) and cohesive (clays) soils and into primarily cohesive Potomac Group soils.

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Excavated materials will need to be handled and legally disposed of off-site. To facilitate off-site disposal, the excavated soil will need to be chemically tested and characterized.

Sample test frequency ranges between 1/150 to 1/1000 cu yd, depending on the quality of soil and disposal facility requirements.

Temporary Construction Dewatering Control of groundwater will be required during and following excavation to avoid disturbing the foundation bearing soil consisting of the Potomac Group of clay soils.

Construction dewatering should be performed as necessary to allow all excavation, foundation, lowest level slab, and underslab drain construction to occur in the dry.

EXISTING UTILITY ANALYSIS & DESCRIPTION

EXISTING UTILITIES

Overview

The St. Elizabeths West Campus is served by an on-site Central Utilities Plant (CUP).

The CUP serves buildings on campus with normal and emergency power, IT/Security fiber lines, and hot/chilled water lines. Sanitary and storm sewer are gravity systems that are collected and generally drain to the western boundary of the site. Domestic water is provided from the existing pump station near Gate 6.

Storm Drainage The proposed Department of Homeland Security (DHS) Gate 7 Parking Garage (Garage) is located in the northwest corner of the campus near the existing Gate 6. Surface flow from the Garage is primarily located within sub-watershed 2-2, with small areas of disturbance within sub-watersheds 2-1 and 2-3 as identified in the St. Elizabeths Utility Integration Plan Overall Stormwater Program, dated December 8, 2010. Watershed 2-2 drains towards existing storm sewer infrastructure in the access road and ultimately to the storm sewer within I-295.

Additionally, there is an unnamed tributary on the south side of the Garage. This tributary was the subject of a stream restoration project, titled St. Elizabeths West Campus Stream and Wetland Mitigation Project, dated December 2, 2016. Per the GSA memo titled “GSA Gate 6 Parking Garage Project Design Guide” dated May 7, 2025, a 25-foot construction buffer for all water bodies is required.

Sanitary Sewer Gate 6 is served by an 8” diameter existing sanitary sewer system that drains offsite to the west. This sewer system serves the existing pump house, generator building, and truck screening building.

Domestic Water The St Elizabeths campus is fed from the existing pump house at Gate 6. An existing 12” waterline runs from the pump house to the east up Sweetgum Lane. Additionally, an existing 14” watermain connection to the East Campus of St. Elizabeths exists within the proposed footprint of the Garage. This water main was previously used to support the East Campus prior to construction of a water storage tank on the East Campus. It is now used as an emergency connection to the East Campus and must remain. The 14” water main runs from the east side of the pump house to the east.

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Hot/Chilled Water There is no existing hot/chilled water in Gate 6 area, and none is expected to be required for the Garage.

Normal/Emergency Power Both normal and emergency power are fed from the CUP and terminate near the truck screening building at Gate 6.

IT/Security Both IT and Security ductbanks are fed from the CUP to the existing buildings at Gate 6.

Natural Gas An existing 2” gas service lateral to the existing truck screening building is the only gas in the Gate 6 area. No gas is expected to be required for the Garage.

Steam Tunnels There are no known steam tunnels in this area of the campus.

UTILITY DISTRIBUTION PLANNING

PROPOSED UTILITIES

Storm Drainage The proposed Department of Homeland Security (DHS) Gate 7 Parking Garage is an above grade parking structure. There is also a surface parking lot on the west side of the garage. Additionally, the site is located in three sub-watersheds that ultimately discharge to the same storm sewer outfall. Refer to the Existing Utility Analysis and Description and the Stormwater Management Planning sections of this narrative for additional information.

1. Roof Drainage: The Garage roof drainage will be directed to one of three (3) at grade bioretentions.

2. Surface Drainage:

a. The majority of the proposed disturbed area will be directed to the at grade proposed bioretentions. Discharge from bioretentions will then be conveyed to the proposed underground detention facility. The proposed underground detention facility is underneath bioretention # 1 along the entrance road. Future design phases of the project may include additional SWM measures.

b. Entrance Road: There will be proposed manufactured treatment devices at the drive entrance off of St. Elizabeths Road SE to treat any Vehicular Access Area (VAA) that isn’t captured by the proposed bioretentions.

Sanitary Sewer Sewer needs for the Garage are expected to be minor. New sanitary will be required heading west from the Garage and down the lower road behind the generator building and pump house before tying into the existing 8” sanitary system at the Gate 6 complex.

Domestic Water Domestic and fire service lines will connect to the existing 12” watermain at the Gate 6 complex. The service lines will run down the lower road behind the generator building and pump house and connect to the southeast corner of the Garage.

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A portion of the existing 14” water main that conflicts with the southern portion of the Garage will be relocated further south outside the footprint of the Garage and any associated retaining walls.

Hot/Chilled Water Not required for the proposed Garage.

Normal/Emergency Power Normal and emergency power will be extended to the Garage by new pathways from existing manholes at the Gate 6 complex. These ductbanks will run along the upper existing Gate 6 roadway and tie into the building. Refer to MEP narrative for connection points and sizing.

IT/Security IT/Security will be extended to the Garage by new pathways from existing boxes at the Gate 6 complex. These ductbanks will run along the upper existing Gate 6 roadway and tie into the building. Refer to IT narrative for connection points and sizing.

STORMWATER MANAGEMENT PLANNING

SUMMARY

Project Area The project will be defined by the total applicable area within the limits of disturbance (LOD) for the construction of the new Gate 6 Parking Garage, driveway, sidewalks, and associated infrastructure. The project is located in an MS4 area and not in the Anacostia Watershed Development Zone (AWDZ). The project discharges to the storm system along I-295, which ultimately discharges to the Anacostia River.

Stormwater Requirements & Compliance The project is subject to the stormwater management regulatory requirements of 21 DCMR Chapter 5 as regulated by the DC Department of Energy and Environment (DOEE) and the stormwater retention requirements of Section 438 of the Energy Independence and Security Act of 2007 (EISA).

The site will propose bioretentions, manufactured treatment filtering devices (Contech Filterra), and a pipe detention facility to meet these requirements. Future design phases of the project may include additional SWM measures (i.e. a dry swale) to reduce retaining walls along the entrance road and to better facilitate maintenance. The site is also proposing to remove two (2) existing SWM facilities – bioretention 2F and stormfilter 2B.

The site is required to replace the lost retention and treatment control from these facilities.

Stormwater Permitting The project is required to submit stormwater management (SWM) and erosion and sediment (E&S) control plans to DOEE for approval.

Since the project disturbance is over one (1) acre, the project will also be required to obtain coverage under the Environmental Protection Agency (EPA) 2022 Construction General Permit (CGP), per permit No. DCR100000. A notice of intent (NOI) is to be filed with the EPA prior to plan approval, and an acknowledgement of receipt from EPA is to be submitted to DOEE. DOEE will not issue plan approval until the acknowledgement of receipt from the EPA has been received. A stormwater pollution prevention plan

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(SWPPP) must also be compiled prior to submission of the NOI to EPA and shall be kept onsite and updated by the contractor during project construction.

References St. Elizabeths Overall Stormwater Management Program for DDOE / DC Water Compliance, dated October 5, 2010, prepared by Gordon, herein referred to as “DDOE / DC Water SWM Master Plan”

St. Elizabeths Utility Integration Plan Overall Stormwater Program, dated December 8, 2010, prepared by Gordon, herein referred to as “Utility SWM Master Plan”

DC Water letter dated November 10, 2010, Subject line: Saint Elizabeths Overall Stormwater Management Program

Comprehensive Maintenance Plan for Best Management Practice (BMPs) St. Elizabeths West Campus, dated September 2021, prepared by Gordon

Previously approved plans on the St. Elizabeths campus

DC Stormwater Management Guidebook, dated January 2020, prepared by DOEE

Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act, dated December 2009, prepared by US EPA

DOEE / DC WATER

Requirements The project is subject to the current DOEE regulations for retention, vehicular access areas (VAA), and detention, as outlined in the 2020 amendment to Chapter 5 of Title 21 of the District of Columbia Municipal Regulations (DCMR) on January 31, 2020. Per a meeting with DOEE stormwater staff on December 12, 2017, development not shown in Appendix A of the “DDOE / DC Water SWM Master Plan” is subject to the current DOEE regulations. This garage and associated development is not shown in Appendix A-8, and therefore the project is subject to the current DOEE regulations. DOEE classifies this as “unplanned development”.

Retention The project is required to retain the 1.2 inch (90th percentile) rainfall event. The stormwater retention volume is calculated in gallons and a function of the project impervious, compacted cover, and natural areas. Each site drainage area (SDA) is required to achieve at least 50% retention or treatment and the entire LOD must achieve 50% retention. The use of banked GSA stormwater retention credits (SRCs) is permitted for compliance of up to 50% of the retention volume required.

The site is also required to replace the retention from the removed bioretention 2F.

Vehicular Access Areas (VAA) Any impervious surfaces subject to vehicular access is required to retain or treat 100% of the VAA with a best management practice (BMP) with at least 80% TSS removal.

The site is also required to replace the treatment from the removed stormfilter 2B.

Detention The project is exempt from the 2-yr post-development peak discharge requirements because the project meets the following criteria:

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• The project discharges flow to the storm sewer system along I-295 which discharges into the Anacostia River.

• The project does not flow into or through a tributary to those waterbodies that runs above ground or that DOEE expects to run above ground.

• The project discharges will not cause erosion of land or transport of sediment.

The project is required to implement detention controls that reduce the post-development peak discharges rates for the 15-yr storm to at or below pre-project peak discharge rates.

The 15-yr storm requirements have not changed from the 1988 regulations implemented in the “DDOE / DC Water SWM Master Plan” and “Utility SWM Master Plan”. Note, the definition of pre-development in the 1988 regulations is equivalent to the definition of pre-project in the 2020 amended regulations. The 2 master plans show compliance with the DOEE 15-yr detention and DC Water adequate outfall capacity requirements. Therefore, the development will continue to follow the detention criteria and methodology established in the 2 master plans.

The project is also subject to the DC Water requirements for the downstream storm sewer capacity. Per the DC Water letter, the maximum allowable flow from the St. Elizabeths property in 15-year storm is 142 cfs. Flows in excess of 142 cfs would surcharge the downstream storm sewer system and cause flooding. The point of analysis of the 142 cfs is labeled as “Point A” in Appendix A-3 of the “DDOE / DC Water SWM Master Plan”.

Compliance To meet the site retention requirements and replace the retention from bioretention 2F, three (3) bioretentions are proposed to capture runoff from the site.

To meet the site vehicular access area (VAA) requirements and replace the treatment from stormfilter 2B, a manufactured treatment filtering device (Contech Filterra) is proposed along the entrance road. A relief from extraordinarily difficult site conditions may be required for any small areas at the driveway road that tie in to the access road for any runoff that cannot be captured by the proposed filtering devices.

To meet the site detention requirements and the DC Water allowable release rate at Point A requirements, a pipe underground detention facility is proposed.

EISA 438

Requirements The project is subject to the requirements of Section 438 of the Energy Independence and Security Act (EISA) enacted in December 2007, which requires federal agencies to reduce stormwater runoff from federal development projects to protect water resources.

The act states:

“The sponsor of any development or redevelopment project involving a Federal facility with a footprint that exceeds 5,000 square feet shall use site planning, design, construction, and maintenance strategies for the property to maintain or restore, to the maximum extent technically feasible, the predevelopment hydrology of the property with regard to the temperature, rate, volume, and duration of flow”.

Per the memo from Office of the Chief Architect (PCA) with GSA, titled “Compliance with section 438 (stormwater) requirements of the energy independence and security act of 2007, dated June 20, 2019, the project is subject to the EISA 438 requirements since the project constitutes more than 5,000 SF of land that is being redesigned and reconfigured from today’s present day use and composition.

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The project is required to achieve retention through the implementation of systems and practices that use or mimic natural processes to infiltrate and recharge, evapotranspire, and/or harvest and use precipitation to the maximum extent technically feasible (METF).

The design storm is the 95th percentile rainfall depth for the 24-hour storm. In the Washington DC region, the 95th percentile rainfall event for the 24-hour storm is 1.7 inches. Pre-development is considered a forested condition prior to any development onsite. Therefore, while the site has some existing development, for the purposes of EISA, pre-development is defined as a site condition prior to any development. Retention is the established metric for evaluation of compliance with EISA requirements.

Compliance The retention of the 1.7” storm has been met to the maximum technically feasible on site using the proposed bioretentions.

Infiltration The site contains previous construction staging areas, and a high groundwater table. In addition, infiltration into fill is not a generally accepted practice. Therefore, infiltration practices are not considered a feasible practice due to the variable soil conditions, unreliable infiltration rates, , and no infiltration capability has been planned for the stormwater management facility design. All proposed SWM facilities will be surrounded by an impermeable liner.

Evapotranspiration

The bioretentions provide an opportunity for evapotranspiration. The bioretentions are sized to provide the maximum 1.7” of retention for their contributing drainage area.

Water reuse There is not sufficient water demand from the project to require a rainwater harvesting system for the garage.

The retention volume provided by the bioretention is computed per the DOEE retention standards. While the site cannot provide the full 1.7” of retention through infiltration, evapotranspiration, or water reuse, the site does also implement SWM facilities that provide detention for portions of the site. The site controls the post-development peak flow rate to the pre-development peak flow rate for the 15-year storm events. Therefore, the proposed onsite detention also helps meet the intent of EISA to mimic the pre-development site hydrology for the rate and duration of flow.

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Code Analysis

14 Building No. DC0253

CODE ANALYSIS

LIFE SAFETY

PROJECT DESCRIPTION

The new parking garage will be a five tier above grade garage (four stories with an occupied roof) and the parking garage will be designed to comply with enclosed parking garage requirements. The parking levels will have an approximate footprint area of 83,000 SF per level. The building’s highest occupied floor is less than 75’-0” in height and therefore, the building will be classified as a low-rise structure.

All levels of the new Gate 7 Parking Garage and surface parking lot will be predominantly passenger vehicle parking with some accessory storage/MEP space. Level 1 of the building will include a screening facility and exterior waiting area. There will be a shuttle service route, exterior to the garage, that will transport occupants from the garage to the campus buildings.

GOVERNING CODES

The proposed Gate 7 Parking Garage project will be subject to the following Building and Fire Codes as enforced by the General Services Administration (GSA):

• 2024 International Building Code (IBC) excluding the means of egress provisions.

• 2024 NFPA 101, Life Safety Code (LSC) for means of egress provisions.

• 2024 International Fire Code (IFC)

• NFPA 13 Standard for Installation of Sprinkler Systems (2022 Edition)

• NFPA 14 Standard for the Installation of Standpipe and Hose Systems (2022 Edition)

• NFPA 10 Standard for Portable Fire Extinguishers (2022 Edition)

• NPFA 88A Standard for Parking Garages (2023 Edition)

• NFPA 72 National Fire Alarm and Signaling Code (2022 Edition)

All parenthetical references in this analysis are to the 2024 edition of the International Building Code (IBC) unless otherwise indicated. Code references from the 2024 NFPA 101, Life Safety Code include an (LSC) notation.

This review should not be construed as a comprehensive review of structural, mechanical, electrical, plumbing, or elevator code provisions (other than those fire protection and life safety items noted). OSHA Standards and energy codes/standards are also not incorporated.

FIRE PROTECTION CONCEPTS

The proposed Gate 7 Parking Garage building will contain the following comprehensive package of fire protection and life safety features:

• Adequate fire department vehicle access.

• Type IA, protected noncombustible construction

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15 Building No. DC0253

• Fire rated separations for exit enclosures, shafts, and specific areas based on use.

• Non-separated mixed-use on each floor level.

• Automatic sprinkler protection (dry system anticipated) throughout the building.

• Class I manual-wetfire department standpipe systems.

• Smoke and heat detection associated with elevators.

• Electrical supervision and central monitoring of the automatic sprinkler system.

• Emergency responder radio coverage.

• Emergency elevator operation.

• Elevator lobby two-way communication system.

• Standby and emergency power systems.

• Egress lighting and exit signage.

• Portable fire extinguishers.

The following sections of this analysis provide further details of the operation and design features of the fire and life safety systems provided for the Gate 7 Parking Garage building.

FIRE DEPARTMENT VEHICLE ACCESS

The fire department vehicle access roads must be provided and maintained under the IFC. Per the IFC, approved fire apparatus access roads are required for all new buildings and facilities. These access roads must comply with the fire code and extend to within 150 feet of all portions of the exterior walls of the first story, as measured by an approved route around the exterior per IFC Section 503.1.1.

Per conversations with GSA (who serves as the AHJ for the campus), Gate 7 Garage is designed with an increase of this distance to 200 feet based on the 503.1.1 Exception 1 (1.1). Under this exception, the fire code official can authorize an increase when the building is protected throughout with an approved automatic sprinkler system in accordance with NFPA 13,. The proposed building is fully sprinklered, meeting the criteria for this exception per IFC.

Justification for the proposed fire access road conditions includes the following:

• Topography challenges necessitate the request.

• One entire side of the open parking garage has a fire access road.

• Direct access into the open parking garage from the access road will be provided.

• The depth of the garage should be no more than 200 feet. Therefore, the Fire Department Operations Team could reach the exterior walls via the interior of the garage.

• The standpipe system in the garage will provide 200-foot coverage and access to the enclosed exit stairs is from grade level of parking. This will provide the Operations Team with complete coverage as well.

CONSTRUCTION CLASSIFICATION & FIRE RATED SEPARATIONS

The building will be designed using the non-separated, mixed-use provisions for each story. The primary occupancy classification will be Group S-2, and the entire parking garage will be fully sprinklered in accordance with NFPA 13.

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The moderate hazard areas within the building are classified as storage (S-1). Group S-1, occupancies will be classified as an accessory use group. An accessory use group area does not exceed 10 percent of the floor area on which the accessory use group is located. Based on the current layout, the Group S-1 spaces qualify as an accessory use.

Finally, Level 1 will include a screening area and an exterior waiting area. These spaces will be classified as Group B and Group A-3 occupancies.

GSA anticipates a future phase 2 will be constructed. In order to ensure compliance regardless of a future phase 2 expansion, the minimum allowable construction type is Type IA, protected non-combustible.

In accordance with IBC Table 601 for Type IA construction, the primary structural frame (columns, beams, trusses and girders) will be 3-hour fire resistance rated. All floor construction will have a fire-resistance rating of 2-hours. The roof will be 1-1/2-hour fire resistance rated.

All code required fire separation assemblies will be constructed of noncombustible materials and protected to provide the required fire-resistance rating as follows:

• Exit stairs and exit passageways: 2-hours

• Shafts and elevator hoist ways: 2-hours

• Elevator machine room enclosure: 2-hour

• Fire command room: 1-hour

• Electric room – standby substation and main electric rooms: 2-hours

Structural elements essential for the support of fire-resistance rated assemblies will be rated to the same degree as the assembly supported.

Additional fire rated wall assemblies may be required by other disciplines such as mechanical or electrical depending upon the equipment within their respective equipment rooms.

Openings in 2-hour fire resistance-rated separation assemblies will be equipped with 1- 1/2-hour fire rated opening protectives. Openings in 1-hour fire resistance rated separation assemblies will be equipped with ¾-hour fire rated opening protectives so that doors provide ratings compatible with the function of the element being penetrated.

AUTOMATIC SPRINKLER SYSTEM

The Gate 7 Parking Garage building will be protected throughout with an automatic sprinkler per IBC 903.2.10. Sprinkler systems will be designed and installed in accordance with NFPA 13. Per IBC Section 903.4.3, an exterior audible and visual waterflow alarm will be provided and activated by flow from the sprinkler system.

Waterflow switches will be electrically supervised and connected to a fire alarm control unit or the building’s fire alarm system. Activation of the sprinkler system will also trigger the building fire alarm devices, where provided.

Where elevator machine rooms, machinery spaces, control rooms and control spaces containing elevator control equipment are protected with automatic sprinklers, the sprinkler system for these areas will be provided with separate manual isolation valves and a separate waterflow switch located outside each room in an accessible location

The fire pump room is accessed from the southern court at grade.

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FIRE DEPARTMENT STANDPIPES

A Class I manual-wet (IBC 905.3.1 Exception 3) standpipe systems will be provided with hose connections located within each exit stairwell. Standpipe hose outlets will be located at each floor level landing within each exit stairway of the building for use by responding firefighters. In addition, each standpipe riser will be provided with a hose connection located on the roof.

All standpipes will be installed in accordance with the requirements of NFPA 14. A combination sprinkler/standpipe system design is expected.

Fire department hose outlets provided on the standpipe will consist of a 2 ½ inch hose connection and a cap. Threads of hose connections must be compatible with local fire department equipment. (IBC 905.4)

PORTABLE FIRE EXTINGUISHERS

As an additional aid for control of incipient fire conditions, portable fire extinguishers of the appropriate type will be selected and located in accordance with the requirements of NFPA 10, Standard for Portable Fire Extinguishers. The recommended fire extinguisher type for this hazard is a 2A:20B:C rated unit, which provides the equivalent of 2.5 gallons of water for Class A fires and is also effective against flammable liquid (Class B) and electrical (Class C) fires (NFPA 10, Table 6.2.1.1, IBC 906.3).

The travel distance to a fire extinguisher will comply with the 75 feet maximum limitation of NFPA 10.

FIRE ALARM SYSTEM & SUPERVISION

IBC Chapter 9 does not require fire alarm systems for the following occupancies:

1. Parking garages; OR

2. Offices (Group B) where:

• The combined Group B occupant load of all floors is less than 500.

• The Group B occupant load is less than 100 persons above or below the lowest level of exit discharge.

For consistency at St. Elizabeths Campus, an emergency voice fire alarm system (with speaker/strobe occupant notification) will be provided in the Gate 7 Garage Building. The emergency voice alarm system will be connected to the mass notification system that DHS is installing throughout the campus.

Upon activation of any sprinkler system, manual pull station, specific smoke detectors, or heat detectors serving the building, an alert tone and prerecorded voice instructions will sound throughout a predetermined and approved alarm zone.

The emergency voice alarm system must be designed and installed in accordance with

NFPA 72.

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SMOKE DETECTION

The automatic fire/smoke detectors will be connected to the fire alarm system and, upon actuation, perform the intended function. This would include smoke detectors used to close fire rated doors on hold open and/or detectors associated with emergency elevator recall operations. The detectors shall be located in accordance with NFPA 72.

Smoke detectors used solely to initiate elevator recall must initiate an alarm signal, unless specifically approved by the GSA regional fire protection engineer to initiate a supervisory signal.

Smoke detectors located at doors for the exclusive operation of automatic door release must initiate an alarm signal, unless specifically approved by the GSA regional fire protection engineer to initiate a supervisory signal.

GARAGE VENTILATION SYSTEM

Mechanical ventilation systems must be provided in accordance with the IBC, and the

Mechanical Code (IBC Section 406.6.2). All enclosed parking garages must be provided with a mechanical ventilation system capable of providing a minimum of 1 ft3/min per ft2 of floor area during hours of normal operation (NFPA 88A:6.3.1).

MASS NOTIFICATION SYSTEM

A mass notification system is not required per LSC 9.14 or LSC Chapter 42 (storage occupancies). However, mass notification systems will be incorporated on St. Elizabeths campus for safety and security reasons. The requirement for a mass notification system should be reviewed with the GSA regional fire protection engineer to determine applicability.

The mass notification system will be designed in accordance with NFPA 72.

FIRE COMMAND…