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3

SITE IMPROVEMENT

3:SITE IMPROVEMENT

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Low-impact development principles minimize the site’s environmental footprint, protect sensitive ecosystems, and reduce infrastructure costs associated with stormwater management.

 

3.1

Mandatory

Environmental Remediation

RATIONALE

An environmental site assessment determines the potential environmental liabilities associated with property acquisition and ownership.

REQUIREMENTS

Determine whether there are any hazardous materials present on-site by conducting either 1) a Phase I Environmental Site Assessment, 2) a Tier II Environmental Review Assessment per HUD funding requirements, 3) an environmental site assessment approved by HUD through the Part 50 or Part 58 process, or 4) an environmental assessment approved by USDA through the 1970 process, and any additional required assessments.

If an environmental site assessment reveals any hazardous materials, mitigate these contaminants before proceeding with development.

RESOURCES

3.2

Mandatory

Minimization of Disturbance during Staging and Construction

RATIONALE

Controlling erosion and sedimentation during site development keeps valuable topsoil on-site to reduce stormwater runoff and the sedimentation and pollution of local waterways that may be caused by construction debris. Protecting healthy soils during construction and remediating compaction minimizes the adverse effects of construction activities—compacted soils are less able to absorb water, resist plant root penetration, and lack the porosity needed for adequate aeration.

REQUIREMENTS

For sites larger than one acre, implement U.S. Environmental Protection Agency (EPA)’s National Pollutant Discharge Elimination System (NPDES)’s Stormwater Discharges from Construction Activities guidance, or local requirements, whichever is more stringent.

For sites with an area equal to or less-than one acre, complete the following:

  • Stockpile and protect high-quality topsoil from erosion, for reuse.
  • Control the path and velocity of runoff with silt fencing or comparable measures.

  • Protect ERPZs, on-site storm sewer inlets, watercourses and water bodies with straw bales, silt fencing, silt sacks, rock filters, or comparable measures.

  • Provide swales to divert surface water from hillsides.

  • Identify and protect significant, high value trees during construction (healthy tree with a diameter at breast height greater than 6"). Install tree protection fencing outside the critical root zone.

  • If soil in a sloped area is disturbed during construction, use tiers, erosion blankets (geotextile mats), compost blankets, filter socks and berms, or some comparable approach, to keep soil stabilized.

RECOMMENDATIONS

  • Create and implement an erosion, sedimentation, and pollutant control plan, commonly referred to as a stormwater pollution prevention plan (SWPPP) or erosion and sedimentation control plan (ESC) for all construction activities associated with the project. Plan should conform to the EPA’s Construction General Permit or local erosion and sedimentation control standards and codes, whichever is more stringent. The plan should list the best management practices (BMPs) employed and describe how the BMPs accomplish the following objectives:

    • Prevent loss of soil during construction by stormwater runoff or wind erosion, including protecting topsoil by stockpiling or covering for reuse.
    • Prevent and reduce sediment discharges into storm conveyances, receiving waters, or other public infrastructure components or systems.
    • Prevent polluting the air with dust and particulate matter.

    • Prevent runoff and infiltration of other pollutants from construction sites (e.g., thermal pollution, concrete wash, fuels, solvents, hazardous chemical runoff, high or low pH discharges, pavement sealants) and ensure proper disposal of all construction related materials.

    • Protection of existing sounds (prevent compaction; implement mitigation/restoration)

    • Protection of existing trees

    • Protection of existing vegetation

  • Critical root zone, or CRZ, is defined as the area of soil where roots required for future tree health and survival are located. This area can also be defined as a circle with a minimum radius of 1' for every 1" in trunk diameter at 4.5" above ground.

  • High-quality topsoil is any topsoil that is suitable for planting. Consult a landscape architect, civil engineer, or your state university cooperative extension about the quality of soils on-site, before determining which soils are suitable for reuse on-site. In general, high-quality topsoils feature organic matter, appropriate pH levels, and nutrients.

  • Support a net-zero waste site and minimize down-cycling of materials by diverting, reusing, or recycling construction and demolition materials to avoid disposal in landfills or combustion in incinerators.

RESOURCES

  • EnviroCert International, Inc. Use the International Registry of Certified Professionals in Environmental Specialties to find erosion and sedimentation control professionals in your state. https://envirocertintl.org/

3.3

Mandatory, if providing landscaping

Ecosystem Services/Landscape

RATIONALE

Ecosystem services are the functions provided by the living landscape. Soil and vegetation absorb and purify stormwater to protect receiving water bodies. Trees create shade, protect from wind, and help to regulate the climate. Plants capture particulate matter and sequester carbon to help moderate climate and reduce air pollution. Native and adaptive plants are more resistant to naturally occurring disease, insects, drought, low levels of nutrients and major storm events, while reducing or eliminating the need for fertilizers, pesticides, herbicides and irrigation. Research suggests that the incorporation of natural elements in the built environment can generate ecosystem services to protect and improve a community’s quality of life and resiliency to climate change.

REQUIREMENTS

If providing plantings, all plantings (trees, shrubs and groundcover, including grasses) should be native or climate-appropriate (adapted) to the region. All new plantings must be appropriate to the site’s soil and microclimate. Do not introduce any invasive plant species. All disturbed areas should be planted, seeded or xeriscaped.

RECOMMENDATIONS

  • Consult a landscape architect or your local arborist during the integrative design process to identify appropriate areas for landscaping and shading.

  • Consider developing a soils management plan to: identify, protect and reuse high-quality site soils; to identify disturbed soils; and to outline a soil restoration process.

  • Provide adequate horticultural soil volume for new tree plantings. Reference the ANSI A300 standards as managed by the Tree Care Industry Association for more details.

  • When removing invasive species, be careful that your removal and transferring of invasive plant material limits site disruption and does not compact soil.
  • Consider the proximity of plantings to your building, especially in areas prone to fires. Reducing or eliminating flammable material in a defined perimeter around your structure can be an effective mitigation technique in areas prone to wildfires.

  • In areas where water shortages are common, consider xeriscaping, a landscaping strategy that uses drought-resistant plants to significantly reduce or eliminate the need for irrigation.

  • Integrate the landscape plans with the stormwater management plan to provide drainage, maximize stormwater absorbption, and direct water to plantings to reduce the need for irrigation.

  • While turf may be appropriate for some landscaping, such as for play areas, it should be minimized wherever possible. Turf grass is resource intensive due to irrigation and mowing requirements. The cumulative effects of regular mowing contribute to air and noise pollution. Applications of chemical fertilizers, and herbicides contribute to pollution of waterways and can adversely affect native habitat.

  • The project team should strive to use only organic and nontoxic fertilizers, pesticides, herbicides, fungicides, and pre-emergents.

  • Where possible, create walking pathways and seating to encourage pedestrian activity. Establishing a tree canopy, especially along pathways and gathering areas like seating, is important to creating a welcoming, comfortable public space.

  • If possible, existing invasives should also be mitigated/removed. Local cooperative extensions often maintain best practices for mitigation.

  • Provide visually appealing environments along paths of travel with visually interesting landscaping (e.g., a variety of colors, textures, and flowering times).

  • Ensure that the expected heights of plants adjacent to pedestrian walkways or seating areas are appropriate to maintain visibility into and out of the corridor in order to facilitate a safe and secure environment.

  • If possible, limit turf or high-water-using species to 20% of the total landscape area, as suggested by the City of Santa Monica (Calif.) Landscape Standards.

RESOURCES

  • U.S. Department of Agriculture, Agricultural Cooperative Extension System. Lists of local drought- tolerant plants may be available from local USDA Agricultural Cooperative Extension System offices, as well as through numerous online resources. https://nifa.usda.gov/cooperative-extension-system

  • U.S. Forest Service, “Celebrating Wildflowers.” This site has extensive information on native gardening, selecting appropriate native plants and invasive plant species, and has basic instructions for restoration and native landscaping projects. https://www.fs.fed.us/wildflowers/

3.4

Mandatory for New Construction projects |

Mandatory for Rehab projects if land disturbed is ≥ 5,000 square feet

Surface Stormwater Management

RATIONALE

Reducing or eliminating stormwater runoff through design and management techniques increases on-site filtration, reduces total suspended solids (TSS) and other pollutants from entering waterways, and reduces soil erosion. From a resiliency standpoint, minimizing stormwater runoff and storm sewer flows also helps reduce downstream flooding—an important concern with more intense storms predicted in the future. Water storage and nutrient collection processes reduce the need for irrigation and contribute to forming a healthier ecological community within the landscape.

REQUIREMENTS

Treat or retain, on-site, the precipitation volume from the 60th percentile precipitation event as defined by the U.S. Environmental Protection Agency in the Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act.

On sites in which retaining the 60th percentile precipitation event is not feasible due to geotechnical issues (e.g., high groundwater elevations, contamination, underground utilities, underground transportation networks), soil conditions (e.g., clay soils) or the size of the site (e.g., zero lot line), the project must treat or retain the maximum possible up to the 60th percentile precipitation event.

RECOMMENDATIONS

  • Improve the water-retention capacity of the soil by increasing the organic matter content of the soil through the addition of compost or other organic soils.
  • Projects may retain precipitation volume through any combination of the following techniques: on-site infiltration, evapotranspiration, water reuse, and cisterns.

  • Implement runoff-reduction strategies (e.g., biofiltration through plantings, soils). These strategies also improve water quality.

  • Evaluate the discharge volumes and rates to ensure that they do not increase the natural rate of erosion in receiving waterways or negatively affect a receiving waterway’s ecological flows or natural groundwater replenishment rates and volumes.

  • Implement strategies to reduce precipitation runoff volumes, peak flows, and pollutant discharges.

  • Use rainwater-harvesting systems to reduce precipitation runoff volumes and rates. Design rainwater harvesting and use systems to maintain the ecological flows of receiving waters and historical groundwater recharge rates.

  • Make use of innovative, low-impact techniques such as disconnected downspouts, permeable paving, swales, retention basins, rain gardens, green roof, rain barrels to convey, capture, infiltrate, and /or reuse stormwater.

  • Minimize impervious areas (surfaces that do not allow stormwater infiltration), including roofs, driveways, sidewalks, and streets, or use porous materials for such areas. Water-permeable materials include pervious interlocking concrete paving blocks, concrete grid pavers, perforated brick pavers, and compacted gravel.

  • Provide a visual reminder that storm sewer inlets connect to area waterways and groundwater storages, use a plaque, tile, painted, or pre-cast message such as “No Dumping. Drains to [name of water source].” If project is unable to label storm inlets due to jurisdictional constraints, the project team must provide documentation.

RESOURCES

3.5

Optional | 10 points maximum

Surface Stormwater Management

RATIONALE

See Rationale for Criterion 3.4.

REQUIREMENTS

Through on-site infiltration, evapotranspiration, and rainwater harvesting, retain the maximum precipitation volume possible beyond the requirements of Criterion 3.4 precipitation on-site.

Retain precipitation volume for the following percentile precipitation events:

70th percentile precipitation event

6 points

80th percentile precipitation event

8 points

90th percentile precipitation event

10 points

Seventieth, 80th, and 90th percentile precipitation events are defined by the U.S. Environmental Protection Agency in the Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act.

RECOMMENDATIONS

See Recommendations for Criterion 3.4.

RESOURCES

See Resources for Criterion 3.4.

3.6

Mandatory, if permanent irrigation is utilized

Efficient Irrigation and Water Reuse

RATIONALE

Using irrigation zones that respond to site conditions and plant material helps to maximize efficient water use. Accurate delivery of water reduces evaporation and eliminates overspray and overwatering. Proper scheduling eliminates fluctuations between wet and dry states that stress plants. These strategies will help to maintain plantings during drought and when outdoor watering restrictions may be in place and will reduce water waste and overwatering during wet weather conditions.

REQUIREMENTS

If irrigation is utilized, install an efficient irrigation system. These irrigation requirements are mandatory only for permanent landscaping that requires regular irrigation.

An efficient irrigation system must include the following:

  • Comply with all local watering restrictions.
  • Design irrigation zones to respond to weather considerations (temperatures, precipitation, wind), solar exposure, reflected light/heat from adjacent building or hardscape, soil type, topography/slope, plant material.

  • Establish irrigation volume and frequency per zone to be appropriate for the climate, soil type, and plants.

  • Select emission devices (e.g., spray sprinklers), valves, pipes, controllers, and sensors suitable to the landscape requirements that will facilitate long‐term reliability and serviceability.

  • Design irrigation system to target each planting area with no overspray of impervious surfaces or adjacent planting areas. Prevent runoff of water from the site.

  • Install timer/controller that activates the valves for each watering zone at the best time of day to minimize evaporative losses while maintaining healthy plants and obeying local regulations and water-use guidance.

  • Install soil moisture sensor controller per vegetation zone (based on irrigation demand) or rain delay controller.

RECOMMENDATIONS

Follow the Best Management Practices from the Irrigation Association, which include:

  • Consider future needs such as expansion of the system to accommodate further development.

  • Consider using non-potable water sources:

    • Captured rainwater
    • Reclaimed water

    • Recycled wastewater

    • Recycled greywater

    • Air-conditioner condensate

    • Blowdown water from boilers and cooling towers

    • Water treated and conveyed by a public agency specifically for non-potable uses

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  • Do not exceed manufacturer’s sprinkler spacing recommendations.

  • Design system so sprinklers operate within manufacturer recommended operating pressure.

  • Use matched precipitation rate sprinklers (+/– 5 percent) within a zone.

  • Size the zone control valve so that flow through the valve is within the manufacturer’s stated flow range and so that pressure loss does not exceed 10% of static pressure.

  • Install valves either above grade or below grade in a valve box large enough to service or access.

  • Valve box location should consider safety and aesthetics of the site, along with long‐term durability of the valve box.

Develop a proactive maintenance plan to ensure the integrity of the irrigation system. As the plants mature, the irrigation system may require adjustments.

RESOURCES

  • City of Santa Monica, Office of Sustainability and the Environment, Landscape Standards Overview. www.smgov.net/Departments/OSE/Categories/Landscape/Landscape_Requirement...

  • American Society of Landscape Architects (ASLA). ASLA is the national professional association representing landscape architects. Their site provides information about members, products, services, publications and events. www.asla.org

  • U.S. Environmental Protection Agency, WaterSense®. This site provides information on the EPA WaterSense labeling program for water-efficient landscape irrigation products, plus tips and recommendations for water-efficient irrigation. Follow the link to Weather- or Sensor-Based Irrigation Control Technologies for related information on high-efficiency irrigation controllers. www.epa.gov/watersense

  • American Water Works Association, WaterWiser®, The Water Efficiency Clearinghouse. This clearinghouse provides articles, reference materials and papers on all forms of water efficiency. www.awwa.org/waterwiser/

3.7

Optional | 4 or 6 points

Efficient Irrigation and Water Reuse

RATIONALE

See Rationale for Criterion 3.6.

REQUIREMENTS

Projects must meet the mandatory requirement of Criterion 3.6 and one of the options below. For all projects, temporary irrigation to establish new trees and plantings is allowed for a period of two years.

Option 1 [4 points]

Design and install an efficient irrigation system equipped with a WaterSense labeled weather-based irrigation controller (WBIC).

OR

Option 2 [6 points]

A minimum of 50% of the site’s irrigation should reuse water from one, or multiple, of the following sources:

  • treated greywater
  • captured rainwater, collected from the roof or site

  • water from a municipal recycled water system specifically treated for non-potable uses

  • air-conditioning condensate

  • blowdown water from boilers and cooling towers

RECOMMENDATIONS

See Recommendations for Criterion 3.6.

RESOURCES

See Resources for Criterion 3.6.

 

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INTRODUCTION

CRITERIA CHECKLIST

      • INTEGRATIVE DESIGN

      • LOCATION +

        NEIGHBORHOOD FABRIC

      • SITE IMPROVEMENT

      • WATER

      • OPERATING ENERGY

      • MATERIALS

      • HEALTHY LIVING ENVIRONMENT

      • OPERATIONS,

        MAINTENANCE +

        RESIDENT ENGAGEMENT APPENDICES

        GLOSSARY