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Home , Soil fertility, Urban agriculture

University of California Cooperative Extension - Los Angeles County in Urban : Testing, Remediation and Best Management Practices for California Community , School Gardens, and Urban

RACHEL SURLS, UC Cooperative Extension Sustainable Systems Advisor; VALERIE BOREL, UC Cooperative Extension Program Representative; ANDRE BISCARO, UC Cooperative Extension Agriculture and Environmental Issues Advisor.

Urban agriculture, including community and school gardens, and small farms in cities, has become a popular means of obtaining fresh local produce. San Francisco, San Diego, Los Angeles and several other California municipalities have changed policies to facilitate these activities. Soils are an important consideration for individuals, community groups, and local governments becoming involved in . In many situations, urban has been contaminated and degraded by past uses and activity, including industry, unauthorized dumping, construction, heavy nearby traffic, and adjacent buildings where lead-based paint has been applied. Elevated levels of lead in particular are fairly common in urban soils, and pose health risks, especially to young children who can ingest soil while playing or helping in gardens. Ongoing exposure to lead can cause damage to Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms the nervous system and interfere with soil, and issues where a contaminant may brain development, along with creating not be harmful to people, but may prevent other health problems. Arsenic, cadmium, growth or production. Physical debris copper, zinc and other naturally occurring such as lumber, concrete, wire, broken glass trace elements in soils can also be elevated or discarded syringes can also create hazards to unsafe levels by various past uses. for the urban . Although soil degradation and Clearly, there are no easy answers. Each contamination are important concerns and site and situation is unique. However, should be addressed, they are not always putting in place reasonable policies and a problem with urban agriculture sites. A encouraging sustainable practices will study conducted at several Los Angeles help to ensure that participants and those area community gardens by University of who consume urban agriculture products California researchers found that “in nearly are not exposed to unsafe levels of lead or all cases concentrations of trace elements other heavy metals and contaminants. This were well within natural ranges” (Hodel, publication outlines strategies for urban soil D.R. and A. C. Chang, 2002). In contrast, contamination assessment, remediation, a study conducted in San Francisco found and municipal policy around safe soils for that “a majority of the gardens exceeded urban agriculture, and offers additional the California Health Screening for further exploration. This Level for arsenic, cadmium, and lead” publication does not cover soil fertility (Gorospe, 2012). or other important topics, Even where there are elevated levels of although resources are listed on page 10. lead or other metals or contaminants Instead, the goal is to provide an overview in soil, relatively little is absorbed by of issues unique to urban soil use for food that can be harmful to , production. although this varies depending on the soil condition and the plant characteristics. Soils Assessment for Urban Agriculture Accidentally swallowing or inhaling Site Selection: Overall soil conditions should contaminated soil and dust is the be a consideration when selecting a site for most likely way urban will be urban agriculture. If plants, even weeds, exposed to unsafe levels of lead or other are growing abundantly on the site, this is contaminants. This can happen easily, for a good indication that the soil will be able example, when people put their fingers in to support . If soil is reasonably easy their mouths without thinking. to dig, this is a positive sign as well. The Beyond heavy metals, other sources presence of plant roots and of and soil hazards can indicate . However, note might include solvents found at sites with that these indicators do not guarantee that a history of manufacturing use, various soil is uncontaminated. When assessing petroleum based chemicals – common potential sites, be aware that properties with at previous gas station sites and other considerable amounts of trash and rubble, or industrial sites, chlorinated and with obvious dead spots where plants do not residual on former agricultural grow, may pose greater challenges. Heavy or public landscaped areas, saline or use may have even

2 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

sterilized the soil on a site. A simple test for their archives. There is also a fee-for-service evaluating soil fertility is to plant bean seeds website, http://www.historicalaerials.com, in soil from the site, perhaps in a pot or some which includes aerial maps of various regions biodegradable paper cups, and compare of California where the history of a site can their germination and growth with an equal be researched. The county tax assessor’s office number of beans grown in purchased potting and city hall are important sources of tax soil. It is also advisable to dig a hole one-to- records and permits that have been obtained two feet deep in several places to assess the for the property, which can help uncover type of debris on the site. past uses of the site. Potential sites can be Site History: It is important to learn as checked on the California Department of much as possible about the history of a Toxic Substances website at http://www. proposed site and how it has been used envirostor.dtsc.ca.gov/public/ to see if there in the past. Walking around the site may are any documented issues or ongoing provide some clues. Adjacent older homes cleanup activity associated with the property. with peeling paint, paint chips or evidence Some examples of prior uses of sites that may of sandblasting indicate potential soil lead have caused soil contamination are parking contamination. Any building built before lots, junkyards, auto repair/auto painting, 1979, with old or peeling paint, may be carpentry, machine shops, dry cleaners, gas a hazard due to use of lead-based paint. stations, railroad yards, and illegal dumping. Proximity to a freeway or heavily trafficked The history of the site will help to determine road is also a source of lead. Although what kind and how much soil testing is leaded gasoline has not been in use since necessary. A site that has been primarily the 1980s, lead particles in vehicle exhaust residential or used as green space is may have settled from the air into the soil. generally lower risk. A site that has had Talking to the property owner and past industrial or commercial uses should neighbors is a good strategy, as neighbors be more carefully analyzed. are often familiar with past use of the property. It may also be necessary to Soil Testing do some internet or library research. Having soil tested at a laboratory is always For example, at some public libraries recommended. This should be considered a it is possible to access Sanborn maps, basic cost of starting any urban agriculture which were used in the past by insurance project. The cost will depend on the size of companies to determine the risk involved the proposed site, the number of soil samples with insuring individual properties. These needed, and the type of analysis conducted maps can provide information about prior by the lab. uses of a proposed site. These are available kits sold at hardware stores at public libraries, and may be available or centers provide some basic online through some libraries. Old aerial estimates of soil fertility, but are not suitable photographs, which can sometimes be for assessing soils at a potential urban found in local libraries or online, can help agriculture site, as they do not provide identify a site’s history as well. information about soil contaminants. The local city hall may also have some Selecting a Soil Testing Lab: Finding a of these aerial photographs accessible in university or commercial lab to do soil

3 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms testing is not difficult; performing an 8. Is a narrative provided with the soil internet search for your region or state test results? Is there an extra charge for should result in several choices. In this? many publications, the Cooperative 9. Do you provide remediation Extension service is listed as a recommendations with the soil tests? for testing soil. However, the University of California Cooperative Extension does 10. What is your turnaround time? not offer soil testing. Some other state The US Environmental Protection Agency land grant universities accept out of state recommends that for urban areas, “at a soil sample submissions by mail at very minimum, the soil test should include reasonable prices, including University of pH, percent organic matter, nutrients, Massachusetts at Amherst and Penn State micronutrients, and metals, including University. lead” (See EPA Publication No. 905R1103, When selecting a soil testing lab, here are “Evaluation of Urban Soils: Suitability for some questions to ask when talking to the or Urban Agriculture”). labs: This level of testing is adequate for a site that has been residential or green space. Most 1. Do you participate in the North commercial soil labs can test for the most American Proficiency Testing important heavy metals, including not only Program (NAPT – this program lead, but also arsenic, cadmium, chromium assures that soil test analyses are and nickel. being performed using validated More testing may be appropriate for a site testing methods). with a history of industrial or commercial 2. Which tests do you recommend for use, which might include CAM-17 testing an urban agriculture site with no site (CAM stands for California Administrative history? Manual. CAM 17 refers to the list of 17 3. Do you recommend any specific tests metals specified in the manual: antimony, for sites with a history of industrial or arsenic, barium, beryllium, cadmium, commercial use? chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, silver, 4. Do you perform tests for elevated thallium, vanadium, and zinc). An EPA- levels of heavy metals and other recognized laboratory is the best choice for contaminants– in particular, those this level of testing. listed in the California Code of Regulations Title 22: Inorganic It is possible that other types of tests may Persistent and Bioaccumulative Toxic be necessary, such as testing for PAHs Substances? (polynuclear aromatic hydrocarbons), a 5. What costs are involved for testing? class of potentially toxic byproducts of incompletely burned garbage, oil, , 6. What is the recommended procedure coal or other organic materials. These for taking soil samples? accumulate in soils and can be a concern 7. Is it okay for people to call the lab for on a site that has been a car wash, parking advice and information? lot, road and maintenance depot, vehicle

4 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

services site, or where coal, oil, gas or and mail it to the lab. Once a lab has been garbage were burned on site. selected, review its website for instructions, or speak to a staff member on the telephone. In many situations, staff members at soils Detailed instructions on collecting soil labs are great sources of information. They samples are also available in several of the are generally willing to talk on the phone resources listed on page 10. It’s important about appropriate testing based on site to review these instructions, since poorly history. However, there are instances where collected or unrepresentative soil samples additional support may be necessary. may not provide good information. Resources for brownfields soil assessment: Generally, it’s essential to approach soil According to the California Department testing with a plan in mind. By making a of Toxic Substance Control (DTSC), simple map of a proposed site, and noting “brownfields are properties that areas with different characteristics, it is are contaminated, or thought to be possible to decide how many samples to contaminated, and are underutilized due collect. to perceived remediation costs and liability concerns.” In some cases involving former Mapping sampling area. industrial or manufacturing sites, old gas 1. If there is an area where plants are not station sites, and some other situations, growing, or the soil is discolored, that expert assistance may be necessary. Some area should be sampled separately. sites may have cleanup issues beyond what a community project can accomplish 2. An area of the site adjacent to a without technical expertise and a building with peeling paint should be significant budget. Some sites may be too sampled separately. expensive to test and remediate. Help may 3. For each area to be sampled, it is sometimes be available, though, through usually appropriate to take five to state and local brownfield programs. seven sub-samples which will be mixed California DTSC oversees a voluntary together to create a composite sample. cleanup program for brownfield sites. Some 4. Samples should be taken from the top cities have brownfields programs that may four to six inches of soil. be able to provide guidance, resources and perhaps even help secure funding for 5. Any litter, leaves, grass, or anything cleanup. Although urban agriculture is else covering the soil should be not yet a common reuse for brownfield removed before sampling. The sub- sites, this is an area for further exploration. samples can then be mixed together Local offices of the USDA Natural thoroughly in a clean bucket to form a Resources Conservation Service (NRCS) composite sample. may also be able to provide technical 6. For each distinct area of the site, this assistance and guidance on a case by case process should be repeated. basis. 7. Keeping track of sampling location is Taking Soil Samples: Laboratories generally important. Once results come back, provide an online instruction sheet on it will be necessary to refer to records how to sample the soil, prepare the sample, that clearly show where on the site samples were taken.

5 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

Transporting samples. so, there is not one standard as to what 1. A clean plastic resealable bag that constitutes safe levels of heavy metals in holds approximately two cups (1 – 1 urban agriculture. Most guidelines that exist ½ lbs.) should be used to are created for residential use scenarios and the soil sample. contact with soil through skin exposure or accidental ingestion, rather than formulated 2. Removing most of the air from a for or farming. Still, they provide double-bagged sample is a good some guidance about what’s acceptable. precaution to prevent spillage. One standard to consider is the California 3. Some labs also supply sample jars, Human Health Screening Level (HHSL), which may be free with testing. which is used by the City and County of 4. The soil sample does not need to San Francisco, and the City of San Jose, in be refrigerated, but keeping it in their guidance on lead hazard assessment the or a cool, dry place until for urban gardens and farms. For lead, shipping or delivery to the lab can be the HHSL is 80 parts per million (ppm). beneficial to achieving accurate test Anything lower is considered “below the results. level of concern for human health.” Another 5. Wet samples should not be shipped – standard is the US EPA’s Soil Screening inaccurate testing may result. Levels (SSLs) for residential use, which consider lead to be a hazard at levels of 400 6. Soil samples can be dried prior to ppm or more. In 2013 the EPA’s Technical shipment by keeping the bag open Review Workgroup (TRW) for Lead in a dry and well-ventilated place provided a bit of clarification specifically or by spreading the soil in a thin for gardening, and deemed soil lead at less layer on clean butcher or waxed than 100 ppm to be “low risk” for home- paper, and allowing it to dry at room grown produce. The HHSL levels for heavy temperature. metals and other potential contaminants Interpreting Soil Test Results: Some are listed in the chart at http://www.oehha. soil labs provide a narrative report ca.gov/risk/chhsltable.html, and some of with recommendations. Most labs are the most common are listed in Table 1 along receptive to phone calls with questions on with the corresponding SSLs. The EPA’s interpretation, upon receipt of test results. TRW chart with specific, tiered soil lead Results of soil testing indicate if plant recommendations for gardening is available nutrients are low and need to be raised for in Table 2. It is important to note that these best plant growth, and if soil pH needs to standards are advisory only. Check with be adjusted. The soil test can also indicate local municipalities (or school districts if there are higher than acceptable levels for school-based projects) to find out if of heavy metals, or other contaminants, more specific requirements have been depending on what tests were requested. established. Heavy metals are the most commonly tested, and there is more guidance available Remediating Soils about heavy metals, especially lead, than If soil testing indicates that there are higher for many other contaminants. Even than acceptable levels of lead or other heavy

6 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

metals, there are strategies to mitigate the when dealing with a brownfield site, is problem. to remove existing soil from the growing Working with existing soil: Many times, area, and replace it with soil that is certified urban farmers automatically plan for raised safe. However, this is an expensive strategy, beds to avoid potential soil problems. and is out of the range of what most However, raised beds do have some community groups or individuals can drawbacks, including the cost of materials, afford. Contaminated soil has to be disposed obtaining quality “clean” soil to fill them, of according to law, and this can prove and the fact that plant roots dry out faster expensive, in addition to the costs involved in raised beds, potentially increasing with excavating soil, removing it, and needs. When possible, it’s more bringing in clean soil. economical to plant in the existing soil. Raised Beds: A more common approach If the site has been residential or green is to build raised beds and fill them with space, without a history of industrial use, clean soil. A study of backyard, school and soil test results are borderline, it may and community garden soils in San be possible to work with existing soil by Francisco showed that raised bed gardens following some best management practices. had significantly lower levels of arsenic, 1. Turn over the soil deeply and cadmium, and lead than in-ground gardens thoroughly. Contaminants are often (Gorospe, 2012). Another study, conducted concentrated in the top two inches in , measured significantly less of soil, and can be diluted through lead in raised bed gardens than in-ground digging and mixing. gardens (Witzling et. al, 2010). 2. Maintain the soil pH at or close to To create raised beds, urban farmers can neutral, 6.5 to 7.0. Soil nutrients are build frames of redwood or other lumber, most available to plants at this pH, brick, concrete, rocks, or any other sturdy while lead and some other heavy material that won’t leach contaminants into metals are less available. the soil. Treated lumber should be avoided since lumber treatments may cause 3. Add organic matter to the soil, and of copper or other metals into the soil. continue to do so each planting season. By adding soil amendments -permeable fabrics can be applied and , the soil will hold water as a barrier between the on-site soil and nutrients more effectively, and and the imported soil used to fill raised heavy metals will bind to organic beds. fabric is liquid- and air- matter and become less available permeable, unlike black plastic. Landscape to plants. Organic matter improves fabrics are made from various materials, , infiltration and including nonwoven polypropylene, woven water-holding capacity, creates a fabric, biodegradable paper , or better environment for plant roots flexible geotextile fabric. and slowly releases plant nutrients. Once the frame has been lined with Adding organic matter also helps to landscape fabric it should be filled with dilute soil contaminants. “clean” soil. One way of ensuring clean soil Soil Removal: The most cautious strategy, is to purchase OMRI (Organic Materials perhaps most likely to be considered Review Institute) -certified or

7 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms planting mix. OMRI performs an company is hired to do the job, though, independent review of products intended asphalt removal can be a major expense. for use in certified organic production, Many sites have created successful urban handling, and processing. OMRI reviews agriculture projects through depaving. For producer-submitted products against the example, in 2006, volunteers removed 5,000 National Organic Standards and generates square feet of asphalt from the grounds a list of acceptable products. See the OMRI of Carthay Center Elementary School in Products list at http://www.omri.org/ Los Angeles and created a thriving garden sites/default/files/opl_pdf/crops_category. – the Garden of Possibilities – which is a pdf. Some products that are not OMRI centerpiece for the entire community. To listed may still meet USDA organic rules; improve the hardened clay soil, tons of soil, the producer may have decided against mulch and compost were donated and tilled the expense of being reviewed by OMRI. into the soil by volunteers. The garden is a Local urban farmers or may have great success for the school; the students recommendations on potential sources of now participate in a year-round garden quality soil. Some vendors may be able to science program. The garden consists of provide documentation that soil has been raised beds and in-ground beds, as well as a tested, and if not, the soil could be sent stone fruit , citrus orchard, tropical to a lab for testing to be sure that it is not garden, butterfly garden and poetry garden. contaminated. If a site plan calls for asphalt removal, it Other Containers: There are other types of is important to test for heavy metals and containers besides raised beds. Some are other contaminants prior to removal. commercially available growing systems Testing soil beneath asphalt requires cutting that are self-watering for smaller-scale triangular holes in the asphalt with a hand- projects. Others are mesh “socks” that are held concrete saw to expose the soil. The filled with growing medium and placed asphalt triangles can then be removed along on top of the soil. These types of “instant with any subgrade debris or stones in order gardens” may be especially appropriate for to obtain a sample (Replacing pavement short term projects. triangles and adding sand or pea gravel is Although tires are sometimes used as necessary afterwards to prevent a tripping planters, this practice is not recommended, hazard). If soil tests show heavy metals above since tires can contaminate soil with recommended levels, rather than removing leached metals as they degrade over time. the asphalt, raised beds or large containers Asphalt Removal: Sometimes, especially might be considered for gardening. at school sites, there is no open ground Choosing Ornamentals over Food Crops: available, and gardens are constructed over Some sites not appropriate for growing food blacktop, or asphalt is removed in order to might still be perfect for ornamental trees have a garden. and shrubs, or a wildflower meadow. Not Asphalt removal, also known as “depaving”, every site needs to be a food production can convert an unused paved area into a site, but can serve other purposes in the garden space. This is a sizeable project to community, such as green space and undertake, especially if doing it manually beautification. with the help of volunteers. If a professional

8 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

Best Management Practices Municipal Policies for Soil Testing and There are several practices that make Urban Agriculture sense in many urban agriculture settings, As urban farming in all its forms becomes whether gardening in the soil, raised beds, or other containers, even where soil more popular, municipalities are beginning testing does not indicate problems. to consider a variety of policies related to for this purpose, including 1. Remove any debris from the site, requirements for soil testing and such as trash, metal, wood, and tires. remediation. Generally, the decision faced Use care in removal and disposal of by municipalities is whether to require these materials, being aware of and soil testing and a remediation plan where following any pertinent regulations. appropriate, or to make recommendations 2. Mulch paths and walkways between and provide educational materials on best planting beds. It is also possible to practices. Requiring soil testing can create use a landscape fabric then cover challenges for municipalities if they do the fabric with mulch. Mulch will not have staff available and qualified to not only keep weeds in check and review and evaluate soil test results and conserve water, it will also help keep remediation plans. Some municipalities dust that may contain lead or other require soil testing for contaminants contaminants from getting on crops (and sometimes other soil properties) for or other surfaces that participants community gardens. Anyone contemplating may touch. establishment of such a garden or should check with the local city or county 3. Wear gloves while working on the environmental health or parks and site. recreation department or other jurisdiction. 4. Facilitate hand washing. Hand It is important to ensure that policies do not washing immediately after working create insurmountable barriers for urban in the urban farm is important. agriculture. Many community groups Incorporate a hand washing station pursuing community gardens or other into the urban farm, and train urban agriculture projects have limited participants to use it frequently. funds to conduct extensive site analysis for Handwashing is important for contaminants and any resulting remediation. everyone but even more so for children, who tend to put their At the same time, contamination of fingers in their mouths. urban soil is an important environmental health consideration. It is possible to have 5. Thoroughly wash produce before urban agriculture that is both safe and storing, cooking and eating. Remove cost-effective. Soil testing is extremely older, outer leaves of lettuce or leafy important and should be facilitated and greens before eating. Peel root encouraged by municipalities. Ideally, vegetables before eating. this would include subsidizing the cost of 6. Wear closed-toe footwear while soil testing and providing assistance with working on the urban farm. If interpretation of soil tests and development possible, remove shoes worn while at of simple remediation plans. Minimally, it the farm before entering the home. would involve a list of best practices, such

9 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms as some of those in this publication, that Extension has trained Master urban farmers would agree to implement at Volunteers available who may be able to help their site. provide education at the local level. Education is important in any case. Many Cities should also foster a connection best management practices, such as adding between their own brownfields program, if organic matter and managing soil pH are one exists, and urban farmers. Municipal important strategies for ensuring safe soils, brownfields programs should be encouraged but are not practical to handle via policy. to work with urban farmers to identify Cities and counties should explore forming potential sites and support testing and partnerships with the local UC Cooperative remediation for urban agriculture projects. Extension office to provide educational This strategy is being used successfully in resources and training on several US cities, including Milwaukee, for urban agriculture. UC Cooperative Wisconsin and Kansas City, Missouri.

TABLE 1. Advisory Levels to Guide Interpretation of Soil Test Results for Heavy Metals in parts per million (ppm)1 Inorganic California US EPA SSLs Chemicals Residential HHSLs Arsenic2 .07 .4 Cadmium and 1.7 70 compounds Chromium III 100,000 120,000 Chromium VI 17 230 Lead and lead 80 400 compounds Nickel and 1,600 1,600 compounds Zinc 23,000 23,000 1 These state and federal soil screening level standards are for advisory purposes only. Please refer to page 6 for details. 2 The screening numbers for arsenic are for contamination resulting from human activity. Concentrations of naturally occurring arsenic may be far above the screening number. When levels of arsenic at a site are a concern, the agency with authority over remediation decisions should be consulted.

10 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

TABLE 2. EPA TRW Lead Committee Recommended Best Management Practices for Gardening in Lead Contaminated Areas (reprinted from publication #OSWER 9200.2-142) Soil-Lead Category Recommendation: Gardening Recommendation: Concentration Practices Choosing Plantsa (ppm) <100 Low risk No specific remedial action needed. No restrictions of crop types. Wash hands, produce, clothes (good gardening and housekeeping practices). >100–400 b Potential Increasing use of good gardening Decrease planting of root 400 - 1200 risk and house- keeping practices as vegetables or relocate root described in Table 3. crop planting to lower risk Relocate garden to lower risk garden areas. areas. Increase use of soil Increasing use of soil amendments amendments and barriers to (e.g., compost, clean fill), barriers reduce soil deposition onto (e.g., mulch), and other remedial leafy vegetables. measures up to and including raised Increase planting of fruiting beds and containers. vegetables, vegetables that Ensure gardeners wear gloves and grow on vines, and fruit use tools to reduce soil contact and trees. ingestion. >1200 High risk All of the above good gardening and Select plants with shallow housekeeping practices. roots for raised beds or Raised beds, soil containers, areas with replacement soil soil replacement (i.e., excavate to ensure that roots do not contaminated soil and replace reach contaminated soil with soil containing low lead that is left in place, if any, concentrations) are strongly otherwise, no restrictions. recommended.c Consider finding other locations for garden. Restrict child access to only established safe areas. Restrict all gardening by or for children in contaminated soils. a Source: Hemphill et al., 1973; Moir and Thornton, 1989; U.S. EPA, 1995; U.S. DOE, 1998; Jorhem et al., 2000; Heinegg et al., 2000; Finster et al., 2003; Pichtel and Bradway, 2008; Shayler et al., 2009; Leake et al., 2009; Chaney et al., 2010; Nabulo et al., 2010; U.S. EPA, 2011a; U.S. EPA, 2011b; Säumel et al., 2012 b While 400 ppm lead in soil is considered an appropriate screening level for residential soil-lead, the TRW recommends that 100 ppm be used as the low end of the range of soil lead concentrations to mitigate exposure to lead in soil when gardening is an important exposure pathway. Lacking the information to support a quantitative approach for estimating risk for gardening scenario to support establishing acceptable concentration of lead in garden areas, best professional judgment was used to establish the low end of the range. This soil concentration is below the 400 ppm soil screening level for lead because the gardening exposure pathway includes other sources of lead exposure not sufficiently accounted for in the soil screening level. The basis for the Soil Screening Level (SSL) is children playing in lead contaminated soil and some other exposures, with the predominant source of exposure from direct soil ingestion or ingestion of soil manifested as house dust. Scientific limitations when it was developed did not allow the SSL for lead to adequately account for consuming home-grown produce. In developing an acceptable concentration of lead in soil for home garden exposures, the same child receptor would be exposed if accompanying the adult in the garden and also exposed through consumption of lead in and on the produce grown in the soil. Hence, the garden-based level is lower than the SSL and reasonable steps to mitigate exposure to lead while gardening in soil lead concentrations between 100–400 ppm would be appropriate. The TRW acknowledges that background soil lead concentrations in some communities may exceed the guidance values recommended for garden areas. Mitigation may be necessary for those communities. c Twenty-four (24) inches of clean soil cover is generally considered adequate for gardening; however, site specific conditions should also be considered. A 24-inch barrier normally is necessary to prevent contact of contaminated soil at depth with plant roots, root vegetables, and clean soil that is mixed via deep rototilling. Raised garden beds could cost effectively add 24 inches of clean soil (U.S. EPA, 2003).

11 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

Where Can I Get More Information? /Soil Health Basic Soil Science The USDA Natural Resources Conservation Service has a great website with a variety The California Master Gardener of resources, including assessment cards to Program’s “Garden Web” offers a helpful use to evaluate soil. See http://soils.usda. list of common questions and answers gov/sqi/index.html. on basic soil science, including , structure, pH, , nutrients, and . http://ucanr.org/sites/ Soil Testing and Remediation for Urban gardenweb/Vegetables/?uid=26&ds=462 Agriculture Cornell University’s Waste Management UC Davis Soil Web Institute has great information on soil testing and remediation. http://cwmi.css. The UC Davis Soil Web is a useful online cornell.edu/soilquality.htm#soil. tool that can give clues to past disturbances, soil removal, fill dirt additions, etc. in many “Heavy Metals and Gardens” offers areas of California. For more information, multilingual resources for urban California please visit http://casoilresource.lawr. residents on soil testing, interpreting ucdavis.edu/soilweb/. results, and remediation. https://sites. google.com/site/healthygardeners/home. Brownfields Reuse Although urban agriculture is not yet a The Organic Materials Review Institute common reuse, the California Department (OMRI) provides lists of certified organic of Toxic Substances Control (DTSC) offers soil and soil amendment sources. This helpful information about brownfields and can help in identifying possible sources California’s voluntary cleanup program of certified clean soils and amendments. at http://www.dtsc.ca.gov/SiteCleanup/ http://omri.org. Brownfields/index.cfm#CP_JUMP_13298. Policy-Related Resources on Urban “Re-Use: Creating Community-Based Agriculture and Soil Brownfield Redevelopment Strategies” is “Seeding the City: Land Use Policies a website and downloadable guidebook to Promote Urban Agriculture” is a that provides details on the reuse of downloadable toolkit focuses on policy brownfield sites, including agricultural best practices for urban agriculture, use of remediated brownfields, and is a with helpful model comprehensive plan helpful guide to community engagement, language on various aspects of farming funding, site assessment and cleanup in cities, including soil testing. http:// of contaminated sites. The guidebook changelabsolutions.org/sites/default/files/ includes a case study of a brownfields site Urban_Ag_SeedingTheCity_FINAL_%28C converted to a successful urban farm. LS_20120530%29_20111021_0.pdf http://www.planning.org/research/ brownfields/.

12 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

“Dig, Eat, and Be Healthy: A Guide Gorospe, J. 2012. Growing Greens and Soiled to Growing Food on Public Property” Soil: Trends in Heavy Metal Contamination is a guidebook that offers strategies in Vegetable Gardens of San Francisco. San for negotiating the use of public land Jose, CA: San Jose State University Master’s for growing food, including types of Theses Paper 4131. agreements and specific suggestions on how to handle the issue of soil Hodel, D.R. and A.C. Chang. 2002. Trace testing in such agreements. It includes elements and urban gardens. University a helpful section on school gardens. of California Cooperative Extension, Los http://changelabsolutions.org/sites/ Angeles. 3 pp. Also on-line at: http:// default/files/Dig_Eat_and_Be_Happy_ celosangeles.ucdavis.edu. Dec. 15, 2002. FINAL_20130610_0.pdf Hodgeson, K, Caton Campbell, M., & Bailkey, M. (2011). Urban Agriculture: References Growing Healthy, Sustainable Places. City and County of San Francisco American Planning Association (Planning Department of Public Health, Occupational Advisory Service Report Number 563). & Environmental Health. 2010. Guidance for San Francisco Residents and Public Kessler, Rebecca. 2013. Environmental Agencies: Lead Hazard Risk Assessment Health Perspectives: Urban Gardening: and Management of Urban Gardens Managing the Risks of Contaminated and Farms. San Francisco: Children’s Soil.Vol. 121, number 11-12; November- Environmental Health Promotion. December 2013.

Craigmill, A. and A. Harivandi. 2010. Peryea, F.L. 1999. Gardening on lead and Home gardens and lead: What you should arsenic contaminated soils. Washington State know about growing plants in lead- University. EB1884. contaminated soil. Oakland: University Shayler, Hannah, McBride, M., & Harrison, of California Agriculture and Natural E. 2009. Guide to Soil Testing and Resources Publication #8424. Interpreting Results. Ithaca, NY: Cornell Depave. 2012. How to Depave: the Guide Waste Management Institute. to Freeing Your Soil. Portland, OR: Parking U.S. Department of Housing and Urban Lots to Paradise Productions. Development. 1995. Report on the National Goodwin, Elizabeth. 2011. Dilmun Survey of Lead-based Paint in Housing. Hill Cornell Student Farm Soil Best HUD Contract NO. HC-5848. Management Practices Project Report. U.S. Environmental Protection Agency. Ithaca, NY: Cornell University. 2007. The Use of Soil Amendments for Remediation, Revitalization, and Reuse. pp. 8-9 (2.1.1.a Phytotoxicity). EPA Publication NO. 542-R-07-013.

13 Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms

References, continued. Thanks to reviewers, who included: Eli U.S. Environmental Protection Agency. Zigas, SPUR Food Systems and Urban 2011. Brownfields and urban agriculture: Agriculture Program Manager; G. Stuart Interim guidelines for safe gardening Pettygrove, UC Cooperative Extension practices. EPA Publication NO. 560-S-11- Soils Specialist Emeritus; Pamela Geisel, 001. Statewide Master Gardener Program Academic Coordinator, Retired; and Rob U.S. Environmental Protection Agency. Bennaton, UC Cooperative Extension Bay 2011. Evaluation of Urban Soils: Area Urban Agriculture Advisor Suitability for Green Infrastructure or Urban Agriculture. EPA Publication NO.

905-R-11-03. The University of California Division of Agriculture & Natural Resources (ANR) prohibits discrimination against or harassment U.S. Geologic Survey. 2013. Polynuclear of any person in any of its programs or activities on the basis Aromatic Hydrocarbons Definition Page. of race, color, national origin, religion, sex, gender identity, USGS Website. pregnancy (which includes pregnancy, childbirth, and medical conditions related to pregnancy or childbirth), physical or Walker-Scott, L. 2009. The Myths of mental disability, medical condition (cancer-related or genetic Rubberized . Puyallup, WA: characteristics), genetic information (including family medical Washington State University. history), ancestry, marital status, age, sexual orientation, citizenship, or service in the uniformed services (as defined Witzling, L., Wander, M. & Phillips, E. by the Uniformed Services Employment and Reemployment Rights Act of 1994: service in the uniformed services includes (2010). Testing and educating on urban membership, application for membership, performance of soil lead: A case of Chicago community service, application for service, or obligation for service in the gardens. Journal of Agriculture, Food uniformed services). Systems, and Community Development, University policy also prohibits retaliation against any employee 1(2), 167-185. or person in any of its programs or activities for bringing a complaint of discrimination or harassment pursuant to this policy. This policy also prohibits retaliation against a person Photography Credits: who assists someone with a complaint of discrimination or Michigan State University Extension: harassment, or participates in any manner in an investigation page1-hands & soil or resolution of a complaint of discrimination or harassment. Retaliation includes threats, intimidation, reprisals, and/or University of California Agriculture & adverse actions related to employment or to any of its programs Natural Resources: pages 1, 2, 3, & 7 or activities. Sheila Golden, UC Davis: pages 4, 13 & 14 Inquiries regarding the University’s equal employment California Waterboards: page 5 opportunity policies may be directed to Linda Marie Manton, Judi Gerber: page 6 Affirmative Action Contact, University of California, Davis, Agriculture and Natural Resources, One Shields Avenue, Davis, Beth Nakamura: page 9 CA 95616, (530) 752-0495. Aziz Baameur, UC ANR: pages 8, 10-12

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