C ITY OF P ORTLAND - BUREAU OF E NVIRONMENTAL S ERVICES Planning Group Sustainable Stormwater Management

FLOW TEST MEMORANDUM

GLENCOE RAIN GARDEN A UGUST 12TH, 2004

Executive Summary

Overview

The Glencoe Rain Garden is a vegetated infiltration basin designed to store, infiltrate, and filter street runoff. Because of their ability to control peak flows, flow volume, and pollutants, infiltration basins are a versatile option in efforts to control basement sewer backups, combined sewer overflows (CSOs), open channel erosion, and effluent water quality. This type of low-impact approach is proving to be a valuable development strategy in Portland’s urban environments.

Glencoe Rain Garden Gathering performance data is critical to quantify the benefit of the facilities, improve overall design and function, and lower maintenance costs. Flow testing provides a relatively inexpensive and accurate method to gather this data for various design storms. Using a fire hydrant and a very accurate flow meter, almost any storm event can be simulated with regards to flow rates and volumes. In combination with accurate outflow monitoring and field observations, reliable performance data can be compiled in a relatively short period of time.

The Glencoe Rain Garden, located at Glencoe Elementary School (SE 51st & Morrison), was completed in Rain Garden Location Map September 2003 in response to a severe basement sewer backup problem in the area. Performance data is necessary to verify how well this

Glencoe Rain Garden 10/20/2004 - 1 - particular facility protects basements from sewer backups, and to evaluate the general ability of vegetated infiltration basins to be a viable sustainable stormwater strategy helping to control combined sewer overflows.

Flow tests performed on August 12th, 2004 assessed the facility’s performance during the basement sewer backup (25-Year1) design storm and the combined sewer overflow (CSO) design storm, also referred to as the ASFO2 design storm.

Results

The table below summarizes the results of the flow test:

25-yr Simulation1 ASFO2 Simulation 15,600 gallons 29,350 gallons* Total Volume In (2,080 ft3) (3,870 ft3) 2,950 gallons 5,930 gallons* Total Volume Out (395 ft3) (790 ft3) Volume Reduction 81 % 80% 1,010 gpm 620 gpm Peak Flow In (2.25 cfs) (1.38 cfs) 210 gpm 200 gpm Peak Flow Out (0.46 cfs) (0.45 cfs) Peak Flow Reduction 79% 67% Peak Flow Delay 28 minutes N/A3 *Includes 25_Year volumes, which approximately equal the volume of water seen by the facility during the first 9.5 hours of the true 24-Hour event.

Basement Sewer Backup Protection The Rain Garden reduced the peak flow by 79% and delayed it for 28 minutes. In fact, no outflow was recorded for the first 16 minutes, which represents the critical period of peak intensity rainfall. However, because of equipment limitations, the maximum runoff intensity could not be achieved and was closer to a 10-year peak flow. The remainder of the storm was simulated as planned.

Combined Sewer Overflow Benefits Time constraints did not allow the simulation of the entire 24-hour storm. The 25-Year test provided an equivalent runoff volume for the first 9 hours of the event, and the tenth hour, which contains the peak intensities of the storm event, was simulated during the ASFO test. For the 10 hours of runoff simulated, the facility captured 80% of the runoff volume. The remaining 14 hours were not simulated, but given the relatively low rainfall intensities during this period, it is unlikely that there would have been any significant overflow.

1 The 25-Year storm (1.89 inches in 6 hours, with a peak intensity of 3.32 inches / hour) represents an intense thunderstorm with the heaviest rainfall in the first 15-minutes. 2 The ASFO storm represents a 3-year, 24-hour summer storm (1.41 inches in 24 hours, with a peak intensity of 0.92 inches / hour). It is the most rigorous protection standard in the Amended Stipulation and Final Order (ASFO) – a legal document specifying the regulatory CSO requirements. 3 CSO events are driven by volume over an extended period of time; peak flow is typically not an issue.

Glencoe Rain Garden 10/20/2004 - 2 - Infiltration Rates Infiltration rates within the facility varied with the depth of standing water and the degree of soil saturation. Average rates varied from 1.2 to 1.8 inches per hour under saturated conditions.

Conclusions

Facilities like the Glencoe Rain Garden show considerable promise as a sustainable stormwater management strategy and further evaluation is recommended. Performance is summarized below for each of the test objectives:

Peak Flow Reduction: The facility is effective at reducing basement sewer backup risk. The simulated peak flow was lower than the 25-Year peak flow, but a comparison of runoff and facility volumes shows the facility would have prevented any overflow to the combined sewer during the first 5-10 minutes of the design storm. Capturing this portion of the storm guarantees at least a 60% A full Glencoe Rain Garden during flow testing peak flow reduction, which is adequate to protect local basements.

Flow Volume Reduction: Use of these facilities could greatly reduce the amount of stormwater volume reaching the CSO tunnel system. The combination of facility storage and infiltration was able to capture 80% of the total inflow volume through the first 10 hours of the storm. This would represent a dramatic reduction in flow volume to the Eastside CSO Tunnel.

Infiltration: Infiltration rates were more than adequate to drain the facility within 6 hours. This ensures capacity for subsequent storms and eliminates the need for vector control. This is an excellent result given that the site’s silt soils would not be considered good for infiltration.

Design Issues / Modifications: The drainfield only passed half of its design flow, causing water levels to rise faster and higher than anticipated. Modifications to the flow restrictor or removal of the flow restrictor from the drainfield would be the easiest solution, while modifications to the drainfield itself may also be an option. Clogging caused by bark mulch contributes to this problem (see Maintenance Issues below).

Maintenance Issues: Large quantities of bark mulch were pushed into the drainfield during both simulations. This has also been an issue during some of the larger storm events over the past year. Because the accumulating mulch can partially clog the drainfield, it would need to be periodically removed. Bark mulch floating into the drainfield The installation of a skimmer at the drainfield weir would help

Glencoe Rain Garden 10/20/2004 - 3 - keep the mulch in the landscaped bays. Another option is to replace the bark mulch with another material such as pea gravel. The pea gravel has performed well in the forebay, and is too heavy to be pushed into the drainfield.

Facility Sizing: The facility footprint is 4-6% of the drainage area, and did a good job of both peak flow reduction and volume retention. Overflow to the sewer never exceeded the design outflow and an adequate freeboard was maintained at all times. This, coupled with low infiltration rates, suggests that the 9% sizing factor recommended in the “Simplified Approach” of the City of Portland’s 2004 Stormwater Management Manual (SWMM)4 may be high – at least for providing combined sewer benefits.

Results and conclusions for any facility are dependent on local conditions. Local soil texture, construction practices, inflow sediment loads, planting varieties and planting densities are among the many variables that will impact the performance of each facility both now and in the future. However, this site has silt soils extending at least 6 feet below the facility, and even with a relatively low infiltration rate, the facility performed well.

Despite these results, additional testing is critical to provide confidence and to identify performance trends. Particular issues for future tests:

Higher peak flows: Because we were unable to reach the 25-Year peak flow during this test, it is important that we reach the desired flow rate in subsequent tests. This will provide confidence in the facilities performance for basement sewer backup protection.

More detailed CSO benefits: Specific testing should be done to better determine the ability of the facility to reduce volumes from the ASFO storm. The result of this test may be a conservative estimate because actual intensities during the first 9 hours are much less than those simulated. The lower intensities may allow infiltration to keep up with inflow and provide greater retention. Though it will not be possible to simulate the entire 24-hour event in a single day, an abbreviated inflow pattern could be generated that is more representative of the volumes and intensities of the entire storm. This information would better inform CSO control efforts throughout the City.

Different antecedent conditions: Conditions in the facility were relatively dry for this test. Other than 0.6 inches of rain that fell one week prior to the tests, there had been no other rainfall of note for 63 days. These antecedent conditions are not unusual for the summer months, during which ASFO compliance is most important (May – Oct) and most basement sewer backup events occur (May, Aug – Oct). However, it is intended that further tests be carried out during the wet winter months to compare with these results.

Performance over time: It is likely that the facility’s performance will change with time due to sediment accumulation, deeper root establishment, and other factors. It is intended that testing will continue to be performed over the next 5 years to document any significant changes.

For more information about the City of Portland’s Sustainable Stormwater Program, as well as further details about this and other flow tests of sustainable stormwater facilities, see the City’s Clean Rivers website at: http://www.cleanrivers-pdx.org/clean_rivers/sustainable_stormwater.htm

4 See SWMM, section 2.2.1 at http://www.portlandonline.com/bes/index.cfm?c=35122

Glencoe Rain Garden 10/20/2004 - 4 - Overview

Homes along SE 52nd between Stark and Morrison have experienced a large number of basement sewer backup events in the last 20 years. A number of proposals for relieving these problems were considered in February 2003, and the selected alternative included a vegetated infiltration basin to control private and right-of-way runoff from SE 51st Avenue and Morrison Street. The design redirected the existing street inlets to the facility located on an unused parcel of land that was obtained from Glencoe Elementary School. The term “Rain Garden” was given to the project because of its aesthetic appeal and close proximity to Glencoe School’s community garden project. Construction of the Rain Garden was completed in September 2003. Figure 1: Glencoe Rain Garden Site Locator Map Flow enters the forebay where the incoming energy of the stormwater is dissipated and sediments are trapped. The forebay must fill with enough water to crest the forebay weir (Weir #1) before entering the main facility. Forebay Drainfield Beehive Weir Weir Overflow

Forebay

Drainfield

Inlet Pipe Figure 2: Glencoe Rain Garden Figure 3: Rain Garden plan view The main facility is visually divided into sections by three rock “berms” – stacked rocks that allow water to move freely through. If water levels continue to rise, they overtop the drainfield weir (Weir #2). The drainfield is designed to limit flow out of the facility to no more than 0.5 cfs (220 gpm). If water levels continue to rise, flow will eventually spill into the “beehive” overflow and will move uncontrolled into the combined sewer. The facility was designed to handle the 25-Year Design Storm without overtopping the beehive.

The site is suitable for sewer flow monitoring, and continuous flow meters have been installed in the inflow and outflow pipes. The outflow meter has been in place since September 2003, and the inflow meter was installed in May 2004. Rainfall data is collected at a raingage on the roof of the school.

Glencoe Rain Garden 10/20/2004 - 5 -

Since completion, there have been several rainfall events that resulted in overflow to the drainfield, but nothing approaching the intensity of the 25-Year Design Storm.

Reason for Flow Testing

Vegetated infiltration basins could be considered primary options for protection against basement sewer backup (a once every 25 year event) and control of combined sewer overflow (CSO) (a once every 3 summers event). Performance data will help guide design modifications and future wide-scale implementation, making it crucial that we gather performance data for larger events representative of these design storms.

Though monitoring real storm events is usually preferred, there are several issues that may complicate conclusions:

1. Facility Inflow – Usually, inflow to the facility is not monitored and must be estimated from rainfall data (gathered some distance from the facility) and an estimated drainage area. This often results in significant uncertainty. This is not an issue at this facility because both facility inflow and rainfall data are gathered at the site.

2. Flow Data – Data is collected at 5-minute intervals. This provides a reasonable battery life for the data logger, and reduces the amount of staff time necessary to gather data and service the meter. While this is adequate in most situations, it can result in significant errors for small drainage areas because the time of concentration is often less than 5-minutes. This means that a large peak flow could pass undetected through the pipe between data readings. The quality of the monitoring data is also subject to error from several sources, including debris accumulation on the sensor, turbulence in the pipe, or technical difficulties with the meter.

3. Cost - Continuous flow monitoring is relatively expensive - approximately $6,000 / year for each meter. Most of this time, the meter is not recording flows of interest, and there is no guarantee that a storm event of sufficient size will occur while the meter is in place.

Flow testing provides a way to mimic design storm events while allowing a more accurate setup for monitoring inflow and outflow. It generally resolves the issues with continuous flow monitoring noted above:

1. Facility Inflow - Inflow to the facility is monitored at the flow meter connected to the hydrant (Figure 6), which records instantaneous flow rates as well as total flow volume. Flow rates can be adjusted at the meter using a valve, allowing reproduction of the actual design storm for a given drainage area.

2. Flow Data – Field Operations staff is on hand with inflows and outflows being recorded at 1-minute intervals, and the data can be reviewed in real time for potential problems. In addition, it is possible to visually observe the runoff entering, flowing through, and exiting the facility.

3. Cost – For this test, approximately $2,100. Includes ~ $50 for Traffic Plan review, ~$50 for Discharge Permit review, and $284 for equipment rental and water usage charges. Signage was loaned out by PDOT without cost. The bulk of the expense is field staff time, estimated to be 73 hours and $1,710.

Glencoe Rain Garden 10/20/2004 - 6 - Table 1: Glencoe Rain Garden Flow Test – Staff Time and Costs # of Total Task Rate Est. cost Staff Hours Acquired permits and consulted with 1 15 $15/hr $225 meter shop about meter use Acquired meters, signs and other 1 4 $15/hr $60 equipment Flow monitoring: Field Operations 2 16 $30/hr $480 Survey work 2 2 $15 - $30/hr $45 Test Procedure: hydrant control, 4 32 $15 - $30/hr $840 monitoring depths, etc Data processing 1 4 $15/hr $60 Total 73 $1710

Objectives The primary objective is to document facility performance for specific storm events, and identify any design issues or modifications that should be made to existing and future facilities to improve their performance. Specific information desired from the test include:

1. Peak flow attenuation (peak out / peak in) – in particular, verify that this facility will perform as expected in protecting nearby homes from basement sewer backups. This information may also be helpful for controlling erosion in open channel systems.

2. Flow volume retention (volume out / volume in) – in particular, determine the benefit to CSO control. This information could also be helpful for flood control in open channels or storm sewer systems.

3. Infiltration rates – determine the ability of the facility to recover its capacity after a large storm event. This is an important issue in facility design and vector control.

4. Maintenance issues – identify any modifications that may decrease the amount or frequency of maintenance required for the facility.

5. Design modifications / improvements – identify any performance issues that would suggest altering the existing design of the facility.

6. Facility sizing – evaluate the performance of the facility as it relates to the ratio of facility area to drainage area. This includes a comparison to the sizing specified in the “Simplified Approach” used in the BES Stormwater Management Manual (SWMM).

7. Performance baseline – test results will begin a baseline for comparison to other times of year and for tracking changes in performance over time.

Glencoe Rain Garden 10/20/2004 - 7 - Design Storms Facility performance is relevant to at least three design storms (see Figure 4):

Basement Sewer Backup 3.5 Protection (25-Year) Design 3.0

Storm [1.89” in 6 hours] 25-Yr Design Storm This event represents an 1.89" in 6 hours intense thunderstorm with 2.5 very heavy rainfall in the first 15-minutes. It creates large 2.0 peak flows that raise sewer 1.5

levels and may threaten local (in/hr) Intensity Rainfall ASFO Design Storm basements. This is the 1.41" in 24 hours Bureau protection standard 1.0 WQ Design Storm for basement flooding and is 0.83" in 24 hours used to size modifications to 0.5 the sewer system that alleviate 0.0 flooding risk. It is based upon 23 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 00 local intensity-duration- Event Time (hrs) frequency rainfall data. Figure 4: Design Storm Comparison

CSO Control (ASFO) Design Storm [1.41” in 24 hours] This event represents the 3-year / 24-hour summer storm, and is the primary regulatory control storm for CSO discharges to the Willamette River. It is based upon local intensity-duration-frequency rainfall data and a slightly modified NRCS Type 1A distribution.

Water Quality (WQ) Design Storm [0.83” in 24 hours] This event represents the water quality treatment standard for stormwater quality facilities. Storms up to this level are treated prior to discharge to a surface drainage system. It is defined as 1/3rd of the 2-yr / 24- hour storm using the NRCS Type 1A distribution. Though overflows from the Rain Garden currently drain to the combined sewer and are treated by the Columbia Boulevard Wastewater Treatment Plant, there is always the possibility that the stormwater and sanitary sewer flows will be separated in the future. The Rain Garden’s attenuation of the WQ event would then be important since the overflow would then eventually drain to the Willamette or Columbia River untreated by any traditional wastewater treatment process.

In general, the water quality design storm will not be simulated. Given the similar pattern, relatively low intensities, and lower total depth, it can be assumed that facility performance during the ASFO event will give a good indication of the performance for the WQ Design Storm.

Glencoe Rain Garden 10/20/2004 - 8 - NE 51st and Morrison Drainage Area A drainage area estimate for the facility is used to set appropriate peak flows and volumes for the flow tests. The facility was designed for an impervious drainage area of 0.8 acres (34,800 ft2). This area includes the school parking lot, which drains to an infiltration bioswale before overflowing to the Rain Garden (Figure 5). During high intensity storms, such as the 25-Year event, there will be some additional runoff from pervious areas, but it is assumed to be negligible compared to the impervious area runoff.

Easily clogged stormwater inlets at SE 51st & Belmont Street and SE 53rd & Morrison Street have been observed slipping additional flow to the facility. Despite maintenance efforts to reduce clogging, it is apparent that flows still routinely bypass the inlets. If the additional Belmont and 53rd street drainage is included, the potential drainage area goes up to 45,100 ft2. Since one of the primary goals of the tests is to evaluate the Rain Garden’s ability to protect homes from basement sewer backups, this larger area would seem to be the best estimate for determining flow targets. It seems to reflect the drainage that typically reaches the facility, and would provide a more conservative estimate of facility performance.

Flow slippage from clogged inlets

Figure 5: Glencoe Rain Garden Site Plan and Drainage Areas

Glencoe Rain Garden 10/20/2004 - 9 - Flow Test Setup

Equipment

• Flow meters: o Inflow: Sensus W1250 (closed channel) Sigma 950A/V (open channel) o Outflow: Sigma 950A/V (open channel) • Fire hose: 2½” diameter, 300 feet (6 x 50 ft sections) Figure 6: Hydrant Setup • Chapman valve • Depth gages (rulers and stakes)

The two sewer flow monitors (Sigma 950A/V) were already installed: one in the 12-inch inflow pipe; and the other in the 8-inch diameter combined sewer outflow pipe located in a manhole at SE 51st & Morrison (Hansen ID AAY329). They’re configured with an ultrasonic level sensor and Doppler-type velocity sensor, and calculate flow based on level, velocity, and pipe shape and size information.

The Chapman valve was used to turn flow from the hydrant on and off, while the W1250 flow meter was used to control flow rate. The hydrant, hose, and meter setup is shown in Figure 6. Two hydrants were necessary to simulate the peak 5-minute flow. The location of the equipment relative to the Rain Garden is shown in Figure 7.

The City Water Bureau routinely calibrates and tests the W1250 meter to accuracy within 1.5 %. This standard holds for intermittent flows of 1,400 gpm and steady flows between 20 and 1,200 gpm. The meter also contains a smaller opening with similar standards for flows less than 20 gpm. Both meters measure total water volume (in 100ths of cubic feet) and instantaneous flow rate (in gallons per minute).

Field Operations setup their equipment (Figure 8) and performed monitor checks prior to the testing. The meters were adjusted to record data points at 1- minute intervals, and test flows were used to check the monitors for accuracy Figure 7: Flow Test Setup at the expected inflow rates. Manual measurements of depth were checked against the monitored data in real time, and small adjustments were made as necessary.

Glencoe Rain Garden 10/20/2004 - 10 - Relative survey elevations were taken to verify the weir heights, the height of the beehive overflow, and to set the depth gages in the facility. Survey data is included in the Appendix.

Permits

Three permits are needed to legally perform a flow test on a public street using a fire hydrant: a Traffic Control Plan from the Portland Department of Transportation, a Potable Water Discharge Request from the Water Bureau, and a Hydrant Permit also from the Water Bureau. Contacts and details of each permit are included in the Appendix. Figure 8: Field Operations Van and setup for monitoring inlet and outlet pipe flows Flow Targets

ArcGIS was used to delineate and measure drainage areas. As discussed earlier, even though the facility was designed to drain an area of 34,800 ft2, there is reason to believe that additional areas also drain to the facility bringing the total drainage area to 45,100 ft2. The larger drainage area was used to calculate flow schedules for simulation of the 25-Year and the ASFO storms prior to the test.

Since the goal of the 25-Year test is to determine peak flow attenuation, only the initial 30-minutes of the 6- hour storm is included in the test. This was justifiable because the remaining 5½ hours of the storm has considerably lower rainfall intensities that will not result in large peak flows in the sewer.

The ASFO test is more problematic because the peak intensity occurs 9½ hours into the storm. Given that determining volume retention is the desired result of the ASFO test, a representative amount of volume must enter the facility to obtain realistic results. The total runoff for the 30-minute 25-Year test (0.61”) is roughly equivalent to the total runoff from the first 9 hours of the ASFO (0.57”). Though the rainfall patterns are different and there was a 3 hour gap between events, the lower intensities and longer duration of the ASFO would seem to be more easily handled by the facility making this a conservative substitution. It was decided that the 25-Year test provided a reasonable pre-volume for the ASFO test, allowing us to just simulate the peak 60-minutes using the hydrant.

An amount of rainfall equal to 0.03” is often subtracted from the runoff to represent depression storage that captures volume that never makes it to the facility. However, it was decided to leave it in to compensate for errors in area estimation or slightly wet antecedent conditions (it amounts to a runoff volume increase of 5% for the 25-Year design storm).

It was expected that the 25-Year simulation would require the use of two hydrants to achieve the flow rate needed for the peak 5 minute period. The Water Bureau provided a combined Flow Availability Estimate of 1,300 gpm from both hydrants. Tables 2 and 3 summarize the 25-Year and ASFO target flows for each drainage area scenario.

Glencoe Rain Garden 10/20/2004 - 11 - Table 2: Target Hydrant Flows for the Design Drainage Area (34,800 ft2) Time 25-Year Storm ASFO Storm Interval Rain Intensity Target Flow Rain Intensity Target Flow (min) (in/hr) (gpm / cfs) (in/hr) (gpm / cfs) 0 – 5 3.32 1,200 / 2.67 5 – 10 1.32 477 / 1.06 0.16 58 / 0.13 10 – 15 1.06 383 / 0.85 15 – 20 0.54 195 / 0.43 20 – 25 0.54 195 / 0.43 0.32 116 / 0.26 25 – 30 0.54 195 / 0.43

30 – 45 0.92 333 / 0.74

0.20 72 / 0.16 45 – 60

Table 3: Target Hydrant Flows for the Estimated Drainage Area (45,100 ft2) Time 25-Year Storm ASFO Storm Interval Rain Intensity Target Flow Rain Intensity Target Flow (min) (in/hr) (gpm / cfs) (in/hr) (gpm / cfs) 0 – 5 3.32 1,555 / 3.46 5 – 10 1.32 618 / 1.38 0.16 75 / 0.16 10 – 15 1.06 496 / 1.11 15 – 20 0.54 253 / 0.56 20 – 25 0.54 253 / 0.56 0.32 150 / 0.32 25 – 30 0.54 253 / 0.56

30 – 45 0.92 431 / 0.92

45 – 60 0.02 94 / 0.20

Glencoe Rain Garden 10/20/2004 - 12 - Hose Test

Antecedent Conditions

The Rain Garden was essentially dry prior to the test. When there is little or no rain, the Rain Garden is watered once a week using an oscillating sprinkler and a hose from the school (the last watering prior to the test was August 6). The Glencoe School Raingage shows two thunderstorms at the site on August 5th and August 6th that dropped a total of 0.60” of rain on the facility. This is the only significant rainfall in the prior two months.

While these conditions are quite dry, they are not unusual for the summer months, during which the majority of ASFO compliance is an issue (May – Oct) and most basement sewer backup events occur (May, Aug – Oct).

Monitor Check

Field Operations staff was on-site and they asked for a test flow (unmetered) to be placed into one of the inlets so that the flow meter could be tested for accuracy during the high flows expected during the simulations. Only the inlet sewer meter was tested, as the outlet meter has performed well in the past and would not be recording higher than typical flows. Water introduced during the pre-test filled the forebay of the facility. All but 1 inch of water was allowed to infiltrate before the 25-Year simulation began.

Pre-Test Design Modifications

Numerous discussions had been held prior to the tests regarding the height of the forebay and drainfield overflow weirs. The weirs are intended to hold back flow volume from the combined sewer so that it can be infiltrated - the higher the weirs, the more volume is infiltrated. During construction, the weirs were set to 2” (using steel plates sealed with silicone caulk). This ensured that if the facility did not Figure 9: Modification to the drainfield weir (weir #2) – raised 4½” and infiltrate well and was full prior to the sealed with a plastic bag storm, only the first 2” of storage would be lost and there would still be ample volume to attenuate the 25-Year Design Storm. However, the low weir heights also cause the facility to overflow to the sewer more often and limits potential volume reduction.

Given the facility’s performance over the first year, it appeared that the infiltration rates were more than adequate to drain the facility within a few hours. To increase the volume retention, and therefore improve performance for CSO control, it was decided to raise the weirs for the test and evaluate the facility’s ability to infiltrate a greater depth of water. Both weirs were raised 3” using wood extensions. The extensions were sealed with silicone to limit leakage. The drainfield weir was further modified just prior to the test by adding another 1½ inch wood extension. This extension was sealed using a plastic bag held

Glencoe Rain Garden 10/20/2004 - 13 - in place by rocks (Figure 9). The tested heights were 5” for the forebay weir (weir #1) and 6½” for the drainfield weir (weir #2).

Basement Sewer Backup Protection (25-Year) Storm Simulation

The dry antecedent conditions are more representative of conditions prior to the 25-Year design storm, during which intense rainfall in the first 15- 1800 minutes generally overwhelms infiltration. Glencoe Hose Test Hydrant Flows - 25 Year The flow schedule called for a 5-minute 1600 Event Simulation 1400 peak flow of 1,555 gpm to be discharged Various Drainage Areas Target gpm - 1200 45070FT^2 from the two hydrants being used. ) However, upon fully opening these 1000 Target gpm - 34800FT^2 800

hydrants, it was discovered that they were (gallons Flow Hydrants only capable of producing 1,010 gpm. The 600 rest of the storm was simulated as planned. 400 Table 5 details the simulated vs. design 200

0 storm statistics for the two drainage areas 1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930 discussed earlier. Time (min) Figure 10: Comparison of Actual and Target Flows for 25- Figure 10 shows the actual flow seen from Year Simulation the hydrants during the 25-Year simulation graphed against target flows for the two drainage areas. The peak flow of the simulated event significantly undershot the target for the larger drainage area (67% of the target), but was much closer to the peak for the design drainage area (86% of the target). Volume was basically right in the middle. In general, this test represents a 10-year peak flow with a 25-Year flow volume, as summarized in Table 4.

Table 4: Summary of the 25-Year Design Storm Simulation Drainage Peak Flow Total Volume

Area (sq ft) (gpm) (gallons) 45,100 1,555 17,152 Flow Targets 34,800 1,200 13,232 Hose Test 1,010 15,588

Depth measurements were taken over the next two hours to determine infiltration rates throughout the facility. A Figure 11: Full Rain Garden significant amount of bark mulch was pushed into the drainfield during this test. This has been an issue during some larger storm events during the past year.

CSO Control (ASFO) Storm Preparation

The main facility still had several inches of water and time constraints required that the ASFO simulation needed to begin. A field drain was opened in Zone 4 (the main bay near the drainfield weir) for about 20 minutes, dropping water levels to the top of the drain - about 1 inch (this did not effect the forebay or drainfield). The intention was to create a more realistic pre-peak condition for the ASFO test, whose initial rainfall intensities are assumed to be too low to create significant

Glencoe Rain Garden 10/20/2004 - 14 - flooding throughout the facility. However, this drained volume was included in the outflow volume totals for the ASFO simulation to ensure a conservative volume reduction benefit.

Right after this, an additional facility inflow was created by efforts to increase the maximum output of the two test hydrants. The test did not result in increased output, but did send approximately 535 gallons into the facility. This volume is included in the total inflow volume for the ASFO simulation.

CSO Control (ASFO) Storm Table 5: Summary of the ASFO Design Storm Simulation Drainage Peak Flow ASFO Test Total Volume

Area (sq ft) (gpm) Volume (gallons) (gallons)5 45,100 430 11,250 28,400 Flow Targets 34,800 330 8,700 21,900 Hose Test 620 13,300 28,900

Figure 12 shows the actual flow seen from the hydrants during the ASFO event simulation graphed with the target flows for the larger (45,100 ft2) drainage area. The hydrant flows exceeded target flows for the ASFO test by a large amount. Average peak flow was 88% greater than the target, and total volume from the hydrant was 2,077 gallons greater.

Glencoe Hose Test Hydrant Flows - ASFO

700 Event Simulation

600 Target gpm Actual gpm 500

400

Flow (gal) 300

200

100

0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 Time (min)

Figure 12: Targeted and Actual Flow rates, ASFO Simulation

5 Total Volume includes the inflow volumes from both the 25-yr and the ASFO Design Storm simulations.

Glencoe Rain Garden 10/20/2004 - 15 - Results & Conclusions

Peak flow / Flow Volume Reductions

Peak flow and volume reductions were excellent, and are summarized in Table 6 along with the peak delay time.

The Rain Garden reduced the peak flow during the 25-Year simulation by 79% and delayed it for 28 minutes. In fact, no outflow was recorded for the first 16 minutes, which covers the critical period of peak intensity rainfall. The long peak delay benefits not only the local area, but also areas farther downstream. The longer the flows are held back, the greater the chance that flows from upstream will pass through and not add together.

It must be noted, that because of flow resistance caused by the fire hoses and the flow meter itself, the desired 5-minute peak flow of 1,550 gpm could not be achieved. The rest of the storm was simulated as planned. The resulting 1,010 gpm peak flow is closer to the 1,200 gpm flow for which the facility was designed, but still leaves some question as to how the facility would have performed with the desired flow.

Given the 16-minute period of no flow and a comparison of volumes, it is safe to say there would have been no outflow from the Rain Garden for at least the first 10 minutes if the target peak flow had been reached. This still covers the most important period of the design storm when peak flows to the combined sewer are the highest. Of course, future flow tests will need to reach the target peak flow to verify this. In addition, changes to the drainfield outflow and beehive elevation may improve peak flow attenuation even more.

Table 6: Peak and Volume Flow Reductions 25-yr Simulation ASFO Simulation 15,600 gallons 29,350 gallons6 Total Volume In (2,080 ft3) (3,870 ft3) 2,950 gallons 5,930 gallons1 Total Volume Out (395 ft3) (790 ft3) Volume Reduction 81 % 80% 1,010 gpm 620 gpm Peak Flow In (2.25 cfs) (1.38 cfs) 210 gpm 200 gpm Peak Flow Out (0.46 cfs) (0.45 cfs) Peak Flow Reduction 79% 67% Peak Flow Delay 28 minutes 9 minutes

For the ASFO Design Storm, volume reduction is the most critical performance measure and the facility was able to retain 80% of the total volume. If the actual rainfall pattern of the ASFO had

6 Includes the volume from the preceding 25-Year simulation.

Glencoe Rain Garden 10/20/2004 - 16 - been tested, it is likely the retention would have been higher since infiltration over the preceding 9 hours would likely have matched or exceeded the inflow rate.

Overflow through the beehive occurred during both tests. This is a concern because the facility was designed to hold the 25-Year Design Storm with overflow to the drainfield only. The drainfield restricted flow more than anticipated, it was designed to pass a maximum of 0.5 cfs (224 gpm) into the combined sewer with no beehive overflow, but during the test the maximum drainfield flow was about 0.21 cfs (94 gpm). The lower outflow rate caused water to continue to backup in the facility and overtop the beehive. The low flow rate is likely the result of clogging of the overlying filter fabric in the drianfield with bark mulch and other debris during the simulations. This issue will be discussed more fully in the Maintenance section of this document.

Fortunately, the total outflow from the facility never exceeded 0.46 cfs - even with the beehive overflowing. This means that the facility protected the combined sewer to the expected 0.5 cfs criteria.

Figure 13 shows the total flow from the hydrants and flows recorded by the inlet and outlet monitoring equipment during the tests. Figure 14 shows the hydrant, inlet and outlet flows during the 25-Year simulation. Figure 15 shows the same for the ASFO Simulation. These figures annotated with significant events can be found in the Appendix.

1200 Complete Flow Data - Glencoe 1100

1000 meter 1+2, (gpm) 900 Inlet Flow (gpm) 800 Outlet flow (gpm)

700 Hydrant Flow Test 600

500 Flow (gpm)

400

300 Z4 Drain Opened 200

100

0 1 15 29 43 57 71 85 99 113 127 141 155 169 183 197 210 224 238 252 266 280 294 308 322 Time (min)

Figure 13: Flow Data for Entire Testing Period

Glencoe Rain Garden 10/20/2004 - 17 - 1100 1050 Glencoe -25 Year Simulation Flows from 1000 950 Hydrants and Facility Inlet/Outlet Pipes 900 850 800 meter 1+2, (gpm) 750 700 Inlet Flow (gpm) 650 Outlet flow (gpm) 600 550 500 450 Flow (gpm) Flow Total flow to outlet (time 1-166 min) = 5124 gallons 400 350 300 Total flow from hydrants = 15,588 gallons 250 200 150 100 50 0 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 Storm Time (min)

Figure 14: Flow Data – 25-Year Simulation

Glencoe -ASFO Storm Simulation

700 Flows from Hydrants and Facility Inlet/Outlet 650 600 Pipes 550 500 meter 1+2, (gpm) 450 Inlet Flow (gpm) 400 Outlet flow (gpm) 350

Flow, gpm Flow, 300 Total flow to outlet (time 1-333 min) = 4107 gallons 250 200 Total flow from hydrants = 13,326 gallons 150 100 50 0 1 11 21 31 41 51 61 71 81 91 101 111 121 131 Storm Time (min)

Figure 15: Flow Data, ASFO Simulation

Glencoe Rain Garden 10/20/2004 - 18 - Infiltration

Rates were calculated from depth data collected during the period after which the facility stopped spilling water to the drainfield. This ensured that decreasing water depth was due only to infiltration and not to outflow from the drainfield or beehive overflow. These time periods are annotated on the hydrant, inlet and outlet flow figures found in the Appendix. The Appendix also contains figures of the infiltration rates for each zone in the facility over time.

Average infiltration rates, as shown in Figures 16 and 17, were scattered randomly with time. This is likely due to the relatively low infiltration rates that correspond to small changes in facility depth. It’s likely that uncertainties in reading the depth gages account for much of the scatter.

The average rate during the 25-Year simulation was 1.8 inches per hour. The rate for the ASFO simulation was 1.2 inches per hour. The lower infiltration rates seen during the ASFO simulation were expected given that the subsurface soils were near saturation at the start of the test. Given the scatter, it seems reasonable to assume a minimum saturated rate of 1 inch per hour for the Rain Garden.

25 year simulation- Storm Time vs 3 Average Infiltration rates (in/hr) 2.5 ) 2

1.5

1

Infiltration Rate (in/hr Infiltration 0.5

0 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 Storm Time (min) Figure 16: 25-Year Simulation Average Infiltration Rates

ASFO Simulation- Storm Time vs Average

2.00 Infiltration rates (in/hr)

1.80

) 1.60

1.40

1.20

1.00

0.80

0.60

Infiltration Rate (in/hr Rate Infiltration 0.40

0.20

0.00 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 Storm Time (min)

Figure 17: ASFO Simulation, Average Infiltration Rates

Glencoe Rain Garden 10/20/2004 - 19 - Maintenance Issues

Bark Mulch in the Drainfield

The drainfield outflow dropped significantly for the ASFO test. The reason for this decrease is probably the deposition of bark-mulch on top of the filter fabric during the preceding 25-Year test. Figure 18 shows evidence of mulch build-up before the ASFO simulation.

The drainfield outflow was found to vary linearly as a function of depth, as shown in Figures 19 and 20. Flows through the drainfield varied from 0.03 cfs (13 gpm) to 0.21 cfs (94 gpm). These flows are Figure 18: Bark mulch in the drainfield significantly less than the designed flow of 0.5 cfs (224 gpm).

The installation of a floatable skimmer at the drainfield weir would help keep the mulch in the landscaped bays. Another option is to replace the bark mulch with another material such as pea gravel. The pea gravel has performed well as the mulch in the forebay, and would be less likely to be pushed into the drainfield.

0.250 25-Year Simulation Flow through Drainfield to Outlet 0.200

0.150

0.100 Flow to Outlet Pipe, cfs

0.050

0.000 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Depth of Water above Drainfield Floor, feet

Figure 19: Flow through the drainfield during the 25-Year simulation

Glencoe Rain Garden 10/20/2004 - 20 -

0.250 25 yr Simulation Flow through Drainfield to Outlet 0.200

0.150

0.100 Flow to Outlet Flow Pipe, cfs 0.050

0.000 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Depth of Water above Drainfield Floor, feet

Figure 20: Flow through the drainfield during the ASFO simulation

Figure 21: Skimming floating debris out of the drainfield during the ASFO simulation

Glencoe Rain Garden 10/20/2004 - 21 - Design Modifications

Forebay Weir Elevation Raising the forebay weir by 3 inches (a total height of 5 inches) appeared to have no negative impacts, and will provide better debris protection. In combination with raising the drainfield weir, it also increases the amount of runoff infiltrated. The forebay drained well following the test and it is recommended that the weir be left at this height.

Drainfield Weir and Beehive Overflow Elevations Raising the drainfield weir by 4½ (a total height of 6½ inches) did contribute to a quicker overflow to the beehive. This is because the beehive elevation was not raised making the elevation difference between the two only 2 inches. Because the drainfield outflow was lower than expected, the 2 inches of storage filled rapidly causing overflow to the beehive.

The benefit of extra volume retention suggests we should maintain the new weir height at 6½ inches. Even with overflow to the beehive, overflows to the combined sewer did not exceed the design outflow. This suggests that the facility can function well at this weir height. However, this will require raising the beehive a few inches (which is possible) and making modifications to the drainfield (see next item) to ensure the design outflow is reached.

Drainfield The Final Design Report for the Glencoe Rain Garden project (BES job No. 7467) states the orifice hole on the cap fitted to the pipe draining the drainage field was designed to limit return flow to the combined sewer to 0.5cfs. The document goes on to state that testing would be required to verify this flow, and modifications would be made to the hole as deemed appropriate.

As mentioned previously, significant decreases in drainfield infiltration rates were seen between the 25-Year and the ASFO tests. It is assumed that this is due to the accumulation of mulch that floated over the drainfield weir during the 25-Year simulation, and not due to an inappropriately sized orifice hole on the drainfield drainage pipe. The mulch likely clogged the pathways water uses to travel into the drainfield pipe, thus reducing the outflow rate during the ASFO simulation. Figure 10: Drainfield pipe orifice. Note that orifice is only partly full. Possible solutions include removal of the mulch in the facility, replacement with another material (perhaps pea gravel as in the forebay), or a debris screen placed in front of the weir. However, the rates experienced before this problem occurred were still significantly lower than the 0.5 cfs expected. This might be due to clogging of the liner between the rocks in the drainfield and the pipe, or some other issue. Resolution of this

Glencoe Rain Garden 10/20/2004 - 22 - limited drainfield infiltration rate could easily avoid all overflows through the beehive and provide additional peak flow delay benefits during both design storms.

Facility Sizing

The Glencoe Rain Garden was designed to capture a volume of 1,270 ft3 (9,500 gallons) during the 25-Year event. Several attempts were made to verify this volume in the facility, including measurements made from design drawings and water volumes measured during the hose tests before the facility spilled water to the beehive overflow. Volumes for various depths in the facility are summarized in the Table 7.

Table 7: Rain Garden Volumes

Forebay volume Total Volume to Total Volume to Total Volume to Total Volume with 5” weir original (2”) 5” Drainfield 6½” Drainfield to Beehive extension Drainfield Weir Weir Weir

Scaled from 1,540 gals 3,700 gals 6,300 gals 7,200 gals 8,500 gals Plans (206 ft3) (495 ft3) (535 ft3) (946 ft3) (1,136 ft3)

25-Year Simulation 6,300 gals 9,880 gals (842 ft3) (1,321ft3) Results7 ASFO Simulation 8,660 gals (1,158 ft3) Results4

The facility footprint is 1,975 ft2, which represents 4 to 6% of the drainage area (34,800 to 45,100 ft2). The Rain Garden maintained a freeboard of 8-12” throughout all tests, and did not exceed the design flow rate into the combined sewer. Given this performance, even in a silt soil with relatively low infiltration rates, it would seem that the 9% sizing criteria recommended in the Stormwater Management Manual is larger than necessary for dealing with peak flow and flow volume issues in the combined sewer.

Continued Testing

While the results for this test were excellent, it is clear that changing moisture conditions, vegetation maturity, and maintenance practices will all influence future performance. Sustainable Stormwater is committed to continued testing to assess performance for different antecedent conditions, as well as tracking changes in performance as the facility ages.

7 The simulation volumes include inflow volume plus infiltration.

Glencoe Rain Garden 10/20/2004 - 23 -

Glencoe Rain Garden 10/20/2004 - 24 - Appendix

Survey Data Prior to starting the test flows, a topographic survey was performed 0.45’ using a laser level and rod. The figures 0.20’ shown at right detail the elevations of 0.0’ the two weirs and the beehive overflow above their own ground elevations. Existing Gate Gate Raised 3” Note that before starting the test the Weir #1 Between Forebay and Zone 1 second weir was raised 1” above the previously raised 3”. The justification for doing so was to increase the detention capacity of the facility. 0.53’ 0.20’ Ground level of the facility overall was 0.0’ found to be quite variable. A total of nine ground elevations were surveyed. Existing Gate Gate Raised 4” The ground level varied 1.6 inches above the average and 1.4 inches Weir #2 Between Zone 4 and Drainfield below. Weir sills sat 0.75 inches above average grade. This variation in grade was in part due to the planting and pea- gravel/landscape bark placed into the 0.72’ facility its’ structure was built.

Beehive Overflow – Zone 4

The figure to the right was taken from the design drawings for the Rain Garden. This figure was used to calculate areas of wetted surface at varying water depths in the facility, using an assumed side slope of 3:1 (from plans). This information was then used to approximate expected facility volumes at three depths – depth just at the top of the first (forebay) weir, depth just over the 2nd (drainfield) weir, and depth just over the beehive overflow.

Glencoe Rain Garden 10/20/2004 - 25 - Results from these calculations are shown in the table, below:

Component Depth Volume (gal) Forebay Top of existing weir 659 Forebay Top of 3” raised weir 1544 Zones 1 - 4 Top of existing weir 2213 Zones 1 - 4 Top of 3” raised weir 2415 Zones 1 - 4 Top of 4” raised weir 5221 Zones 1 - 4 To Beehive overflow 6414

Attendees

BES/Sustainable Stormwater Matthew Hickey Tim Kurtz Henry Stevens Kevin Perry Tom Liptan Gretchen Tellesen Susan Garland BES/Engineering Services Scott Gibson Don Henry Seth Garey BES/Field Operations Doug Hutchinson Jordan McCann

Contacts This flow test, being the second in a series, required the assistance of a number of City staff. The following is a list of those consulted and their contact numbers:

Name Role Played Contact Mitch Dakar Hydrant pressure/flow modelling 3-7392 Doug Hutchinson Flow Monitoring 3-5615 Peter Mason Traffic Plan Review -NE 3-5234 Bret Davison Potable Water Discharge Permit 3-7588 Rich Brown Equipment Procural (valves/meters/hose and wrench) 3-1532 Rob Kaufman Traffic Signs and Cones 3-1780

Permits A total of three permits were needed to legally perform a flow test using a public street and hydrant; a Traffic Control Plan from PDOT, a Potable Water Discharge Request from the Water Bureau, and a Hydrant Permit also from the Water Bureau.

Traffic Plan A traffic plan was necessary due to the temporary closing of a section of SE Morrison Street. The traffic plan referenced the MUTCD (Manual Urban Traffic Control Devices), and indicated coneage and signage. It was drawn using the Cities GIS layers taxlots, curbs and sidewalks. The Engineer at PDOT responsible for reviewing traffic plans in SE Portland is Peter Mason (3-5234). A copy of the document was kept on-site during the test.

Glencoe Rain Garden 10/20/2004 - 26 - Potable Water Discharge Request A potable water discharge request was applied for in order to discharge water into the Cities’ storm drains. The permit ensures that all personnel downstream of the discharge are aware of the work being performed. The permit required estimates of the peak and total flow volumes as well as discharge location. dates and Hydrant ID used. The completed form was sent for approval to Bret Davison (ES, WG/Maint Engineering: 3- 7588).

Hydrant Permit This permit was necessary to open the City fire Hydrant. It was applied for the day before the test. The permit covers the rental costs of two Chapman valves, two W1250 meters (by special arrangement) and hydrant wrenches, as well as the fee for the amount of water discharged.

Glencoe Rain Garden 10/20/2004 - 27 - Metered Hydrant and Inlet/Outlet Pipe Flows

Table 1: 25-Year Simulation - Flows from hydrants and into Rain Garden Inlet and Outlet Pipes. All flows in gpm Storm Hydrants Inlet Outlet Storm Hydrants Inlet Outlet Storm Hydrants Inlet Outlet Storm Hydrants Inlet Outlet Time Pipe Pipe Time Pipe Pipe Time Pipe Pipe Time Pipe Pipe 1 1012 0 41 0 8 77 81 0 2 9 121 0 0 5 2 855 592 0 42 0 6 83 82 0 2 9 122 0 0 4 3 967 775 0 43 0 13 91 83 0 1 8 123 0 0 3 4 967 825 0 44 0 13 66 84 0 3 8 124 0 0 5 5 987 871 0 45 0 8 66 85 0 0 9 125 0 0 4 6 718 1084 0 46 0 12 63 86 0 1 7 126 0 0 4 7 673 1052 0 47 0 12 62 87 0 4 7 127 0 0 2 8 823 939 0 48 0 6 95 88 0 2 7 128 0 0 4 9 733 984 0 49 0 4 58 89 0 2 5 129 0 0 2 10 770 962 0 50 0 7 56 90 0 1 5 130 0 0 5 11 494 953 0 51 0 8 52 91 0 1 7 131 0 0 4 12 524 793 0 52 0 11 54 92 0 0 6 132 0 0 2 13 524 757 0 53 0 15 52 93 0 1 6 133 0 0 2 14 524 737 24 54 0 3 51 94 0 1 5 134 0 0 4 15 516 719 57 55 0 11 49 95 0 0 5 135 0 0 5 16 329 599 56 56 0 5 51 96 0 0 6 136 0 0 2 17 299 523 60 57 0 0 50 97 0 0 6 137 0 0 3 18 299 482 65 58 0 4 45 98 0 0 6 138 0 0 4 19 296 380 102 59 0 2 48 99 0 0 5 139 0 0 3 20 295 390 93 60 0 14 48 100 0 0 6 140 0 0 3 21 299 398 101 61 0 2 42 101 0 0 7 141 0 0 2 22 292 387 95 62 0 3 43 102 0 0 5 142 0 0 5 23 297 383 95 63 0 4 42 103 0 0 6 143 0 0 5 24 297 378 107 64 0 -1 39 104 0 0 5 144 0 0 3 25 297 393 114 65 0 19 36 105 0 1 5 145 0 0 5 26 299 394 123 66 0 8 34 106 0 0 6 146 0 0 3 27 299 399 126 67 0 5 36 107 0 0 5 147 0 0 4 28 299 398 148 68 0 5 35 108 0 0 7 148 0 0 3 29 307 370 208 69 0 5 18 109 0 0 5 149 0 0 2 30 299 355 165 70 0 5 26 110 0 0 4 150 0 0 3 31 0 338 172 71 0 5 22 111 0 0 4 151 0 0 3 32 0 98 197 72 0 5 20 112 0 0 5 152 0 0 4 33 0 58 167 73 0 2 17 113 0 0 4 153 0 0 5 34 0 35 151 74 0 5 13 114 0 0 2 154 0 0 5 35 0 9 155 75 0 1 12 115 0 0 2 155 0 0 3 36 0 8 107 76 0 2 11 116 0 0 2 156 0 0 4 37 0 13 107 77 0 2 11 117 0 0 3 157 0 0 3 38 0 13 87 78 0 3 10 118 0 0 4 158 0 0 2 39 0 11 81 79 0 3 8 119 0 0 2 159 0 0 4 40 0 10 76 80 0 2 8 120 0 0 5 160 0 0 5

Glencoe Rain Garden 10/20/2004 - 28 -

Storm Hydrants Inlet Outlet Time Pipe Pipe 161 0 0 4 162 0 0 4 163 0 0 4 164 0 0 5

165 0 0 5

166 0 0 4

1100 1050 1000 Glencoe 25-Year Storm 950 900 Pipe/Hydrant Flow 850 800 750 700 Meter 1+2, (gpm) 650 600 550 Inlet Flow (gpm) 500 Total Volume to Outlet = 5124 gallons Outlet flow (gpm) 450 Total Volume at Inlet Meter = 19,136 gallons Flow (gpm) Flow 400 Total Volume from Hydrant = 15,588 gallons 350 300 250 200 150 Drainfield Calculations Infiltration Calcs 100 50 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101 106 111 116 121 126 131 136 141 146 151 156 161 166

Spill to beehive Stopped Spill to Beehive Stopped Overflow to drainfield

Storm Time (min)

Glencoe Rain Garden 10/20/2004 - 29 - Table 2: ASFO Simulation - Flows from Hydrants and into Rain Garden Inlet and Outlet Pipes. All flows in gpm Storm Hydrants Inlet Outlet Storm Hydrants Inlet Outlet Storm Hydrants Inlet Outlet Storm Hydrants Inlet Outlet Time Pipe Pipe Time Pipe Pipe Time Pipe Pipe Time Pipe Pipe 1 52 12 0 41 546 606 0 81 0 7 40 81 0 7 40 2 127 4 0 42 621 593 2 82 0 8 41 82 0 8 41 3 90 1 0 43 449 557 6 83 0 5 38 83 0 5 38 4 90 0 0 44 524 593 33 84 0 9 36 84 0 9 36 5 97 67 0 45 501 642 45 85 0 0 37 85 0 0 37 6 90 84 0 46 165 587 57 86 0 9 40 86 0 9 40 7 97 79 0 47 127 649 75 87 0 8 51 87 0 8 51 8 82 102 0 48 90 665 114 88 0 7 52 88 0 7 52 9 97 106 0 49 105 164 155 89 0 7 44 89 0 7 44 10 82 108 0 50 112 156 201 90 0 6 35 90 0 6 35 11 90 105 0 51 105 156 203 91 0 7 34 91 0 7 34 12 90 107 0 52 112 158 191 92 0 10 34 92 0 10 34 13 90 112 0 53 108 140 188 93 0 5 32 93 0 5 32 14 90 114 0 54 108 123 167 94 0 5 31 94 0 5 31 15 90 109 0 55 105 122 200 95 0 5 32 95 0 5 32 16 172 115 0 56 112 125 142 96 0 8 28 96 0 8 28 17 180 108 0 57 105 113 126 97 0 6 28 97 0 6 28 18 172 110 0 58 112 128 124 98 0 13 28 98 0 13 28 19 180 166 0 59 105 128 119 99 0 9 32 99 0 9 32 20 180 213 0 60 102 131 121 100 0 5 26 100 0 5 26 21 202 223 0 61 0 100 136 101 0 3 27 101 0 3 27 22 150 245 0 62 0 122 93 102 0 2 26 102 0 2 26 23 165 211 0 63 0 118 89 103 0 2 25 103 0 2 25 24 180 192 0 64 0 6 79 104 0 2 26 104 0 2 26 25 180 189 0 65 0 29 80 105 0 2 28 105 0 2 28 26 172 209 0 66 0 9 70 106 0 2 28 106 0 2 28 27 172 225 0 67 0 9 60 107 0 1 34 107 0 1 34 28 165 218 0 68 0 7 56 108 0 0 27 108 0 0 27 29 202 220 0 69 0 8 52 109 0 0 23 109 0 0 23 30 150 214 0 70 0 9 50 110 0 5 24 110 0 5 24 31 475 189 0 71 0 15 43 111 0 0 24 111 0 0 24 32 475 187 0 72 0 16 44 112 0 2 20 112 0 2 20 33 561 182 0 73 0 10 46 113 0 3 19 113 0 3 19 34 479 318 0 74 0 8 43 114 0 13 20 114 0 13 20 35 509 484 0 75 0 8 44 115 0 9 18 115 0 9 18 36 501 524 0 76 0 8 43 116 0 3 16 116 0 3 16 37 516 524 0 77 0 5 43 117 0 12 16 117 0 12 16 38 501 498 0 78 0 6 44 118 0 0 14 118 0 0 14 39 524 566 0 79 0 5 42 119 0 0 11 119 0 0 11 40 501 606 0 80 0 7 43 120 0 1 11 120 0 1 11 121 0 3 8 122 0 14 8

Glencoe Rain Garden 10/20/2004 - 30 - Storm Hydrants Inlet Outlet Time Pipe Pipe 123 0 0 7 124 0 0 6 125 0 10 7 126 0 6 7 127 0 1 6 128 0 -6 6 129 0 2 5 130 0 4 5 131 0 4 5 132 0 0 5 133 0 0 6 134 0 3 3 135 0 2 136 0 2

700 Glencoe -ASFO Storm Simulation 650 600 Meter 1+2, (gpm) 550 Inlet Flow (gpm) 500 Hydrant Flow Test Outlet flow (gpm) 450

400

350 Total Volume to Outlet = 4707 gallons Total Volume at Inlet Meter = 15,335 gallons 300 Total Volume from Hydrant = 13,326 gallons Flow (gpm) Flow 250

200

150

100 Drainfield Calculations Infiltration Calcs

50

0 1 11 21 31 41 51 61 71 81 91 Beehive Stopped Spilling 101 111 121 131 Spill to Beehive

Equalized over Drainfield 2nd Wier Stops Spilling

Spill to Drainfield Storm Time (min)

Glencoe Rain Garden 10/20/2004 - 31 -

Rain Garden Water Depths

Glencoe - 25 year Simulation 1150 0.900 meter 1 + 2 Hydrant flow and Facility Depths 1100 Spilling to Beehive 0.850 Avg F 1050 (normalized to lowest point in facility) 0.800 Z3 1000 Stopped Spill to Beehive 0.750 950 Beehive Overflow Height 900 0.700 850 0.650 800 750 0.600 700 0.550 4" Weir Height 650 0.500 600 0.450 550 Flow (gpm) Flow 500 Stopped Overflow to Drainfield 0.400 450 0.350 400 0.300 350 300 0.250 Depth (ft) 250 0.200 200 0.150 150 0.100 100 50 0.050 0 0.000 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 Time (min)100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175

650 0.90 meter 1 + 2 Glencoe - ASFO Simulation 0.85 Avg F 600 Hydrant Flow and Facility Depths 0.80 Z3 550 Stopped spilling over Beehive 0.75 Beehive Overflow Height 500 0.70 Started spilling over Beehive 450 0.65 0.60 400 Stopped spilling over Drainfield Weir 0.55 350 4 " Weir Height 0.50

300 Started spilling over Drainfield Weir 0.45 0.40

Flow (gpm) Flow 250 0.35 200 0.30 150 0.25 100 0.20 0.15 50 0.10 0 0.05 0 10 20 30 40 50 60 70 80 90

-50 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 0.00 Storm Time (min)

Glencoe Rain Garden 10/20/2004 - 32 -

Infiltration

25 year simulation- Storm Time vs Infiltration 5.0 Rates (in/hr) - All Zones 4.5 F infiltration 4.0 z2 infiltration

3.5 z3 infiltration )

3.0 z4 infiltration

2.5

2.0

1.5

1.0 Infiltration Rate(in/hr 0.5

0.0 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 Storm Time (min)

ASFO Simulation- Storm Time vs Infiltration

2.5 Rates (in/hr)

) 2.0

1.5 F infiltration 1.0 z3 infiltration z4 infiltration

Infiltration Rate(in/hr 0.5

0.0 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 Storm Time (min)

Glencoe Rain Garden 10/20/2004 - 33 -