cms collaborative, inc. p: 831.425.3743 www.cms-collaborative.com 28 November 2023
To: CC:
City of Pleasant Hill Robert Nebolon Architects
100 Gregory Lane RNarchitect.com
Pleasant Hill, CA 94523 Tel: (510) 525-2725
Attention: Deirdre Castillo and Robert Nebolon
Re: City of Pleasant Hill Water Feature – Site Review and Concept Assessment Deirdre, Robert,
The below report briefly summarizes the current state of the water features at Pleasant Hill City Hall, describes the existing equipment and piping, discusses options for addressing the current operational issues, and then provides some insight and opinions into the redesign options to be considered. The information presented below is gathered from historical construction documents, in-person discussions with City staff, and information and drawings provided by your office.
Summary of Existing Conditions
Figure 1 - Aerial view of Pleasant Hill City Hall. Source: Google Maps.
The site incorporates three water features that are hydraulically interconnected to comprise one body of water approximately 270,000 gallons. Integrated into the City Hall building is a turbulent, cascading Lake
Pond
Fountain
Community
Room Building
Council Chambers
Building
City Offices
N
Maintenance Yard
Curved Arcade
East Curved
Arcade Entrance
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 2 of 18 “Fountain” comprised of a series of angled steps that calms into flatter, terraced pools. A large, cobblelined lake is visually split into a smaller “Pond” and a main “Lake” by a walkway extending from the parking lot to the City Hall buildings. The Pond, roughly two feet deep, wraps around the northern side of the Community Room. The Lake is three times as large and twice as deep as the pond. It is surrounded by a curved, elevated walkway along the north and west sides and an approachable, landscaped edge along the south and east sides. All features are constructed of concrete, and the Pond and Lake are waterproofed with a 40-mil PVC liner below the concrete. An on-site well provides make-up water.
Water feature equipment is housed in the Council Chambers building, in a room directly behind and below the Fountain. The Community Room Building’s AC system utilizes the water feature water via a heat pump system, with associated equipment located in the water feature equipment room.
The City Hall buildings and water features were designed in 1989 with construction completed in 1991.
The design team included Architects Charles Moore, Fisher Friedman Associates, and Urban Innovations Group, and Landscape Architect Carducci & Associates.
The design was originally constructed as a traditional, architectural water feature. At some point after construction aquatic life such as koi and turtles were introduced into the water feature and have since thrived.
Water Flow
The water feature outside the City Hall building starts the main circulation path with water pouring out the Fountain “grotto” onto an octagonal, stepped cascade. Water is supplied via one display pump moving water through three 8" supply pipes. The activated water calms as it spills down a set of terraced pools, flowing northeast into the Pond. The water continues a clockwise motion by then transferring through eight 8" Schedule 40 PVC pipes (hidden under the east curved arcade entrance) to the Lake.
Figure 2 - Fountain operating 7 August 2023. Grotto tiled in red and green.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 3 of 18 The Lake contains two skimmers along the southern perimeter, connected in series by 8" piping to two suction sumps (one original to the site and one added in 2011). A 12" suction pipe routed below the Lake delivers water from the suction sumps (and skimmers) to the equipment space pumps.
As part of the work completed in 2011 (CO 02), the new suction sump for the 12" pipe also has a smaller pipe installed that connects to a “gravel filter” locally along the bottom surface of the Lake. This is simply a parallel array of perforated, suction piping covered in gravel, which helps with circulation and promotes biological means of processing fish excrement. This setup is common with large-scale koi ponds.
Two other pumps located in the equipment room also draw water through the 12" suction pipe and help recirculate water throughout the Pond and Lake. One pump supplies water to jets at two places in the Lake and one place in the Pond via two 2" PVC pipes to help disturb the water surface (see “aerating jet” in the figure below). The other pump provides filtered and Ultraviolet-sterilized water to standpipes in the Pond. Smooth bore nozzles embedded in the wall at the North-East corner of the Pond are a part of this latter flow path but are currently not functional.
Figure 3 - Existing fittings in and around the Lake. Circular flow path of water indicated with blue arrows.
Original
main drain Original
skimmers
Aerating jet
(clogged)
New (2011)
main drain and
gravel filter.
New (2011)
aeration diffuser.
Aerating jet
(non-op)
New (2011)
aeration diffusers.
Aeration jet
(partially clogged)
Wall jets
(non-op)
Filter effluent
standpipes
Qty. (8) x 8"
transfer pipes
(below walkway)
Three supply
pipes in grotto
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 4 of 18 To further help with water circulation, one 2" pipe (previously used for water flow) was converted in 2011 to be an air-supply pipe for a new aeration system. This system has diffuser plates in a few places along the base of the Lake. Rising water bubbles help water circulation by pushing water up from the bottom of the lake towards the surface, where the most effective aeration can occur.
Part of the original design included a potable water supply; however, the water feature currently uses water from an on-site well for all water make-up needs. In 2009 the water quality was tested and found to be very hard at 360 mg/L of total hardness (as calcium carbonate). Part of the work completed in 2011 included adding a water softener system to treat the supplied well water.
HVAC System Tie-In
The HVAC system for part of the building utilizes the feature water as part of a heat pump system. Filter effluent water is partially directed to a heat pump and heat exchanger. The water returns to the feature inside the equipment room at the 12" suction pipe. The HVAC system inlet and outlet points are depicted below. Currently there is no isolating valve between the HVAC system return and the Water Feature, so the Lake must be drained to work on the return tap fitting (right image, below). Additionally, the feature filter pump must be operating for the HVAC system to function properly.
Figure 4 - HVAC system uses feature water. System inlet taps into feature filter effluent, left, and system outlet taps into feature main suction pipe, right.
Visible Issues
There are several conditions detracting from the overall enjoyment of the space:
1. The water feature water is currently green, murky, and has an unpleasant odor.
2. Algae is intermittently growing throughout the entire water feature.
3. The Lake contains several inches of sediment, which helps feed algae growth and contributes to water turbidity. The sediment is highly visible near the Lake’s original main drain and along its perimeter, where the water depth is minimal.
4. Damp lawn areas adjacent to the southeast portion of the Lake are muddy and slippery. This may be due to overwatering or potential leaks through the Lake liner.
5. The Fountain tiles are partially covered with living and dead algae (see Figure 5).
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 5 of 18 Figure 5 - Fountain water is green, murky, and harbors algae, which is partially covering Fountain tiles.
6. Scaling is an issue on the concrete surfaces at the water line and where water is allowed to splash on the tiled surfaces. This is common for fountains that have scaling potential, where minerals can build up along the wet-dry interfaces.
Figure 6 - White scale buildup on fountain's tiled surface.
7. Fountain tiles have spalled off the concrete substrate in several locations. Some tiles have lost the color layer, making them appear white in color.
8. The fountain’s fiberoptic lighting and spotlights are non-functional. 2011 System Improvements
After commissioning an evaluation report for the Water Feature, the City proceeded with revisions to the plumbing systems to address circulation, water clarity, and hardness. MWH Americas, Inc., the company that produced the report, also prepared plans and specifications for this revision work. The construction project was awarded to Pyxis Water Systems, Inc. in 2011. Work completed included the following:
1. 100 koi and 13 turtles were temporarily removed to be able to safely drain the lake (performed by City).
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2. Muck accumulated throughout the lake was vacuumed out and disposed of (performed by City).
3. The pond was also drained and cleaned as part of change order 12.
Figure 7 - Muck removal 9 February 2011.
4. Concrete and tile surfaces were pressure-washed.
5. An acid wash was completed on some of the smaller supply piping including the 2” piping for the lake’s aerator jets and the piping for the pond’s filter effluent points.
6. Cracks in the concrete liner were locally repaired and any breaches in liner patched.
7. A new suction sump was installed near the center of the lake by excavating a portion of the existing 12" suction pipe and tapping into it with a PVC tee fitting. This created a second bottom suction point in the lake, with the first (original) one being towards the south-east end of the lake.
Figure 8 - New suction sump under construction in the center of the Lake. New 12" tee fitting shown. Smaller piping, right side, is for aeration jets.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 7 of 18
8. Change order 02 included the addition of a gravel bio filter, which involved adding a grid of piping with drain rock layered throughout the piping. This suction piping tapped into the new 12" suction piping mentioned previously.
9. The existing filter pump (3 HP) was replaced with a more powerful pump and motor (7.5 HP) to achieve a higher filtration rate through the sand filters as part of change order 11. Filter piping inside the equipment room was upsized from 3" to 4" to support the increased flowrate without adding excessive head loss (resistance). A digital flow meter/transmitter was added to monitor and report flow readings.
10. An Ultraviolet (UV) Sterilizer was added downstream of the filters with the idea of helping reduce the amount of algae able to survive in the water feature.
11. One of the pipes supplying the Lake’s aerator jets was converted to an air supply pipe for aeration diffuser discs added in a few places along the Lake bottom. An air compressor was added inside the equipment space to provide pressurized air to the discs. This work was completed as part of change order 03 and reduced in scope as part of change order 05.
Figure 9 - Original piping to Lake and Pond jets, left. Middle piping repurposed in 2011 for aeration system, right.
12. Existing, buried piping to the Lake and Pond aerator jets were cut where the new sump was added to the 12" suction pipe. The jet piping beyond the cut points were abandoned in place.
New piping was routed along the Lake floor for the aerator jets and new aeration system.
13. A water softening system was added to the well water supply piping, located outside in the maintenance yard. The system was designed to backwash every 18,000 gallons treated. A pressure tank was installed due to some concerns about water being pumped directly to the system by the well pump, which may fluctuate in pressure and put unnecessary stress on the water softener tank.
14. The lake’s aeration jets were replaced with new jets as part of change order 10.
Assessment of Existing Conditions and Recommendations
The visible characteristics of the water (color, clarity, odor) indicate that the water is overloaded with phosphates and nitrates and has insufficient circulation, thereby creating an anaerobic environment in some portions of the water body. The pancake-like geometry of the Lake, being so large in area but only a maximum of four feet deep, makes it challenging to provide proper water circulation. Typically, water CMS Collaborative, Inc. 28 November 2023
City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 8 of 18 bodies with such a substantial area and that support aquatic life are significantly deeper (over 8 feet deep) with driven vertical circulation paths or have a stronger current moving the water laterally (i.e., a natural pond with river inflow/outflow).
There are several options to consider that can help address the water quality:
Water Additives
Additives to help control growth of undesirables such as algae and anaerobic bacteria are available but can adversely affect the health of the koi living in the Lake. It’s our understanding that additives have been dosed in the past with mixed success. Additionally, additives are often not allowed to enter the storm drain system, which is where the filtration system currently diverts backwash water. Therefore, we would not recommend using them at this time. If they are to be considered, we would recommend contacting the chemical manufacturer or a local representative for guidance prior to dosing.
Controlling Runoff
Nitrates and phosphates are effective fertilizers for lawns, and also feed algae. Currently there is no barrier between the Lake/Pond and adjacent lawn, so anytime it rains or the lawn is overwatered, this nutrientrich water flows directly into the Lake. In fact, during our site review we noticed that a groove was intentionally cut into the Lake’s concrete barrier seemingly as a drainage channel from the lawn into the Lake. Additionally, when the lawn is mowed some clippings are blown into the water where they are left to biodegrade. This, coupled with excrement from aquatic life, is a recipe for persistent and plentiful algae growth.
With natural (non-chemically-treated) features, it’s always a constant battle against nitrate and phosphate levels to control algae growth. Runoff needs to be diverted elsewhere, and any plant matter should be promptly removed. If not, an algae bloom is almost a certainty as the nitrate and phosphate levels rise.
This applies to a koi system as well.
We recommend a wider barrier be added between the Pond/Lake and the adjacent lawn in addition to a trench drain running along the perimeter to catch and divert any lawn runoff to drain rather than into the water body.
Revised Circulation Strategy in the Lake
With shallow water bodies such as this, aeration discs are generally considered less effective since there is insufficient depth of water to create a strong circulation path. Aeration works when rising bubbles push water up to the surface where it can be oxygenated (see next figure). As it disperses along the surface the oxygenated water eventually drops to the floor, creating a circular path back to the aeration supply point.
This circulation path is most effective when the water body is well over six feet deep, closer to 10-15 feet deep.
Floating aeration jets at the water surface can help with shallow water circulation, as can long runs of weighted aeration tubing strung along the Lake floor. Currently, the aeration jets are minimally functional because they are clogged and barely spray water. The jets should be cleaned to restore this circulation path.
The aeration diffusers (installed in 2011) help create smaller circulation paths for the deeper water to become aerated at the surface, but a linear tubing designed for the site geometry will be more effective.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 9 of 18 Figure 10 - Circular path of water due to sub-surface aeration. Image source: cwsenvironmental.com.
Verify Appropriate, Regular Maintenance
Pyxis Water System’s supplied Installation Operation Maintenance Manual included a “Preventative Maintenance Schedule”. We recommend following all items listed under “weekly”, “monthly”, and “annually” as well as the following additional steps:
Weekly
• Brush fountain surfaces with a firm-bristle, non-metallic brush. • Measure and record water parameters such as pH and temperature. • Check all circuit breakers to be sure that none have tripped. If any breakers have tripped, isolate and correct the problem.
• Record the water meter reading.
Quarterly
• Check air supply hoses for wear/cracks/leaks and replace items as necessary. • Measure and record water parameters such as TDS, dissolved oxygen, total phosphorus, nitratenitrogen, ammonia-nitrogen, hardness. • Inspect the filter tank beds. Replace the filter media every 3-7 years, depending on condition. • Inspect the water level sensor and verify it is reporting an accurate water level measurement.
Remove any debris that may have settled nearby.
• Check mechanical pump seals for leaks.
• Check functionality of the float switch inside the equipment room.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 10 of 18 Annually or as required
• Service pumps, compressor, and other equipment per manufacturer instructions. • Check all hoses, clamps, and connections, and replace/tighten as necessary. • Sludge removal (see next item).
Regularly-Scheduled Sludge Removal
A gravel filter was added as part of the 2011 renovation work, which is common with large koi features.
Similar to the sand filters in the equipment room, the gravel filter needs to be regularly cleaned, though not as often. Based on our past research into koi features 200,000 gallons and larger, we would recommend the gravel filter be vacuumed clean twice per year. It’s our understanding that the Lake floor has been left uncleaned for years at a time, which will contribute to a buildup of food for algae and could cause a buildup of residuals toxic to koi. While cleaning the Lake has been a considerable undertaking in the past, we think at least annual cleaning is a necessary step to keep the water clear and healthy. If the City decides to keep the koi in the Lake portion of the water feature, we strongly recommend that they allocate an appropriate, yearly budget for this maintenance. For an additional reference we recommend contacting:
Rick Blazo
Blazo Pond Services
(831) 234-1176
https://www.blazopondservices.com/
Removal or Relocation of Aquatic Life
While it can be a delight to see koi and turtles floating throughout the Lake area, their excrement, when not thoroughly removed or filtered from the water body, often causes murky water, algae growth, and strong odors. As mentioned above, the features at the City Hall were not originally designed to support such life, which is exemplified by the wide and shallow nature of the Lake’s design. Removing the aquatic life, cleaning all surfaces, and refilling with the intent of using chemical treatment will result in easier maintenance and clearer, cleaner water.
An alternative to complete removal would be relocation of the aquatic life to a distinct portion of the site that is hydraulically independent from the rest of the water features (fountain and Lake). This option is discussed later in this document.
RO + Water Softener
To reduce the amount of scale buildup throughout the water features, piping, and equipment, the 2009 report by MWH recommended the addition of a water softening system. They also mentioned concerns about salt content in the water potentially rising, which could be addressed with the addition of a reverse osmosis (RO) system. We recommend the water be tested for hardness and salt content to determine the efficacy of the water softener (when it’s operating) and the level of salts suspended in the water.
Depending on the levels measured, it may be wise to refurbish the water softener system and/or add a RO system. Again, the purpose of this equipment would be to reduce the amount of scale (white buildup) on the concrete and tile surfaces and inside the piping and equipment. This has an aesthetic impact and affects how well the pumping, filtration, and HVAC systems operate.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 11 of 18 Potable Water Supply
The water supplied by the well pump is categorized as “very hard”. The hard water is likely strongly contributing to the scale buildup on the fountain’s tile, the white buildup at the water line throughout the Pond and Lake, and the buildup inside the piping system.
The City’s potable water supply, according to the Contra Costa Water District’s 2022 report, contains less hardness (at 120 mg/L vs. the well’s 360mg/L). However, it contains levels of ammonia and chlorine that may be problematic for the koi at 0.7 mg/L and 1.7 mg/L respectively. MWH’s 2009 report recommended that the pond be refilled with potable water with the caveat that the chlorine and ammonia be neutralized.
We recommend considering the use of potable water for make-up purposes, especially if the water feature is redesigned to split off the koi into a separate, dedicated system. In such a scenario, the koi system could still be supplied by well water, whereas the other system could be supplied by potable water (or a mixture with well water to reduce water use costs).
Decouple the HVAC System
During the summer when the HVAC system is cooling part of the Community Room Building, the heat exchanger is adding heat to the Lake water. Algae already has a propensity to thrive in warmer summer months, and increasing the water temperature in this manner only increases the likelihood of algae growth. Decoupling the HVAC system from the Lake will help keep the water temperature as low as possible, which will help mitigate algae growth.
Verify Efficacy of Filters and UV
The filtration system currently includes:
1. One filter pump with an operating point at 407 gpm @ 52.6 feet, PACO model 30957 LC, 7.5 HP.
2. One magnetic flow transmitter, Rosemount model 8732E with 4-20 mA output, and one flowtube mount, Rosemount model 8711.
3. Three high-rate sand filter tanks, Pentair Triton II Commercial model TR140C-3, 36" diameter tank,
7.06 sf filter area, with filtration rates of 106 gpm min and 141 gpm max (318 gpm to 423 gpm total for the three filters). Filter media is one-third (by volume) pea gravel at the bottom of the tank and two-thirds (by volume) 30-grit sand on top per MWH’s 2009 report.
4. One UV sterilizer, Aqua Ultraviolet model Viper SS 1200 Watt was installed in 2011 but has since been removed and replaced with a straight run of PVC pipe.
With the above equipment operating as intended, the entire water feature should experience one turnover through the filter tanks every eleven hours. Considering an operating day of 7am to 10pm, this corresponds to 1.36 turnovers per day. If this was a swimming pool, this would be insufficient, but for a large koi feature, it can be appropriate. This depends on how well the water is circulating, the dissolved oxygen content, and how often the Lake surfaces are being cleaned (i.e., brushed and vacuumed). We would want to see a daily record of filter flowrate (read at the Rosemount flow transmitter) over at least a month to better understand how well the filter system is performing. If it is underperforming, chances are that its contribution to the water quality issues are not as significant as the need to clean the Lake floor and address runoff from the adjacent lawn. Note that we disagree with the MWH 2009 report’s recommendation to lower the filtration rate to “6 to 10 gpm/ft2” since these filters often require at least CMS Collaborative, Inc. 28 November 2023
City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 12 of 18 12 gpm/ft2for proper filtration and backwashing. With too low of a flowrate, the sand bed is not sufficiently disturbed during backwash, which results in the need to backwash more frequently.
The filter tanks should be opened, and sand examined. If the sand has not been replaced within the last seven years, it probably should. If replacing, we recommend considering an alternative media that is more compatible with koi systems. Often when koi systems use pressurized filter tanks, the media is a small plastic granule shaped to have a high surface area. This is to promote biological filtration processes inside the filter tank, which helps process koi excrement sucked into the filter by the bottom drains. For additional information about the media, we recommend contacting a koi consultant.
As mentioned in point #4 above, the UV sterilizer has been replaced with a length of PVC pipe. Typically with water this turbid a UV sterilizer is largely ineffective. However, since it was located after the filter tanks, the water should have been clear enough for it to destroy many of the algae cells passing through.
While algae cell destruction was its intended purpose, as described in MWH’s 2009 report, our experience informs us that UV sterilizers are minimally effective at mitigating algae growth with such a low turnover of water through the UV unit itself. They can still be an effective means of killing “bad” bacteria that often thrive in a nutrient-rich environment. We recommend replacing the PVC piping with a functioning UV system for this purpose.
Electrical Code Requirements
The National Electric Code (NEC) requires three feet of clearance in front of electrical panels 150V to ground and lower, and 42 inches of clearance in front of panels 600V - 151V to ground. The electrical panels inside the equipment space pump pit (depressed area) do not comply with this requirement as they have the display and filter pumps directly in front. Unrelated to this requirement, the panels are in a part of the room that floods if a pipe breaks. We recommend that the panels be relocated to either where the filter tanks reside, or outside the equipment room in an adjacent space. Relocating the panels out of the line-of-site of the pumps will require disconnect switches to be added in the equipment room. While this doesn’t affect water quality, it does have an impact on safety and reliability of the electrical system.
Figure 11 - Pumps directly in front of electrical equipment, not complying with code.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 13 of 18 Fountain Lighting
The fountain was originally constructed with integrated fiber optic lighting, which has since failed. There have been significant improvements to lighting products with most fixtures now being low-voltage LED.
We recommend that the lighting strategy be revisited with a focus on switching to LEDs, either solid white or DMX-controlled RGBW.
Future Concept Analysis
Below are our thoughts on the concepts being considered to improve the Water Feature experience at the City Hall, as envisioned by Robert Nebolon Architects (RNA). Where cost estimates are included, they are for the purpose of rough guidance for installed costs. For more accurate values a cost estimator should be consulted, and a more developed narrative of changes may be required.
Concept 1, Base Package
Summary:
• Retile the fountain as-is, no structure modifications. Cost estimate by RNA. • New fountain lighting. $30,000.
• Drain and clean entire water feature. Clean piping of scale buildup as required. $80,000. • New piping and aeration in the Lake to address circulation issues. $40,000. • Refresh equipment room. $180,000.
• Move electrical equipment to comply with code. $40,000. • Koi stay in the Lake and Pond.
Thoughts
Some refinements to the equipment room will be beneficial such as adding some service valves, and rearranging equipment for easier maintenance access and to comply with codes. A refresh of the tile is exactly what they need. However, maintenance will still need to be top-of-mind for them. With a big koi feature, maintenance needs to be a part of the weekly/monthly/yearly budget. Proper equipment helps reduce but does not eliminate the maintenance burden. Reducing the number of koi in the pond will help clarify the water due to the reduced waste load. Hard water will still be an issue, especially if they continue to use the well for make-up.
Concept 2, Partition Out a Small Koi Pond
Summary:
• Retile the fountain. Cost estimate by RNA.
• New fountain lighting and koi feature lighting. $50,000. • Partition the northeast corner of the Pond as a small, dedicated koi system with skimmers and main drains added. Koi equipment to be housed in a shed in the maintenance yard northeast of the Council Chambers Building. $275,000.
• Excavate deepest portion of the new koi pond, at least 30 square feet, to have a depth of three to four feet below water level. Main drain(s) will be located here. Cost estimate by RNA. • Convert the Lake, west side of the Pond, and Fountain into one chemically treated system.
Chemical equipment for the Fountain to be housed in a shed in the maintenance yard. Update plumbing system as required. $200,000.
• Shed to enclose koi equipment and chemical system. Cost estimate by RNA.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 14 of 18 • New blue tiling on the plaza per Architect’s plans, to conceal demolition of plaza section for new piping work from Fountain to Lake. Cost estimate by RNA. • Minimal landscaping. Cost estimate by RNA.
• New electrical system. $70,000.
• Drain and clean entire water feature. Clean piping of scale buildup as required. $80,000.
Thoughts
Partitioning out a separate system for the koi is a necessary design consideration based on our understanding of the amount of maintenance available for allocation to this feature. Large koi ponds, especially ones with gravel filters, require draining/cleaning at least once per year; the City may not have the budget to do this. Shifting to a smaller koi pond will drastically reduce the burden of maintaining it.
Ideally the new koi pond is re-graded for optimal koi waste removal, as shown in the figure below. To reduce anticipated costs, a smaller re-grading footprint is included in the summary above. This would entail only a partial demo of the northeast Pond’s concrete basin rather than a complete demo of the whole pond floor. Skimmers and filter effluent fittings should be included around the perimeter, with all suction and discharge piping routed in grade between the koi pond and the maintenance yard.
The equipment room would house the Fountain and Lake pumps and filters. Chemical treatment would be outside in a shed with the koi pump, filter, and UV sterilizer system. The electrical equipment may be able to stay in the equipment room pump pit or could be moved to the space Ananthan suggested.
We recommend that this concept include a larger buffer between the Lake and lawn as well as perimeter drainage if the budget allows, as discussed earlier in this report.
Figure 12 – Recommended self-cleaning pond shape with steep sides, safety shelf, and a floor that slopes to bottom drains. Source: lagunakoi.com.
Concept 3, Partition Out a Large Koi Pond
Summary, Concept 2 plus:
• Build new land-bridge between Fountain and Koi Pond. Koi Pond is larger, encompassing entire Pond on the northeast side of the site, per Architect’s plans. Cost estimate for bridge work by RNA. Larger Koi Pond estimated at an additional $70,000 ($345,000 total) for additional/larger equipment, piping, and fittings.
• Landscaping along the northern edge, along the street. Cost estimate by RNA. • New decorative water features in the Koi Pond with lighting. $30,000.
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City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 15 of 18 • Additional excavated portion for second main drain point, like what is described in Concept 2.
Cost estimate by RNA.
Thoughts
See our comments on Concept 2 above. Having the Koi Pond encompass the entire Pond space on the northern side of the site (rather than just a portion as included in Concept 2) would support two to three times the capacity of koi as what is allocated in Concept 2. The detractors are larger equipment and an elevated level of maintenance required. Either way, with concepts 2 or 3, reducing the koi feature size from what it is currently will result in less effort required to keep the water clear and looking clean.
With this option water can no longer flow from the Fountain to the Lake along the north side of the site.
New piping would have to be routed from the lowest Fountain pool to the Lake. The blue tile included by RNA is designed to help hide new trenching required for this piping. The particulars of how the water is transferred would require the design team’s attention and refinement.
Concept 4
Summary, Concept 3 plus:
• Add new concrete walks, benches, and metal bridge all around the new, larger Koi Pond. Cost estimate by RNA.
• New commemorative wall-mounted plaques. Cost estimate by RNA. • New inlaid brickwork in existing parking lot area. Cost estimate by RNA. • New decorative water features in the Lake plus lighting. $10,000-$20,000 each.
Thoughts
See our thoughts on the earlier concept 3. Expanding the beauty of the area around the koi feature should only add to the public’s enjoyment of the space. The koi are currently in a prominent location, visible at the Lake edge whenever walking along the Curved Arcade. Moving them to a space that is thoughtfully landscaped with planting and walking paths should help counteract their diminished presence after being moved to a smaller pond farther away from the Curved Arcade.
If the new decorative features in the Lake are intended to involve submersible pumps with a jet and LED ring light, you can expect the price to be around $20,000 each, installed. Maintaining them will be a regular task, especially if well water continues to be used for make-up purposes. Scale would become an important issue to address. Adding a stain/scale inhibitor as part of the automated chemical system can help with scale on sensitive components such as this but does not eliminate the issue.
Concept 5
Summary:
• Everything shown on the 10-year plan documents, installed in phases.
Thoughts
Phasing work typically leads to 20-30% increased construction costs and can cause confusion during construction if different contractors are selected for different phases. Our recommendation if phasing is expected would be to ensure that the design team intentionally plans for and documents phasing in the Contract Documents. Phasing the water feature would present challenges since typically the entire system CMS Collaborative, Inc. 28 November 2023
City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 16 of 18 needs to be constructed before it can be made operational; months or years between phases of water feature construction could mean that the features are inactive for that length of time.
Concept 6
Summary:
• Remove the koi permanently.
• Build new land-bridge between the Fountain and Pond to provide a new walking path to the north grass area. Cost estimate by RNA.
• Landscaping along the northern edge, along the street. Cost estimate by RNA. • Keep the current site piping and general flow path from Fountain to Lake. • Retile the fountain as-is, no structure modifications. Cost estimate by RNA. • New fountain lighting. $30,000.
• Remove Lake’s gravel filter and update sump added in 2011. $50,000. • Drain and clean entire water feature. Clean piping of scale buildup as required. $80,000. • New piping and aeration in the Lake to address circulation issues. $40,000. • Refresh equipment room. Add chemical treatment system, to be housed in a shed in the maintenance yard. $250,000.
• New electrical system, relocated to comply with code. $70,000. • New decorative water features in the Lake plus lighting. $10,000-$20,000 each.
Thoughts
This is likely the lowest-maintenance option, and it restores the site’s original design intent. Removing the koi would be a loss of a seemingly important site amenity, but the water would be easier to keep clean, clear, and free of odors. Using the well water for make-up purposes would still result in scale buildup, but the addition of chemicals could help reduce the buildup and make it easier to brush surfaces clean.
Based on our current understanding and observations, the buried piping could remain but may need to be cleaned internally. We would advocate for redesigning the water supply and aeration methods in the Lake to improve circulation. There may end up being a need to install some new piping from the equipment room to the Lake, but we are unable to determine that with any certainty at this time.
With clearer water, the Lake and Pond floors will become visible. The piping routed along the Lake floor has the potential to become an eyesore. Any design team pursuing this concept should consider the aesthetics of any piping and equipment located in the Lake and Pond. Dirt or debris settling in the feature could also appear unsightly, especially if the Pond and Lake bottoms are to remain light in color. Weekly brushing of the Lake floor, pushing sediment to the suction piping, may be desired to keep it looking as clean as possible. There are automated and remote-controlled pool cleaners that could be purchased to help with cleaning the Lake and Pond floors.
The land bridge and landscaping included in RNA’s designs will help refresh and revitalize the site and especially the area around the Fountain. Adding new circulation paths with allow the public to appreciate the proposed design updates more fully.
CMS Collaborative, Inc. 28 November 2023
City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 17 of 18 Concept 7
Summary, Concept 6 plus:
• New, separate koi system partially above ground and partially set within grade, to achieve a total water depth of at least three feet. Equipment located in the maintenance yard, with this new koi pond somewhere nearby. $250,000.
• Benches and other decorative elements surrounding the new concrete koi pond’s raised perimeter. Cost estimate by RNA.
Thoughts
Including the koi in a way that does not require substantial disturbances to the Pond’s concrete and waterproofing should reduce chances of errors or change orders during construction. If the City wants to keep koi on the property, we think this is a reasonable opportunity to do so. Refer to Concept 7 above for additional thoughts.
Additional Considerations
Electrical
With Concepts 2 through 6, where the pumping system is being renovated or expanded, additional power requirements would need to be coordinated. The design team would need to work closely with City staff to ensure the required power draw can be met by the power available in the panels inside Level 1 of the Council Chambers Building, adjacent to the water feature equipment room. At the time of our visit, it was not apparent which panels could source additional power.
Our standard practice is to include all fountain equipment inside one combined control & power panel whenever possible. While the water feature’s electrical system is still functional and appears to be in good shape, combining all devices into one new panel has the benefits of simplicity and providing new features such as remote monitoring and control. These panels can cost between $30,000 and $40,000 for features of this size and complexity. Our $70,000 estimate for Concept #2’s “new electrical system” includes this work.
Waterproofing
At the time of our visit, the water features were coated in debris, so we were unable to visually assess the concrete floors. Additionally, the waterproofing membrane is located underneath the concrete as a 40-mil PVC liner, so it could not be examined. Any work completed could expose failures in the concrete or liner.
We would recommend allocating $50,000 - $70,000 for possible repairs.
One idea being considered is to apply a waterproofing membrane to the Lake’s concrete surface. A fluidapplied product such as CIM-1000 is commonly used to coat concrete for fountain purposes. The membrane could be coated with a pigmented topcoat or plaster. This would address any potential points of leakage along the Lake floor. Note that such membranes are flexible enough to retain their characteristics across small gaps but would likely fail with the roughly ½" gaps seen during the 2011 repairs.
We are not waterproofing or concrete experts, so specialized consultants should be retained if a detailed analysis is desired.
CMS Collaborative, Inc. 28 November 2023
City of Pleasant Hill Water Feature - Site Review and Concept Assessment Page 18 of 18 If large cracks are found in the concrete, it could be a sign of stress being applied to piping. If this is the case, we would recommend the pipes be pressure-tested, which could cost around $5,000.
While there are some unknowns with how the current system operates, we feel this report accurately captures the issues observed throughout the water features and our recommendations to address them.
Should you have any questions or comments, do not hesitate to contact us.
Sincerely,
Geno Viscuso
CMS Collaborative, Inc.
831.425.3743