First Phase: Proposed Changes for the CY 2017 Construction Season

Based on analysis of the 2016 construction season results, input from stakeholders and previous direction from Council, staff is recommending modifications to the dewatering requirements in two phases. The First Phase is making relatively minor changes to the requirements which were adopted by Council for the Calendar Year (CY) 2016 construction season. These new changes (and the pre-existing requirements) would apply to the CY 2017 construction season for those sites not having Building permit before Council adoption of these changes. The Second Phase would be implemented through the ordinance process, with a goal of being effective for the CY 2018 construction season. Requirements under consideration for CY 2018 will be further vetted by staff, stakeholders and Council prior to ordinance adoption. The two phases are described below:

First Phase: Proposed changes for the CY 2017 Construction Season

1)Fill Stations: Demonstrate a maximum 10 minute truck fill time and 2 simultaneous, 100’ hose, 10 gallons per minute (gpm) deliveries (for each hose) during the two week start up period defined below. Design the tank system so that the storage tank is always at least one-half full. (Ongoing Metering of instantaneous and total flow of fill stations is currently required)

2)At the basement slab center, pump the groundwater down no deeper than 3 feetbelow the depth of the slab, following the two week start-up period. Once the slab is poured, the depth to the Center of the slab shall be 1 foot.

3)Pump for no more than 10 weeks for residential sites. A two week start- up period ahead of the 10 weeks is allowed. At the end of the two week start-up period, compliance with all performance standards and water quality standards shall be demonstrated. (Sections A1, A2 , A4, B3b, B2, and Turbidity requirements)

4)Offer to water trees/plants on adjacent properties and do so if requested.

5)Report on all measurements and requirements (reports due at the end of the 2-week start-up period, then bi-weekly, and then a final report at the end of pumping)

6)Add supplemental City contract resources to manage information, review submittals, verify compliance and prepare public reports; and add those costs to City permit fees (this will average to approximately $10,000 per site).

7) Geotechnical Study Enhancements

a)Currently a Geotechnical Study is required to determine groundwater drawdown levels and any associated impacts. The key change for CY 2017 is to require verification of the anticipated drawdown curve with a pump test using actual wells, by the end of the 2 week start-up period. Cone Penetrometer Tests (CPT) are also encouraged to verify soils data. The actual pumping rates, following the two week start-up period, shall be limited to the rates used in in the verification. The maximum amount of water pumped over the 10 week period, (excluding the 2 week start- up period) shall be limited to that calculated during verification. This activity will add on the order of $10,000 to the cost of basement construction.

b)To support the work in (a) above, measure the ground water level at a distance representative of the distance to the nearest adjacent structure, or farthest feasible point on the subject site. This monitoring shall be daily for the first week (including the two week start-up period), then weekly thereafter. If drawdown results are greater than anticipated by the Geotechnical Study, at the end of the 2 week start-up period or thereafter, submit revised a Geotechnical Study, and any revised conclusions on impacts of the groundwater drawdown. The cost of this activity is largely covered by the cost of (a) above, but some additional cost will be incurred.

c)Survey and mark land elevations on adjacent structures (assuming permission is obtained) prior to any pumping. This activity will not add significantly to construction costs, as survey measurements are routinely taken.

d)The Geotechnical Study and verification shall not be required if the storm drain pumping is continuously limited to 30 gallons per minute (gpm) following the two week start-up period. This could be accomplished through installation of groundwater cut-off walls or similar construction techniques; re-injection or percolation of the water to the ground water; or beneficial use on trees and vegetation. (These optional activities would, if implemented, add significantly to the cost of constructing basements.) Similarly, the 10 week pumping period can be extended if the 30 gpm flow rate is continuously achieved following the two-week start-up period. The fee described in 6) above would also be lowered dramatically or eliminated. Additionally, the Contractor need only provide off-site hauling of water sufficient to meet the needs of adjacent neighbors, as opposed to the one-day per week requirement for 2016 .

Second Phase: Potential Calendar Year (CY) 2018 Construction Season Changes:

a) Determine whether existing wells from other sites/purposes can be used to satisfy the groundwater monitoring requirements; utilize such existing wells if practical.

b)Limit the groundwater level drawdown at the closest off-site adjacent structure to 3’.

c)Determine whether existing wells can be used to satisfy the requirement in (c) above; if not, install a new monitoring well.

d)Potentially, require the use of groundwater cut-off walls, or other construction methods, which will limit the pumping (following a two week start-up period) to 30 gallons per minute (gpm) .

Resource Impact

Testing, refining and implementing the suggested measures to improve the dewatering program will require approximately $100,000 in Citycontract funds. If this approach is approved by Council, a Budget Amendment will be submitted for Council approval. The Municipal Fee schedule will also be proposed to be amended to allow the City to recover these costs from applicants. If approved, staff estimates that this would increase the cost of basement construction by approximately $10,000 per site. The Group 3 suggestions are varied and require thoughtful review and have potentially large costs. Therefore, staff is only recommending the analysis of three of them at this time.

Environmental Review

The 2017 recommended program enhancements are minor modifications to an existing regulatory program designed to be protective of the environment. These modifications are not subject to the California Environmental Quality Act (CEQA) because there is no possibility that the modifications may have a significant effect on the environment (CEQA Guidelines Section 15061(b)(3)).

The Group 3 requirements will be evaluated and appropriate environmental review prepared as specific proposals are developed.

Attachment A: February 1, 2016 CMR 6478

Attachment B: 2016 Pumping Requirements

Attachment C: April 11, 2016 CMR 6700